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Sample records for calcium channel currents

  1. Glucocorticoids specifically enhance L-type calcium current amplitude and affect calcium channel subunit expression in the mouse hippocampus.

    Science.gov (United States)

    Chameau, Pascal; Qin, Yongjun; Spijker, Sabine; Smit, August Benjamin; Smit, Guus; Joëls, Marian

    2007-01-01

    Previous studies have shown that corticosterone enhances whole cell calcium currents in CA1 pyramidal neurons, through a pathway involving binding of glucocorticoid receptor homodimers to the DNA. We examined whether glucocorticoids show selectivity for L- over N-type of calcium currents. Moreover, we addressed the putative gene targets that eventually lead to the enhanced calcium currents. Electrophysiological recordings were performed in nucleated patches that allow excellent voltage control. Calcium currents in these patches almost exclusively involve N- and L-type channels. We found that L- but not N-type calcium currents were largely enhanced after treatment with a high dose of corticosterone sufficient to activate glucocorticoid receptors. Voltage dependency and kinetic properties of the currents were unaffected by the hormone. Nonstationary noise analysis suggests that the increased current is not caused by a larger unitary conductance, but rather to a doubling of the number of functional channels. Quantitative real-time PCR revealed that transcripts of the Ca(v)1 subunits encoding for the N- or L-type calcium channels are not upregulated in the mouse CA1 area; instead, a strong, direct, and consistent upregulation of the beta4 subunit was observed. This indicates that the corticosteroid-induced increase in number of L-type calcium channels is not caused by a simple transcriptional regulation of the pore-forming subunit of the channels.

  2. Calcium current-dependent and voltage-dependent inactivation of calcium channels in Helix aspersa

    Science.gov (United States)

    Brown, A. M.; Morimoto, K.; Tsuda, Y.; Wilson, D. L.

    1981-01-01

    -exponential inactivation process that persists in the presence of EGTAi is similar to that occurring when extracellular Ba ion carries current through the Ca channel. Steady-state inactivation also persists and is similar in the two cases. Therefore it is concluded that inactivation is voltage-dependent as well as Ca current-dependent. 8. Diffusion models that included reasonable values for the effect of binding on diffusion, even when combined with declining influxes, did not account for this `mixed' form of calcium- and voltage-dependent inactivation. A compartmental model in which the particular kinetic model of voltage-dependent inactivation was not critical described the Ca current-dependent inactivation. PMID:6275075

  3. Calcium channel blocker overdose

    Science.gov (United States)

    ... page: //medlineplus.gov/ency/article/002580.htm Calcium-channel blocker overdose To use the sharing features on this page, please enable JavaScript. Calcium-channel blockers are a type of medicine used to ...

  4. Effect of gingerol on colonic motility via inhibition of calcium channel currents in rats.

    Science.gov (United States)

    Cai, Zheng-Xu; Tang, Xu-Dong; Wang, Feng-Yun; Duan, Zhi-Jun; Li, Yu-Chun; Qiu, Juan-Juan; Guo, Hui-Shu

    2015-12-28

    To investigate the effect of gingerol on colonic motility and the action of L-type calcium channel currents in this process. The distal colon was cut along the mesenteric border and cleaned with Ca(2+)-free physiological saline solution. Muscle strips were removed and placed in Ca(2+)-free physiological saline solution, which was oxygenated continuously. Longitudinal smooth muscle samples were prepared by cutting along the muscle strips and were then placed in a chamber. Mechanical contractile activities of isolated colonic segments in rats were recorded by a 4-channel physiograph. Colon smooth muscle cells were dissociated by enzymatic digestion. L-type calcium currents were recorded using the conventional whole-cell patch-clamp technique. Gingerol inhibited the spontaneous contraction of colonic longitudinal smooth muscle in a dose-dependent manner with inhibition percentages of 13.3% ± 4.1%, 43.4% ± 3.9%, 78.2% ± 3.6% and 80.5% ± 4.5% at 25 μmol/L, 50 μmol/L, 75 μmol/L and 100 μmol/L, respectively (P gingerol. Gingerol inhibited L-type calcium channel currents in colonic longitudinal myocytes of rats. At a 75 μmol/L concentration of gingerol, the percentage of gingerol-induced inhibition was diminished by nifedipine from 77.1% ± 4.2% to 42.6% ± 3.6% (P Gingerol suppressed IBa in a dose-dependent manner, and the inhibition rates were 22.7% ± 2.38%, 35.77% ± 3.14%, 49.78% ± 3.48% and 53.78% ± 4.16% of control at 0 mV, respectively, at concentrations of 25 μmol/L, 50 μmol/L, 75 μmol/L and 100 μmol/L (P gingerol. The value of half activation was -14.23 ± 1.12 mV in the control group and -10.56 ± 1.04 mV in the 75 μmol/L group (P gingerol group (P > 0.05), and a slope factor, K, of 13.24 ± 1.62 in the control group and 13.45 ± 1.68 (P > 0.05) in the 75 μmol/L gingerol group. Gingerol inhibits colonic motility by preventing Ca(2+) influx through L-type calcium channels.

  5. Glucocorticoids specifically enhance L-type calcium current amplitude and affect calcium channel subunit expression in the mouse hippocampus

    NARCIS (Netherlands)

    Chameau, P.; Qin, Y.; Spijker, S.; Smit, A.B.; Joels, M.

    2007-01-01

    Previous studies have shown that corticosterone enhances whole cell calcium currents in CA1 pyramidal neurons, through a pathway involving binding of glucocorticoid receptor homodimers to the DNA. We examined whether glucocorticoids show selectivity for L- over N-type of calcium currents. Moreover,

  6. Glucocorticoids specifically enhance L-type calcium current amplitude and affect calcium channel subunit expression in the mouse hippocampus.

    NARCIS (Netherlands)

    Chameau, P.J.P.; Qin, Y.J.; Smit, G.; Joëls, M.

    2007-01-01

    Previous studies have shown that corticosterone enhances whole cell calcium currents in CA1 pyramidal neurons, through a pathway involving binding of glucocorticoid receptor homodimers to the DNA. We examined whether glucocorticoids show selectivity for L- over N-type of calcium currents. Moreover,

  7. Inhibitors of arachidonate-regulated calcium channel signaling suppress triggered activity induced by the late sodium current.

    Science.gov (United States)

    Wolkowicz, Paul; Umeda, Patrick K; Sharifov, Oleg F; White, C Roger; Huang, Jian; Mahtani, Harry; Urthaler, Ferdinand

    2014-02-05

    Disturbances in myocyte calcium homeostasis are hypothesized to be one cause for cardiac arrhythmia. The full development of this hypothesis requires (i) the identification of all sources of arrhythmogenic calcium and (ii) an understanding of the mechanism(s) through which calcium initiates arrhythmia. To these ends we superfused rat left atria with the late sodium current activator type II Anemonia sulcata toxin (ATXII). This toxin prolonged atrial action potentials, induced early afterdepolarization, and provoked triggered activity. The calmodulin-dependent protein kinase II (CaMKII) inhibitor KN-93 (N-[2-[[[3-(4-chlorophenyl)-2-propenyl]methylamino]methyl]phenyl]-N-(2-hydroxyethyl)-4-methoxybenzenesulphon-amide) suppressed ATXII triggered activity but its inactive congener KN-92 (2-[N-(4-methoxy benzenesulfonyl)]amino-N-(4-chlorocinnamyl)-N-methylbenzylamine) did not. Neither drug affected normal atrial contractility. Calcium entry via L-type channels or calcium leakage from sarcoplasmic reticulum stores are not critical for this type of ectopy as neither verapamil ((RS)-2-(3,4-dimethoxyphenyl)-5-{[2-(3,4-dimethoxyphenyl)ethyl]-(methyl)amino}-2-prop-2-ylpentanenitrile) nor ryanodine affected ATXII triggered activity. By contrast, inhibitors of the voltage independent arachidonate-regulated calcium (ARC) channel and the store-operated calcium channel specifically suppressed ATXII triggered activity without normalizing action potentials or affecting atrial contractility. Inhibitors of cytosolic calcium-dependent phospholipase A2 also suppressed triggered activity suggesting that this lipase, which generates free arachidonate, plays a key role in ATXII ectopy. Thus, increased left atrial late sodium current appears to activate atrial Orai-linked ARC and store operated calcium channels, and these voltage-independent channels may be unexpected sources for the arrhythmogenic calcium that underlies triggered activity. Copyright © 2013 Elsevier B.V. All rights reserved.

  8. Calcium channel blocker poisoning

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    Miran Brvar

    2005-04-01

    Full Text Available Background: Calcium channel blockers act at L-type calcium channels in cardiac and vascular smooth muscles by preventing calcium influx into cells with resultant decrease in vascular tone and cardiac inotropy, chronotropy and dromotropy. Poisoning with calcium channel blockers results in reduced cardiac output, bradycardia, atrioventricular block, hypotension and shock. The findings of hypotension and bradycardia should suggest poisoning with calcium channel blockers.Conclusions: Treatment includes immediate gastric lavage and whole-bowel irrigation in case of ingestion of sustainedrelease products. All patients should receive an activated charcoal orally. Specific treatment includes calcium, glucagone and insulin, which proved especially useful in shocked patients. Supportive care including the use of catecholamines is not always effective. In the setting of failure of pharmacological therapy transvenous pacing, balloon pump and cardiopulmonary by-pass may be necessary.

  9. The effects of propofol and enflurane on single calcium channel currents of guinea-pig isolated ventricular myocytes.

    OpenAIRE

    Takahashi, H.; Puttick, R. M.; Terrar, D. A.

    1994-01-01

    1. The effects of the anaesthetics, propofol (100 microM) and enflurane (3%, 1.46 mM), on single L type calcium channel currents were investigated in single myocytes isolated from guinea-pig ventricles. Channel activity was recorded from membrane patches by use of the 'cell-attached' patch-clamp technique (pipette solution containing 110 mM BaCl2, 5 microM Bay K 8644, 5 microM HEPES, pH 7.4; temperature 36 degrees C). 2. Channel conductance was calculated from the slope of the relationship be...

  10. Assay for calcium channels

    Energy Technology Data Exchange (ETDEWEB)

    Glossmann, H.; Ferry, D.R.

    1985-01-01

    This chapter focuses on biochemical assays for Ca/sup 2 +/-selective channels in electrically excitable membranes which are blocked in electrophysiological and pharmacological experiments by verapamil, 1,4-dihydropyridines, diltiazen (and various other drugs), as well as inorganic di- or trivalent cations. The strategy employed is to use radiolabeled 1,4-dihydropyridine derivatives which block calcium channels with ED/sub 50/ values in the nanomolar range. Although tritiated d-cis-diltiazem and verapamil can be used to label calcium channels, the 1,4-dihydropyridines offer numerous advantages. The various sections cover tissue specificity of channel labeling, the complex interactions of divalent cations with the (/sup 3/H)nimodipine-labeled calcium channels, and the allosteric regulation of (/sup 3/H)nimodipine binding by the optically pure enantiomers of phenylalkylamine and benzothiazepine calcium channel blockers. A comparison of the properties of different tritiated 1,4-dihydropyridine radioligands and the iodinated channel probe (/sup 125/I)iodipine is given.

  11. Alternative Splicing at C Terminus of CaV1.4 Calcium Channel Modulates Calcium-dependent Inactivation, Activation Potential, and Current Density

    Science.gov (United States)

    Tan, Gregory Ming Yeong; Yu, Dejie; Wang, Juejin; Soong, Tuck Wah

    2012-01-01

    The CaV1.4 voltage-gated calcium channel is predominantly expressed in the retina, and mutations to this channel have been associated with human congenital stationary night blindness type-2. The L-type CaV1.4 channel displays distinct properties such as absence of calcium-dependent inactivation (CDI) and slow voltage-dependent inactivation (VDI) due to the presence of an autoinhibitory domain (inhibitor of CDI) in the distal C terminus. We hypothesized that native CaV1.4 is subjected to extensive alternative splicing, much like the other voltage-gated calcium channels, and employed the transcript scanning method to identify alternatively spliced exons within the CaV1.4 transcripts isolated from the human retina. In total, we identified 19 alternative splice variations, of which 16 variations have not been previously reported. Characterization of the C terminus alternatively spliced exons using whole-cell patch clamp electrophysiology revealed a splice variant that exhibits robust CDI. This splice variant arose from the splicing of a novel alternate exon (43*) that can be found in 13.6% of the full-length transcripts screened. Inclusion of exon 43* inserts a stop codon that truncates half the C terminus. The CaV1.4 43* channel exhibited robust CDI, a larger current density, a hyperpolarized shift in activation potential by ∼10 mV, and a slower VDI. Through deletional experiments, we showed that the inhibitor of CDI was responsible for modulating channel activation and VDI, in addition to CDI. Calcium currents in the photoreceptors were observed to exhibit CDI and are more negatively activated as compared with currents elicited from heterologously expressed full-length CaV1.4. Naturally occurring alternative splice variants may in part contribute to the properties of the native CaV1.4 channels. PMID:22069316

  12. Channelrhodopsin-2-expressed dorsal root ganglion neurons activates calcium channel currents and increases action potential in spinal cord.

    Science.gov (United States)

    Zhang, Yi; Yue, Jing; Ai, Midan; Ji, Zhigang; Liu, Zhiguo; Cao, Xuehong; Li, Li

    2014-07-01

    We used optogenetic techniques in spinal cord and dorsal root ganglion (DRG) neuron studies. This study investigated changes in channelrhodopsin-2 (ChR2) expression in the spinal cord and DRG neurons using optogenetic techniques. The results show the possibility of using optogenetics to treat neuropathic pain. Previous studies have shown that activated ChR2 induces an increase in DRG neuron action potential. Western blot analysis was used to measure ChR2 protein levels in the spinal cord and DRG neurons or rats intrathecally injected with ChR2 lentivirus. Electrophysiology recording was used to detect differences in action potential levels in the spinal cord and calcium channel currents in the DRG neurons. Our studies showed that ChR2 expression increased the action potential in the spinal cord and increased calcium channel currents in DRG neurons. We successfully expressed the ChR2 protein in the spinal cord and DRG neurons. We also found that ChR2 increased the action potential in the spinal cord and activated the calcium channel in DRG neurons. These findings support the research possibilities of using optogenetic studies to improve treatment for neuropathic pain. N/A.

  13. Specific inhibition of stretch‐induced increase in L‐type calcium channel currents by herbimycin A in canine basilar arterial myocytes

    National Research Council Canada - National Science Library

    Kimura, Makoto; Obara, Kazuo; Sasase, Tomohiko; Ishikawa, Tomohisa; Tanabe, Yoshiyuki; Nakayama, Koichi

    2000-01-01

    ...‐activated barium currents (I Ba ) through L‐type calcium channels increased by hypotonic solution were investigated in canine basilar arterial myocytes by the whole‐cell patch‐clamp technique...

  14. Voltage-activated currents through calcium channels in normal bovine lactotrophs.

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    Cobbett, P; Ingram, C D; Mason, W T

    1987-11-01

    The properties of whole cell Ba2+ currents were studied in immunocytochemically identified, normal bovine lactotrophs using the patch clamp technique. In the current clamp mode, current-induced and spontaneous Ba2+ action potentials were recorded. These were of longer duration and showed less inactivation with stimulation frequency when compared with Na+ action potentials. Under voltage clamp, isolated Ba2+ currents had an activation threshold of about -35 mV and peak value at -15 mV to +20 mV. Inactivation of the current to a potential-dependent, non-zero steady-state level indicated the presence of one rapidly and one slowly inactivating component to the current. These two components were also distinguished by: (1) the voltage dependence of the inactivation time constant of the current, (2) the differential frequency-dependent inactivation of the peak and steady-state currents, and (3) the presence of two half-inactivation potentials for the current. Analysis of the ensemble current variance of the non-inactivating component gave a single-channel amplitude of 0.19 pA at 0 mV and a slope conductance of 3 pS. Fluctuation analysis of the voltage-activated Ba2+ current noise revealed two time constants, one which was voltage dependent and the other was independent of potential. The contribution of these two currents to Ca2+-dependent hormone secretion remains to be clarified.

  15. Current insights into the physiology of the epithelial calcium and magnesium channels

    NARCIS (Netherlands)

    Topala, C.N.

    2008-01-01

    Ion channels are specialized proteins that span the plasma membrane of living cells allowing ion fluxes through this essentially impermeable barrier. Most ion channels show selectivity in that their pores are more permeable to some ions than to others. The development of the patch-clamp technique

  16. Investigation into in vitro anti-leishmanial combinations of calcium channel blockers and current anti-leishmanial drugs

    Directory of Open Access Journals (Sweden)

    Juliana Quero Reimão

    2011-12-01

    Full Text Available The need for drug combinations to treat visceral leishmaniasis (VL arose because of resistance to antimonials, the toxicity of current treatments and the length of the course of therapy. Calcium channel blockers (CCBs have shown anti-leishmanial activity; therefore their use in combination with standard drugs could provide new alternatives for the treatment of VL. In this work, in vitro isobolograms of Leishmania (Leishmania chagasi using promastigotes or intracellular amastigotes were utilised to identify the interactions between five CCBs and the standard drugs pentamidine, amphotericin B and glucantime. The drug interactions were assessed with a fixed ratio isobologram method and the fractional inhibitory concentrations (FICs, sum of FICs (ΣFICs and the overall mean ΣFIC were calculated for each combination. Graphical isobologram analysis showed that the combination of nimodipine and glucantime was the most promising in amastigotes with an overall mean ΣFIC value of 0.79. Interactions between CCBs and the anti-leishmanial drugs were classified as indifferent according to the overall mean ΣFIC and the isobologram graphic analysis.

  17. IgG from Amyotrophic Lateral Sclerosis Patients Increases Current Through P-Type Calcium Channels in Mammalian Cerebellar Purkinje Cells and in Isolated Channel Protein in Lipid Bilayer

    Science.gov (United States)

    Llinas, R.; Sugimori, M.; Cherksey, B. D.; Smith, R. Glenn; Delbono, O.; Stefani, E.; Appel, S.

    1993-12-01

    The effect of the IgG from amyotrophic lateral sclerosis (ALS) patients was tested on the voltage-dependent barium currents (IBa) in mammalian dissociated Purkinje cells and in isolated P-type calcium channels in lipid bilayers. Whole cell clamp of Purkinje cells demonstrates that ALS IgG increases the amplitude of IBa without modifying their voltage kinetics. This increased IBa could be blocked by a purified nonpeptide toxin from Agelenopsis aperta venom (purified funnel-web spider toxin) or by a synthetic polyamine analog (synthetic funnel-web spider toxin) and by a peptide toxin from the same spider venom, ω-Aga-IVA. Similar results were obtained on single-channel recordings from purified P channel protein. The addition of ALS IgG increased single-channel IBa open time without affecting slope conductance. The results described above were not seen with normal human IgG nor with boiled ALS IgG. It is concluded that ALS IgG enhances inward current through P-type calcium channels. Since P-type Ca2+ channels are present in motoneuron axon terminals, we propose that the enhanced calcium current triggered by ALS IgG may contribute to neuronal damage in ALS.

  18. Current concepts in combination therapy for the treatment of hypertension: combined calcium channel blockers and RAAS inhibitors

    Directory of Open Access Journals (Sweden)

    Alberto F Rubio-Guerra

    2009-11-01

    Full Text Available Alberto F Rubio-Guerra1, David Castro-Serna2, Cesar I Elizalde Barrera2, Luz M Ramos-Brizuela21Metabolic and Research Clinic, 2Internal Medicine Department, Hospital General de Ticomán SS DF, MéxicoAbstract: Recent guidelines for the management of hypertension recommend target blood pressures <140/90 mmHg in hypertensive patients, or <130/80 mmHg in subjects with diabetes, chronic kidney disease, or coronary artery disease. Despite the availability and efficacy of antihypertensive drugs, most hypertensive patients do not reach the recommended treatment targets with monotherapy, making combination therapy necessary to achieve the therapeutic goal. Combination therapy with 2 or more agents is the most effective method for achieving strict blood pressure goals. Fixed-dose combination simplifies treatment, reduces costs, and improves adherence. There are many drug choices for combination therapy, but few data are available about the efficacy and safety of some specific combinations. Combination therapy of calcium antagonists and inhibitors of the renin-angiotensin-aldosterone system (RAAS are efficacious and safe, and have been considered rational by both the JNC 7 and the 2007 European Society of Hypertension – European Society of Cardiology guidelines for the management of arterial hypertension. The aim of this review is to discuss some relevant issues about the use of combinations with calcium channel blockers and RAAS inhibitors in the treatment of hypertension.Keywords: hypertension, calcium channel blockers, renin-angiotensin-aldosterone system inhibitors, fixed-dose combination, adherence

  19. Modulation of L-type calcium channels by sodium ions.

    OpenAIRE

    Balke, C W; Wier, W G

    1992-01-01

    It is universally believed that the removal of external sodium ions is without effect on calcium current. We now report that in enzymatically isolated guinea pig ventricular cells, the replacement of external sodium ions with certain other cations causes a 3- to 6-fold increase in peak L-type calcium current. The increase in current is reversibly blocked by L-type calcium-channel antagonists, not mediated by changes in internal calcium, and is inhibited by intracellular 5'-adenylyl imidodipho...

  20. Selective Small Molecule Activators of TREK-2 Channels Stimulate Dorsal Root Ganglion c-Fiber Nociceptor Two-Pore-Domain Potassium Channel Currents and Limit Calcium Influx.

    Science.gov (United States)

    Dadi, Prasanna K; Vierra, Nicholas C; Days, Emily; Dickerson, Matthew T; Vinson, Paige N; Weaver, C David; Jacobson, David A

    2017-03-15

    The two-pore-domain potassium (K2P) channel TREK-2 serves to modulate plasma membrane potential in dorsal root ganglia c-fiber nociceptors, which tunes electrical excitability and nociception. Thus, TREK-2 channels are considered a potential therapeutic target for treating pain; however, there are currently no selective pharmacological tools for TREK-2 channels. Here we report the identification of the first TREK-2 selective activators using a high-throughput fluorescence-based thallium (Tl+) flux screen (HTS). An initial pilot screen with a bioactive lipid library identified 11-deoxy prostaglandin F2α as a potent activator of TREK-2 channels (EC50 ≈ 0.294 μM), which was utilized to optimize the TREK-2 Tl+ flux assay (Z' = 0.752). A HTS was then performed with 76 575 structurally diverse small molecules. Many small molecules that selectively activate TREK-2 were discovered. As these molecules were able to activate single TREK-2 channels in excised membrane patches, they are likely direct TREK-2 activators. Furthermore, TREK-2 activators reduced primary dorsal root ganglion (DRG) c-fiber Ca2+ influx. Interestingly, some of the selective TREK-2 activators such as 11-deoxy prostaglandin F2α were found to inhibit the K2P channel TREK-1. Utilizing chimeric channels containing portions of TREK-1 and TREK-2, the region of the TREK channels that allows for either small molecule activation or inhibition was identified. This region lies within the second pore domain containing extracellular loop and is predicted to play an important role in modulating TREK channel activity. Moreover, the selective TREK-2 activators identified in this HTS provide important tools for assessing human TREK-2 channel function and investigating their therapeutic potential for treating chronic pain.

  1. Inactivation of gating currents of L-type calcium channels. Specific role of the alpha 2 delta subunit.

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    Shirokov, R; Ferreira, G; Yi, J; Ríos, E

    1998-06-01

    In studies of gating currents of rabbit cardiac Ca channels expressed as alpha 1C/beta 2a or alpha 1C/beta 2a/alpha 2 delta subunit combinations in tsA201 cells, we found that long-lasting depolarization shifted the distribution of mobile charge to very negative potentials. The phenomenon has been termed charge interconversion in native skeletal muscle (Brum, G., and E. Ríos. 1987. J. Physiol. (Camb.). 387:489-517) and cardiac Ca channels (Shirokov, R., R. Levis, N. Shirokova, and E. Ríos. 1992. J. Gen. Physiol. 99:863-895). Charge 1 (voltage of half-maximal transfer, V1/2 approximately 0 mV) gates noninactivated channels, while charge 2 (V1/2 approximately -90 mV) is generated in inactivated channels. In alpha 1C/beta 2a cells, the available charge 1 decreased upon inactivating depolarization with a time constant tau approximately 8, while the available charge 2 decreased upon recovery from inactivation (at -200 mV) with tau approximately 0.3 s. These processes therefore are much slower than charge movement, which takes charge movement and that of changes in their availability, which was even wider in the presence of alpha 2 delta, implies that charges 1 and 2 originate from separate channel modes. Because clear modal separation characterizes slow (C-type) inactivation of Na and K channels, this observation establishes the nature of voltage-dependent inactivation of L-type Ca channels as slow or C-type. The presence of the alpha 2 delta subunit did not change the V1/2 of charge 2, but sped up the reduction of charge 1 upon inactivation at 40 mV (to tau approximately 2 s), while slowing the reduction of charge 2 upon recovery (tau approximately 2 s). The observations were well simulated with a model that describes activation as continuous electrodiffusion (Levitt, D. 1989. Biophys. J. 55:489-498) and inactivation as discrete modal change. The effects of alpha 2 delta are reproduced assuming that the subunit lowers the free energy of the inactivated mode.

  2. Activation of endogenous c-Src or a related tyrosine kinase by intracellular (pY)EEI peptide increases voltage-operated calcium channel currents in rabbit ear artery cells.

    Science.gov (United States)

    Wijetunge, S; Hughes, A D

    1996-12-09

    The effect of activation of endogenous c-Src tyrosine kinase by (pY)EEI peptide was examined on voltage-operated calcium channel (VOC) currents in arterial smooth muscle cells. In single rabbit ear artery cells intracellular application of (pY)EEI peptide increased calcium channel currents. Inactive, non-phosphorylated YEEI peptide had no effect on currents. Peptide-A, a 21 amino acid inhibitor of c-Src inhibited currents and prevented the effect of (pY)EEI peptide on calcium channel currents. These results indicate that activation of intrinsic c-Src increases VOC and support a role for c-Src in the regulation of VOC in vascular smooth muscle cells.

  3. Inhibition of late sodium current suppresses calcium-related ventricular arrhythmias by reducing the phosphorylation of CaMK-II and sodium channel expressions

    OpenAIRE

    Xiao-Hong Wei; Shan-Dong Yu; Lu Ren; Si-Hui Huang; Qiao-Mei Yang; Ping Wang; Yan-Peng Chu; Wei Yang; Yan-Sheng Ding; Yong Huo; Lin Wu

    2017-01-01

    Cardiac arrhythmias associated with intracellular calcium inhomeostasis are refractory to antiarrhythmic therapy. We hypothesized that late sodium current (I Na) contributed to the calcium-related arrhythmias. Monophasic action potential duration at 90% completion of repolarization (MAPD90) was significantly increased and ventricular arrhythmias were observed in hearts with increased intracellular calcium concentration ([Ca2+]i) by using Bay K 8644, and the increase became greater in hearts t...

  4. Voltage-Gated Calcium Channels in Nociception

    Science.gov (United States)

    Yasuda, Takahiro; Adams, David J.

    Voltage-gated calcium channels (VGCCs) are a large and functionally diverse group of membrane ion channels ubiquitously expressed throughout the central and peripheral nervous systems. VGCCs contribute to various physiological processes and transduce electrical activity into other cellular functions. This chapter provides an overview of biophysical properties of VGCCs, including regulation by auxiliary subunits, and their physiological role in neuronal functions. Subsequently, then we focus on N-type calcium (Cav2.2) channels, in particular their diversity and specific antagonists. We also discuss the role of N-type calcium channels in nociception and pain transmission through primary sensory dorsal root ganglion neurons (nociceptors). It has been shown that these channels are expressed predominantly in nerve terminals of the nociceptors and that they control neurotransmitter release. To date, important roles of N-type calcium channels in pain sensation have been elucidated genetically and pharmacologically, indicating that specific N-type calcium channel antagonists or modulators are particularly useful as therapeutic drugs targeting chronic and neuropathic pain.

  5. ß-Adrenoceptor Activation Enhances L-Type Calcium Channel Currents in Anterior Piriform Cortex Pyramidal Cells of Neonatal Mice: Implication for Odor Learning

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    Ghosh, Abhinaba; Mukherjee, Bandhan; Chen, Xihua; Yuan, Qi

    2017-01-01

    Early odor preference learning occurs in one-week-old rodents when a novel odor is paired with a tactile stimulation mimicking maternal care. ß-Adrenoceptors and L-type calcium channels (LTCCs) in the anterior piriform cortex (aPC) are critically involved in this learning. However, whether ß-adrenoceptors interact directly with LTCCs in aPC…

  6. Role of tumour necrosis factor-a in the regulation of T-type calcium channel current in HL-1 cells.

    Science.gov (United States)

    Rao, Fang; Xue, Yu-Mei; Wei, Wei; Yang, Hui; Liu, Fang-Zhou; Chen, Shao-Xian; Kuang, Su-Juan; Zhu, Jie-Ning; Wu, Shu-Lin; Deng, Chun-Yu

    2016-07-01

    Increasing evidence indicates that inflammation contributes to the initiation and perpetuation of atrial fibrillation (AF). Although tumour necrosis factor (TNF)-α levels are increased in patients with AF, the role of TNF-α in the pathogenesis of AF remains unclear. Besides L-type Ca(2+) currents (IC a,L ), T-type Ca(2+) currents (IC a,T ) also plays an important role in the pathogenesis of AF. This study was designed to use the whole-cell voltage-clamp technique and biochemical assays to explore if TNF-α is involved in the pathogenesis of AF through regulating IC a,T in atrial myocytes. It was found that compared with sinus rhythm (SR) controls, T-type calcium channel (TCC) subunit mRNA levels were decreased, while TNF-α expression levels were increased, in human atrial tissue from patients with AF. In murine atrial myocyte HL-1 cells, after culturing for 24 h, 12.5, 25 and 50 ng/mL TNF-α significantly reduced the protein expression levels of the TCC α1G subunit in a concentration-dependent manner. The peak current was reduced by the application of 12.5 or 25 ng/mL TNF-α in a concentration-dependent manner (from -15.08 ± 1.11 pA/pF in controls to -11.89 ± 0.83 pA/pF and -8.54 ± 1.55 pA/pF in 12.5 or 25 ng/mL TNF-α group respectively). TNF-α application also inhibited voltage-dependent inactivation of IC a,T, shifted the inactivation curve to the left. These results suggest that TNF-α is involved in the pathogenesis of AF, probably via decreasing IC a,T current density in atrium-derived myocytes through impaired channel function and down-regulation of channel protein expression. This pathway thus represents a potential pathogenic mechanism in AF. © 2016 John Wiley & Sons Australia, Ltd.

  7. Computational study of a calcium release-activated calcium channel

    Science.gov (United States)

    Talukdar, Keka; Shantappa, Anil

    2016-05-01

    The naturally occurring proteins that form hole in membrane are commonly known as ion channels. They play multiple roles in many important biological processes. Deletion or alteration of these channels often leads to serious problems in the physiological processes as it controls the flow of ions through it. The proper maintenance of the flow of ions, in turn, is required for normal health. Here we have investigated the behavior of a calcium release-activated calcium ion channel with pdb entry 4HKR in Drosophila Melanogaster. The equilibrium energy as well as molecular dynamics simulation is performed first. The protein is subjected to molecular dynamics simulation to find their energy minimized value. Simulation of the protein in the environment of water and ions has given us important results too. The solvation energy is also found using Charmm potential.

  8. STIM and calcium channel complexes in cancer.

    Science.gov (United States)

    Jardin, Isaac; Rosado, Juan A

    2016-06-01

    The ion Ca(2+) is a ubiquitous second messenger that mediates a variety of cellular functions. Dysfunction of the mechanisms involved in Ca(2+) homeostasis underlies a number of pathological processes, including cancer. Store-operated Ca(2+) entry (SOCE) is a major mechanism for Ca(2+) entry modulated by the intracellular Ca(2+) stores. The Ca(2+)-selective store-operated current (ICRAC) is mediated by the endoplasmic reticulum (ER) Ca(2+) sensor STIM1 and the store-operated Ca(2+) (SOC) channel Orai1, while other non-selective cation currents (ISOC) involves the participation of members of the canonical transient receptor potential (TRPC) channel family, including TRPC1. Distinct isoforms of the key components of SOCE have been described in mammalian cells, STIM1 and 2, Orai1-3 and TRPC1-7. In cancer cells, SOCE has been reported to play an important role in cell cycle progression and proliferation, migration, metastasis and evasion of apoptosis. Changes in the expression of the key elements of SOCE and Ca(2+) homeostasis remodeling have been account to play important roles in the phenotypic changes observed in transformed cells. Despite there are differences in the expression level of the molecular components of SOCE, as well as in the relevance of the STIM, Orai and TRPC isoforms in SOCE and tumorigenesis among cancer cell types, there is a body of evidence supporting an important role for SOCE underlying the phenotypic modifications of cancer cells that propose STIM and the SOC channels as suitable candidate targets for future prognostic or therapeutic strategies. This article is part of a Special Issue entitled: Calcium and Cell Fate. Guest Editors: Jacques Haiech, Claus Heizmann, Joachim Krebs, Thierry Capiod and Olivier Mignen. Copyright © 2015 Elsevier B.V. All rights reserved.

  9. Diltiazem and verapamil preferentially block inactivated cardiac calcium channels.

    Science.gov (United States)

    Kanaya, S; Arlock, P; Katzung, B G; Hondeghem, L M

    1983-02-01

    Diltiazem has been proposed to act by blocking calcium channels of cardiac and smooth muscle since it has pharmacological [12-14] and clinical [10] effects that resemble those of verapamil, an agent that has been shown to block these channels [3]. However, block of the slow inward current by diltiazem has not been directly demonstrated. In fact, it has been suggested that diltiazem has an entirely different mechanism of action [7]. We therefore studied the blocking effects of diltiazem and verapamil on cardiac calcium channels by measuring the slow inward current in voltage-clamped ferret myocardium. Both drugs blocked the slow inward current in a use-dependent fashion, i.e. the block was enhanced by increased frequency of activating clamps and by more positive holding potentials. However, we found that short single activating clamps resulted in minimal block, whereas prolonging the clamp step progressively enhanced the blockade. Thus, a single long clamp caused as much blockade as a train of shorter pulses. These results demonstrate that diltiazem and verapamil block the slow inward current by binding to calcium channels in a state-dependent fashion, i.e. inactivated channels have a high affinity for the drugs, while rested and open channels have a lower affinity.

  10. T-type calcium channels in synaptic plasticity.

    Science.gov (United States)

    Leresche, Nathalie; Lambert, Régis C

    2017-03-04

    The role of T-type calcium currents is rarely considered in the extensive literature covering the mechanisms of long-term synaptic plasticity. This situation reflects the lack of suitable T-type channel antagonists that till recently has hampered investigations of the functional roles of these channels. However, with the development of new pharmacological and genetic tools, a clear involvement of T-type channels in synaptic plasticity is starting to emerge. Here, we review a number of studies showing that T-type channels participate to numerous homo- and hetero-synaptic plasticity mechanisms that involve different molecular partners and both pre- and post-synaptic modifications. The existence of T-channel dependent and independent plasticity at the same synapse strongly suggests a subcellular localization of these channels and their partners that allows specific interactions. Moreover, we illustrate the functional importance of T-channel dependent synaptic plasticity in neocortex and thalamus.

  11. Discovery and Development of Calcium Channel Blockers

    Directory of Open Access Journals (Sweden)

    Théophile Godfraind

    2017-05-01

    Full Text Available In the mid 1960s, experimental work on molecules under screening as coronary dilators allowed the discovery of the mechanism of calcium entry blockade by drugs later named calcium channel blockers. This paper summarizes scientific research on these small molecules interacting directly with L-type voltage-operated calcium channels. It also reports on experimental approaches translated into understanding of their therapeutic actions. The importance of calcium in muscle contraction was discovered by Sidney Ringer who reported this fact in 1883. Interest in the intracellular role of calcium arose 60 years later out of Kamada (Japan and Heibrunn (USA experiments in the early 1940s. Studies on pharmacology of calcium function were initiated in the mid 1960s and their therapeutic applications globally occurred in the the 1980s. The first part of this report deals with basic pharmacology in the cardiovascular system particularly in isolated arteries. In the section entitled from calcium antagonists to calcium channel blockers, it is recalled that drugs of a series of diphenylpiperazines screened in vivo on coronary bed precontracted by angiotensin were initially named calcium antagonists on the basis of their effect in depolarized arteries contracted by calcium. Studies on arteries contracted by catecholamines showed that the vasorelaxation resulted from blockade of calcium entry. Radiochemical and electrophysiological studies performed with dihydropyridines allowed their cellular targets to be identified with L-type voltage-operated calcium channels. The modulated receptor theory helped the understanding of their variation in affinity dependent on arterial cell membrane potential and promoted the terminology calcium channel blocker (CCB of which the various chemical families are introduced in the paper. In the section entitled tissue selectivity of CCBs, it is shown that characteristics of the drug, properties of the tissue, and of the stimuli are

  12. Inhibition of late sodium current suppresses calcium-related ventricular arrhythmias by reducing the phosphorylation of CaMK-II and sodium channel expressions.

    Science.gov (United States)

    Wei, Xiao-Hong; Yu, Shan-Dong; Ren, Lu; Huang, Si-Hui; Yang, Qiao-Mei; Wang, Ping; Chu, Yan-Peng; Yang, Wei; Ding, Yan-Sheng; Huo, Yong; Wu, Lin

    2017-04-20

    Cardiac arrhythmias associated with intracellular calcium inhomeostasis are refractory to antiarrhythmic therapy. We hypothesized that late sodium current (I Na) contributed to the calcium-related arrhythmias. Monophasic action potential duration at 90% completion of repolarization (MAPD90) was significantly increased and ventricular arrhythmias were observed in hearts with increased intracellular calcium concentration ([Ca(2+)]i) by using Bay K 8644, and the increase became greater in hearts treated with a combination of ATX-II and Bay K 8644 compared to Bay K 8644 alone. The prolongations caused by Bay K 8644 and frequent episodes of ventricular tachycardias, both in absence and presence of ATX-II, were significantly attenuated or abolished by late I Na inhibitors TTX and eleclazine. In rabbit ventricular myocytes, Bay K 8644 increased I CaL density, calcium transient and myocyte contraction. TTX and eleclazine decreased the amplitude of late I Na, the reverse use dependence of MAPD90 at slower heart rate, and attenuated the increase of intracellular calcium transient and myocyte contraction. TTX diminished the phosphorylation of CaMKII-δ and Nav 1.5 in hearts treated with Bay K 8644 and ATX-II. In conclusion, late I Na contributes to ventricular arrhythmias and its inhibition is plausible to treat arrhythmias in hearts with increased [Ca(2+)]i.

  13. Regulation of voltage-gated calcium channels by proteolysis

    Science.gov (United States)

    Kathryn, ABELE; Jian, YANG

    2015-01-01

    Voltage gated calcium channels (VGCCs) are multi-subunit membrane proteins present in a variety of tissues and control many essential physiological processes. Due to their vital importance, VGCCs are regulated by a myriad of proteins and signaling pathways. Here we review the literature on the regulation of VGCCs by proteolysis of the pore-forming α1 subunit, Cavα1. This form of regulation modulates channel function and degradation and affects cellular gene expression and excitability. L-type Ca2+ channels are proteolyzed in two ways, depending on tissue localization. In the heart and skeletal muscle, the distal C-terminus of Cavα1 is cleaved and acts as an autoinhibitor when it reassociates with the proximal C-terminus. Relief of this autoinhibition underlies the β-adrenergic stimulation-induced enhancement of cardiac and skeletal muscle calcium currents, part of the “fight or flight” response. Proteolysis of the distal C-terminus of L-type channels also occurs in the brain and is probably catalyzed by a calpain-like protease. In some brain regions, the entire C-terminus of L-type Ca2+ channels can be cleaved by an unknown protease and translocates to the nucleus acting as a transcription factor. The distal C-terminus of P/Q-channel Cavα1 is also proteolyzed and translocates to the nucleus. Truncated forms of the PQ-channel Cavα1 are produced by many disease-causing mutations and interfere with the function of full-length channels. Truncated forms of N-type channel Cavα1, generated by mutagenesis, affect the expression of full-length channels. New forms of proteolysis of VGCC subunits remain to be discovered and may represent a fruitful area of VGCC research. PMID:23090491

  14. Reconstruction of Cell Surface Densities of Ion Pumps, Exchangers, and Channels from mRNA Expression, Conductance Kinetics, Whole-Cell Calcium, and Current-Clamp Voltage Recordings, with an Application to Human Uterine Smooth Muscle Cells.

    Directory of Open Access Journals (Sweden)

    Jolene Atia

    2016-04-01

    Full Text Available Uterine smooth muscle cells remain quiescent throughout most of gestation, only generating spontaneous action potentials immediately prior to, and during, labor. This study presents a method that combines transcriptomics with biophysical recordings to characterise the conductance repertoire of these cells, the 'conductance repertoire' being the total complement of ion channels and transporters expressed by an electrically active cell. Transcriptomic analysis provides a set of potential electrogenic entities, of which the conductance repertoire is a subset. Each entity within the conductance repertoire was modeled independently and its gating parameter values were fixed using the available biophysical data. The only remaining free parameters were the surface densities for each entity. We characterise the space of combinations of surface densities (density vectors consistent with experimentally observed membrane potential and calcium waveforms. This yields insights on the functional redundancy of the system as well as its behavioral versatility. Our approach couples high-throughput transcriptomic data with physiological behaviors in health and disease, and provides a formal method to link genotype to phenotype in excitable systems. We accurately predict current densities and chart functional redundancy. For example, we find that to evoke the observed voltage waveform, the BK channel is functionally redundant whereas hERG is essential. Furthermore, our analysis suggests that activation of calcium-activated chloride conductances by intracellular calcium release is the key factor underlying spontaneous depolarisations.

  15. T-Type Calcium Channels Are Required to Maintain Viability of Neural Progenitor Cells.

    Science.gov (United States)

    Kim, Ji-Woon; Oh, Hyun Ah; Lee, Sung Hoon; Kim, Ki Chan; Eun, Pyung Hwa; Ko, Mee Jung; Gonzales, Edson Luck T; Seung, Hana; Kim, Seonmin; Bahn, Geon Ho; Shin, Chan Young

    2018-02-21

    T-type calcium channels are low voltage-activated calcium channels that evoke small and transient calcium currents. Recently, T-type calcium channels have been implicated in neurodevelopmental disorders such as autism spectrum disorder and neural tube defects. However, their function during embryonic development is largely unknown. Here, we investigated the function and expression of T-type calcium channels in embryonic neural progenitor cells (NPCs). First, we compared the expression of T-type calcium channel subtypes (CaV3.1, 3.2, and 3.3) in NPCs and differentiated neural cells (neurons and astrocytes). We detected all subtypes in neurons but not in astrocytes. In NPCs, CaV3.1 was the dominant subtype, whereas CaV3.2 was weakly expressed, and CaV3.3 was not detected. Next, we determined CaV3.1 expression levels in the cortex during early brain development. Expression levels of CaV3.1 in the embryonic period were transiently decreased during the perinatal period and increased at postnatal day 11. We then pharmacologically blocked T-type calcium channels to determine the effects in neuronal cells. The blockade of T-type calcium channels reduced cell viability, and induced apoptotic cell death in NPCs but not in differentiated astrocytes. Furthermore, blocking T-type calcium channels rapidly reduced AKT-phosphorylation (Ser473) and GSK3β-phosphorylation (Ser9). Our results suggest that T-type calcium channels play essential roles in maintaining NPC viability, and T-type calcium channel blockers are toxic to embryonic neural cells, and may potentially be responsible for neurodevelopmental disorders.

  16. Lack of direct evidence for a functional role of voltage-operated calcium channels in juxtaglomerular cells

    DEFF Research Database (Denmark)

    Kurtz, A; Skott, O; Chegini, S

    1990-01-01

    In this study we have examined the role of voltage-gated calcium channels in the regulation of calcium in juxtaglomerular cells. Using a combination of patch-clamp and single-cell calcium measurement we obtained evidence neither for voltage-operated calcium currents nor for changes of the intrace...

  17. Signal processing by T-type calcium channel interactions in the cerebellum.

    Science.gov (United States)

    Engbers, Jordan D T; Anderson, Dustin; Zamponi, Gerald W; Turner, Ray W

    2013-11-27

    T-type calcium channels of the Cav3 family are unique among voltage-gated calcium channels due to their low activation voltage, rapid inactivation, and small single channel conductance. These special properties allow Cav3 calcium channels to regulate neuronal processing in the subthreshold voltage range. Here, we review two different subthreshold ion channel interactions involving Cav3 channels and explore the ability of these interactions to expand the functional roles of Cav3 channels. In cerebellar Purkinje cells, Cav3 and intermediate conductance calcium-activated potassium (IKCa) channels form a novel complex which creates a low voltage-activated, transient outward current capable of suppressing temporal summation of excitatory postsynaptic potentials (EPSPs). In large diameter neurons of the deep cerebellar nuclei, Cav3-mediated calcium current (I T) and hyperpolarization-activated cation current (I H) are activated during trains of inhibitory postsynaptic potentials. These currents have distinct, and yet synergistic, roles in the subthreshold domain with I T generating a rebound burst and I H controlling first spike latency and rebound spike precision. However, by shortening the membrane time constant the membrane returns towards resting value at a faster rate, allowing I H to increase the efficacy of I T and increase the range of burst frequencies that can be generated. The net effect of Cav3 channels thus depends on the channels with which they are paired. When expressed in a complex with a KCa channel, Cav3 channels reduce excitability when processing excitatory inputs. If functionally coupled with an HCN channel, the depolarizing effect of Cav3 channels is accentuated, allowing for efficient inversion of inhibitory inputs to generate a rebound burst output. Therefore, signal processing relies not only on the activity of individual subtypes of channels but also on complex interactions between ion channels whether based on a physical complex or by indirect

  18. Signal processing by T-type calcium channel interactions in the cerebellum

    Directory of Open Access Journals (Sweden)

    Jordan D.T. Engbers

    2013-11-01

    Full Text Available T-type calcium channels of the Cav3 family are unique among voltage-gated calcium channels due to their low activation voltage, rapid inactivation, and small single channel conductance. These special properties allow Cav3 calcium channels to regulate neuronal processing in the subthreshold voltage range. Here, we review two different subthreshold ion channel interactions involving Cav3 channels and explore the ability of these interactions to expand the functional roles of Cav3 channels. In cerebellar Purkinje cells, Cav3 and intermediate conductance calcium-activated potassium (IKCa channels form a novel complex which creates a low voltage-activated, transient outward current capable of suppressing temporal summation of excitatory postsynaptic potentials (EPSPs. In large diameter neurons of the deep cerebellar nuclei, Cav3-mediated calcium current (IT and hyperpolarization-activated cation current (IH are activated during trains of IPSPs. These currents have distinct, and yet synergistic, roles in the subthreshold domain with IT generating a rebound burst and IH controlling first spike latency and rebound spike precision. However, by shortening the membrane time constant the membrane returns towards resting value at a faster rate, allowing IH to increase the efficacy of IT, and increase the range of burst frequencies that can be generated. The net effect of Cav3 channels thus depends on the channels with which they are paired. When expressed in a complex with a KCa channel, Cav3 channels reduce excitability when processing excitatory inputs. If functionally coupled with an HCN channel, the depolarizing effect of Cav3 channels is accentuated, allowing for efficient inversion of inhibitory inputs to generate a rebound burst output. Therefore, signal processing relies not only on the activity of individual subtypes of channels but also on complex interactions between ion channels whether based on a physical complex or by indirect effects on

  19. The ?2? Subunit and Absence Epilepsy: Beyond Calcium Channels?

    National Research Council Canada - National Science Library

    Roberta Celli; Ines Santolini; Michela Guiducci; Gilles van Luijtelaar; Pasquale Parisi; Pasquale Striano; Roberto Gradini; Giuseppe Battaglia; Richard T. Ngomba; Ferdinando Nicoletti

    2017-01-01

    .... Activation of T-type voltage-sensitive calcium channels (VSCCs) contributes to the pathological oscillatory activity of this network, and some of the first-line drugs used in the treatment of absence epilepsy inhibit T-type calcium channels. The ?2...

  20. Analytical models of calcium binding in a calcium channel

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jinn-Liang [Department of Applied Mathematics, National Hsinchu University of Education, Hsinchu 300, Taiwan (China); Eisenberg, Bob [Department of Molecular Biophysics and Physiology, Rush University, Chicago, Illinois 60612 (United States)

    2014-08-21

    The anomalous mole fraction effect of L-type calcium channels is analyzed using a Fermi like distribution with the experimental data of Almers and McCleskey [J. Physiol. 353, 585 (1984)] and the atomic resolution model of Lipkind and Fozzard [Biochemistry 40, 6786 (2001)] of the selectivity filter of the channel. Much of the analysis is algebraic, independent of differential equations. The Fermi distribution is derived from the configuration entropy of ions and water molecules with different sizes, different valences, and interstitial voids between particles. It allows us to calculate potentials and distances (between the binding ion and the oxygen ions of the glutamate side chains) directly from the experimental data using algebraic formulas. The spatial resolution of these results is comparable with those of molecular models, but of course the accuracy is no better than that implied by the experimental data. The glutamate side chains in our model are flexible enough to accommodate different types of binding ions in different bath conditions. The binding curves of Na{sup +} and Ca{sup 2+} for [CaCl{sub 2}] ranging from 10{sup −8} to 10{sup −2} M with a fixed 32 mM background [NaCl] are shown to agree with published Monte Carlo simulations. The Poisson-Fermi differential equation—that includes both steric and correlation effects—is then used to obtain the spatial profiles of energy, concentration, and dielectric coefficient from the solvent region to the filter. The energy profiles of ions are shown to depend sensitively on the steric energy that is not taken into account in the classical rate theory. We improve the rate theory by introducing a steric energy that lumps the effects of excluded volumes of all ions and water molecules and empty spaces between particles created by Lennard-Jones type and electrostatic forces. We show that the energy landscape varies significantly with bath concentrations. The energy landscape is not constant.

  1. Physiology and Regulation of Calcium Channels in Stomatal Guard Cells

    Energy Technology Data Exchange (ETDEWEB)

    Schroeder, Julian I.

    2007-05-02

    Stomatal pores in the epidermis of leaves regulate the diffusion of CO2 into leaves for photosynthetic carbon fixation and control water loss of plants during drought periods. Guard cells sense CO2, water status, light and other environmental conditions to regulate stomatal apertures for optimization of CO2 intake and plant growth under drought stress. The cytosolic second messenger calcium contributes to stomatal movements by transducing signals and regulating ion channels in guard cells. Studies suggest that both plasma membrane Ca2+ influx channels and vacuolar/organellar Ca2+ release channels contribute to ABA-induced Ca2+ elevations in guard cells. Recent research in the P.I.'s laboratory has led to identification of a novel major cation-selective Ca2+-permeable influx channel (Ica) in the plasma membrane of Arabidopsis guard cells. These advances will allow detailed characterization of Ica plasma membrane Ca2+ influx channels in guard cells. The long term goal of this research project is to gain a first detailed characterization of these novel plasma membrane Ca2+-permeable channel currents in Arabidopsis guard cells. The proposed research will investigate the hypothesis that Ica represents an important Ca2+ influx pathway for ABA and CO2 signal transduction in Arabidopsis guard cells. These studies will lead to elucidation of key signal transduction mechanisms by which plants balance CO2 influx into leaves and transpirational water loss and may contribute to future strategies for manipulating gas exchange for improved growth of crop plants and for biomass production.

  2. Calcium-activated chloride channels in the apical region of mouse vomeronasal sensory neurons.

    Science.gov (United States)

    Dibattista, Michele; Amjad, Asma; Maurya, Devendra Kumar; Sagheddu, Claudia; Montani, Giorgia; Tirindelli, Roberto; Menini, Anna

    2012-07-01

    The rodent vomeronasal organ plays a crucial role in several social behaviors. Detection of pheromones or other emitted signaling molecules occurs in the dendritic microvilli of vomeronasal sensory neurons, where the binding of molecules to vomeronasal receptors leads to the influx of sodium and calcium ions mainly through the transient receptor potential canonical 2 (TRPC2) channel. To investigate the physiological role played by the increase in intracellular calcium concentration in the apical region of these neurons, we produced localized, rapid, and reproducible increases in calcium concentration with flash photolysis of caged calcium and measured calcium-activated currents with the whole cell voltage-clamp technique. On average, a large inward calcium-activated current of -261 pA was measured at -50 mV, rising with a time constant of 13 ms. Ion substitution experiments showed that this current is anion selective. Moreover, the chloride channel blockers niflumic acid and 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid partially inhibited the calcium-activated current. These results directly demonstrate that a large chloride current can be activated by calcium in the apical region of mouse vomeronasal sensory neurons. Furthermore, we showed by immunohistochemistry that the calcium-activated chloride channels TMEM16A/anoctamin1 and TMEM16B/anoctamin2 are present in the apical layer of the vomeronasal epithelium, where they largely colocalize with the TRPC2 transduction channel. Immunocytochemistry on isolated vomeronasal sensory neurons showed that TMEM16A and TMEM16B coexpress in the neuronal microvilli. Therefore, we conclude that microvilli of mouse vomeronasal sensory neurons have a high density of calcium-activated chloride channels that may play an important role in vomeronasal transduction.

  3. Calcium dependent current recordings in Xenopus laevis oocytes in microgravity

    Science.gov (United States)

    Wuest, Simon L.; Roesch, Christian; Ille, Fabian; Egli, Marcel

    2017-12-01

    Mechanical unloading by microgravity (or weightlessness) conditions triggers profound adaptation processes at the cellular and organ levels. Among other mechanisms, mechanosensitive ion channels are thought to play a key role in allowing cells to transduce mechanical forces. Previous experiments performed under microgravity have shown that gravity affects the gating properties of ion channels. Here, a method is described to record a calcium-dependent current in native Xenopus laevis oocytes under microgravity conditions during a parabolic flight. A 3-voltage-step protocol was applied to provoke a calcium-dependent current. This current increased with extracellular calcium concentration and could be reduced by applying extracellular gadolinium. The custom-made ;OoClamp; hardware was validated by comparing the results of the 3-voltage-step protocol to results obtained with a well-established two-electrode voltage clamp (TEVC). In the context of the 2nd Swiss Parabolic Flight Campaign, we tested the OoClamp and the method. The setup and experiment protocol worked well in parabolic flight. A tendency that the calcium-dependent current was smaller under microgravity than under 1 g condition could be observed. However, a conclusive statement was not possible due to the small size of the data base that could be gathered.

  4. Calcium channels in the brain as targets for the calcium-channel modulators used in the treatment of neurological disorders

    NARCIS (Netherlands)

    Peters, Thies; WILFFERT, B; VANHOUTTE, PM; VANZWIETEN, PA

    1991-01-01

    Recent investigations of calcium channels in brain cells by voltage-clamp techniques have revealed that, in spite of electrophysiological similarities, the pharmacological properties of these channels differ considerably from channels in peripheral tissues, e.g., heart and smooth muscle. Therefore,

  5. Roles of subthreshold calcium current and sodium current in spontaneous firing of mouse midbrain dopamine neurons.

    Science.gov (United States)

    Puopolo, Michelino; Raviola, Elio; Bean, Bruce P

    2007-01-17

    We used a preparation of acutely dissociated neurons to quantify the ionic currents driving the spontaneous firing of substantia nigra pars compacta neurons, isolated from transgenic mice in which the tyrosine hydroxylase promoter drives expression of human placental alkaline phosphatase (PLAP) on the outer surface of the cell membrane. Dissociated neurons identified by fluorescent antibodies to PLAP showed firing properties similar to those of dopaminergic neurons in brain slice, including rhythmic spontaneous firing of broad action potentials and, in some cells, rhythmic oscillatory activity in the presence of tetrodotoxin (TTX). Spontaneous activity in TTX had broader, smaller spikes than normal pacemaking and was stopped by removal of external calcium. Normal pacemaking was also consistently silenced by replacement of external calcium by cobalt and was slowed by more specific calcium channel blockers. Nimodipine produced a slowing of pacemaking frequency. Pacemaking was also slowed by the P/Q-channel blocker omega-Aga-IVA, but the N-type channel blocker omega-conotoxin GVIA had no effect. In voltage-clamp experiments, using records of pacemaking as command voltage, cobalt-sensitive current and TTX-sensitive current were both sizeable at subthreshold voltages between spikes. Cobalt-sensitive current was consistently larger than TTX-sensitive current at interspike voltages from -70 to -50 mV, with TTX-sensitive current larger at voltages positive to -45 mV. These results support previous evidence for a major role of voltage-dependent calcium channels in driving pacemaking of midbrain dopamine neurons and suggest that multiple calcium channel types contribute to this function. The results also show a significant contribution of subthreshold TTX-sensitive sodium current.

  6. Low threshold T-type calcium channels as targets for novel epilepsy treatments.

    Science.gov (United States)

    Powell, Kim L; Cain, Stuart M; Snutch, Terrance P; O'Brien, Terence J

    2014-05-01

    Low voltage-activated T-type calcium channels were originally cloned in the 1990s and much research has since focused on identifying the physiological roles of these channels in health and disease states. T-type calcium channels are expressed widely throughout the brain and peripheral tissues, and thus have been proposed as therapeutic targets for a variety of diseases such as epilepsy, insomnia, pain, cancer and hypertension. This review discusses the literature concerning the role of T-type calcium channels in physiological and pathological processes related to epilepsy. T-type calcium channels have been implicated in pathology of both the genetic and acquired epilepsies and several anti-epileptic drugs (AEDs) in clinical use are known to suppress seizures via inhibition of T-type calcium channels. Despite the fact that more than 15 new AEDs have become clinically available over the past 20 years at least 30% of epilepsy patients still fail to achieve seizure control, and many patients experience unwanted side effects. Furthermore there are no treatments that prevent the development of epilepsy or mitigate the epileptic state once established. Therefore there is an urgent need for the development of new AEDs that are effective in patients with drug resistant epilepsy, are anti-epileptogenic and are better tolerated. We also review the mechanisms of action of the current AEDs with known effects on T-type calcium channels and discuss novel compounds that are being investigated as new treatments for epilepsy. © 2013 The British Pharmacological Society.

  7. The Physiology, Pathology, and Pharmacology of Voltage-Gated Calcium Channels and Their Future Therapeutic Potential

    Science.gov (United States)

    Zamponi, Gerald W.; Striessnig, Joerg; Koschak, Alexandra

    2015-01-01

    Voltage-gated calcium channels are required for many key functions in the body. In this review, the different subtypes of voltage-gated calcium channels are described and their physiologic roles and pharmacology are outlined. We describe the current uses of drugs interacting with the different calcium channel subtypes and subunits, as well as specific areas in which there is strong potential for future drug development. Current therapeutic agents include drugs targeting L-type CaV1.2 calcium channels, particularly 1,4-dihydropyridines, which are widely used in the treatment of hypertension. T-type (CaV3) channels are a target of ethosuximide, widely used in absence epilepsy. The auxiliary subunit α2δ-1 is the therapeutic target of the gabapentinoid drugs, which are of value in certain epilepsies and chronic neuropathic pain. The limited use of intrathecal ziconotide, a peptide blocker of N-type (CaV2.2) calcium channels, as a treatment of intractable pain, gives an indication that these channels represent excellent drug targets for various pain conditions. We describe how selectivity for different subtypes of calcium channels (e.g., CaV1.2 and CaV1.3 L-type channels) may be achieved in the future by exploiting differences between channel isoforms in terms of sequence and biophysical properties, variation in splicing in different target tissues, and differences in the properties of the target tissues themselves in terms of membrane potential or firing frequency. Thus, use-dependent blockers of the different isoforms could selectively block calcium channels in particular pathologies, such as nociceptive neurons in pain states or in epileptic brain circuits. Of important future potential are selective CaV1.3 blockers for neuropsychiatric diseases, neuroprotection in Parkinson’s disease, and resistant hypertension. In addition, selective or nonselective T-type channel blockers are considered potential therapeutic targets in epilepsy, pain, obesity, sleep, and

  8. Interactions of divalent cations with single calcium channels from rat brain synaptosomes.

    Science.gov (United States)

    Nelson, M T

    1986-02-01

    Voltage-dependent calcium channels from a rat brain membrane preparation ("synaptosomes") were incorporated into planar lipid bilayers. The effects of calcium, barium, strontium, manganese, and cadmium ions on the amplitudes and kinetics of single channel currents were examined. The order of single channel conductances was gBa greater than gSr greater than gMn, which was the inverse of the order of the mean channel open times: TMn greater than TCa = TSr greater than TBa. In contrast, the identity of the charge carrier had little or no effect on the mean closed times of the channel. Manganese, in the absence of other permeant ions, can pass through single channels (gMn = 4 pS). However, when added to a solution that contained another type of permeant divalent cation, manganese reduced the single channel current in a voltage-dependent manner. Cadmium, a potent blocker of macroscopic "ensemble" calcium currents in many preparations, reduced the current through an open channel in a manner consistent with Cd ions both not being measurably permeant and interacting with a single site. The permeant ions competed with cadmium for this site with the following order: Mn greater than Sr = Ca greater than Ba. These results are consistent with the existence of no less than one divalent cation binding site in the channel that regulates ion permeation.

  9. Acute exposure to low-level CW and GSM-modulated 900 MHz radiofrequency does not affect Ba 2+ currents through voltage-gated calcium channels in rat cortical neurons.

    Science.gov (United States)

    Platano, Daniela; Mesirca, Pietro; Paffi, Alessandra; Pellegrino, Monica; Liberti, Micaela; Apollonio, Francesca; Bersani, Ferdinando; Aicardi, Giorgio

    2007-12-01

    We have studied the non-thermal effects of radiofrequency (RF) electromagnetic fields (EMFs) on Ba(2+) currents (I Ba 2+) through voltage-gated calcium channels (VGCC), recorded in primary cultures of rat cortical neurons using the patch-clamp technique. To assess whether low-level acute RF field exposure could modify the amplitude and/or the voltage-dependence of I Ba 2+, Petri dishes containing cultured neurons were exposed for 1-3 periods of 90 s to 900 MHz RF-EMF continuous wave (CW) or amplitude-modulated according to global system mobile communication standard (GSM) during whole-cell recording. The specific absorption rates (SARs) were 2 W/kg for CW and 2 W/kg (time average value) for GSM-modulated signals, respectively. The results obtained indicate that single or multiple acute exposures to either CW or GSM-modulated 900 MHz RF-EMFs do not significantly alter the current amplitude or the current-voltage relationship of I Ba 2+, through VGCC. (c) 2007 Wiley-Liss, Inc.

  10. T-type calcium channel: a privileged gate for calcium entry and control of adrenal steroidogenesis

    Directory of Open Access Journals (Sweden)

    Michel Florian Rossier

    2016-05-01

    Full Text Available Intracellular calcium plays a crucial role in modulating a variety of functions such as muscle contraction, hormone secretion, gene expression or cell growth. Calcium signaling has been however shown to be more complex than initially thought. Indeed, it is confined within cell microdomains and different calcium channels are associated with different functions, as shown by various channelopathies.Sporadic mutations on voltage-operated L-type calcium channels in adrenal glomerulosa cells have been shown recently to be the second most prevalent genetic abnormalities present in human aldosterone-producing adenoma. The observed modification of the threshold of activation of the mutated channels not only provides an explanation for this gain of function but reminds us on the importance of maintaining adequate electrophysiological characteristics to make channels able to exert specific cellular functions. Indeed, the contribution to steroid production of the various calcium channels expressed in adrenocortical cells is not equal and the reason has been investigated for a long time. Given the very negative resting potential of these cells, and the small membrane depolarization induced by their physiological agonists, low threshold T-type calcium channels are particularly well suited for responding under these conditions and conveying calcium into the cell, at the right place for controlling steroidogenesis. In contrast, high threshold L-type channels are normally activated by much stronger cell depolarizations. The fact that dihydropyridine calcium antagonists, specific for L-type channels, are poorly efficient for reducing aldosterone secretion either in vivo or in vitro, strongly supports the view that these two types of channels differently affect steroid biosynthesis.Whether a similar analysis is transposable to fasciculata cells and cortisol secretion is one of the questions addressed in the present review. No similar mutations on L-type or T

  11. Spontaneous and CRH-Induced Excitability and Calcium Signaling in Mice Corticotrophs Involves Sodium, Calcium, and Cation-Conducting Channels.

    Science.gov (United States)

    Zemkova, Hana; Tomić, Melanija; Kucka, Marek; Aguilera, Greti; Stojilkovic, Stanko S

    2016-04-01

    Transgenic mice expressing the tdimer2(12) form of Discosoma red fluorescent protein under control of the proopiomelanocortin gene's regulatory elements are a useful model for studying corticotrophs. Using these mice, we studied the ion channels and mechanisms controlling corticotroph excitability. Corticotrophs were either quiescent or electrically active, with a 22-mV difference in the resting membrane potential (RMP) between the 2 groups. In quiescent cells, CRH depolarized the membrane, leading to initial single spiking and sustained bursting; in active cells, CRH further facilitated or inhibited electrical activity and calcium spiking, depending on the initial activity pattern and CRH concentration. The stimulatory but not inhibitory action of CRH on electrical activity was mimicked by cAMP independently of the presence or absence of arachidonic acid. Removal of bath sodium silenced spiking and hyperpolarized the majority of cells; in contrast, the removal of bath calcium did not affect RMP but reduced CRH-induced depolarization, which abolished bursting electrical activity and decreased the spiking frequency but not the amplitude of single spikes. Corticotrophs with inhibited voltage-gated sodium channels fired calcium-dependent action potentials, whereas cells with inhibited L-type calcium channels fired sodium-dependent spikes; blockade of both channels abolished spiking without affecting the RMP. These results indicate that the background voltage-insensitive sodium conductance influences RMP, the CRH-depolarization current is driven by a cationic conductance, and the interplay between voltage-gated sodium and calcium channels plays a critical role in determining the status and pattern of electrical activity and calcium signaling.

  12. The medieval physician Avicenna used an herbal calcium channel blocker, Taxus baccata L.

    Science.gov (United States)

    Tekol, Yalcin

    2007-07-01

    Calcium channel blockers are drugs which are important for current medical therapy. The first examples of synthetic congeners of this class of drugs appear around at the beginning of the 1960s. Review of the current and historical literature shows that Avicenna (Ibn Sina) (980-1037) had used the herbal drug 'Zarnab' (Taxus baccata L.) as a cardiac remedy. The leaves of T. baccata contain an alkaloid mixture (taxines). It was recently demonstrated that this drug possessed calcium channel blocking activity. So, it is evident that Avicenna used a drug with calcium channel blocking activity much earlier than the arrival of synthetic drugs belonging to the same pharmacological group. Copyright 2007 John Wiley & Sons, Ltd.

  13. Activation of L-type calcium channels is required for gap junction-mediated intercellular calcium signaling in osteoblastic cells

    DEFF Research Database (Denmark)

    Jørgensen, Niklas Rye; Teilmann, Stefan Cuoni; Henriksen, Zanne

    2003-01-01

    The propagation of mechanically induced intercellular calcium waves (ICW) among osteoblastic cells occurs both by activation of P2Y (purinergic) receptors by extracellular nucleotides, resulting in "fast" ICW, and by gap junctional communication in cells that express connexin43 (Cx43), resulting...... in "slow" ICW. Human osteoblastic cells transmit intercellular calcium signals by both of these mechanisms. In the current studies we have examined the mechanism of slow gap junction-dependent ICW in osteoblastic cells. In ROS rat osteoblastic cells, gap junction-dependent ICW were inhibited by removal......43 (UMR/Cx43) we confirmed that nifedipine sensitivity of ICW required Cx43 expression. In human osteoblastic cells, gap junction-dependent ICW also required activation of L-type calcium channels and influx of extracellular calcium....

  14. TRPV5: an ingeniously controlled calcium channel.

    NARCIS (Netherlands)

    Groot, T. de; Bindels, R.J.M.; Hoenderop, J.G.J.

    2008-01-01

    Body Ca(2+) homeostasis is tightly controlled and slight disturbances in renal Ca(2+) reabsorption can lead to excessive urine Ca(2+) excretion and promote kidney stone formation. The epithelial Ca(2+) channel TRPV5 constitutes the rate-limiting step of active Ca(2+) reabsorption in the kidney.

  15. Calcium channel blockers and cancer risk using the UK CPRD

    NARCIS (Netherlands)

    Grimaldi-Bensouda, Lamiae; De Groot, Mark; Reynolds, Robert; Klungel, Olaf; Rossignol, Michel

    2014-01-01

    Background: This study was part of the Pharmacoepidemiological Research on Outcomes (PROTECT) project which aims at monitoring of the benefit-risk of medicines in Europe. Few epidemiological studies have investigated the association between calcium channel blockers (CCB) and cancer, and have

  16. [Obtaining antibodies to 1,4-dihydropyridine calcium channel blockers].

    Science.gov (United States)

    Burkin, A A; Murkin, M A

    2008-01-01

    Immunization of rabbits with amlodipine conjugated with horseradish peroxidase resulted in raising polyclonal antibodies that allowed group determination of 1,4-dihydropyridine calcium channel blockers in aqueous solutions by ELISA with a sensitivity of 0.1 to 1.0 ng/ml for amlodipine, felodipine, nifedipine, and isradipine.

  17. Evaluation of nitrendipine -a new calcium channel blocker ...

    African Journals Online (AJOL)

    Nitrendipine (Baypress; Bayer-Miles), a new calcium channel blocker, was administered to 38 hypertensive patients in an oral dose of 20 mg once or twice daily. Both systolic and diastolic blood pressures were reduced to a clinically relevant extent within 2 hours of taking the medication. There was no loss of effect during ...

  18. Effects of Calcium Ion, Calpains, and Calcium Channel Blockers on Retinitis Pigmentosa

    Directory of Open Access Journals (Sweden)

    Mitsuru Nakazawa

    2011-01-01

    Full Text Available Recent advances in molecular genetic studies have revealed many of the causative genes of retinitis pigmentosa (RP. These achievements have provided clues to the mechanisms of photoreceptor degeneration in RP. Apoptosis is known to be a final common pathway in RP and, therefore, a possible therapeutic target for photoreceptor rescue. However, apoptosis is not a single molecular cascade, but consists of many different reactions such as caspase-dependent and caspase-independent pathways commonly leading to DNA fractionation and cell death. The intracellular concentration of calcium ions is also known to increase in apoptosis. These findings suggest that calpains, one of the calcium-dependent proteinases, play some roles in the process of photoreceptor apoptosis and that calcium channel antagonists may potentially inhibit photoreceptor apoptosis. Herein, the effects of calpains and calcium channel antagonists on photoreceptor degeneration are reviewed.

  19. D1 receptors physically interact with N-type calcium channels to regulate channel distribution and dendritic calcium entry.

    Science.gov (United States)

    Kisilevsky, Alexandra E; Mulligan, Sean J; Altier, Christophe; Iftinca, Mircea C; Varela, Diego; Tai, Chao; Chen, Lina; Hameed, Shahid; Hamid, Jawed; Macvicar, Brian A; Zamponi, Gerald W

    2008-05-22

    Dopamine signaling through D1 receptors in the prefrontal cortex (PFC) plays a critical role in the maintenance of higher cognitive functions, such as working memory. At the cellular level, these functions are predicated to involve alterations in neuronal calcium levels. The dendrites of PFC neurons express D1 receptors and N-type calcium channels, yet little information exists regarding their coupling. Here, we show that D1 receptors potently inhibit N-type channels in dendrites of rat PFC neurons. Using coimmunoprecipitation, we demonstrate the existence of a D1 receptor-N-type channel signaling complex in this region, and we provide evidence for a direct receptor-channel interaction. Finally, we demonstrate the importance of this complex to receptor-channel colocalization in heterologous systems and in PFC neurons. Our data indicate that the N-type calcium channel is an important physiological target of D1 receptors and reveal a mechanism for D1 receptor-mediated regulation of cognitive function in the PFC.

  20. Calcium channel-dependent molecular maturation of photoreceptor synapses.

    Directory of Open Access Journals (Sweden)

    Nawal Zabouri

    Full Text Available Several studies have shown the importance of calcium channels in the development and/or maturation of synapses. The Ca(V1.4(α(1F knockout mouse is a unique model to study the role of calcium channels in photoreceptor synapse formation. It features abnormal ribbon synapses and aberrant cone morphology. We investigated the expression and targeting of several key elements of ribbon synapses and analyzed the cone morphology in the Ca(V1.4(α(1F knockout retina. Our data demonstrate that most abnormalities occur after eye opening. Indeed, scaffolding proteins such as Bassoon and RIM2 are properly targeted at first, but their expression and localization are not maintained in adulthood. This indicates that either calcium or the Ca(V1.4 channel, or both are necessary for the maintenance of their normal expression and distribution in photoreceptors. Other proteins, such as Veli3 and PSD-95, also display abnormal expression in rods prior to eye opening. Conversely, vesicle related proteins appear normal. Our data demonstrate that the Ca(V1.4 channel is important for maintaining scaffolding proteins in the ribbon synapse but less vital for proteins related to vesicular release. This study also confirms that in adult retinae, cones show developmental features such as sprouting and synaptogenesis. Overall we present evidence that in the absence of the Ca(V1.4 channel, photoreceptor synapses remain immature and are unable to stabilize.

  1. Dissociation of charge movement from calcium release and calcium current in skeletal myotubes by gabapentin.

    Science.gov (United States)

    Alden, Kris J; García, Jesús

    2002-09-01

    The skeletal muscle L-type calcium channel or dihydropyridine receptor (DHPR) plays an integral role in excitation-contraction (E-C) coupling. Its activation initiates three sequential events: charge movement (Q(r)), calcium release, and calcium current (I(Ca,L)). This relationship suggests that changes in Q(r) might affect release and I(Ca,L). Here we studied the effect of gabapentin (GBP) on the three events generated by DHPRs in skeletal myotubes in culture. GBP specifically binds to the alpha(2)/delta(1) subunit of the brain and skeletal muscle DHPR. Myotubes were stimulated with a protocol that included a depolarizing prepulse to inactivate voltage-dependent proteins other than DHPRs. Gabapentin (50 microM) significantly increased Q(r) while decreasing the rate of rise of calcium transients. Gabapentin also reduced the maximum amplitude of the I(Ca,L) (as we previously reported) without modifying the kinetics of activation. Exposure of GBP-treated myotubes to 10 microM nifedipine prevented the increase of Q(r) promoted by this drug, indicating that the extra charge recorded originated from DHPRs. Our data suggest that GBP dissociates the functions of the DHPR from the initial voltage-sensing step and implicates a role for the alpha(2)/delta(1) subunit in E-C coupling.

  2. Acetaldehyde - ethanol interactions on calcium-activated potassium (BK channels in pituitary tumor (GH3 cells

    Directory of Open Access Journals (Sweden)

    Astrid G. Handlechner

    2013-06-01

    Full Text Available Background: In the central nervous system ethanol (EtOH is metabolized to acetaldehyde (ACA primarily by the oxidative enzyme catalase. Evidence suggests that ACA is responsible for at least some of the effects on the brain that have been attributed to EtOH. Various types of ion channels which are involved in electrical signaling are targets of EtOH like maxi calcium-activated potassium (BK channels. BK channels exhibit various functions like action potential repolarization, blood pressure regulation, hormone secretion, or transmitter release. In most neuronal and neuroendocrine preparations at physiological intracellular calcium levels, EtOH increases BK channel activity. The simultaneous presence of ACA and EtOH reflects the physiological situation after drinking and may result in synergistic as well as antagonistic actions compared to a single application of either drug. The action of ACA on electrical activity has yet not been fully established.Methods: GH3 pituitary tumor cells were used for outside-out and inside-out patch-clamp recordings of BK activity in excised patches. Unitary current amplitude, open probability and channel mean open time of BK channels were measured. Results: Extracellular EtOH raised BK channel activity. In the presence of intracellular ACA this increment of BK activity was suppressed in a dose- as well as calcium-dependent manner. Mean channel open time was significantly reduced by internal ACA, whereas BK channel amplitudes were not affected. The EtOH counteracting effect of ACA was found to depend on succession of application. EtOH was prevented from activating BK channels by pre-exposure of membrane patches to ACA. In contrast BK activation by a hypotonic solution was not affected by internal ACA. Conclusions: Our data suggest an inhibitory impact of ACA on BK activation by EtOH. ACA appears to interact specifically with EtOH at BK channels since intracellular ACA had no effect when BK channels were activated by

  3. The TRPM7 channel kinase regulates store-operated calcium entry.

    Science.gov (United States)

    Faouzi, Malika; Kilch, Tatiana; Horgen, F David; Fleig, Andrea; Penner, Reinhold

    2017-05-15

    Pharmacological and molecular inhibition of transient receptor potential melastatin 7 (TRPM7) reduces store-operated calcium entry (SOCE). Overexpression of TRPM7 in TRPM7-/- cells restores SOCE. TRPM7 is not a store-operated calcium channel. TRPM7 kinase rather than channel modulates SOCE. TRPM7 channel activity contributes to the maintenance of store Ca2+ levels at rest. The transient receptor potential melastatin 7 (TRPM7) is a protein that combines an ion channel with an intrinsic kinase domain, enabling it to modulate cellular functions either by conducting ions through the pore or by phosphorylating downstream proteins via its kinase domain. In the present study, we report store-operated calcium entry (SOCE) as a novel target of TRPM7 kinase activity. TRPM7-deficient chicken DT40 B lymphocytes exhibit a strongly impaired SOCE compared to wild-type cells as a result of reduced calcium release activated calcium currents, and independently of potassium channel regulation, membrane potential changes or changes in cell-cycle distribution. Pharmacological blockade of TRPM7 with NS8593 or waixenicin A in wild-type B lymphocytes results in a significant decrease in SOCE, confirming that TRPM7 activity is acutely linked to SOCE, without TRPM7 representing a store-operated channel itself. Using kinase-deficient mutants, we find that TRPM7 regulates SOCE through its kinase domain. Furthermore, Ca2+ influx through TRPM7 is essential for the maintenance of endoplasmic reticulum Ca2+ concentration in resting cells, and for the refilling of Ca2+ stores after a Ca2+ signalling event. We conclude that the channel kinase TRPM7 and SOCE are synergistic mechanisms regulating intracellular Ca2+ homeostasis. © 2017 The Authors. The Journal of Physiology © 2017 The Physiological Society.

  4. Localization of calcium channels in Paramecium caudatum.

    Science.gov (United States)

    Dunlap, K

    1977-01-01

    1. Electrical recordings from Paramecium caudatum were made after removal of the cilia with chloral hydrate and during ciliary regrowth to study the electrical properties of that portion of the surface membrane enclosing the ciliary axoneme. 2. Removal of the somatic cilia (a 50% reduction in membrane surface area) results in an almost complete elimination of the regenerative Ca response, all-or-none Ba2+ spike, and delayed rectification. 3. A twofold increase in input resistance resulted from the 50% reduction in membrane surface area. 4. The electrical properties remained unchanged, despite prolonged exposure to the chloral hydrate, until the cilia were mechanically removed. 5. Restoration of the Ca response accompanied ciliary regrowth, so that complete excitability returns when the cilia regain their original lengths. 6. It is concluded that the voltage-sensitive Ca channels are localized to that portion of surface membrane surrounding the cilia. 7. Measurements of membrane constants before and after deciliation and estimations of the cable constants of a single cilium suggest that the cilia of Paramecium may be fully isopotential along their length and with the major cell compartment. Images Plate 1 Plate 2 PMID:915829

  5. Calcium signalling through L-type calcium channels: role in pathophysiology of spinal nociceptive transmission.

    Science.gov (United States)

    Roca-Lapirot, Olivier; Radwani, Houda; Aby, Franck; Nagy, Frédéric; Landry, Marc; Fossat, Pascal

    2017-02-18

    L-type voltage-gated calcium channels are ubiquitous channels in the CNS. L-type calcium channels (LTCs) are mostly post-synaptic channels regulating neuronal firing and gene expression. They play a role in important physio-pathological processes such as learning and memory, Parkinson's disease, autism and, as recognized more recently, in the pathophysiology of pain processes. Classically, the fundamental role of these channels in cardiovascular functions has limited the use of classical molecules to treat LTC-dependent disorders. However, when applied locally in the dorsal horn of the spinal cord, the three families of LTC pharmacological blockers - dihydropyridines (nifedipine), phenylalkylamines (verapamil) and benzothiazepines (diltiazem) - proved effective in altering short-term sensitization to pain, inflammation-induced hyperexcitability and neuropathy-induced allodynia. Two subtypes of LTCs, Cav 1.2 and Cav 1.3, are expressed in the dorsal horn of the spinal cord, where Cav 1.2 channels are localized mostly in the soma and proximal dendritic shafts, and Cav 1.3 channels are more distally located in the somato-dendritic compartment. Together with their different kinetics and pharmacological properties, this spatial distribution contributes to their separate roles in shaping short- and long-term sensitization to pain. Cav 1.3 channels sustain the expression of plateau potentials, an input/output amplification phenomenon that contributes to short-term sensitization to pain such as prolonged after-discharges, dynamic receptive fields and windup. The Cav 1.2 channels support calcium influx that is crucial for the excitation-transcription coupling underlying nerve injury-induced dorsal horn hyperexcitability. These subtype-specific cellular mechanisms may have different consequences in the development and/or the maintenance of pathological pain. Recent progress in developing more specific compounds for each subunit will offer new opportunities to modulate LTCs

  6. AII amacrine cells express L-type calcium channels at their output synapses.

    Science.gov (United States)

    Habermann, Christopher J; O'Brien, Brendan J; Wässle, Heinz; Protti, Dario A

    2003-07-30

    AII amacrine cells play a critical role in the high-fidelity signal transmission pathways involved with nighttime vision. The temporal properties of the light responses strongly depend on the transfer function at different synaptic stages and consequently on presynaptic calcium influx. AII light responses are complex waveforms generated by graded input, they comprise Na+-based spikes as well as a sustained component, and they are transferred to graded cone bipolar cells. It is, therefore, of interest to determine the properties of AII voltage-dependent calcium channels (VDCCs) to establish whether these cells express N-type and/or P/Q-type VDCCs, characteristic of spiking neurons, or whether they are more like graded neurons, which mostly use L-type VDCCs. We combined electrophysiological, molecular biological, and imaging techniques to characterize calcium currents and their sites of origin in mouse AII amacrine cells. Calcium currents activated at potentials more positive than -60 mV (maximally between -50 and -20 mV) and inactivated slowly. These currents were blocked by dihydropyridine (DHP) antagonists and were enhanced by the DHP agonist BayK 8644. Single-cell RT-PCR analysis of mRNA encoding for different calcium channel alpha subunits in AIIs revealed a consistent expression of the alpha1-D subunit. Calcium imaging of AII cells showed that the greatest change in intracellular calcium occurred in the lobular appendages, with minor changes being observed in the arboreal dendrites. Depolarization-induced calcium rises were also modulated by DHPs, suggesting that a particular kind of L-type VDCC, mainly localized to the lobular appendages, enables these spiking-capable neurons to release neurotransmitter in a sustained manner onto OFF-cone bipolar cells.

  7. Structures and functions of calcium channel beta subunits.

    Science.gov (United States)

    Birnbaumer, L; Qin, N; Olcese, R; Tareilus, E; Platano, D; Costantin, J; Stefani, E

    1998-08-01

    Calcium channel beta subunits have profound effects on how alpha1 subunits perform. In this article we summarize our present knowledge of the primary structures of beta subunits as deduced from cDNAs and illustrate their different properties. Upon co-expression with alpha1 subunits, the effects of beta subunits vary somewhat between L-type and non-L-type channels mostly because the two types of channels have different responses to voltage which are affected by beta subunits, such as long-lasting prepulse facilitation of alpha1C (absent in alpha1E) and inhibition by G protein betagamma dimer of alpha1E, absent in alpha1C. One beta subunit, a brain beta2a splice variant that is palmitoylated, has several effects not seen with any of the others, and these are due to palmitoylation. We also illustrate the finding that functional expression of alpha1 in oocytes requires a beta subunit even if the final channel shows no evidence for its presence. We propose two structural models for Ca2+ channels to account for "alpha1 alone" channels seen in cells with limited beta subunit expression. In one model, beta dissociates from the mature alpha1 after proper folding and membrane insertion. Regulated channels seen upon co-expression of high levels of beta would then have subunit composition alpha1beta. In the other model, the "chaperoning" beta remains associated with the mature channel and "alpha1 alone" channels would in fact be alpha1beta channels. Upon co-expression of high levels of beta the regulated channels would have composition [alpha1beta]beta.

  8. Localization and pharmacological characterization of voltage dependent calcium channels in cultured neocortical neurons

    DEFF Research Database (Denmark)

    Timmermann, D B; Lund, Trine Meldgaard; Belhage, B

    2001-01-01

    The physiological significance and subcellular distribution of voltage dependent calcium channels was defined using calcium channel blockers to inhibit potassium induced rises in cytosolic calcium concentration in cultured mouse neocortical neurons. The cytosolic calcium concentration was measured...... channels were differentially distributed in somata, neurites and nerve terminals. omega-conotoxin MVIIC (omega-CgTx MVIIC) inhibited approximately 40% of the Ca(2+)-rise in both somata and neurites and 60% of the potassium induced [3H]GABA release, indicating that the Q-type channel is the quantitatively...... using the fluorescent calcium chelator fura-2. The types of calcium channels present at the synaptic terminal were determined by the inhibitory action of calcium channel blockers on potassium-induced [3H]GABA release in the same cell preparation. L-, N-, P-, Q- and R-/T-type voltage dependent calcium...

  9. Active Dendrites and Differential Distribution of Calcium Channels Enable Functional Compartmentalization of Golgi Cells.

    Science.gov (United States)

    Rudolph, Stephanie; Hull, Court; Regehr, Wade G

    2015-11-25

    Interneurons are essential to controlling excitability, timing, and synaptic integration in neuronal networks. Golgi cells (GoCs) serve these roles at the input layer of the cerebellar cortex by releasing GABA to inhibit granule cells (grcs). GoCs are excited by mossy fibers (MFs) and grcs and provide feedforward and feedback inhibition to grcs. Here we investigate two important aspects of GoC physiology: the properties of GoC dendrites and the role of calcium signaling in regulating GoC spontaneous activity. Although GoC dendrites are extensive, previous studies concluded they are devoid of voltage-gated ion channels. Hence, the current view holds that somatic voltage signals decay passively within GoC dendrites, and grc synapses onto distal dendrites are not amplified and are therefore ineffective at firing GoCs because of strong passive attenuation. Using whole-cell recording and calcium imaging in rat slices, we find that dendritic voltage-gated sodium channels allow somatic action potentials to activate voltage-gated calcium channels (VGCCs) along the entire dendritic length, with R-type and T-type VGCCs preferentially located distally. We show that R- and T-type VGCCs located in the dendrites can boost distal synaptic inputs and promote burst firing. Active dendrites are thus critical to the regulation of GoC activity, and consequently, to the processing of input to the cerebellar cortex. In contrast, we find that N-type channels are preferentially located near the soma, and control the frequency and pattern of spontaneous firing through their close association with calcium-activated potassium (KCa) channels. Thus, VGCC types are differentially distributed and serve specialized functions within GoCs. Interneurons are essential to neural processing because they modulate excitability, timing, and synaptic integration within circuits. At the input layer of the cerebellar cortex, a single type of interneuron, the Golgi cell (GoC), carries these functions. The

  10. Estimation of presynaptic calcium currents and endogenous calcium buffers at the frog neuromuscular junction with two different calcium fluorescent dyes

    Directory of Open Access Journals (Sweden)

    Dmitry eSamigullin

    2015-01-01

    Full Text Available At the frog neuromuscular junction, under physiological conditions, the direct measurement of calcium currents and of the concentration of intracellular calcium buffers—which determine the kinetics of calcium concentration and neurotransmitter release from the nerve terminal—has hitherto been technically impossible. With the aim of quantifying both Ca2+ currents and the intracellular calcium buffers, we measured fluorescence signals from nerve terminals loaded with the low-affinity calcium dye Magnesium Green or the high-affinity dye Oregon Green BAPTA-1, simultaneously with microelectrode recordings of nerve-action potentials and end-plate currents. The action-potential-induced fluorescence signals in the nerve terminals developed much more slowly than the postsynaptic response. To clarify the reasons for this observation and to define a spatiotemporal profile of intracellular calcium and of the concentration of mobile and fixed calcium buffers, mathematical modeling was employed. The best approximations of the experimental calcium transients for both calcium dyes were obtained when the calcium current had an amplitude of 1.6 ± 0.08 рА and a half-decay time of 1.2 ± 0.06 ms, and when the concentrations of mobile and fixed calcium buffers were 250 ± 13 µM and 8 ± 0.4 mM, respectively. High concentrations of endogenous buffers define the time course of calcium transients after an action potential in the axoplasm, and may modify synaptic plasticity.

  11. Zebrafish CaV2.1 Calcium Channels Are Tailored for Fast Synchronous Neuromuscular Transmission

    Science.gov (United States)

    Naranjo, David; Wen, Hua; Brehm, Paul

    2015-01-01

    The CaV2.2 (N-type) and CaV2.1 (P/Q-type) voltage-dependent calcium channels are prevalent throughout the nervous system where they mediate synaptic transmission, but the basis for the selective presence at individual synapses still remains an open question. The CaV2.1 channels have been proposed to respond more effectively to brief action potentials (APs), an idea supported by computational modeling. However, the side-by-side comparison of CaV2.1 and CaV2.2 kinetics in intact neurons failed to reveal differences. As an alternative means for direct functional comparison we expressed zebrafish CaV2.1 and CaV2.2 α-subunits, along with their accessory subunits, in HEK293 cells. HEK cells lack calcium currents, thereby circumventing the need for pharmacological inhibition of mixed calcium channel isoforms present in neurons. HEK cells also have a simplified morphology compared to neurons, which improves voltage control. Our measurements revealed faster kinetics and shallower voltage-dependence of activation and deactivation for CaV2.1. Additionally, recordings of calcium current in response to a command waveform based on the motorneuron AP show, directly, more effective activation of CaV2.1. Analysis of calcium currents associated with the AP waveform indicate an approximately fourfold greater open probability (PO) for CaV2.1. The efficient activation of CaV2.1 channels during APs may contribute to the highly reliable transmission at zebrafish neuromuscular junctions. PMID:25650925

  12. Voltage sensitive calcium channels (VSCC) in cultured neuronal hybrid cells

    Energy Technology Data Exchange (ETDEWEB)

    Richard, C.L.; U' Prichard, D.C.; Noronha-Blob, L.

    1986-03-01

    Calcium entry via VSCC has been identified in selected, neuronal clonal cell lines using /sup 45/Ca uptake and the fluorescent calcium indicator, quin 2. VSCC in NG108-15 hybrid cells, differentiated with dibutyryl cyclic AMP (1 mM, 4 days) have been further characterized. Depolarization (50 mM K/sup +/, dp) resulted in a rapid (15 sec) influx of Ca/sup 2 +/. Intracellular calcium concentrations were elevated approx. 3 fold from 223 +- 68 nM to 666 +- 74 nM. Dp-sensitive calcium entry was voltage dependent, independent of Na/sup +/, stimulated (40%) by the agonist Bay K 8644 (1..mu..M) and blocked by divalent cations (..mu..M range) and organic calcium channel antagonists (nM range) Bay K 8644, in the absence of KCl, failed to stimulate Ca/sup 2 +/ influx. Tetrodotoxin (TTX) and tetraethylammonium had no effect on VSCC activity. Blockage of VSCC by nimodipine was reversed by increasing Ca/sup 2 +/ ions. IC/sub 50/ values were right shifted from 6.5 nM (1mM/sup 0/Ca/sup 2 +/) to 840 nM (10 mM Ca/sup 2 +/). Ca/sup 2 +/ entry was also stimulated by veratridine (VE), in a Na/sup +//sub 0/-sensitive manner. VE-induced Ca/sup 2 +/ entry was voltage-independent, TTX-sensitive, and was only 25% of dp-sensitive Ca/sup 2 +/ entry. These results together indicate that VSCC in neuronal cells offer a useful system for studying ion channel regulation.

  13. Calcium currents in a fast-twitch skeletal muscle of the rat.

    Science.gov (United States)

    Donaldson, P L; Beam, K G

    1983-10-01

    Slow ionic currents were measured in the rat omohyoid muscle with the three-microelectrode voltage-clamp technique. Sodium and delayed rectifier potassium currents were blocked pharmacologically. Under these conditions, depolarizing test pulses elicited an early outward current, followed by a transient slow inward current, followed in turn by a late outward current. The early outward current appeared to be a residual delayed rectifier current. The slow inward current was identified as a calcium current on the basis that (a) its magnitude depended on extracellular calcium concentration, (b) it was blocked by the addition of the divalent cations cadmium or nickel, and reduced in magnitude by the addition of manganese or cobalt, and (c) barium was able to replace calcium as an inward current carrier. The threshold potential for inward calcium current was around -20 mV in 10mM extracellular calcium and about -35 mV in 2 mM calcium. Currents were net inward over part of their time course for potentials up to at least +30 mV. At temperatures of 20-26 degrees C, the peak inward current (at approximately 0 mV) was 139 +/- 14 microA/cm2 (mean +/- SD), increasing to 226 +/- 28 microA/cm2 at temperatures of 27-37 degrees C. The late outward current exhibited considerable fiber-to-fiber variability. In some fibers it was primarily a time-independent, nonlinear leakage current. In other fibers it was primarily a time-independent, nonlinear leakage current. In other fibers it appeared to be the sum of both leak and a slowly activated outward current. The rate of activation of inward calcium current was strongly temperature dependent. For example, in a representative fiber, the time-to-peak inward current for a +10-mV test pulse decreased from approximately 250 ms at 20 degrees C to 100 ms at 30 degrees C. At 37 degrees C, the time-to-peak current was typically approximately 25 ms. The earliest phase of activation was difficult to quantify because the ionic current was partially

  14. Localization and pharmacological characterization of voltage dependent calcium channels in cultured neocortical neurons

    DEFF Research Database (Denmark)

    Timmermann, D B; Lund, T M; Belhage, B

    2001-01-01

    using the fluorescent calcium chelator fura-2. The types of calcium channels present at the synaptic terminal were determined by the inhibitory action of calcium channel blockers on potassium-induced [3H]GABA release in the same cell preparation. L-, N-, P-, Q- and R-/T-type voltage dependent calcium...... channels were differentially distributed in somata, neurites and nerve terminals. omega-conotoxin MVIIC (omega-CgTx MVIIC) inhibited approximately 40% of the Ca(2+)-rise in both somata and neurites and 60% of the potassium induced [3H]GABA release, indicating that the Q-type channel is the quantitatively...... in cytosolic calcium concentration. The results of this investigation demonstrate that pharmacologically distinct types of voltage dependent calcium channels are differentially localized in cell bodies, neurites and nerve terminals of mouse cortical neurons but that the Q-type calcium channel appears...

  15. Magnesium: Effect on ocular health as a calcium channel antagonist

    Directory of Open Access Journals (Sweden)

    Şafak Korkmaz

    2013-06-01

    Full Text Available Magnesium is the physiologic calcium channel blocker,involving in many different metabolic processes by maintainingcell membrane function, modulating smooth musclecontraction and influencing enzymatic activities. Magnesiumhas been shown to increase blood flow to tissuesby modifying endothelial function via endothelin-1 (ET-1and nitric Oxide (NO pathways. Magnesium also exhibitsneuroprotective role by blocking N-methyl-D-aspartate(NMDA receptor related calcium influx and by inhibitingthe release of glutamate, hence protects the cell againstoxidative stress and apoptosis. Both increase in bloodflow and its neuroprotective effect make magnesium agood candidate for glaucoma studies. Magnesium hasbeen shown to decrease oxidative stress and apoptosisin retinal tissue and to have retinal ganglion cell sparingeffect. A series of studies has been conducted aboutmagnesium could decrease insulin resistance in diabeticpatients, ease glycemia control and prevent diabetic retinopathy.Magnesium is found to be critically important inmaintaining normal ionic homeostasis of lens. Magnesiumdeficiency has been shown to cause increased lenticularoxidative stress and ionic imbalance in the lens so triggercataractogenesis. J Clin Exp Invest 2013; 4 (2: 244-251Key words: Magnesium, calcium channel blockage,glaucoma, neuroprotection, diabetic retinopathy, cataract

  16. Coronary artery calcium score: current status

    Science.gov (United States)

    Neves, Priscilla Ornellas; Andrade, Joalbo; Monção, Henry

    2017-01-01

    The coronary artery calcium score plays an Important role In cardiovascular risk stratification, showing a significant association with the medium- or long-term occurrence of major cardiovascular events. Here, we discuss the following: protocols for the acquisition and quantification of the coronary artery calcium score by multidetector computed tomography; the role of the coronary artery calcium score in coronary risk stratification and its comparison with other clinical scores; its indications, interpretation, and prognosis in asymptomatic patients; and its use in patients who are symptomatic or have diabetes. PMID:28670030

  17. Mechanism of sodium hydrosulfide modulation of L-type calcium channels in rat colonic smooth muscle cells.

    Science.gov (United States)

    Tang, Qincai; Quan, Xiaojing; Yan, Lin; Ren, Haixia; Chen, Wei; Xia, Hong; Luo, Hesheng

    2018-01-05

    Hydrogen sulfide (H 2 S) can exert different effects on the gastrointestinal tract by modulating ion channels. Previously, we found that H 2 S donor sodium hydrosulfide (NaHS) regulates colonic motility through L-type calcium channels, but the molecular mechanism remains unknown. The present study was designed to investigate possible mechanisms underlying the modulation of L-type calcium channels by NaHS in rat colonic smooth muscle cells. L-type calcium currents in colonic smooth muscle cells were recorded using the whole-cell patch-clamp technique. Spontaneous contractions of mid-colonic smooth muscle strips were measured in an organ bath system and a biological signal acquisition system. NaHS evoked a significant rightward shift in the steady-state activation curve of L-type calcium channels, changed the shape of the current-voltage (I-V) curve, and decreased the peak current density at 0mV, although it significantly increased with higher stimulatory voltage. The sulfhydryl-modifying reagent DL-dithiothreitol (DTT) enhanced the effects of NaHS on L-type calcium channels, while diamide (DM) and reduced L-glutathione (GSH) alleviated the effects of NaHS. Additionally, NaHS inhibited the spontaneous high-amplitude contractions of both longitudinal and circular smooth muscle strips in a dose-dependent manner. The inhibitory effects were reversible. DTT and GSH enhanced the effects of NaHS, while DM attenuated the effects of NaHS. In conclusion, NaHS modulates L-type calcium channels in rat colonic smooth muscle cells and regulates the contractile activity of colonic smooth muscle, potentially by modifying the free sulfhydryl groups of L-type calcium channels. Copyright © 2017 Elsevier B.V. All rights reserved.

  18. Support for calcium channel gene defects in autism spectrum disorders

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    Lu Ake Tzu-Hui

    2012-12-01

    Full Text Available Abstract Background Alternation of synaptic homeostasis is a biological process whose disruption might predispose children to autism spectrum disorders (ASD. Calcium channel genes (CCG contribute to modulating neuronal function and evidence implicating CCG in ASD has been accumulating. We conducted a targeted association analysis of CCG using existing genome-wide association study (GWAS data and imputation methods in a combined sample of parent/affected child trios from two ASD family collections to explore this hypothesis. Methods A total of 2,176 single-nucleotide polymorphisms (SNP (703 genotyped and 1,473 imputed covering the genes that encode the α1 subunit proteins of 10 calcium channels were tested for association with ASD in a combined sample of 2,781 parent/affected child trios from 543 multiplex Caucasian ASD families from the Autism Genetics Resource Exchange (AGRE and 1,651 multiplex and simplex Caucasian ASD families from the Autism Genome Project (AGP. SNP imputation using IMPUTE2 and a combined reference panel from the HapMap3 and the 1,000 Genomes Project increased coverage density of the CCG. Family-based association was tested using the FBAT software which controls for population stratification and accounts for the non-independence of siblings within multiplex families. The level of significance for association was set at 2.3E-05, providing a Bonferroni correction for this targeted 10-gene panel. Results Four SNPs in three CCGs were associated with ASD. One, rs10848653, is located in CACNA1C, a gene in which rare de novo mutations are responsible for Timothy syndrome, a Mendelian disorder that features ASD. Two others, rs198538 and rs198545, located in CACN1G, and a fourth, rs5750860, located in CACNA1I, are in CCGs that encode T-type calcium channels, genes with previous ASD associations. Conclusions These associations support a role for common CCG SNPs in ASD.

  19. Fear conditioning suppresses large-conductance calcium-activated potassium channels in lateral amygdala neurons.

    Science.gov (United States)

    Sun, P; Zhang, Q; Zhang, Y; Wang, F; Wang, L; Yamamoto, R; Sugai, T; Kato, N

    2015-01-01

    It was previously shown that depression-like behavior is accompanied with suppression of the large-conductance calcium activated potassium (BK) channel in cingulate cortex pyramidal cells. To test whether BK channels are also involved in fear conditioning, we studied neuronal properties of amygdala principal cells in fear conditioned mice. After behavior, we made brain slices containing the amygdala, the structure critically relevant to fear memory. The resting membrane potential in lateral amygdala (LA) neurons obtained from fear conditioned mice (FC group) was more depolarized than in neurons from naïve controls. The frequencies of spikes evoked by current injections were higher in neurons from FC mice, demonstrating that excitability of LA neurons was elevated by fear conditioning. The depolarization in neurons from FC mice was shown to depend on BK channels by using the BK channel blocker charybdotoxin. Suppression of BK channels in LA neurons from the FC group was further confirmed on the basis of the spike width, since BK channels affect the descending phase of spikes. Spikes were broader in the FC group than those in the naïve control in a manner dependent on BK channels. Consistently, quantitative real-time PCR revealed a decreased expression of BK channel mRNA. The present findings suggest that emotional disorder manifested in the forms of fear conditioning is accompanied with BK channel suppression in the amygdala, the brain structure critical to this emotional disorder. Copyright © 2014 Elsevier Inc. All rights reserved.

  20. Interaction of H2S with Calcium Permeable Channels and Transporters

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    Weihua Zhang

    2015-01-01

    Full Text Available A growing amount of evidence has suggested that hydrogen sulfide (H2S, as a gasotransmitter, is involved in intensive physiological and pathological processes. More and more research groups have found that H2S mediates diverse cellular biological functions related to regulating intracellular calcium concentration. These groups have demonstrated the reciprocal interaction between H2S and calcium ion channels and transporters, such as L-type calcium channels (LTCC, T-type calcium channels (TTCC, sodium/calcium exchangers (NCX, transient receptor potential (TRP channels, β-adrenergic receptors, and N-methyl-D-aspartate receptors (NMDAR in different cells. However, the understanding of the molecular targets and mechanisms is incomplete. Recently, some research groups demonstrated that H2S modulates the activity of calcium ion channels through protein S-sulfhydration and polysulfide reactions. In this review, we elucidate that H2S controls intracellular calcium homeostasis and the underlying mechanisms.

  1. Shaker and Shal mediate transient calcium-independent potassium current in a Drosophila flight motoneuron.

    Science.gov (United States)

    Ryglewski, Stefanie; Duch, Carsten

    2009-12-01

    Ionic currents underlie the firing patterns, excitability, and synaptic integration of neurons. Despite complete sequence information in multiple species, our knowledge about ion channel function in central neurons remains incomplete. This study analyzes the potassium currents of an identified Drosophila flight motoneuron, MN5, in situ. MN5 exhibits four different potassium currents, two fast-activating transient ones and two sustained ones, one of each is calcium activated. Pharmacological and genetic manipulations unravel the specific contributions of Shaker and Shal to the calcium independent transient A-type potassium currents. alpha-dendrotoxin (Shaker specific) and phrixotoxin-2 (Shal specific) block different portions of the transient calcium independent A-type potassium current. Following targeted expression of a Shaker dominant negative transgene in MN5, the remaining A-type potassium current is alpha-dendrotoxin insensitive. In Shal RNAi knock down the remaining A-type potassium current is phrixotoxin-2 insensitive. Additionally, barium blocks calcium-activated potassium currents but also a large portion of phrixotoxin-2-sensitive A-type currents. Targeted knock down of Shaker or Shal channels each cause identical reduction in total potassium current amplitude as acute application of alpha-dendrotoxin or phrixotoxin-2, respectively. This shows that the knock downs do not cause upregulation of potassium channels underlying other A-type channels during development. Immunocytochemistry and targeted expression of modified GFP-tagged Shaker channels with intact targeting sequence in MN5 indicate predominant axonal localization. These data can now be used to investigate the roles of Shaker and Shal for motoneuron intrinsic properties, synaptic integration, and spiking output during behavior by targeted genetic manipulations.

  2. Sigma-1 Receptor Plays a Negative Modulation on N-type Calcium Channel

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    Kang Zhang

    2017-05-01

    Full Text Available The sigma-1 receptor is a 223 amino acids molecular chaperone with a single transmembrane domain. It is resident to eukaryotic mitochondrial-associated endoplasmic reticulum and plasma membranes. By chaperone-mediated interactions with ion channels, G-protein coupled receptors and cell-signaling molecules, the sigma-1 receptor performs broad physiological and pharmacological functions. Despite sigma-1 receptors have been confirmed to regulate various types of ion channels, the relationship between the sigma-1 receptor and N-type Ca2+ channel is still unclear. Considering both sigma-1 receptors and N-type Ca2+ channels are involved in intracellular calcium homeostasis and neurotransmission, we undertake studies to explore the possible interaction between these two proteins. In the experiment, we confirmed the expression of the sigma-1 receptors and the N-type calcium channels in the cholinergic interneurons (ChIs in rat striatum by using single-cell reverse transcription-polymerase chain reaction (scRT-PCR and immunofluorescence staining. N-type Ca2+ currents recorded from ChIs in the brain slice of rat striatum was depressed when sigma-1 receptor agonists (SKF-10047 and Pre-084 were administrated. The inhibition was completely abolished by sigma-1 receptor antagonist (BD-1063. Co-expression of the sigma-1 receptors and the N-type calcium channels in Xenopus oocytes presented a decrease of N-type Ca2+ current amplitude with an increase of sigma-1 receptor expression. SKF-10047 could further depress N-type Ca2+ currents recorded from oocytes. The fluorescence resonance energy transfer (FRET assays and co-immunoprecipitation (Co-IP demonstrated that sigma-1 receptors and N-type Ca2+ channels formed a protein complex when they were co-expressed in HEK-293T (Human Embryonic Kidney -293T cells. Our results revealed that the sigma-1 receptors played a negative modulation on N-type Ca2+ channels. The mechanism for the inhibition of sigma-1 receptors on

  3. A toxin from the spider Phoneutria nigriventer that blocks calcium channels coupled to exocytosis

    Science.gov (United States)

    Guatimosim, C; Romano-Silva, M A; Cruz, J S; Beirão, P S L; Kalapothakis, E; Moraes-Santos, T; Cordeiro, M N; Diniz, C R; Gomez, M V; Prado, M A M

    1997-01-01

    The aim of the present experiments was to investigate the pharmacological action of a toxin from the spider Phoneutria nigriventer, Tx3-3, on the function of calcium channels that control exocytosis of synaptic vesicles. Tx3-3, in confirmation of previous work, diminished the intracellular calcium increase induced by membrane depolarization with KCl (25 mM) in rat cerebrocortical synaptosomes. The toxin was very potent (IC50 0.9 nM) at inhibiting calcium channels that regulate calcium entry in synaptosomes. In addition, Tx3-3 blocked the exocytosis of synaptic vesicles, as measured with the fluorescent dye FM1-43. Using ω-toxins that interact selectively with distinct neuronal calcium channels, we investigated whether the target of Tx3-3 overlaps with known channels that mediate exocytosis. The results indicate that the main population of voltage-sensitive calcium channels altered by Tx3-3 can also be inhibited by ω-agatoxin IVA, an antagonist of P/Q calcium channels. ω-conotoxin GVIA, which inhibits N type calcium channels did not decrease significantly the entry of calcium or exocytosis of synaptic vesicles in depolarized synaptosomes. It is concluded that Tx3-3 potently inhibits ω-agatoxin IVA-sensitive calcium channels, which are involved in controlling exocytosis in rat brain cortical synaptosomes. PMID:9351520

  4. Contribution of presynaptic calcium-activated potassium currents to transmitter release regulation in cultured Xenopus nerve-muscle synapses.

    Science.gov (United States)

    Pattillo, J M; Yazejian, B; DiGregorio, D A; Vergara, J L; Grinnell, A D; Meriney, S D

    2001-01-01

    Using Xenopus nerve-muscle co-cultures, we have examined the contribution of calcium-activated potassium (K(Ca)) channels to the regulation of transmitter release evoked by single action potentials. The presynaptic varicosities that form on muscle cells in these cultures were studied directly using patch-clamp recording techniques. In these developing synapses, blockade of K(Ca) channels with iberiotoxin or charybdotoxin decreased transmitter release by an average of 35%. This effect would be expected to be caused by changes in the late phases of action potential repolarization. We hypothesize that these changes are due to a reduction in the driving force for calcium that is normally enhanced by the local hyperpolarization at the active zone caused by potassium current through the K(Ca) channels that co-localize with calcium channels. In support of this hypothesis, we have shown that when action potential waveforms were used as voltage-clamp commands to elicit calcium current in varicosities, peak calcium current was reduced only when these waveforms were broadened beginning when action potential repolarization was 20% complete. In contrast to peak calcium current, total calcium influx was consistently increased following action potential broadening. A model, based on previously reported properties of ion channels, faithfully reproduced predicted effects on action potential repolarization and calcium currents. From these data, we suggest that the large-conductance K(Ca) channels expressed at presynaptic varicosities regulate transmitter release magnitude during single action potentials by altering the rate of action potential repolarization, and thus the magnitude of peak calcium current.

  5. Voltage-Gated Calcium Channel Antagonists and Traumatic Brain Injury

    Directory of Open Access Journals (Sweden)

    Bruce Lyeth

    2013-06-01

    Full Text Available Traumatic brain injury (TBI is a leading cause of death and disability in the United States. Despite more than 30 years of research, no pharmacological agents have been identified that improve neurological function following TBI. However, several lines of research described in this review provide support for further development of voltage gated calcium channel (VGCC antagonists as potential therapeutic agents. Following TBI, neurons and astrocytes experience a rapid and sometimes enduring increase in intracellular calcium ([Ca2+]i. These fluxes in [Ca2+]i drive not only apoptotic and necrotic cell death, but also can lead to long-term cell dysfunction in surviving cells. In a limited number of in vitro experiments, both L-type and N-type VGCC antagonists successfully reduced calcium loads as well as neuronal and astrocytic cell death following mechanical injury. In rodent models of TBI, administration of VGCC antagonists reduced cell death and improved cognitive function. It is clear that there is a critical need to find effective therapeutics and rational drug delivery strategies for the management and treatment of TBI, and we believe that further investigation of VGCC antagonists should be pursued before ruling out the possibility of successful translation to the clinic.

  6. Activation and inhibition of TMEM16A calcium-activated chloride channels.

    Directory of Open Access Journals (Sweden)

    Yu-Li Ni

    Full Text Available Calcium-activated chloride channels (CaCC encoded by family members of transmembrane proteins of unknown function 16 (TMEM16 have recently been intensely studied for functional properties as well as their physiological roles as chloride channels in various tissues. One technical hurdle in studying these channels is the well-known channel rundown that frequently impairs the precision of electrophysiological measurements for the channels. Using experimental protocols that employ fast-solution exchange, we circumvented the problem of channel rundown by normalizing the Ca(2+-induced current to the maximally-activated current obtained within a time period in which the channel rundown was negligible. We characterized the activation of the TMEM16A-encoded CaCC (also called ANO1 by Ca(2+, Sr(2+, and Ba(2+, and discovered that Mg(2+ competes with Ca(2+ in binding to the divalent-cation binding site without activating the channel. We also studied the permeability of the ANO1 pore for various anions and found that the anion occupancy in the pore-as revealed by the permeability ratios of these anions-appeared to be inversely correlated with the apparent affinity of the ANO1 inhibition by niflumic acid (NFA. On the other hand, the NFA inhibition was neither affected by the degree of the channel activation nor influenced by the types of divalent cations used for the channel activation. These results suggest that the NFA inhibition of ANO1 is likely mediated by altering the pore function but not through changing the channel gating. Our study provides a precise characterization of ANO1 and documents factors that can affect divalent cation activation and NFA inhibition of ANO1.

  7. Regulation of CaV2 calcium channels by G protein coupled receptors

    Science.gov (United States)

    Zamponi, Gerald W.; Currie, Kevin P.M.

    2012-01-01

    Voltage gated calcium channels (Ca2+ channels) are key mediators of depolarization induced calcium influx into excitable cells, and thereby play pivotal roles in a wide array of physiological responses. This review focuses on the inhibition of CaV2 (N- and P/Q-type) Ca2+-channels by G protein coupled receptors (GPCRs), which exerts important autocrine/paracrine control over synaptic transmission and neuroendocrine secretion. Voltage-dependent inhibition is the most widespread mechanism, and involves direct binding of the G protein βγ dimer (Gβγ) to the α1 subunit of CaV2 channels. GPCRs can also recruit several other distinct mechanisms including phosphorylation, lipid signaling pathways, and channel trafficking that result in voltage-independent inhibition. Current knowledge of Gβγ-mediated inhibition is reviewed, including the molecular interactions involved, determinants of voltage-dependence, and crosstalk with other cell signaling pathways. A summary of recent developments in understanding the voltage-independent mechanisms prominent in sympathetic and sensory neurons is also included. PMID:23063655

  8. Development of multiple calcium channel types in cultured mouse hippocampal neurons.

    Science.gov (United States)

    Chameau, P; Lucas, P; Melliti, K; Bournaud, R; Shimahara, T

    1999-05-01

    The development of multiple calcium channel activities was studied in mouse hippocampal neurons in culture, using the patch-clamp technique. A depolarizing pulse (40-50 ms duration) from the holding potential of -80 mV to levels more depolarized than -40 mV produced a low threshold T-type current. The T-type current was observed in 52% of four days in vitro neurons. The number of neurons which expressed T-type current decreased with age of culture, so that the current was detected in only 18% of neurons after 16 days in vitro. The T-type current densities varied between 1.9 pA/pF and 3.29 pA/pF in the mean values during the period studied (4-16 days in vitro). A depolarizing pulse from -80 mV to levels more depolarized than -35 mV evoked a high threshold calcium channel current. The high threshold current density increased in the mean values from 3.9 pA/pF in four days in vitro neurons to 28 pA/pF in 16 days in vitro neurons. We have then examined the effect of nifedipine, omega-Agatoxin IVA and omega-conotoxin GVIA on the high threshold current. Nifedipine (1-5 microM) sensitive current density stayed in the range of 1.9-2.1 pA/pF during 4-16 days in vitro, while omega-Agatoxin IVA (200 nM) sensitive current density increased in the mean values from 1.54 pA/pF in four days in vitro neurons to 21.5 pA/pF in 16 days in vitro neurons. The omega-conotoxin GVIA sensitive N-type channel current was maximum at eight days in vitro (5.44 pA/pF) and it reduced progressively to reach almost half (2.46 pA/pF) in 16 days in vitro neurons. These results showed that diverse subtypes of calcium channels change in density during the early period of culture. We suggest that the temporal expression of each type of channel may be linked to the development of neural activities.

  9. The impact of calcium current reversal on neurotransmitter release in the electrically stimulated retina

    Science.gov (United States)

    Werginz, Paul; Rattay, Frank

    2016-08-01

    Objective. In spite of intense theoretical and experimental investigations on electrical nerve stimulation, the influence of reversed ion currents on network activity during extracellular stimulation has not been investigated so far. Approach. Here, the impact of calcium current reversal on neurotransmitter release during subretinal stimulation was analyzed with a computational multi-compartment model of a retinal bipolar cell (BC) that was coupled with a four-pool model for the exocytosis from its ribbon synapses. Emphasis was laid on calcium channel dynamics and how these channels influence synaptic release. Main results. Stronger stimulation with anodic pulses caused transmembrane voltages above the Nernst potential of calcium in the terminals and, by this means, forced calcium ions to flow in the reversed direction from inside to the outside of the cell. Consequently, intracellular calcium concentration decreased resulting in a reduced vesicle release or preventing release at all. This mechanism is expected to lead to a pronounced ring-shaped pattern of exocytosis within a group of neighbored BCs when the stronger stimulated cells close to the electrode fail in releasing vesicles. Significance. Stronger subretinal stimulation causes failure of synaptic exocytosis due to reversal of calcium flow into the extracellular space in cells close to the electrode.

  10. Noradrenaline upregulates T-type calcium channels in rat pinealocytes.

    Science.gov (United States)

    Yu, Haijie; Seo, Jong Bae; Jung, Seung-Ryoung; Koh, Duk-Su; Hille, Bertil

    2015-02-15

    The mammalian pineal gland is a neuroendocrine organ that responds to circadian and seasonal rhythms. Its major function is to secrete melatonin as a hormonal night signal in response to nocturnal delivery of noradrenaline from sympathetic neurons. Culturing rat pinealocytes in noradrenaline for 24 h induced a low-voltage activated transient Ca(2+) current whose pharmacology and kinetics corresponded to a CaV3.1 T-type channel. The upregulation of the T-type Ca(2+) current is initiated by β-adrenergic receptors, cyclic AMP and cyclic AMP-dependent protein kinase. Messenger RNA for CaV3.1 T-type channels is significantly elevated by noradrenaline at 8 h and 24 h. The noradrenaline-induced T-type channel mediated an increased Ca(2+) entry and supported modest transient electrical responses to depolarizing stimuli, revealing the potential for circadian regulation of pinealocyte electrical excitability and Ca(2+) signalling. Our basic hypothesis is that mammalian pinealocytes have cycling electrical excitability and Ca(2+) signalling that may contribute to the circadian rhythm of pineal melatonin secretion. This study asked whether the functional expression of voltage-gated Ca(2+) channels (CaV channels) in rat pinealocytes is changed by culturing them in noradrenaline (NA) as a surrogate for the night signal. Channel activity was assayed as ionic currents under patch clamp and as optical signals from a Ca(2+)-sensitive dye. Channel mRNAs were assayed by quantitative polymerase chain reaction. Cultured without NA, pinealocytes showed only non-inactivating L-type dihydropyridine-sensitive Ca(2+) current. After 24 h in NA, additional low-voltage activated transient Ca(2+) current developed whose pharmacology and kinetics corresponded to a T-type CaV3.1 channel. This change was initiated by β-adrenergic receptors, cyclic AMP and protein kinase A as revealed by pharmacological experiments. mRNA for CaV3.1 T-type channels became significantly elevated, but mRNA for

  11. Direct Current-Induced Calcium Trafficking in Different Neuronal Preparations

    Directory of Open Access Journals (Sweden)

    Andrzej Wieraszko

    2016-01-01

    Full Text Available The influence of direct current (DC stimulation on radioactive calcium trafficking in sciatic nerve in vivo and in vitro, spinal cord, and synaptosomes was investigated. The exposure to DC enhanced calcium redistribution in all of these preparations. The effect was dependent on the strength of the stimulation and extended beyond the phase of exposure to DC. The DC-induced increase in calcium sequestration by synaptosomes was significantly reduced by cobalt and rupture of synaptosomes by osmotic shock. Although both anodal and cathodal currents were effective, the experiments with two electrodes of different areas revealed that cathodal stimulation exerted stronger effect. The exposure to DC induced not only relocation but also redistribution of calcium within segments of the sciatic nerve. Enzymatic removal of sialic acid by preincubation of synaptosomes with neuroaminidase, or carrying out the experiments in sodium-free environment, amplified DC-induced calcium accumulation.

  12. Selectivity and permeation in calcium release channel of cardiac muscle: alkali metal ions.

    Science.gov (United States)

    Chen, D P; Xu, L; Tripathy, A; Meissner, G; Eisenberg, B

    1999-03-01

    Current was measured from single open channels of the calcium release channel (CRC) of cardiac sarcoplasmic reticulum (over the range +/-180 mV) in pure and mixed solutions (e.g., biionic conditions) of the alkali metal ions Li+, K+, Na+, Rb+, Cs+, ranging in concentration from 25 mM to 2 M. The current-voltage (I-V) relations were analyzed by an extension of the Poisson-Nernst-Planck (PNP) formulation of electrodiffusion, which includes local chemical interaction described by an offset in chemical potential, which likely reflects the difference in dehydration/solvation/rehydration energies in the entry/exit steps of permeation. The theory fits all of the data with few adjustable parameters: the diffusion coefficient of each ion species, the average effective charge distribution on the wall of the pore, and an offset in chemical potential for lithium and sodium ions. In particular, the theory explains the discrepancy between "selectivities" defined by conductance sequence and "selectivities" determined by the permeability ratios (i.e., reversal potentials) in biionic conditions. The extended PNP formulation seems to offer a successful combined treatment of selectivity and permeation. Conductance selectivity in this channel arises mostly from friction: different species of ions have different diffusion coefficients in the channel. Permeability selectivity of an ion is determined by its electrochemical potential gradient and local chemical interaction with the channel. Neither selectivity (in CRC) seems to involve different electrostatic interaction of different ions with the channel protein, even though the ions have widely varying diameters.

  13. Plasma membrane calcium channels in cancer: Alterations and consequences for cell proliferation and migration.

    Science.gov (United States)

    Déliot, Nadine; Constantin, Bruno

    2015-10-01

    The study of calcium channels in molecular mechanisms of cancer transformation is still a novel area of research. Several studies, mostly conducted on cancer cell lines, however support the idea that a diversity of plasma membrane channels participates in the remodeling of Ca2+ homeostasis, which regulates various cancer hallmarks such as uncontrolled multiplication and increase in migration and invasion abilities. However few is still understood concerning the intracellular signaling cascades mobilized by calcium influx participating to cancer cell behavior. This review intends to gather some of these pathways dependent on plasma membrane calcium channels and described in prostate, breast and lung cancer cell lines. In these cancer cell types, the calcium channels involved in calcium signaling pathways promoting cancer behaviors are mostly non-voltage activated calcium channels and belong to the TRP superfamily (TRPC, TPRPV and TRPM families) and the Orai family. TRP and Orai channels are part of many signaling cascades involving the activation of transmembrane receptors by extracellular ligand from the tumor environment. TRPV can sense changes in the physical and chemical environment of cancer cells and TRPM7 are stretch activated and sensitive to cholesterol. Changes in activation and or expression of plasma-membrane calcium channels affect calcium-dependent signaling processes relevant to tumorigenesis. The studies cited in this review suggest that an increase in plasma membrane calcium channel expression and/or activity sustain an elevated calcium entry (constitutive or under the control of extracellular signals) promoting higher cell proliferation and migration in most cases. A variety of non-voltage-operated calcium channels display change expression and/or activity in a same cancer type and cooperate to the same process relevant to cancer cell behavior, or can be involved in a different sequence of events during the tumorigenesis. This article is part of a

  14. Ziconotide: neuronal calcium channel blocker for treating severe chronic pain.

    Science.gov (United States)

    Miljanich, G P

    2004-12-01

    Ziconotide (PRIALT) is a neuroactive peptide in the final stages of clinical development as a novel non-opioid treatment for severe chronic pain. It is the synthetic equivalent of omega-MVIIA, a component of the venom of the marine snail, Conus magus. The mechanism of action underlying ziconotide's therapeutic profile derives from its potent and selective blockade of neuronal N-type voltage-sensitive calcium channels (N-VSCCs). Direct blockade of N-VSCCs inhibits the activity of a subset of neurons, including pain-sensing primary nociceptors. This mechanism of action distinguishes ziconotide from all other analgesics, including opioid analgesics. In fact, ziconotide is potently anti-nociceptive in animal models of pain in which morphine exhibits poor anti-nociceptive activity. Moreover, in contrast to opiates, tolerance to ziconotide is not observed. Clinical studies of ziconotide in more than 2,000 patients reveal important correlations to ziconotide's non-clinical pharmacology. For example, ziconotide provides significant pain relief to severe chronic pain sufferers who have failed to obtain relief from opiate therapy and no evidence of tolerance to ziconotide is seen in these patients. Contingent on regulatory approval, ziconotide will be the first in a new class of neurological drugs: the N-type calcium channel blockers, or NCCBs. Its novel mechanism of action as a non-opioid analgesic suggests ziconotide has the potential to play a valuable role in treatment regimens for severe chronic pain. If approved for clinical use, ziconotide will further validate the neuroactive venom peptides as a source of new and useful medicines.

  15. The α2δ subunit and absence epilepsy: Beyond calcium channels?

    National Research Council Canada - National Science Library

    Celli, R; Santolini, I; Guiducci, M; Luijtelaar, E.L.J.M. van; Parisi, P; Striano, P; Gradini, R; Battaglia, G; Ngomba, R.T; Nicoletti, F

    2017-01-01

    .... Activation of T-type voltage-sensitive calcium channels (VSCCs) contributes to the pathological oscillatory activity of this network, and some of the first-line drugs used in the treatment of absence epilepsy inhibit T-type calcium channels. The α2δ...

  16. Role of L-type calcium-channel modulation in nonconvulsive epilepsy in rats

    NARCIS (Netherlands)

    Luijtelaar, E.L.J.M. van; Ates, N.; Coenen, A.M.L.

    1995-01-01

    Old male Wistar rats spontaneously showing hundreds of spike-wave discharges daily were used to investigate the role of calcium ions in nonconvulsive epilepsy. The effects of the L-type calcium channel blocker nimodipine and the L-type channel opener BAY K 8644 on number and duration of these

  17. Brain-derived neurotrophic factor inhibits calcium channel activation, exocytosis, and endocytosis at a central nerve terminal.

    Science.gov (United States)

    Baydyuk, Maryna; Wu, Xin-Sheng; He, Liming; Wu, Ling-Gang

    2015-03-18

    Brain-derived neurotrophic factor (BDNF) is a neurotrophin that regulates synaptic function and plasticity and plays important roles in neuronal development, survival, and brain disorders. Despite such diverse and important roles, how BDNF, or more generally speaking, neurotrophins affect synapses, particularly nerve terminals, remains unclear. By measuring calcium currents and membrane capacitance during depolarization at a large mammalian central nerve terminal, the rat calyx of Held, we report for the first time that BDNF slows down calcium channel activation, including P/Q-type channels, and inhibits exocytosis induced by brief depolarization or single action potentials, inhibits slow and rapid endocytosis, and inhibits vesicle mobilization to the readily releasable pool. These presynaptic mechanisms may contribute to the important roles of BDNF in regulating synapses and neuronal circuits and suggest that regulation of presynaptic calcium channels, exocytosis, and endocytosis are potential mechanisms by which neurotrophins achieve diverse neuronal functions. Copyright © 2015 the authors 0270-6474/15/354676-07$15.00/0.

  18. Calcium Activated K+ Channels in The Electroreceptor of the Skate Confirmed by Cloning. Details of Subunits and Splicing

    OpenAIRE

    King, Benjamin L.; Shi, Ling Fang; Kao, Peter; Clusin, William T.

    2015-01-01

    Elasmobranchs detect small potentials using excitable cells of the ampulla of Lorenzini which have calcium-activated K+ channels, first described in l974. A distinctive feature of the outward current in voltage clamped ampullae is its apparent insensitivity to voltage. The sequence of a BK channel ? isoform expressed in the ampulla of the skate was characterized. A signal peptide is present at the beginning of the gene. When compared to human isoform 1 (the canonical sequence), the largest di...

  19. CRAC channels, calcium, and cancer in light of the driver and passenger concept.

    Science.gov (United States)

    Hoth, Markus

    2016-06-01

    Advances in next-generation sequencing allow very comprehensive analyses of large numbers of cancer genomes leading to an increasingly better characterization and classification of cancers. Comparing genomic data predicts candidate genes driving development, growth, or metastasis of cancer. Cancer driver genes are defined as genes whose mutations are causally implicated in oncogenesis whereas passenger mutations are defined as not being oncogenic. Currently, a list of several hundred cancer driver mutations is discussed including prominent members like TP53, BRAF, NRAS, or NF1. According to the vast literature on Ca(2+) and cancer, Ca(2+) signals and the underlying Ca(2+) channels and transporters certainly influence the development, growth, and metastasis of many cancers. In this review, I focus on the calcium release-activated calcium (CRAC) channel genes STIM and Orai and their role for cancer development, growth, and metastasis. STIM and Orai genes are being discussed in the context of current cancer concepts with a focus on the driver-passenger hypothesis. One result of this discussion is the hypothesis that a driver analysis of Ca(2+) homeostasis-related genes should not be carried out by looking at isolated genes. Rather a pool of “Ca(2+) genes” might be considered to act as one potential cancer driver. This article is part of a Special Issue entitled: Calcium and Cell Fate. Guest Editors: Jacques Haiech, Claus Heizmann, Joachim Krebs, Thierry Capiod and Olivier Mignen.

  20. Outward potassium current oscillations in macrophage polykaryons: extracellular calcium entry and calcium-induced calcium release

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    Saraiva R.M.

    1997-01-01

    Full Text Available Outward current oscillations associated with transient membrane hyperpolarizations were induced in murine macrophage polykaryons by membrane depolarization in the absence of external Na+. Oscillations corresponded to a cyclic activation of Ca2+-dependent K+ currents (IKCa probably correlated with variations in intracellular Ca2+ concentration. Addition of external Na+ (8 mM immediately abolished the outward current oscillations, suggesting that the absence of the cation is necessary not only for their induction but also for their maintenance. Oscillations were completely blocked by nisoldipine. Ruthenium red and ryanodine reduced the number of outward current cycles in each episode, whereas quercetin prolonged the hyperpolarization 2- to 15-fold. Neither low molecular weight heparin nor the absence of a Na+ gradient across the membrane had any influence on oscillations. The evidence suggests that Ca2+ entry through a pathway sensitive to Ca2+ channel blockers is elicited by membrane depolarization in Na+-free medium and is essential to initiate oscillations, which are also dependent on the cyclic release of Ca2+ from intracellular Ca2+-sensitive stores; Ca2+ ATPase acts by reducing intracellular Ca2+, thus allowing slow deactivation of IKCa. Evidence is presented that neither a Na+/Ca2+ antiporter nor Ca2+ release from IP3-sensitive Ca2+ stores participate directly in the mechanism of oscillation

  1. H2O2augments cytosolic calcium in nucleus tractus solitarii neurons via multiple voltage-gated calcium channels.

    Science.gov (United States)

    Ostrowski, Tim D; Dantzler, Heather A; Polo-Parada, Luis; Kline, David D

    2017-05-01

    Reactive oxygen species (ROS) play a profound role in cardiorespiratory function under normal physiological conditions and disease states. ROS can influence neuronal activity by altering various ion channels and transporters. Within the nucleus tractus solitarii (nTS), a vital brainstem area for cardiorespiratory control, hydrogen peroxide (H 2 O 2 ) induces sustained hyperexcitability following an initial depression of neuronal activity. The mechanism(s) associated with the delayed hyperexcitability are unknown. Here we evaluate the effect(s) of H 2 O 2 on cytosolic Ca 2+ (via fura-2 imaging) and voltage-dependent calcium currents in dissociated rat nTS neurons. H 2 O 2 perfusion (200 µM; 1 min) induced a delayed, slow, and moderate increase (~27%) in intracellular Ca 2+ concentration ([Ca 2+ ] i ). The H 2 O 2 -mediated increase in [Ca 2+ ] i prevailed during thapsigargin, excluding the endoplasmic reticulum as a Ca 2+ source. The effect, however, was abolished by removal of extracellular Ca 2+ or the addition of cadmium to the bath solution, suggesting voltage-gated Ca 2+ channels (VGCCs) as targets for H 2 O 2 modulation. Recording of the total voltage-dependent Ca 2+ current confirmed H 2 O 2 enhanced Ca 2+ entry. Blocking VGCC L, N, and P/Q subtypes decreased the number of cells and their calcium currents that respond to H 2 O 2 The number of responder cells to H 2 O 2 also decreased in the presence of dithiothreitol, suggesting the actions of H 2 O 2 were dependent on sulfhydryl oxidation. In summary, here, we have shown that H 2 O 2 increases [Ca 2+ ] i and its Ca 2+ currents, which is dependent on multiple VGCCs likely by oxidation of sulfhydryl groups. These processes presumably contribute to the previously observed delayed hyperexcitability of nTS neurons in in vitro brainstem slices. Copyright © 2017 the American Physiological Society.

  2. LRRK2 regulates voltage-gated calcium channel function.

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    Cade eBedford

    2016-05-01

    Full Text Available Voltage-gated Ca2+ (CaV channels enable Ca2+ influx in response to membrane depolarization. CaV2.1 channels are localized to the presynaptic membrane of many types of neurons where they are involved in triggering neurotransmitter release. Several signaling proteins have been identified as important CaV2.1 regulators including protein kinases, G-proteins and Ca2+ binding proteins. Recently, we discovered that leucine rich repeat kinase 2 (LRRK2, a protein associated with inherited Parkinson’s disease, interacts with specific synaptic proteins and influences synaptic transmission. Since synaptic proteins functionally interact with CaV2.1 channels and synaptic transmission is triggered by Ca2+ entry via CaV2.1, we investigated whether LRRK2 could impact CaV2.1 channel function. CaV2.1 channel properties were measured using whole cell patch clamp electrophysiology in HEK293 cells transfected with CaV2.1 subunits and various LRRK2 constructs. Our results demonstrate that both wild type LRRK2 and the G2019S LRRK2 mutant caused a significant increase in whole cell Ca2+ current density compared to cells expressing only the CaV2.1 channel complex. In addition, LRRK2 expression caused a significant hyperpolarizing shift in voltage-dependent activation while having no significant effect on inactivation properties. These functional changes in CaV2.1 activity are likely due to a direct action of LRRK2 as we detected a physical interaction between LRRK2 and the β3 CaV channel subunit via coimmunoprecipitation. Furthermore, effects on CaV2.1 channel function are dependent on LRRK2 kinase activity as these could be reversed via treatment with a LRRK2 inhibitor. Interestingly, LRRK2 also augmented endogenous voltage-gated Ca2+ channel function in PC12 cells suggesting other CaV channels could also be regulated by LRRK2. Overall, our findings support a novel physiological role for LRRK2 in regulating CaV2.1 function that could have implications for how

  3. L-type calcium channels refine the neural population code of sound level.

    Science.gov (United States)

    Grimsley, Calum Alex; Green, David Brian; Sivaramakrishnan, Shobhana

    2016-12-01

    The coding of sound level by ensembles of neurons improves the accuracy with which listeners identify how loud a sound is. In the auditory system, the rate at which neurons fire in response to changes in sound level is shaped by local networks. Voltage-gated conductances alter local output by regulating neuronal firing, but their role in modulating responses to sound level is unclear. We tested the effects of L-type calcium channels (CaL: CaV1.1-1.4) on sound-level coding in the central nucleus of the inferior colliculus (ICC) in the auditory midbrain. We characterized the contribution of CaL to the total calcium current in brain slices and then examined its effects on rate-level functions (RLFs) in vivo using single-unit recordings in awake mice. CaL is a high-threshold current and comprises ∼50% of the total calcium current in ICC neurons. In vivo, CaL activates at sound levels that evoke high firing rates. In RLFs that increase monotonically with sound level, CaL boosts spike rates at high sound levels and increases the maximum firing rate achieved. In different populations of RLFs that change nonmonotonically with sound level, CaL either suppresses or enhances firing at sound levels that evoke maximum firing. CaL multiplies the gain of monotonic RLFs with dynamic range and divides the gain of nonmonotonic RLFs with the width of the RLF. These results suggest that a single broad class of calcium channels activates enhancing and suppressing local circuits to regulate the sensitivity of neuronal populations to sound level. Copyright © 2016 the American Physiological Society.

  4. Calcium and Vitamin D increase mRNA levels for the growth control hIK1 channel in human epidermal keratinocytes but functional channels are not observed

    Directory of Open Access Journals (Sweden)

    Rossie Sandra

    2004-06-01

    Full Text Available Abstract Background Intermediate-conductance, calcium-activated potassium channels (IKs modulate proliferation and differentiation in mesodermal cells by enhancing calcium influx, and they contribute to the physiology of fluid movement in certain epithelia. Previous reports suggest that IK channels stimulate proliferative growth in a keratinocyte cell line; however, because these channels indirectly promote calcium influx, a critically unique component of the keratinocyte differentiation program, an alternative hypothesis is that they would be anti-proliferative and pro-differentiating. This study addresses these hypotheses. Methods Real-time PCR, patch clamp electrophysiology, and proliferation assays were used to determine if human IK1 (hIK1 expression and function are correlated with either proliferation or differentiation in cultured human skin epidermal keratinocytes, and skin biopsies grown in explant culture. Results hIK1 mRNA expression in human keratinocytes and skin was increased in response to anti-proliferative/pro-differentiating stimuli (elevated calcium and Vitamin D. Correspondingly, the hIK1 agonist 1-EBIO inhibited keratinocyte proliferation suggesting that the channel could be anti-proliferative and pro-differentiating. However, this proliferative inhibition by 1-EBIO was not reversed by a panel of hIK1 blockers, calling into question the mechanism of 1-EBIO action. Subsequent patch clamp electrophysiological analysis failed to detect hIK1 channel currents in keratinocytes, even those expressing substantial hIK1 mRNA in response to calcium and Vitamin D induced differentiation. Identical electrophysiological recording conditions were then used to observe robust IK1 currents in fibroblasts which express IK1 mRNA levels comparable to those of keratinocytes. Thus, the absence of observable hIK1 currents in keratinocytes was not a function of the electrophysiological techniques. Conclusion Human keratinocyte differentiation is

  5. The influence of environmental calcium concentrations on calcium flux, compensatory drinking and epithelial calcium channel expression in a freshwater cartilaginous fish.

    Science.gov (United States)

    Allen, Peter J; Weihrauch, Dirk; Grandmaison, Vanessa; Dasiewicz, Patricia; Peake, Stephan J; Anderson, W Gary

    2011-03-15

    Calcium metabolism and mRNA levels of the epithelial calcium channel (ECaC) were examined in a freshwater cartilaginous fish, the lake sturgeon Acipenser fulvescens. Lake sturgeon were acclimated for ≥2 weeks to 0.1 (low), 0.4 (normal) or 3.3 (high) mmol l(-1) environmental calcium. Whole-body calcium flux was examined using (45)Ca as a radioactive marker. Net calcium flux was inward in all treatment groups; however, calcium influx was greatest in the low calcium environment and lowest in the high calcium environment, whereas efflux had the opposite relationship. A significant difference in the concentration of (45)Ca in the gastrointestinal tract (GIT) of fish in the low calcium environment led to the examination of drinking rate and calcium flux across the anterior-middle (mid) intestine. Drinking rate was not different between treatments; however, calcium influx across the mid-intestine in the low calcium treatment was significantly greater than that in both the normal and high calcium treatments. The lake sturgeon ECaC was 2831 bp in length, with a predicted protein sequence of 683 amino acids that shared a 66% identity with the closest sequenced ECaCs from the vertebrate phyla. ECaC mRNA levels were examined in the gills, kidney, pyloric caeca, mid-intestine and spiral intestine. Expression levels were highest in the gills, then the kidneys, and were orders of magnitude lower in the GIT. Contrary to existing models for calcium uptake in the teleost gill, ECaC expression was greatest in high calcium conditions and kidney ECaC expression was lowest in low calcium conditions, suggesting that cellular transport mechanisms for calcium may be distinctly different in these freshwater cartilaginous fishes.

  6. Voltage-dependent sodium channels and calcium-activated potassium channels in human odontoblasts in vitro.

    Science.gov (United States)

    Ichikawa, Hideki; Kim, Hyong-Jung; Shuprisha, Apichai; Shikano, Tetsuo; Tsumura, Maki; Shibukawa, Yoshiyuki; Tazaki, Masakazu

    2012-10-01

    Transmembrane ionic signaling regulates many cellular processes in both physiological and pathologic settings. In this study, the biophysical properties of voltage-dependent Na(+) channels in odontoblasts derived from human dental pulp (HOB cells) were investigated together with the effect of bradykinin on intracellular Ca(2+) signaling and expression of Ca(2+)-activated K(+) channels. Ionic channel activity was characterized by using whole-cell patch-clamp recording and fura-2 fluorescence. Mean resting membrane potential in the HOB cells was -38 mV. Depolarizing steps from a holding potential of -80 mV activated transient voltage-dependent inward currents with rapid activation/inactivation properties. At a holding potential of -50 mV, no inward current was recorded. Fast-activation kinetics exhibited dependence on membrane potential, whereas fast-inactivation kinetics did not. Steady-state inactivation was described by a Boltzmann function with a half-maximal inactivation potential of -70 mV, indicating that whereas the channels were completely inactivated at physiological resting membrane potential, they could be activated when the cells were hyperpolarized. Inward currents disappeared in Na(+)-free extracellular solution. Bradykinin activated intracellular Ca(2+)-releasing and influx pathways. When the HOB cells were clamped at a holding potential of -50 mV, outward currents were recorded at positive potentials, indicating sensitivity to inhibitors of intermediate-conductance Ca(2+)-activated K(+) channels. Human odontoblasts expressed voltage-dependent Na(+) channels, bradykinin receptors, and Ca(2+)-activated K(+) channels, which play an important role in driving cellular functions by channel-receptor signal interaction and membrane potential regulation. Copyright © 2012 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  7. Protein kinase D regulates the human cardiac L-type voltage-gated calcium channel through serine 1884.

    Science.gov (United States)

    Aita, Yusuke; Kurebayashi, Nagomi; Hirose, Shigehisa; Maturana, Andrés D

    2011-12-15

    Protein kinase D (PKD) regulates the activity of the L-type calcium channel in rat ventricular cardiomyocytes. However, the functional target residues of PKD on the L-type calcium channel remain to be identified. Our aim was to identify the functional phosphorylation sites of PKD on the human L-type calcium channel. The pore subunit of the human CaV1.2 (hCaV1.2) was stably expressed in HEK293 cells. Both the expression of a dominant-negative mutant of PKD and the mutation of serine 1884 but not serine 1930, putative targets of PKD, strongly reduced L-type calcium currents and single channel activity without affecting the channel's expression at the plasma membrane. Our results suggest that serine 1884 is essential for the regulation of hCaV1.2 by PKD. Copyright © 2011 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

  8. Divergent action of calcium channel blockers on ATP-binding cassette protein expression.

    Science.gov (United States)

    Hasegawa, Kazuhiro; Wakino, Shu; Kanda, Takeshi; Yoshioka, Kyoko; Tatematsu, Satoru; Homma, Koichiro; Takamatsu, Ichiro; Sugano, Naoki; Hayashi, Koichi

    2005-12-01

    Calcium channel blockers (CCBs) are widely used in clinical practice, and have been reported to be effective in preventing the progression of atherosclerosis. We examined whether various types of calcium channel blockers affected the expression of ATP binding cassette transporter A1 (ABCA1), a factor contributing to anti-atherogenesis. Undifferentiated monocytic cell line, THP-1 cells were maintained in RPMI 1640 medium and treated with different kinds of calcium channel blockers. Among the calcium channel blockers tested, aranidipine and efonidipine increased ABCA1 protein expression without an increase in ABCA1 mRNA expression, whereas other calcium channel blockers (eg, nifedipine, amlodipine, and nicardipine) or T-type calcium channel blockers (eg, mibefradil and nickel chloride) failed to upregulate ABCA1 expression. H89, a protein kinase A inhibitor inhibited the aranidipine-induced ABCA1 protein expression, whereas genistein (a tyrosine kinase inhibitor), or AG490 (a JAK-2 inhibitor) had no effects. Neither of these inhibitors suppressed the efonidipine-induced ABCA1 protein expression. Intracellular cAMP levels were elevated only by aranidipine, but not by efonidipine. In conclusion, aranidipine and efonidipine have the ability to induce ABCA1 protein by distinct mechanisms; protein kinase A is involved in the aranidipine-induced ABCA1 upregulation. This non-class effect of calcium channel blockers may potentially offer beneficial action in the treatment of hypertensive subjects with atherosclerosis.

  9. Immunolocalization and expression of small-conductance calcium-activated potassium channels in human myometrium

    DEFF Research Database (Denmark)

    Rosenbaum, Sofia T; Svalø, Julie; Nielsen, Karsten

    2012-01-01

    Small-conductance calcium-activated potassium (SK3) channels have been detected in human myometrium and we have previously shown a functional role of SK channels in human myometrium in vitro. The aims of this study were to identify the precise localization of SK3 channels and to quantify SK3 mRNA...

  10. New Role of P/Q-type Voltage-gated Calcium Channels

    DEFF Research Database (Denmark)

    Hansen, Pernille B L

    2015-01-01

    Voltage-gated calcium channels are important for the depolarization-evoked contraction of vascular smooth muscle cells (SMCs), with L-type channels being the classical channel involved in this mechanism. However, it has been demonstrated that the CaV2.1 subunit, which encodes a neuronal isoform o...

  11. 5,6-EET potently inhibits T-type calcium channels

    DEFF Research Database (Denmark)

    Cazade, M.; Bidaud, I.; Hansen, Pernille B. Lærkegaard

    2014-01-01

    T-type calcium channels (T-channels) are important actors in neuronal pacemaking, in heart rhythm, and in the control of the vascular tone. T-channels are regulated by several endogenous lipids including the primary eicosanoid arachidonic acid (AA), which display an important role in vasodilation...

  12. Different calcium sources control somatic versus dendritic SK channel activation during action potentials.

    Science.gov (United States)

    Jones, Scott L; Stuart, Greg J

    2013-12-11

    Small-conductance calcium-activated potassium (SK) channels play an important role in regulating neuronal excitability. While SK channels at the soma have long been known to contribute to the medium afterhyperpolarization (mAHP), recent evidence indicates they also regulate NMDA receptor activation in dendritic spines. Here we investigate the activation of SK channels in spines and dendrites of rat cortical pyramidal neurons during action potentials (APs), and compare this to SK channel activation at the soma. Using confocal calcium imaging, we demonstrate that the inhibition of SK channels with apamin results in a location-dependent increase in calcium influx into dendrites and spines during backpropagating APs (average increase, ~40%). This effect was occluded by block of R-type voltage-dependent calcium channels (VDCCs), but not by inhibition of N- or P/Q-type VDCCs, or block of calcium release from intracellular stores. During these experiments, we noticed that the calcium indicator (Oregon Green BAPTA-1) blocked the mAHP. Subsequent experiments using low concentrations of EGTA (1 mm) produced the same result, suggesting that somatic SK channels are not tightly colocalized with their calcium source. Consistent with this idea, all known subtypes of VDCCs except R-type were calcium sources for the apamin-sensitive mAHP at the soma. We conclude that SK channels in spines and dendrites of cortical pyramidal neurons regulate calcium influx during backpropagating APs in a distance-dependent manner, and are tightly coupled to R-type VDCCs. In contrast, SK channels activated by APs at the soma of these neurons are weakly coupled to a variety of VDCCs.

  13. Mechanism of preservation of myocardial calcium channel function by pyruvate cardioplegic solution.

    Science.gov (United States)

    Ono, K; Wada, T; Lee, T S; Gondo, N; Hadama, T; Arita, M

    1998-02-01

    We evaluated the effects of adding pyruvate to a cardioplegic solution on the preservation of the dihydropyridine-sensitive calcium (Ca2+) current responses to beta-adrenergic stimulation in rabbit cardiac myocytes by measurement of single-channel open probability. Single ventricular myocytes were isolated and stored in St. Thomas' solution with or without pyruvate at 4 degrees C for 2, 6, 12, or 24 hours, and cell-attached single Ca2+ channel currents recordings were made at 20 degrees to 22 degrees C after each storage period. When 0.1 micromol/L isoproterenol (ISO) was applied to the cells, the percent mean open probability of the Ca2+ channels tested in freshly isolated cells was 181% +/- 27% (n = 12) of control values. These responses decreased with an increasing duration of the hypothermic storage and were only 112% +/- 22% (n = 5) of control values after 24 hours of storage in the absence of pyruvate. Conversely, the responses were significantly preserved, to as much as 143% +/- 17% (n = 7), in the presence of 10 mmol/L pyruvate in the storage solution. The application of forskolin to stimulate adenylate cyclase or a membrane-permeable cyclic adenosine monophosphate mimicked the effects of ISO when the myocytes were stored with pyruvate. Pyruvate did not alter the open-channel kinetics or single-channel conductance and lacked any apparent direct effect on the Ca2+ channel activity. We suggest that pyruvate added to the hypothermic storage solution preserves the high-energy phosphates in myocytes that are responsible for Ca2+ channel phosphorylation via beta-adrenergic stimulation. (J Lab

  14. Dehydroepiandrosterone (DHEA) inhibits voltage-gated T-type calcium channels.

    Science.gov (United States)

    Chevalier, M; Gilbert, G; Lory, P; Marthan, R; Quignard, J F; Savineau, J P

    2012-06-01

    Dehydroepiandrosterone (DHEA) and its sulfated form, DHEAS, are the most abundant steroid hormones in the mammalian blood flow. DHEA may have beneficial effects in various pathophysiological conditions such as cardiovascular diseases or deterioration of the sense of well-being. However to date, the cellular mechanism underlying DHEA action remains elusive and may involve ion channel modulation. In this study, we have characterized the effect of DHEA on T-type voltage-activated calcium channels (T-channels), which are involved in several cardiovascular and neuronal diseases. Using the whole-cell patch-clamp technique, we demonstrate that DHEA inhibits the three recombinant T-channels (Ca(V)3.1, Ca(V)3.2 and Ca(V)3.3) expressed in NG108-15 cell line, as well as native T-channels in pulmonary artery smooth muscle cells. This effect of DHEA is both concentration (IC(50) between 2 and 7μM) and voltage-dependent and results in a significant shift of the steady-state inactivation curves toward hyperpolarized potentials. Consequently, DHEA reduces window T-current and inhibits membrane potential oscillations induced by Ca(V)3 channels. DHEA inhibition is not dependent on the activation of nuclear androgen or estrogen receptors and implicates a PTX-sensitive Gi protein pathway. Functionally, DHEA and the T-type inhibitor NNC 55-0396 inhibited KCl-induced contraction of pulmonary artery rings and their effect was not cumulative. Altogether, the present data demonstrate that DHEA inhibits T-channels by a Gi protein dependent pathway. DHEA-induced alteration in T-channel activity could thus account for its therapeutic action and/or physiological effects. Copyright © 2012 Elsevier Inc. All rights reserved.

  15. The role of T-type calcium channel genes in absence seizures

    Directory of Open Access Journals (Sweden)

    Yucai eChen

    2014-05-01

    Full Text Available The thalamic relay neurons, reticular thalamic nucleus, and neocortical pyramidal cells form a circuit that sustains oscillatory burst firing, and is regarded as the underlying mechanism of absence seizures. T-type calcium channels play a key role in this circuit. Here we review the role of T-type calcium channel genes in the development of absence seizures, and emphasize gain or loss of function mutations, and other variations that alter both quantity and quality of transcripts, and methylation status of isoforms of T-type calcium channel proteins might be of equal importance in understanding the pathological mechanism of absence seizures.

  16. Small and Intermediate Calcium-Activated Potassium Channel Openers Improve Rat Endothelial and Erectile Function

    Science.gov (United States)

    Comerma-Steffensen, Simon G.; Carvacho, Ingrid; Hedegaard, Elise R.; Simonsen, Ulf

    2017-01-01

    Modulation of endothelial calcium-activated potassium (KCa) channels has been proposed as an approach to restore endothelial function. The present study investigated whether novel openers of KCa channels with small (KCa2.x) and intermediate (KCa3.1) conductance, NS309 and NS4591, improve endothelium-dependent relaxation and erectile function. Rat corpus cavernosum (CC) strips were mounted for isometric tension recording and processed for immunoblotting. Mean arterial pressure (MAP), intracavernosal pressure (ICP), and electrocardiographic (ECG) measurements were conducted in anesthetized rats. Immunoblotting revealed the presence of KCa2.3 and large KCa conductance (KCa1.1) channels in the corpus cavernosum. NS309 and NS4591 increased current in CC endothelial cells in whole cell patch clamp experiments. Relaxation induced by NS309 (cavernous nerve stimulation with NS309 were unchanged, whereas NS4591 significantly improved erectile function. Administration of NS309 and NS4591 caused small changes in the electrocardiogram, but neither arrhythmic events nor prolongation of the QTc interval were observed. The present study suggests that openers of KCa2.x and KCa3.1 channels improve endothelial and erectile function. The effects of NS309 and NS4591 on heart rate and ECG are small, but will require additional safety studies before evaluating whether activation of KCa2.3 channels has a potential for treatment of erectile dysfunction. PMID:28993731

  17. Calcium channels and their blockers in intraocular pressure and glaucoma.

    Science.gov (United States)

    Mayama, Chihiro

    2014-09-15

    Several factors besides high intraocular pressure assumed to be associated with the development and progression of glaucoma, and calcium channel blockers (CCBs) have been an anticipated option for glaucoma treatment by improving ocular perfusion and/or exerting neuroprotective effects on retinal ganglion cells with safety established in wide and long-term usage. Decrease in IOP has been reported after topical application of CCBs, however, the effect is much smaller and almost negligible after systemic application. Various CCBs have been reported to increase posterior ocular blood flow in vivo and to exert direct neuroprotection in neurons in vitro. Distribution of the drug at a pharmacologically active concentration in the posterior ocular tissues across the blood-brain barrier or blood-retina barrier, especially in the optic nerve head and retina where the ganglion cells mainly suffer from glaucomatous damage, is essential for clinical treatment of glaucoma. Improved visual functions such as sensitivity in the visual field test have been reported after administration of CCBs, but evidences from the randomized studies have been limited and effects of CCBs on blood flow and direct neuroprotection are hardly distinguished from each other. © 2013 Published by Elsevier B.V.

  18. ATP-sensitive voltage- and calcium-dependent chloride channels in sarcoplasmic reticulum vesicles from rabbit skeletal muscle.

    Science.gov (United States)

    Kourie, J I

    1997-05-01

    Chloride channels in the sarcoplasmic reticulum (SR) are thought to play an essential role in excitation-contraction (E-C) coupling by balancing charge movement during calcium release and uptake. In this study the nucleotide-sensitivity of Cl- channels in the SR from rabbit skeletal muscle was investigated using the lipid bilayer technique. Two distinct ATP-sensitive Cl- channels that differ in their conductance and kinetic properties and in the mechanism of ATP-induced channel inhibition were observed. The first, a nonfrequent 150 pS channel was inhibited by trans (luminal) ATP, and the second, a common 75 pS small chloride (SCl) channel was inhibited by cis (cytoplasmic) ATP. In the case of the SCl channel the ATP-induced reversible decline in the values of current (maximal current amplitude, Imax and integral current, I') and kinetic parameters (frequency of opening FO, probability of the channel being open PO, mean open TO and closed Tc times) show a nonspecific block of the voltage- and Ca2+-dependent SCl channel. ATP was a more potent blocker from the cytoplasmic side than from the luminal side of the channel. The SCl channel block was not due to Ca2+ chelation by ATP, nor to phosphorylation of the channel protein. The inhibitory action of ATP was mimicked by the nonhydrolyzable analogue adenylylimidodiphosphate (AMP-PNP) in the absence of Mg2+. The inhibitory potency of the adenine nucleotides was charge dependent in the following order ATP4- > ADP3- > > > AMP2-. The data suggest that ATP-induced effects are mediated via an open channel block mechanism. Modulation of the SCl channel by [ATP]cis and [Ca2+]cis indicates that (i) this channel senses the bioenergetic state of the muscle fiber and (ii) it is linked to the ATP-dependent cycling of the Ca2+ between the SR and the sarcoplasm.

  19. Effect of antiarrhythmic drugs on small conductance calcium –activated potassium channels

    DEFF Research Database (Denmark)

    Simo Vicens, Rafel; Sauter, Daniel Rafael Peter; Grunnet, Morten

    2017-01-01

    . Whether antiarrhythmic drugs (AADs) recommended for treating AF target KCa2.X channels is unknown. To this end, we tested a large number of AADs on the human KCa2.2 and KCa2.3 channels to assess their effect on this new target using automated whole-cell patch clamp. Of the AADs recommended for treatment...... for their antiarrhythmic effect is unlikely, as the calculated IC50 values are very high compared to the effective free therapeutic plasma concentration of the drugs when used for AF treatment, 40,000-fold for dofetilide and 140- fold higher for propafenone.......Atrial fibrillation (AF) is the most common type of arrhythmia. Current pharmacological treatment for AF is moderately effective and/or increases the risk of serious ventricular adverse effects. To avoid ventricular adverse effects, a new target has been considered, the small conductance calcium...

  20. Calcium channel blockers for inhibiting preterm labour and birth.

    Science.gov (United States)

    Flenady, Vicki; Wojcieszek, Aleena M; Papatsonis, Dimitri N M; Stock, Owen M; Murray, Linda; Jardine, Luke A; Carbonne, Bruno

    2014-06-05

    Preterm birth is a major contributor to perinatal mortality and morbidity, affecting around 9% of births in high-income countries and an estimated 13% of births in low- and middle-income countries. Tocolytics are drugs used to suppress uterine contractions for women in preterm labour. The most widely used tocolytic are the betamimetics, however, these are associated with a high frequency of unpleasant and sometimes severe maternal side effects. Calcium channel blockers (CCBs) (such as nifedipine) may have similar tocolytic efficacy with less side effects than betamimetics. Oxytocin receptor antagonists (ORAs) (e.g. atosiban) also have a low side-effect profile. To assess the effects on maternal, fetal and neonatal outcomes of CCBs, administered as a tocolytic agent, to women in preterm labour. We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (12 November 2013). All published and unpublished randomised trials in which CCBs were used for tocolysis for women in labour between 20 and 36 completed weeks' gestation. Two review authors independently assessed trial eligibility, undertook quality assessment and data extraction. Results are presented using risk ratio (RR) for categorical data and mean difference (MD) for data measured on a continuous scale with the 95% confidence interval (CI). The number needed to treat to benefit (NNTB) and the number needed to treat to harm (NNTH) were calculated for categorical outcomes that were statistically significantly different. This update includes 26 additional trials involving 2511 women, giving a total of 38 included trials (3550 women). Thirty-five trials used nifedipine as the CCB and three trials used nicardipine. Blinding of intervention and outcome assessment was undertaken in only one of the trials (a placebo controlled trial). However, objective outcomes defined according to timing of birth and perinatal mortality were considered to have low risk of detection bias.Two small trials comparing CCBs

  1. Exclusion of alternative exon 33 of CaV1.2 calcium channels in heart is proarrhythmogenic.

    Science.gov (United States)

    Li, Guang; Wang, Juejin; Liao, Ping; Bartels, Peter; Zhang, Hengyu; Yu, Dejie; Liang, Mui Cheng; Poh, Kian Keong; Yu, Chye Yun; Jiang, Fengli; Yong, Tan Fong; Wong, Yuk Peng; Hu, Zhenyu; Huang, Hua; Zhang, Guangqin; Galupo, Mary Joyce; Bian, Jin-Song; Ponniah, Sathivel; Trasti, Scott Lee; See, Kelvin; Foo, Roger; Hoppe, Uta C; Herzig, Stefan; Soong, Tuck Wah

    2017-05-23

    Alternative splicing changes the CaV1.2 calcium channel electrophysiological property, but the in vivo significance of such altered channel function is lacking. Structure-function studies of heterologously expressed CaV1.2 channels could not recapitulate channel function in the native milieu of the cardiomyocyte. To address this gap in knowledge, we investigated the role of alternative exon 33 of the CaV1.2 calcium channel in heart function. Exclusion of exon 33 in CaV1.2 channels has been reported to shift the activation potential -10.4 mV to the hyperpolarized direction, and increased expression of CaV1.2Δ33 channels was observed in rat myocardial infarcted hearts. However, how a change in CaV1.2 channel electrophysiological property, due to alternative splicing, might affect cardiac function in vivo is unknown. To address these questions, we generated mCacna1c exon 33(-/-)-null mice. These mice contained CaV1.2Δ33 channels with a gain-of-function that included conduction of larger currents that reflects a shift in voltage dependence and a modest increase in single-channel open probability. This altered channel property underscored the development of ventricular arrhythmia, which is reflected in significantly more deaths of exon 33(-/-) mice from β-adrenergic stimulation. In vivo telemetric recordings also confirmed increased frequencies in premature ventricular contractions, tachycardia, and lengthened QT interval. Taken together, the significant decrease or absence of exon 33-containing CaV1.2 channels is potentially proarrhythmic in the heart. Of clinical relevance, human ischemic and dilated cardiomyopathy hearts showed increased inclusion of exon 33. However, the possible role that inclusion of exon 33 in CaV1.2 channels may play in the pathogenesis of human heart failure remains unclear.

  2. Calcium Homeostasis Modulator 1-Like Currents in Rat Fungiform Taste Cells Expressing Amiloride-Sensitive Sodium Currents.

    Science.gov (United States)

    Bigiani, Albertino

    2017-05-01

    Salt reception by taste cells is still the less understood transduction process occurring in taste buds, the peripheral sensory organs for the detection of food chemicals. Although there is evidence suggesting that the epithelial sodium channel (ENaC) works as sodium receptor, yet it is not clear how salt-detecting cells signal the relevant information to nerve endings. Taste cells responding to sweet, bitter, and umami substances release ATP as neurotransmitter through a nonvesicular mechanism. Three different channel proteins have been proposed as conduit for ATP secretion: pannexin channels, connexin hemichannels, and calcium homeostasis modulator 1 (CALHM1) channels. In heterologous expression systems, these channels mediate outwardly rectifying membrane currents with distinct biophysical and pharmacological properties. I therefore tested whether also salt-detecting taste cells were endowed with these currents. To this aim, I applied the patch-clamp techniques to single cells in isolated taste buds from rat fungiform papillae. Salt-detecting cells were functionally identified by exploiting the effect of amiloride, which induces a current response by shutting down ENaCs. I looked for the presence of outwardly rectifying currents by using appropriate voltage-clamp protocols and specific pharmacological tools. I found that indeed salt-detecting cells possessed these currents with properties consistent with the presence, at least in part, of CALHM1 channels. Unexpectedly, CALHM1-like currents in taste cells were potentiated by known blockers of pannexin, suggesting a possible inhibitory action of this protein on CALMH1. These findings indicate that communication between salt-detecting cells and nerve endings might involve ATP release by CALMH1 channels. © The Author 2017. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  3. Mapping of dihydropyridine binding residues in a less sensitive invertebrate L-type calcium channel (LCa v 1).

    Science.gov (United States)

    Senatore, Adriano; Boone, Adrienne; Lam, Stanley; Dawson, Taylor F; Zhorov, Boris; Spafford, J David

    2011-01-01

    Invertebrate L-type calcium channel, LCa(v) 1, isolated from the pond snail Lymnaea stagnalis is nearly indistinguishable from mammalian Ca(v) 1.2 (α1C) calcium channel in biophysical characteristics observed in vitro. These L-type channels are likely constrained within a narrow range of biophysical parameters to perform similar functions in the snail and mammalian cardiovascular systems. What distinguishes snail and mammalian L-type channels is a difference in dihydropyridine sensitivity: 100 nM isradipine exhibits a significant block of mammalian Ca(v) 1.2 currents without effect on snail LCa(v)1 currents. The native snail channel serves as a valuable surrogate for validating key residue differences identified from previous experimental and molecular modeling work. As predicted, three residue changes in LCa(v)1 (N_3o18, F_3i10, and I_4i12) replaced with DHP-sensing residues in respective positions of Ca(v) 1.2, (Q_3o18, Y_3i10, and M_4i12) raises the potency of isradipine block of LCa(v)1 channels to that of mammalian Ca(v) 1.2. Interestingly, the single N_3o18_Q mutation in LCa(v) 1 channels lowers DHP sensitivity even further and the triple mutation bearing enhanced isradipine sensitivity, still retains a reduced potency of agonist, (S)-Bay K8644.

  4. Effect of antiarrhythmic drugs on small conductance calcium - activated potassium channels.

    Science.gov (United States)

    Simó-Vicens, Rafel; Sauter, Daniel R P; Grunnet, Morten; Diness, Jonas G; Bentzen, Bo H

    2017-05-15

    Atrial fibrillation (AF) is the most common type of arrhythmia. Current pharmacological treatment for AF is moderately effective and/or increases the risk of serious ventricular adverse effects. To avoid ventricular adverse effects, a new target has been considered, the small conductance calcium-activated K+ channels (KCa2.X, SK channels). In the heart, KCa2.X channels are functionally more important in atria compared to ventricles, and pharmacological inhibition of the channel confers atrial selective prolongation of the cardiac action potential and converts AF to sinus rhythm in animal models of AF. Whether antiarrhythmic drugs (AADs) recommended for treating AF target KCa2.X channels is unknown. To this end, we tested a large number of AADs on the human KCa2.2 and KCa2.3 channels to assess their effect on this new target using automated whole-cell patch clamp. Of the AADs recommended for treatment of AF only dofetilide and propafenone inhibited hKCa2.X channels, with no subtype selectivity. The calculated IC50 were 90±10µmol/l vs 60±10µmol/l for dofetilide and 42±4µmol/l vs 80±20µmol/l for propafenone (hKCa2.3 vs hKCa2.2). Whether this inhibition has clinical importance for their antiarrhythmic effect is unlikely, as the calculated IC50 values are very high compared to the effective free therapeutic plasma concentration of the drugs when used for AF treatment, 40,000-fold for dofetilide and 140-fold higher for propafenone. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Low threshold T‐type calcium channels as targets for novel epilepsy treatments

    National Research Council Canada - National Science Library

    Powell, Kim L; Cain, Stuart M; Snutch, Terrance P; O'Brien, Terence J

    2014-01-01

    .... T ‐type calcium channels are expressed widely throughout the brain and peripheral tissues, and thus have been proposed as therapeutic targets for a variety of diseases such as epilepsy, insomnia, pain...

  6. A deleterious gene-by-environment interaction imposed by calcium channel blockers in Marfan syndrome.

    NARCIS (Netherlands)

    Doyle, J.J.; Doyle, A.J.; Wilson, N.K.; Habashi, J.P.; Bedja, D.; Whitworth, R.E.; Lindsay, M.E.; Schoenhoff, F.; Myers, L.; Huso, N.; Bachir, S.; Squires, O.; Rusholme, B.; Ehsan, H.; Huso, D.; Thomas, C.J.; Caulfield, M.J.; Eyk, J.E. Van; Judge, D.P.; Dietz, H.C.; Loeys, B.L.

    2015-01-01

    Calcium channel blockers (CCBs) are prescribed to patients with Marfan syndrome for prophylaxis against aortic aneurysm progression, despite limited evidence for their efficacy and safety in the disorder. Unexpectedly, Marfan mice treated with CCBs show accelerated aneurysm expansion, rupture, and

  7. Plasma Membrane Cyclic Nucleotide Gated Calcium Channels Control Land Plant Thermal Sensing and Acquired Thermotolerance

    National Research Council Canada - National Science Library

    Andrija Finka; America Farinia Henriquez Cuendet; Frans J.M. Maathuis; Younousse Saidi; Pierre Goloubinoff

    2012-01-01

    .... Here, we found that the cyclic nucleotide gated calcium channel (CNGC) CNGCb gene from Physcomitrella patens and its Arabidopsis thaliana ortholog CNGC2, encode a component of cyclic nucleotide gated Ca²...

  8. Extremely Low Frequency Electromagnetic Fields Facilitate Vesicle Endocytosis by Increasing Presynaptic Calcium Channel Expression at a Central Synapse.

    Science.gov (United States)

    Sun, Zhi-cheng; Ge, Jian-long; Guo, Bin; Guo, Jun; Hao, Mei; Wu, Yi-chen; Lin, Yi-an; La, Ting; Yao, Pan-tong; Mei, Yan-ai; Feng, Yi; Xue, Lei

    2016-02-18

    Accumulating evidence suggests significant biological effects caused by extremely low frequency electromagnetic fields (ELF-EMF). Although exo-endocytosis plays crucial physical and biological roles in neuronal communication, studies on how ELF-EMF regulates this process are scarce. By directly measuring calcium currents and membrane capacitance at a large mammalian central nervous synapse, the calyx of Held, we report for the first time that ELF-EMF critically affects synaptic transmission and plasticity. Exposure to ELF-EMF for 8 to 10 days dramatically increases the calcium influx upon stimulation and facilitates all forms of vesicle endocytosis, including slow and rapid endocytosis, endocytosis overshoot and bulk endocytosis, but does not affect the RRP size and exocytosis. Exposure to ELF-EMF also potentiates PTP, a form of short-term plasticity, increasing its peak amplitude without impacting its time course. We further investigated the underlying mechanisms and found that calcium channel expression, including the P/Q, N, and R subtypes, at the presynaptic nerve terminal was enhanced, accounting for the increased calcium influx upon stimulation. Thus, we conclude that exposure to ELF-EMF facilitates vesicle endocytosis and synaptic plasticity in a calcium-dependent manner by increasing calcium channel expression at the nerve terminal.

  9. Calcium-activated chloride current determines action potential morphology during calcium alternans in atrial myocytes.

    Science.gov (United States)

    Kanaporis, Giedrius; Blatter, Lothar A

    2016-02-01

    Cardiac alternans--periodic beat-to-beat alternations in contraction, action potential (AP) morphology or cytosolic calcium transient (CaT) amplitude--is a high risk indicator for cardiac arrhythmias and sudden cardiac death. However, it remains an unresolved issue whether beat-to-beat alternations in intracellular Ca(2+) ([Ca(2+)]i ) or AP morphology are the primary cause of pro-arrhythmic alternans. Here we show that in atria AP alternans occurs secondary to CaT alternans. CaT alternans leads to complex beat-to-beat changes in Ca(2+)-regulated ion currents that determine alternans of AP morphology. We report the novel finding that alternans of AP morphology is largely sustained by the activity of Ca(2+)-activated Cl(-) channels (CaCCs). Suppression of the CaCCs significantly reduces AP alternans, while CaT alternans remains unaffected. The demonstration of a major role of CaCCs in the development of AP alternans opens new possibilities for atrial alternans and arrhythmia prevention. Cardiac alternans, described as periodic beat-to-beat alternations in contraction, action potential (AP) morphology or cytosolic Ca transient (CaT) amplitude, is a high risk indicator for cardiac arrhythmias and sudden cardiac death. We investigated mechanisms of cardiac alternans in single rabbit atrial myocytes. CaTs were monitored simultaneously with membrane currents or APs recorded with the patch clamp technique. Beat-to-beat alternations of AP morphology and CaT amplitude revealed a strong quantitative correlation. Application of voltage clamp protocols in the form of pre-recorded APs (AP-clamp) during pacing-induced CaT alternans revealed a Ca(2+)-dependent current consisting of a large outward component (4.78 ± 0.58 pA pF(-1) in amplitude) coinciding with AP phases 1 and 2 that was followed by an inward current (-0.42 ± 0.03 pA pF(-1); n = 21) during AP repolarization. Approximately 90% of the initial outward current was blocked by substitution of Cl(-) ions or application

  10. Adenosine versus intravenous calcium channel antagonists for supraventricular tachycardia.

    Science.gov (United States)

    Alabed, Samer; Sabouni, Ammar; Providencia, Rui; Atallah, Edmond; Qintar, Mohammed; Chico, Timothy Ja

    2017-10-12

    People with supraventricular tachycardia (SVT) frequently are symptomatic and present to the emergency department for treatment. Although vagal manoeuvres may terminate SVT, they often fail, and subsequently adenosine or calcium channel antagonists (CCAs) are administered. Both are known to be effective, but both have a significant side effect profile. This is an update of a Cochrane review previously published in 2006. To review all randomised controlled trials (RCTs) that compare effects of adenosine versus CCAs in terminating SVT. We identified studies by searching CENTRAL, MEDLINE, Embase, and two trial registers in July 2017. We checked bibliographies of identified studies and applied no language restrictions. We planned to include all RCTs that compare adenosine versus a CCA for patients of any age presenting with SVT. We used standard methodological procedures as expected by Cochrane. Two review authors independently checked results of searches to identify relevant studies and resolved differences by discussion with a third review author. At least two review authors independently assessed each included study and extracted study data. We entered extracted data into Review Manager 5. Primary outcomes were rate of reversion to sinus rhythm and major adverse effects of adenosine and CCAs. Secondary outcomes were rate of recurrence, time to reversion, and minor adverse outcomes. We measured outcomes by calculating odds ratios (ORs) and assessed the quality of primary outcomes using the GRADE approach through the GRADEproGDT website. We identified two new studies for inclusion in the review update; the review now includes seven trials with 622 participants who presented to an emergency department with SVT. All included studies were RCTs, but only three described the randomisation process, and none had blinded participants, personnel, or outcome assessors to the intervention given. Moderate-quality evidence shows no differences in the number of people reverting to

  11. Ryanodine receptor/calcium release channel PKA phosphorylation: A critical mediator of heart failure progression

    OpenAIRE

    Wehrens, Xander H. T.; Lehnart, Stephan E.; Reiken, Steven; Vest, John A.; Wronska, Anetta; Marks, Andrew R.

    2006-01-01

    Defective regulation of the cardiac ryanodine receptor (RyR2)/calcium release channel, required for excitation-contraction coupling in the heart, has been linked to cardiac arrhythmias and heart failure. For example, diastolic calcium “leak” via RyR2 channels in the sarcoplasmic reticulum has been identified as an important factor contributing to impaired contractility in heart failure and ventricular arrhythmias that cause sudden cardiac death. In patients with heart failure, chronic activat...

  12. Role of T-type calcium channels in myogenic tone of skeletal muscle resistance arteries

    DEFF Research Database (Denmark)

    VanBavel, Ed; Sorop, Oana; Andreasen, Ditte

    2002-01-01

    T-type calcium channels may be involved in the maintenance of myogenic tone. We tested their role in isolated rat cremaster arterioles obtained after CO(2) anesthesia and decapitation. Total RNA was analyzed by RT-PCR and Southern blotting for calcium channel expression. We observed expression......); K(+) -5.4 +/- 0.3 (n = 4); all log(IC(50)) P maintenance of myogenic tone in rat cremaster muscle arterioles....

  13. Glycosylation of voltage-gated calcium channels in health and disease

    Czech Academy of Sciences Publication Activity Database

    Lazniewska, Joanna; Weiss, Norbert

    2017-01-01

    Roč. 1859, č. 5 (2017), s. 662-668 ISSN 0005-2736 R&D Projects: GA ČR GA15-13556S; GA MŠk 7AMB15FR015 Institutional support: RVO:61388963 Keywords : calcium channels * voltage-gated calcium channels * N-glycosylation * ancillary subunit * trafficking * stability Subject RIV: CE - Biochemistry Impact factor: 3.498, year: 2016

  14. Phylogeny unites animal sodium leak channels with fungal calcium channels in an ancient, voltage-insensitive clade.

    Science.gov (United States)

    Liebeskind, Benjamin J; Hillis, David M; Zakon, Harold H

    2012-12-01

    Proteins in the superfamily of voltage-gated ion channels mediate behavior across the tree of life. These proteins regulate the movement of ions across cell membranes by opening and closing a central pore that controls ion flow. The best-known members of this superfamily are the voltage-gated potassium, calcium (Ca(v)), and sodium (Na(v)) channels, which underlie impulse conduction in nerve and muscle. Not all members of this family are opened by changes in voltage, however. NALCN (NA(+) leak channel nonselective) channels, which encode a voltage-insensitive "sodium leak" channel, have garnered a growing interest. This study examines the phylogenetic relationship among Na(v)/Ca(v) voltage-gated and voltage-insensitive channels in the eukaryotic group Opisthokonta, which includes animals, fungi, and their unicellular relatives. We show that NALCN channels diverged from voltage-gated channels before the divergence of fungi and animals and that the closest relatives of NALCN channels are fungal calcium channels, which they functionally resemble.

  15. In vivo impact of presynaptic calcium channel dysfunction on motor axons in episodic ataxia type 2.

    Science.gov (United States)

    Tomlinson, Susan E; Tan, S Veronica; Burke, David; Labrum, Robyn W; Haworth, Andrea; Gibbons, Vaneesha S; Sweeney, Mary G; Griggs, Robert C; Kullmann, Dimitri M; Bostock, Hugh; Hanna, Michael G

    2016-02-01

    Ion channel dysfunction causes a range of neurological disorders by altering transmembrane ion fluxes, neuronal or muscle excitability, and neurotransmitter release. Genetic neuronal channelopathies affecting peripheral axons provide a unique opportunity to examine the impact of dysfunction of a single channel subtype in detail in vivo. Episodic ataxia type 2 is caused by mutations in CACNA1A, which encodes the pore-forming subunit of the neuronal voltage-gated calcium channel Cav2.1. In peripheral motor axons, this channel is highly expressed at the presynaptic neuromuscular junction where it contributes to action potential-evoked neurotransmitter release, but it is not expressed mid-axon or thought to contribute to action potential generation. Eight patients from five families with genetically confirmed episodic ataxia type 2 underwent neurophysiological assessment to determine whether axonal excitability was normal and, if not, whether changes could be explained by Cav2.1 dysfunction. New mutations in the CACNA1A gene were identified in two families. Nerve conduction studies were normal, but increased jitter in single-fibre EMG studies indicated unstable neuromuscular transmission in two patients. Excitability properties of median motor axons were compared with those in 30 age-matched healthy control subjects. All patients had similar excitability abnormalities, including a high electrical threshold and increased responses to hyperpolarizing (P ataxia type 2 thus has unexpected effects on axon excitability, which may reflect an indirect effect of abnormal calcium current fluxes during development. © The Author (2016). Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved.

  16. Blockade of L-type calcium channel in myocardium and calcium-induced contractions of vascular smooth muscle by CPU 86017.

    Science.gov (United States)

    Dai, De-zai; Hu, Hui-juan; Zhao, Jing; Hao, Xue-mei; Yang, Dong-mei; Zhou, Pei-ai; Wu, Cai-hong

    2004-04-01

    To assess the blockade by CPU 86017 on the L-type calcium channels in the myocardium and on the Ca(2+)-related contractions of vascular smooth muscle. The whole-cell patch-clamp was applied to investigate the blocking effect of CPU 86017 on the L-type calcium current in isolated guinea pig myocytes and contractions by KCl or phenylephrine (Phe) of the isolated rat tail arteries were measured. Suppression of the L-type current of the isolated myocytes by CPU 86017 was moderate, in time- and concentration-dependent manner and with no influence on the activation and inactivation curves. The IC(50) was 11.5 micromol/L. Suppressive effect of CPU 86017 on vaso-contractions induced by KCl 100 mmol/L, phenylephrine 1 micromol/L in KH solution (phase 1), Ca(2+) free KH solution ( phase 2), and by addition of CaCl(2) into Ca(2+)-free KH solution (phase 3) were observed. The IC(50) to suppress vaso-contractions by calcium entry via the receptor operated channel (ROC) and voltage-dependent channel (VDC) was 0.324 micromol/L and 16.3 micromol/L, respectively. The relative potency of CPU 86017 to suppress vascular tone by Ca(2+) entry through ROC and VDC is 1/187 of prazosin and 1/37 of verapamil, respectively. The blocking effects of CPU 86017 on the L-type calcium channel of myocardium and vessel are moderate and non-selective. CPU 86017 is approximately 50 times more potent in inhibiting ROC than VDC.

  17. TMEM16 proteins: the long awaited calcium-activated chloride channels?

    Directory of Open Access Journals (Sweden)

    C.A. Flores

    2009-11-01

    Full Text Available Currents mediated by calcium-activated chloride channels (CaCCs, observed for the first time in Xenopus oocytes, have been recorded in many cells and tissues ranging from different types of neurons to epithelial and muscle cells. CaCCs play a role in the regulation of excitability in neurons including sensory receptors. In addition, they are crucial mediators of chloride movements in epithelial cells where their activity regulates electrolyte and fluid transport. The roles of CaCCs, particularly in epithelia, are briefly reviewed with emphasis on their function in secretory epithelia. The recent identification by three independent groups, using different strategies, of TMEM16A as the molecular counterpart of the CaCC is discussed. TMEM16A is part of a family that has 10 other members in mice. The discovery of the potential TMEM16 anion channel activity opens the way for the molecular investigation of the role of these anion channels in specific cells and in organ physiology and pathophysiology. The identification of TMEM16A protein as a CaCC chloride channel molecule represents a great triumph of scientific perseverance and ingenuity. The varied approaches used by the three independent research groups also augur well for the solidity of the discovery.

  18. Extracellular protons enable activation of the calcium-dependent chloride channel TMEM16A.

    Science.gov (United States)

    Cruz-Rangel, Silvia; De Jesús-Pérez, José J; Aréchiga-Figueroa, Iván A; Rodríguez-Menchaca, Aldo A; Pérez-Cornejo, Patricia; Hartzell, H Criss; Arreola, Jorge

    2017-03-01

    The calcium-activated chloride channel TMEM16A provides a pathway for chloride ion movements that are key in preventing polyspermy, allowing fluid secretion, controlling blood pressure, and enabling gastrointestinal activity. TMEM16A is opened by voltage-dependent calcium binding and regulated by permeant anions and intracellular protons. Here we show that a low proton concentration reduces TMEM16A activity while maximum activation is obtained when the external proton concentration is high. In addition, protonation conditions determine the open probability of TMEM16A without changing its calcium sensitivity. External glutamic acid 623 (E623) is key for TMEM16A's ability to respond to external protons. At physiological pH, E623 is un-protonated and TMEM16A is activated when intracellular calcium increases; however, under acidic conditions E623 is partially protonated and works synergistically with intracellular calcium to activate the channel. These findings are critical for understanding physiological and pathological processes that involve changes in pH and chloride flux via TMEM16A. Transmembrane protein 16A (TMEM16A), also known as ANO1, the pore-forming subunit of a Ca(2+) -dependent Cl(-) channel (CaCC), is activated by direct, voltage-dependent, binding of intracellular Ca(2+) . Endogenous CaCCs are regulated by extracellular protons; however, the molecular basis of such regulation remains unidentified. Here, we evaluated the effects of different extracellular proton concentrations ([H(+) ]o ) on mouse TMEM16A expressed in HEK-293 cells using whole-cell and inside-out patch-clamp recordings. We found that increasing the [H(+) ]o from 10(-10) to 10(-5.5)  m caused a progressive increase in the chloride current (ICl ) that is described by titration of a protonatable site with pK = 7.3. Protons regulate TMEM16A in a voltage-independent manner, regardless of channel state (open or closed), and without altering its apparent Ca(2+) sensitivity. Noise analysis

  19. Tidal currents in the Yucatan Channel

    Energy Technology Data Exchange (ETDEWEB)

    Carrillo Gonzalez, Fatima [Centro Universitario de la Costa, Universidad de Guadalajara, Guadalajara, Jalisco (Mexico); Ochoa, Jose; Candela, Julio; Badan, Antonio; Sheinbaum; Gonzalez Navarro, Juan Ignacio [Departamento de Oceanografia Fisica, Centro de Investigacion Cientifica y de Educacion Superior de Ensenada, Ensenada, Baja California (Mexico)

    2007-07-15

    Currents data from a ten-month period at 197 measuring points covering all Yucatan Channel were processed by harmonic analysis to estimate tidal parameters for the O{sub 1}, K{sub 1}, M{sub 2} and S{sub 2} components. The highly detailed coverage confirms the known dominance for the O{sub 1} and K{sub 1} diurnal components, but also showed, for the first time, their intensification in the deep eastern margin of the channel where maximum amplitudes in main axis are 17 and 19 cm.s{sup -}1. The data also confirms weak semi-diurnal components, of which the most intense, M{sub 2} and S{sub 2}, have amplitudes only up to 2 cm.s{sup -}1. The tidal ellipses were elongated (i.e. with eccentricities close to one) in the NNW direction. The O{sub 1}, K{sub 1}, M{sub 2} and S{sub 2} contributions in transport variability through the channel have amplitudes of 11.7, 12.5, 1.2 and 1.0 Sv, all well determined above noise. [Spanish] Se presentan, a detalle sin precedente, las caracteristicas de las corrientes de marea O{sub 1}, K{sub 1}, M{sub 2} y S{sub 2} en el canal de Yucatan. Mapas de los parametros que definen las elipses, como son las amplitudes en los ejes principales, la orientacion, la fase y la razon-senal-ruido se obtienen, por el clasico analisis armonico en mediciones de 10 meses en duracion, en 197 puntos que cubren ampliamente un plano vertical del canal. En acuerdo con reportes anteriores, las senales diurnas O{sub 1} y K{sub 1} dominan, demostrandose aqui que sus amplitudes alcanzan, en la parte profunda y Este, 17 y 19 cm.s{sup -}1. El analisis tambien revela senales semidiurnas M{sub 2} y S{sub 2} muy debiles con amplitudes maximas de 2 y 1cm.s{sup -}1. Las elipses son muy alargadas (i.e. con excentricidad cercana a uno) y orientadas al nornoroeste. Los valores de la razon senal a ruido indican que los parametros de las dos constituyentes diurnas se encuentran bien determinados, mientras que las semidiurnas quedan muy contaminadas por el ruido. El rasgo mas

  20. Long-term use of calcium channel blocking drugs and breast cancer risk in a prospective cohort of US and Puerto Rican women.

    Science.gov (United States)

    Wilson, Lauren E; D'Aloisio, Aimee A; Sandler, Dale P; Taylor, Jack A

    2016-07-05

    In a recent case-control study, long-term use of calcium channel blocking drugs was associated with a greater-than-twofold increased breast cancer risk. If prospectively collected data confirm that calcium channel blocker use increases breast cancer risk, this would have major implications for hypertension treatment. The objective of this study was to determine whether women using calcium channel blockers for 10 years or more were at increased risk of developing breast cancer compared with women not using calcium channel blockers. The Sister Study is a prospective volunteer cohort study of women from the USA and Puerto Rico designed to evaluate environmental and genetic risk factors for breast cancer. Beginning in 2003, women between the ages of 35 and 74 were recruited. They were eligible to participate if they had a sister with breast cancer but had not been diagnosed with breast cancer themselves. In total, 50,884 women enrolled in the cohort between 2003 and 2009; 50,757 women with relevant baseline data and available follow-up data are included in this study. The exposure of interest is current use of calcium channel blocking drugs and the reported duration of use at entry into the cohort. Secondary exposures of interest were the duration and frequency of use for all other subclasses of antihypertensive drugs. Our main outcome is a self-reported diagnosis of breast cancer during the study follow-up period. With patient permission, self-reported diagnoses were confirmed using medical records. Results showed 15,817 participants were currently using an antihypertensive drug, and 3316 women were currently using a calcium channel blocker at study baseline; 1965 women reported a breast cancer diagnosis during study follow-up. Using Cox proportional hazards modeling, we found no increased risk of breast cancer among women who had been using calcium channel blockers for 10 years or more compared with never users of calcium channel blockers (HR 0.88, 95 % CI 0

  1. Calcium channel TRPV6 is involved in murine maternal-fetal calcium transport.

    Science.gov (United States)

    Suzuki, Yoshiro; Kovacs, Christopher S; Takanaga, Hitomi; Peng, Ji-Bin; Landowski, Christopher P; Hediger, Matthias A

    2008-08-01

    Maternal-fetal calcium (Ca(2+)) transport is crucial for fetal Ca(2+) homeostasis and bone mineralization. In this study, the physiological significance of the transient receptor potential, vanilloid 6 (TRPV6) Ca(2+) channel in maternal-fetal Ca(2+) transport was investigated using Trpv6 knockout mice. The Ca(2+) concentration in fetal blood and amniotic fluid was significantly lower in Trpv6 knockout fetuses than in wildtypes. The transport activity of radioactive Ca(2+) ((45)Ca) from mother to fetuses was 40% lower in Trpv6 knockout fetuses than in wildtypes. The ash weight was also lower in Trpv6 knockout fetuses compared with wildtype fetuses. TRPV6 mRNA and protein were mainly localized in intraplacental yolk sac and the visceral layer of extraplacental yolk sac, which are thought to be the places for maternal-fetal Ca(2+) transport in mice. These expression sites were co-localized with calbindin D(9K) in the yolk sac. In wildtype mice, placental TRPV6 mRNA increased 14-fold during the last 4 days of gestation, which coincides with fetal bone mineralization. These results provide the first in vivo evidence that TRPV6 is involved in maternal-fetal Ca(2+) transport. We propose that TRPV6 functions as a Ca(2+) entry pathway, which is critical for fetal Ca(2+) homeostasis.

  2. Oxidized Low-density Lipoprotein (ox-LDL) Cholesterol Induces the Expression of miRNA-223 and L-type Calcium Channel Protein in Atrial Fibrillation

    Science.gov (United States)

    He, Fengping; Xu, Xin; Yuan, Shuguo; Tan, Liangqiu; Gao, Lingjun; Ma, Shaochun; Zhang, Shebin; Ma, Zhanzhong; Jiang, Wei; Liu, Fenglian; Chen, Baofeng; Zhang, Beibei; Pang, Jungang; Huang, Xiuyan; Weng, Jiaqiang

    2016-08-01

    Atrial fibrillation (AF) is the most common sustained arrhythmia causing high morbidity and mortality. While changing of the cellular calcium homeostasis plays a critical role in AF, the L-type calcium channel α1c protein has suggested as an important regulator of reentrant spiral dynamics and is a major component of AF-related electrical remodeling. Our computational modeling predicted that miRNA-223 may regulate the CACNA1C gene which encodes the cardiac L-type calcium channel α1c subunit. We found that oxidized low-density lipoprotein (ox-LDL) cholesterol significantly up-regulates both the expression of miRNA-223 and L-type calcium channel protein. In contrast, knockdown of miRNA-223 reduced L-type calcium channel protein expression, while genetic knockdown of endogenous miRNA-223 dampened AF vulnerability. Transfection of miRNA-223 by adenovirus-mediated expression enhanced L-type calcium currents and promoted AF in mice while co-injection of a CACNA1C-specific miR-mimic counteracted the effect. Taken together, ox-LDL, as a known factor in AF-associated remodeling, positively regulates miRNA-223 transcription and L-type calcium channel protein expression. Our results implicate a new molecular mechanism for AF in which miRNA-223 can be used as an biomarker of AF rheumatic heart disease.

  3. Alternative splicing modulates diltiazem sensitivity of cardiac and vascular smooth muscle Cav1.2 calcium channels

    Science.gov (United States)

    Zhang, Heng Yu; Liao, Ping; Wang, Jue Jin; Yu, De Jie; Soong, Tuck Wah

    2010-01-01

    Background and purpose: As a calcium channel blocker, diltiazem acts mainly on the voltage-gated calcium channels, Cav1.2, for its beneficial effects in cardiovascular diseases such as hypertension, angina and/or supraventricular arrhythmias. However, the effects of diltiazem on different isoforms of Cav1.2 channels expressed in heart and vascular smooth muscles remain to be investigated. Here, we characterized the effects of diltiazem on the splice variants of Cav1.2 channels, predominant in cardiac and vascular smooth muscles. Experimental approach: Cardiac and smooth muscle isoforms of Cav1.2 channels were expressed in human embryonic kidney cells and their electrophysiological properties were characterized using whole-cell patch-clamp techniques. Key results: Under closed-channel and use-dependent block (0.03 Hz), cardiac splice variant Cav1.2CM was less sensitive to diltiazem than two major smooth muscle splice variants, Cav1.2SM and Cav1.2b. Cav1.2CM has a more positive half-inactivation potential than the smooth muscle channels, and diltiazem shifted it less to negative potential. Additionally, the current decay was slower in Cav1.2CM channels. When we modified alternatively spliced exons of cardiac Cav1.2CM channels into smooth muscle exons, we found that all three loci contribute to the different diltiazem sensitivity between cardiac and smooth muscle splice isoforms. Conclusions and implications: Alternative splicing of Cav1.2 channels modifies diltiazem sensitivity in the heart and blood vessels. Gating properties altered by diltiazem are different in the three channels. PMID:20649567

  4. Small and Intermediate Calcium-Activated Potassium Channel Openers Improve Rat Endothelial and Erectile Function

    Directory of Open Access Journals (Sweden)

    Simon G. Comerma-Steffensen

    2017-09-01

    Full Text Available Modulation of endothelial calcium-activated potassium (KCa channels has been proposed as an approach to restore endothelial function. The present study investigated whether novel openers of KCa channels with small (KCa2.x and intermediate (KCa3.1 conductance, NS309 and NS4591, improve endothelium-dependent relaxation and erectile function. Rat corpus cavernosum (CC strips were mounted for isometric tension recording and processed for immunoblotting. Mean arterial pressure (MAP, intracavernosal pressure (ICP, and electrocardiographic (ECG measurements were conducted in anesthetized rats. Immunoblotting revealed the presence of KCa2.3 and large KCa conductance (KCa1.1 channels in the corpus cavernosum. NS309 and NS4591 increased current in CC endothelial cells in whole cell patch clamp experiments. Relaxation induced by NS309 (<1 μM was inhibited by endothelial cell removal and high extracellular potassium. An inhibitor of nitric oxide (NO synthase, and blockers of KCa2.x and KCa1.1 channels, apamin and iberiotoxin also inhibited NS309 relaxation. Incubation with NS309 (0.5 μM markedly enhanced acetylcholine relaxation. Basal erectile function (ICP/MAP increased during administration of NS309. Increases in ICP/MAP after cavernous nerve stimulation with NS309 were unchanged, whereas NS4591 significantly improved erectile function. Administration of NS309 and NS4591 caused small changes in the electrocardiogram, but neither arrhythmic events nor prolongation of the QTc interval were observed. The present study suggests that openers of KCa2.x and KCa3.1 channels improve endothelial and erectile function. The effects of NS309 and NS4591 on heart rate and ECG are small, but will require additional safety studies before evaluating whether activation of KCa2.3 channels has a potential for treatment of erectile dysfunction.

  5. Effect of L- type Calcium Channel Blocker Nimodipine and T-type Calcium Channel Blocker Flunarizine on Motor Control in Mice

    Directory of Open Access Journals (Sweden)

    Swapnil Balkrishna Kaikade

    2015-05-01

    Full Text Available Objective: To study the effect of L-type of Calcium channel blocker nimodipine and T-type of calcium channel blocker funarizine on locomotor activity in mice without pretreatment by any other drug. Materials and method: The study was carried out following permission from the Institutional animal ethics committee. Healthy Swiss albino mice of either sex were selected by the strict inclusion and exclusion criteria and the grouping is done. Group A is control treated with normal saline, Group B and C received two titrated doses of nimodipine while Group D and E received two titrated doses of flunarizine. The animals were then observed for motor control on inclined plane and the Statistical analysis was done by using unpaired‘t’ test. Results: L-type calcium channel blocker nimodipine has dose dependent effect on motor control on inclined plane while the T- type calcium channel blocker flunarizine has no effect on motor control. Conclusion: Nimodipine has significant dose dependent depressant action on motor control on inclined plane while flunarizine has no effect on the above mentioned parameter.

  6. T-type voltage-gated calcium channels regulate the tone of mouse efferent arterioles

    DEFF Research Database (Denmark)

    Poulsen, Christian B; Al-Mashhadi, Rozh H; Cribbs, Leanne L

    2011-01-01

    Voltage-gated calcium channels are important for the regulation of renal blood flow and the glomerular filtration rate. Excitation-contraction coupling in afferent arterioles is known to require activation of these channels and we studied their role in the regulation of cortical efferent arteriol...... publication, 10 November 2010; doi:10.1038/ki.2010.429....

  7. The TRPV5/6 calcium channels contain multiple calmodulin binding sites with differential binding properties.

    NARCIS (Netherlands)

    Kovalevskaya, N.V.; Bokhovchuk, F.M.; Vuister, G.W.

    2012-01-01

    The epithelial Ca(2+) channels TRPV5/6 (transient receptor potential vanilloid 5/6) are thoroughly regulated in order to fine-tune the amount of Ca(2+) reabsorption. Calmodulin has been shown to be involved into calcium-dependent inactivation of TRPV5/6 channels by binding directly to the distal

  8. The genetic background affects the vascular response in T-type calcium channels 3.2 deficient mice

    DEFF Research Database (Denmark)

    Svenningsen, Per; Hansen, Pernille B L

    2016-01-01

    Voltage-gated calcium channels (Cav ) are important regulators of vascular tone and are attractive targets for pharmacological treatment of hypertension. The clinical used calcium blockers are often not selective for one channel but affect several types of calcium channels (Hansen 2015). L......-type channels are the dominant Ca(2+) entry pathway in vascular smooth muscle cells, however, T-type calcium channels are also expressed in the cardiovascular system where they play a functional role in the regulation of both contraction and vasodilation in (Chen et al. 2003; Hansen et al. 2001). This article...... is protected by copyright. All rights reserved....

  9. Inhibitory effect of calcium channel blockers on proliferation of human glioma cells in vitro

    Energy Technology Data Exchange (ETDEWEB)

    Kunert-Radek, J.; Stepien, H.; Lyson, K.; Pawlikowski, M.; Radek, A.

    1989-01-01

    The effects of 2 specific calcium channel blockers, verapamil and nimodipine, on the proliferation of human glioma tumour cells were investigated in vitro. Tumour tissues for primary cell cultures were obtained bioptically from 3 patients with the histopathological diagnosis of glioblastoma. The (/sup 3/H)-thymidine incorporation into glioma tumour cells DNA was used as a sensitive index of the cell proliferation. It was found that varapamil (10/sup 4/-10/sup 5/M) and nimodipine (10/sup 4/-10/sup 6/M) significantly inhibited the (/sup 3/H)-thymidine uptake in a dose-related manner. The inhibitory effect of both calcium channel antagonists was reversed by stimultancous addition of calcium chloride (5x10/sup 3/M). These results indicate that verapamil and nimodipine may exert an antiproliferative effect on glioma cells growth acting through a blokade of specific voltage-dependent calcium channels.

  10. Functional and pharmacological consequences of the distribution of voltage-gated calcium channels in the renal blood vessels

    DEFF Research Database (Denmark)

    Hansen, P B L

    2013-01-01

    Calcium channel blockers are widely used to treat hypertension because they inhibit voltage-gated calcium channels that mediate transmembrane calcium influx in, for example, vascular smooth muscle and cardiomyocytes. The calcium channel family consists of several subfamilies, of which the L......-type is usually associated with vascular contractility. However, the L-, T- and P-/Q-types of calcium channels are present in the renal vasculature and are differentially involved in controlling vascular contractility, thereby contributing to regulation of kidney function and blood pressure. In the preglomerular...... vascular bed, all the three channel families are present. However, the T-type channel is the only channel in cortical efferent arterioles which is in contrast to the juxtamedullary efferent arteriole, and that leads to diverse functional effects of L- and T-type channel inhibition. Furthermore...

  11. Differential effects of organic calcium-channel blockers on diastolic SR calcium-handling in the frog heart.

    Science.gov (United States)

    Subramani, Sathya; Vijayanand, Caroline; Tharion, Elizabeth

    2002-11-01

    1. Gradual loss of sarcoplasmic reticular (SR) calcium during a rest-period is responsible for the rest-induced decay (RID) of force in mammalian myocardium. Effect of verapamil and diltiazem on a similar RID in the frog myocardium suggests a new mechanism of action of these drugs. 2. Strips of frog-ventricle were paced at 0.2 Hz and the rhythm was interrupted by varying rest-periods ranging from 10 to 180 s. In control conditions, the amplitude of the post-rest beat was significantly lower than that of the pre-rest beat for rest-periods more than 40 s (RID). 3. Verapamil and diltiazem (which are organic calcium-channel blockers (OCCB)) changed the pattern of RID in the control solution to a 'rest-induced potentiation' (RIP) in the same preparation while another OCCB nifedipine and the inorganic calcium-channel blocker cadmium did not alter the post-rest phenomenon. 4. We propose that verapamil and diltiazem produce an RIP due to either blockade of SR calcium-leak during rest or enhancement of SR calcium-uptake during rest.

  12. A Calcium-Dependent Plasticity Rule for HCN Channels Maintains Activity Homeostasis and Stable Synaptic Learning

    Science.gov (United States)

    Honnuraiah, Suraj; Narayanan, Rishikesh

    2013-01-01

    Theoretical and computational frameworks for synaptic plasticity and learning have a long and cherished history, with few parallels within the well-established literature for plasticity of voltage-gated ion channels. In this study, we derive rules for plasticity in the hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, and assess the synergy between synaptic and HCN channel plasticity in establishing stability during synaptic learning. To do this, we employ a conductance-based model for the hippocampal pyramidal neuron, and incorporate synaptic plasticity through the well-established Bienenstock-Cooper-Munro (BCM)-like rule for synaptic plasticity, wherein the direction and strength of the plasticity is dependent on the concentration of calcium influx. Under this framework, we derive a rule for HCN channel plasticity to establish homeostasis in synaptically-driven firing rate, and incorporate such plasticity into our model. In demonstrating that this rule for HCN channel plasticity helps maintain firing rate homeostasis after bidirectional synaptic plasticity, we observe a linear relationship between synaptic plasticity and HCN channel plasticity for maintaining firing rate homeostasis. Motivated by this linear relationship, we derive a calcium-dependent rule for HCN-channel plasticity, and demonstrate that firing rate homeostasis is maintained in the face of synaptic plasticity when moderate and high levels of cytosolic calcium influx induced depression and potentiation of the HCN-channel conductance, respectively. Additionally, we show that such synergy between synaptic and HCN-channel plasticity enhances the stability of synaptic learning through metaplasticity in the BCM-like synaptic plasticity profile. Finally, we demonstrate that the synergistic interaction between synaptic and HCN-channel plasticity preserves robustness of information transfer across the neuron under a rate-coding schema. Our results establish specific physiological roles

  13. High-dose insulin therapy in beta-blocker and calcium channel-blocker poisoning.

    Science.gov (United States)

    Engebretsen, Kristin M; Kaczmarek, Kathleen M; Morgan, Jenifer; Holger, Joel S

    2011-04-01

    -DOSE INSULIN. Animal models have shown high-dose insulin to be superior to calcium salts, glucagon, epinephrine, and vasopressin in terms of survival. Currently, there are no published controlled clinical trials in humans, but a review of case reports and case series supports the use of high-dose insulin as an initial therapy. HIGH-DOSE INSULIN TREATMENT PROTOCOLS. When first introduced, insulin doses were cautiously initiated at 0.5 U/kg bolus followed by a 0.5-1 U/kg/h continuous infusion due to concern for hypoglycemia and electrolyte imbalances. With increasing clinical experience and the publication of animal studies, high-dose insulin dosing recommendations have been increased to 1 U/kg insulin bolus followed by a 1-10 U/kg/h continuous infusion. Although the optimal regimen is still to be determined, bolus doses up to 10 U/kg and continuous infusions as high as 22 U/kg/h have been administered with good outcomes and minimal adverse events. ADVERSE EFFECTS OF HIGH-DOSE INSULIN. The major anticipated adverse events associated with high-dose insulin are hypoglycemia and hypokalemia. Glucose concentrations must be monitored regularly and supplementation of glucose will likely be required throughout therapy and for up to 24 h after discontinuation of high-dose insulin. The change in serum potassium concentrations reflects a shifting of potassium from the extracellular to intracellular space rather than a decrease in total body stores. CONCLUSIONS. While more clinical data are needed, animal studies and human case reports demonstrate that high-dose insulin (1-10 U/kg/hour) is a superior treatment in terms of safety and survival in both beta-blocker and calcium-channel blocker poisoning. High-dose insulin should be considered initial therapy in these poisonings.

  14. The channel hypothesis of Alzheimer's disease: current status.

    Science.gov (United States)

    Kagan, Bruce L; Hirakura, Yutaka; Azimov, Rustam; Azimova, Rushana; Lin, Meng-Chin

    2002-07-01

    The channel hypothesis of Alzheimer's disease (AD) proposes that the beta-amyloid (Abeta) peptides which accumulate in plaques in the brain actually damage and/or kill neurons by forming ion channels. Evidence from a number of laboratories has demonstrated that Abeta peptides can form ion channels in lipid bilayers, liposomes, neurons, oocyctes, and endothelial cells. These channels possess distinct physiologic characteristics that would be consistent with their toxic properties. Abeta channels are heterogeneous in size, selectivity, blockade, and gating. They are generally large, voltage-independent, and relatively poorly selective amongst physiologic ions, admitting calcium ion (Ca(2+)), Na(+), K(+), Cs(+), Li(+), and possibly Cl(-). They are reversibly blocked by zinc ion (Zn(2+)), and tromethamine (tris), and irreversibly by aluminum ion (Al(3+)). Congo red inhibits channel formation, but does not block inserted channels. Although much evidence implicates Abeta peptides in the neurotoxicity of AD, no other toxic mechanism has been demonstrated to be the underlying etiology of AD. Channel formation by several other amyloid peptides lends credence to the notion that this is a critical mechanism of cytotoxicity.

  15. /sup 3/H)Nitrendipine binding to calcium channels in bovine and rat pituitary

    Energy Technology Data Exchange (ETDEWEB)

    Titeler, M.; De Souza, E.B.; Kuhar, M.J.

    1985-06-01

    (/sup 3/H)Nitrendipine was used to label sites in homogenates of bovine anterior and neurointermediate lobes of the pituitary gland. The amount of specific binding in the anterior lobe was 1.82 +/- 0.30 pmol/g wet weight of tissue and the KD was 1.44 +/- 0.02 X 10(-10) M. Preliminary experiments indicated a similar amount of binding in bovine neurointermediate lobe. In competition studies nimodipine and nisoldipine (two potent voltage-sensitive calcium channel blockers) displayed IC50 values of 1.6 and 6.8 X 10(-10) M, respectively. Verapamil and the verapamil-like calcium channel blockers D-600 and tiapamil competed in a complex manner for the (/sup 3/H)nitrendipine specific binding to bovine anterior pituitary homogenates. Autoradiographical studies demonstrated specific (/sup 3/H)nitrendipine binding sites distributed approximately equally in the anterior and posterior lobes, but not in the intermediate lobe of the rat pituitary. In general the properties of (/sup 3/H)nitrendipine binding in the pituitary tissue resemble strongly the properties of (/sup 3/H)nitrendipine binding in the brain which is believed to be to voltage-sensitive calcium channels. These results provide support for the hypothesis that calcium channels are involved in pituitary hormone secretion and that drugs that interact with calcium channels may modulate the secretory process directly at the level of the pituitary.

  16. L-type calcium channels regulate filopodia stability and cancer cell invasion downstream of integrin signalling.

    Science.gov (United States)

    Jacquemet, Guillaume; Baghirov, Habib; Georgiadou, Maria; Sihto, Harri; Peuhu, Emilia; Cettour-Janet, Pierre; He, Tao; Perälä, Merja; Kronqvist, Pauliina; Joensuu, Heikki; Ivaska, Johanna

    2016-12-02

    Mounting in vitro, in vivo and clinical evidence suggest an important role for filopodia in driving cancer cell invasion. Using a high-throughput microscopic-based drug screen, we identify FDA-approved calcium channel blockers (CCBs) as potent inhibitors of filopodia formation in cancer cells. Unexpectedly, we discover that L-type calcium channels are functional and frequently expressed in cancer cells suggesting a previously unappreciated role for these channels during tumorigenesis. We further demonstrate that, at filopodia, L-type calcium channels are activated by integrin inside-out signalling, integrin activation and Src. Moreover, L-type calcium channels promote filopodia stability and maturation into talin-rich adhesions through the spatially restricted regulation of calcium entry and subsequent activation of the protease calpain-1. Altogether we uncover a novel and clinically relevant signalling pathway that regulates filopodia formation in cancer cells and propose that cycles of filopodia stabilization, followed by maturation into focal adhesions, directs cancer cell migration and invasion.

  17. Voltage gated calcium channels negatively regulate protective immunity to Mycobacterium tuberculosis.

    Directory of Open Access Journals (Sweden)

    Shashank Gupta

    Full Text Available Mycobacterium tuberculosis modulates levels and activity of key intracellular second messengers to evade protective immune responses. Calcium release from voltage gated calcium channels (VGCC regulates immune responses to pathogens. In this study, we investigated the roles of VGCC in regulating protective immunity to mycobacteria in vitro and in vivo. Inhibiting L-type or R-type VGCC in dendritic cells (DCs either using antibodies or by siRNA increased calcium influx in an inositol 1,4,5-phosphate and calcium release calcium activated channel dependent mechanism that resulted in increased expression of genes favoring pro-inflammatory responses. Further, VGCC-blocked DCs activated T cells that in turn mediated killing of M. tuberculosis inside macrophages. Likewise, inhibiting VGCC in infected macrophages and PBMCs induced calcium influx, upregulated the expression of pro-inflammatory genes and resulted in enhanced killing of intracellular M. tuberculosis. Importantly, compared to healthy controls, PBMCs of tuberculosis patients expressed higher levels of both VGCC, which were significantly reduced following chemotherapy. Finally, blocking VGCC in vivo in M. tuberculosis infected mice using specific antibodies increased intracellular calcium and significantly reduced bacterial loads. These results indicate that L-type and R-type VGCC play a negative role in M. tuberculosis infection by regulating calcium mobilization in cells that determine protective immunity.

  18. Voltage-gated calcium channels of Paramecium cilia.

    Science.gov (United States)

    Lodh, Sukanya; Yano, Junji; Valentine, Megan S; Van Houten, Judith L

    2016-10-01

    Paramecium cells swim by beating their cilia, and make turns by transiently reversing their power stroke. Reversal is caused by Ca2+ entering the cilium through voltage-gated Ca2+ (CaV) channels that are found exclusively in the cilia. As ciliary Ca2+ levels return to normal, the cell pivots and swims forward in a new direction. Thus, the activation of the CaV channels causes cells to make a turn in their swimming paths. For 45 years, the physiological characteristics of the Paramecium ciliary CaV channels have been known, but the proteins were not identified until recently, when the P. tetraurelia ciliary membrane proteome was determined. Three CaVα1 subunits that were identified among the proteins were cloned and confirmed to be expressed in the cilia. We demonstrate using RNA interference that these channels function as the ciliary CaV channels that are responsible for the reversal of ciliary beating. Furthermore, we show that Pawn (pw) mutants of Paramecium that cannot swim backward for lack of CaV channel activity do not express any of the three CaV1 channels in their ciliary membrane, until they are rescued from the mutant phenotype by expression of the wild-type PW gene. These results reinforce the correlation of the three CaV channels with backward swimming through ciliary reversal. The PwB protein, found in endoplasmic reticulum fractions, co-immunoprecipitates with the CaV1c channel and perhaps functions in trafficking. The PwA protein does not appear to have an interaction with the channel proteins but affects their appearance in the cilia. © 2016. Published by The Company of Biologists Ltd.

  19. Spatial distribution of calcium-gated chloride channels in olfactory cilia.

    Science.gov (United States)

    French, Donald A; Badamdorj, Dorjsuren; Kleene, Steven J

    2010-12-30

    In vertebrate olfactory receptor neurons, sensory cilia transduce odor stimuli into changes in neuronal membrane potential. The voltage changes are primarily caused by the sequential openings of two types of channel: a cyclic-nucleotide-gated (CNG) cationic channel and a calcium-gated chloride channel. In frog, the cilia are 25 to 200 µm in length, so the spatial distributions of the channels may be an important determinant of odor sensitivity. To determine the spatial distribution of the chloride channels, we recorded from single cilia as calcium was allowed to diffuse down the length of the cilium and activate the channels. A computational model of this experiment allowed an estimate of the spatial distribution of the chloride channels. On average, the channels were concentrated in a narrow band centered at a distance of 29% of the ciliary length, measured from the base of the cilium. This matches the location of the CNG channels determined previously. This non-uniform distribution of transduction proteins is consistent with similar findings in other cilia. On average, the two types of olfactory transduction channel are concentrated in the same region of the cilium. This may contribute to the efficient detection of weak stimuli.

  20. Oxidative Regulation of Large Conductance Calcium-Activated Potassium Channels

    Science.gov (United States)

    Tang, Xiang D.; Daggett, Heather; Hanner, Markus; Garcia, Maria L.; McManus, Owen B.; Brot, Nathan; Weissbach, Herbert; Heinemann, Stefan H.; Hoshi, Toshinori

    2001-01-01

    Reactive oxygen/nitrogen species are readily generated in vivo, playing roles in many physiological and pathological conditions, such as Alzheimer's disease and Parkinson's disease, by oxidatively modifying various proteins. Previous studies indicate that large conductance Ca2+-activated K+ channels (BKCa or Slo) are subject to redox regulation. However, conflicting results exist whether oxidation increases or decreases the channel activity. We used chloramine-T, which preferentially oxidizes methionine, to examine the functional consequences of methionine oxidation in the cloned human Slo (hSlo) channel expressed in mammalian cells. In the virtual absence of Ca2+, the oxidant shifted the steady-state macroscopic conductance to a more negative direction and slowed deactivation. The results obtained suggest that oxidation enhances specific voltage-dependent opening transitions and slows the rate-limiting closing transition. Enhancement of the hSlo activity was partially reversed by the enzyme peptide methionine sulfoxide reductase, suggesting that the upregulation is mediated by methionine oxidation. In contrast, hydrogen peroxide and cysteine-specific reagents, DTNB, MTSEA, and PCMB, decreased the channel activity. Chloramine-T was much less effective when concurrently applied with the K+ channel blocker TEA, which is consistent with the possibility that the target methionine lies within the channel pore. Regulation of the Slo channel by methionine oxidation may represent an important link between cellular electrical excitability and metabolism. PMID:11222629

  1. Neurotransmitter Release Can Be Stabilized by a Mechanism That Prevents Voltage Changes Near the End of Action Potentials from Affecting Calcium Currents.

    Science.gov (United States)

    Clarke, Stephen G; Scarnati, Matthew S; Paradiso, Kenneth G

    2016-11-09

    postsynaptic responses. We hypothesized that afterpotentials, which often follow APs, affect calcium entry and neurotransmitter release. We tested this in calyx of Held nerve terminals, which allow simultaneous recording of presynaptic calcium currents and postsynaptic responses. Surprisingly, presynaptic afterpotentials did not alter calcium current or neurotransmitter release. We show that the AP falling phase causes afterpotential-induced changes in electrical driving force and calcium channel gating to cancel each other out. This mechanism regulates calcium entry at the end of APs and therefore stabilizes synaptic transmission. This also stabilizes responses when the presynaptic resting potential changes. Copyright © 2016 the authors 0270-6474/16/3611559-14$15.00/0.

  2. How voltage-gated calcium channels gate forms of homeostatic synaptic plasticity

    Directory of Open Access Journals (Sweden)

    C. Andrew eFrank

    2014-02-01

    Full Text Available Throughout life, animals face a variety of challenges such as developmental growth, the presence of toxins, or changes in temperature. Neuronal circuits and synapses respond to challenges by executing an array of neuroplasticity paradigms. Some paradigms allow neurons to up- or downregulate activity outputs, while countervailing ones ensure that outputs remain within appropriate physiological ranges. A growing body of evidence suggests that homeostatic synaptic plasticity (HSP is critical in the latter case. Voltage-gated calcium channels gate forms of HSP. Presynaptically, the aggregate data show that when synapse activity is weakened, homeostatic signaling systems can act to correct impairments, in part by increasing calcium influx through presynaptic CaV2-type channels. Increased calcium influx is often accompanied by parallel increases in the size of active zones and the size of the readily releasable pool of presynaptic vesicles. These changes coincide with homeostatic enhancements of neurotransmitter release. Postsynaptically, there is a great deal of evidence that reduced network activity and loss of calcium influx through CaV1-type calcium channels also results in adaptive homeostatic signaling. Some adaptations drive presynaptic enhancements of vesicle pool size and turnover rate via retrograde signaling, as well as de novo insertion of postsynaptic neurotransmitter receptors. Enhanced calcium influx through CaV1 after network activation or single cell stimulation can elicit the opposite response – homeostatic depression via removal of excitatory receptors.There exist intriguing links between HSP and calcium channelopathies – such as forms of epilepsy, migraine, ataxia, and myasthenia. The episodic nature of some of these disorders suggests alternating periods of stable and unstable function. Uncovering information about how calcium channels are regulated in the context of HSP could be relevant toward understanding these and other

  3. Emerging roles of calcium-activated K channels and TRPV4 channels in lung oedema and pulmonary circulatory collapse.

    Science.gov (United States)

    Simonsen, U; Wandall-Frostholm, C; Oliván-Viguera, A; Köhler, R

    2017-01-01

    It has been suggested that the transient receptor potential cation (TRP) channel subfamily V (vanilloid) type 4 (TRPV4) and intermediate conductance calcium-activated potassium (KCa3.1) channels contribute to endothelium-dependent vasodilation. Here, we summarize very recent evidence for a synergistic interplay of TRPV4 and KCa3.1 channels in lung disease. Among the endothelial Ca2+ -permeable TRPs, TRPV4 is best characterized and produces arterial dilation by stimulating Ca2+ -dependent nitric oxide synthesis and endothelium-dependent hyperpolarization. Besides these roles, some TRP channels control endothelial/epithelial barrier functions and vascular integrity, while KCa3.1 channels provide the driving force required for Cl- and water transport in some cells and most secretory epithelia. The three conditions, increased pulmonary venous pressure caused by left heart disease, high inflation pressure and chemically induced lung injury, may lead to activation of TRPV4 channels followed by Ca2+ influx leading to activation of KCa3.1 channels in endothelial cells ultimately leading to acute lung injury. We find that a deficiency in KCa3.1 channels protects against TRPV4-induced pulmonary arterial relaxation, fluid extravasation, haemorrhage, pulmonary circulatory collapse and cardiac arrest in vivo. These data identify KCa3.1 channels as crucial molecular components in downstream TRPV4 signal transduction and as a potential target for the prevention of undesired fluid extravasation, vasodilatation and pulmonary circulatory collapse. © 2016 Scandinavian Physiological Society. Published by John Wiley & Sons Ltd.

  4. Nuclear-localized cyclic nucleotide-gated channels mediate symbiotic calcium oscillations.

    Science.gov (United States)

    Charpentier, Myriam; Sun, Jongho; Vaz Martins, Teresa; Radhakrishnan, Guru V; Findlay, Kim; Soumpourou, Eleni; Thouin, Julien; Véry, Anne-Aliénor; Sanders, Dale; Morris, Richard J; Oldroyd, Giles E D

    2016-05-27

    Nuclear-associated Ca(2+) oscillations mediate plant responses to beneficial microbial partners--namely, nitrogen-fixing rhizobial bacteria that colonize roots of legumes and arbuscular mycorrhizal fungi that colonize roots of the majority of plant species. A potassium-permeable channel is known to be required for symbiotic Ca(2+) oscillations, but the calcium channels themselves have been unknown until now. We show that three cyclic nucleotide-gated channels in Medicago truncatula are required for nuclear Ca(2+) oscillations and subsequent symbiotic responses. These cyclic nucleotide-gated channels are located at the nuclear envelope and are permeable to Ca(2+) We demonstrate that the cyclic nucleotide-gated channels form a complex with the postassium-permeable channel, which modulates nuclear Ca(2+) release. These channels, like their counterparts in animal cells, might regulate multiple nuclear Ca(2+) responses to developmental and environmental conditions. Copyright © 2016, American Association for the Advancement of Science.

  5. L-type calcium channel targeting and local signalling in cardiac myocytes.

    Science.gov (United States)

    Shaw, Robin M; Colecraft, Henry M

    2013-05-01

    In the heart, Ca(2+) influx via Ca(V)1.2 L-type calcium channels (LTCCs) is a multi-functional signal that triggers muscle contraction, controls action potential duration, and regulates gene expression. The use of LTCC Ca(2+) as a multi-dimensional signalling molecule in the heart is complicated by several aspects of cardiac physiology. Cytosolic Ca(2+) continuously cycles between ~100 nM and ~1 μM with each heartbeat due to Ca(2+) linked signalling from LTCCs to ryanodine receptors. This rapid cycling raises the question as to how cardiac myocytes distinguish the Ca(2+) fluxes originating through L-type channels that are dedicated to contraction from Ca(2+) fluxes originating from other L-type channels that are used for non-contraction-related signalling. In general, disparate Ca(2+) sources in cardiac myocytes such as current through differently localized LTCCs as well as from IP3 receptors can signal selectively to Ca(2+)-dependent effectors in local microdomains that can be impervious to the cytoplasmic Ca(2+) transients that drive contraction. A particular challenge for diversified signalling via cardiac LTCCs is that they are voltage-gated and, therefore, open and presumably flood their microdomains with Ca(2+) with each action potential. Thus spatial localization of Cav1.2 channels to different types of microdomains of the ventricular cardiomyocyte membrane as well as the existence of particular macromolecular complexes in each Cav1.2 microdomain are important to effect different types of Cav1.2 signalling. In this review we examine aspects of Cav1.2 structure, targeting and signalling in two specialized membrane microdomains--transverse tubules and caveolae.

  6. Zn2+Interaction with Alzheimer Amyloid β Protein Calcium Channels

    National Research Council Canada - National Science Library

    Nelson Arispe; Harvey B. Pollard; Eduardo Rojas

    1996-01-01

    The Alzheimer disease 40-residue amyloid β protein (Aβ P[1-40]) forms cation-selective channels across acidic phospholipid bilayer membranes with spontaneous transitions over a wide range of conductances ranging from 40 to 4000 pS...

  7. A key role for STIM1 in store operated calcium channel activation in airway smooth muscle

    Directory of Open Access Journals (Sweden)

    Peel Samantha E

    2006-09-01

    Full Text Available Abstract Background Control of cytosolic calcium plays a key role in airway myocyte function. Changes in intracellular Ca2+ stores can modulate contractile responses, modulate proliferation and regulate synthetic activity. Influx of Ca2+ in non excitable smooth muscle is believed to be predominantly through store operated channels (SOC or receptor operated channels (ROC. Whereas agonists can activate both SOC and ROC in a range of smooth muscle types, the specific trigger for SOC activation is depletion of the sarcoplasmic reticulum Ca2+ stores. The mechanism underlying SOC activation following depletion of intracellular Ca2+ stores in smooth muscle has not been identified. Methods To investigate the roles of the STIM homologues in SOC activation in airway myocytes, specific siRNA sequences were utilised to target and selectively suppress both STIM1 and STIM2. Quantitative real time PCR was employed to assess the efficiency and the specificity of the siRNA mediated knockdown of mRNA. Activation of SOC was investigated by both whole cell patch clamp electrophysiology and a fluorescence based calcium assay. Results Transfection of 20 nM siRNA specific for STIM1 or 2 resulted in robust decreases (>70% of the relevant mRNA. siRNA targeted at STIM1 resulted in a reduction of SOC associated Ca2+ influx in response to store depletion by cyclopiazonic acid (60% or histamine but not bradykinin. siRNA to STIM2 had no effect on these responses. In addition STIM1 suppression resulted in a more or less complete abrogation of SOC associated inward currents assessed by whole cell patch clamp. Conclusion Here we show that STIM1 acts as a key signal for SOC activation following intracellular Ca2+ store depletion or following agonist stimulation with histamine in human airway myocytes. These are the first data demonstrating a role for STIM1 in a physiologically relevant, non-transformed endogenous expression cell model.

  8. Expanded alternative splice isoform profiling of the mouse Cav3.1/α1G T-type calcium channel

    Directory of Open Access Journals (Sweden)

    Ernst Wayne L

    2009-05-01

    Full Text Available Abstract Background Alternative splicing of low-voltage-activated T-type calcium channels contributes to the molecular and functional diversity mediating complex network oscillations in the normal brain. Transcript scanning of the human CACNA1G gene has revealed the presence of 11 regions within the coding sequence subjected to alternative splicing, some of which enhance T-type current. In mouse models of absence epilepsy, elevated T-type calcium currents without clear increases in channel expression are found in thalamic neurons that promote abnormal neuronal synchronization. To test whether enhanced T-type currents in these models reflect pathogenic alterations in channel splice isoforms, we determined the extent of alternative splicing of mouse Cacna1g transcripts and whether evidence of altered transcript splicing could be detected in mouse absence epilepsy models. Results Transcript scanning of the murine Cacna1g gene detected 12 regions encoding alternative splice isoforms of Cav3.1/α1G T-type calcium channels. Of the 12 splice sites, six displayed homology to the human CACNA1G splice sites, while six novel mouse-specific splicing events were identified, including one intron retention, three alternative acceptor sites, one alternative donor site, and one exon exclusion. In addition, two brain region-specific alternative splice patterns were observed in the cerebellum. Comparative analyses of brain regions from four monogenic absence epilepsy mouse models with altered thalamic T-type currents and wildtype controls failed to reveal differences in Cacna1g splicing patterns. Conclusion The determination of six novel alternative splice sites within the coding region of the mouse Cacna1g gene greatly expands the potential biophysical diversity of voltage-gated T-type channels in the mouse central nervous system. Although alternative splicing of Cav3.1/α1G channels does not explain the enhancement of T-type current identified in four mouse

  9. Effect of propionyl-L-carnitine on L-type calcium channels in human heart sarcolemma

    Energy Technology Data Exchange (ETDEWEB)

    Bevilacqua, M.; Vago, T.; Norbiato, G. (Servizio di Endocrinologia, Milano, (Italy))

    1991-02-01

    Propionyl-L-carnitine (PC) protects perfused rat hearts against damage by ischemia-reperfusion. Activation of L-type calcium channel play a role on ischemia-reperfusion damage. Therefore, we studied the effect of PC on some properties of L-type calcium channels in an in vitro preparation from human myocardium sarcolemma (from patients with idiopathic dilated cardiomyopathy). Binding of the L-type calcium channel blockers isradipine ({sup 3}H)-PN 200-110 (PN) to plasma membrane preparations revealed a single population of binding sites (total number: Bmax = 213 +/- 34 fM/mg protein and affinity: Kd = 152 +/- 19 nM; n = 6). The characteristics of these binding sites were evaluated in the presence and in the absence of Ca{sup 2}{sup +} and of calcium blockers (D-888, a verapamillike drug, and diltiazem). Incubation in a Ca{sup 2}{sup +}-containing buffer increased the affinity of PN binding sites. Binding sites for PN were modulated by organic calcium channel blockers; in competition isotherms at 37{degree}C, D-888 (desmethoxyverapamil) decreased the PN binding, whereas diltiazem increased it. These results strongly suggest that the site labelled by PN is the voltage-operated calcium channel of the human myocardium. The addition of PC (1 mM) to plasma membranes labelled with PN at 37{degree}C decreased the affinity of the binding; this effect was counteracted by the addition of Ca{sup 2}{sup +} to the medium. This result was consistent with a competition between Ca{sup 2}{sup +} and PC. The effect of PC incubation at 4{degree}C was the opposite; at this temperature PC increased the affinity of the binding sites and the effect was obscured by Ca{sup 2}{sup +}.

  10. Identifying Calcium Channels and Porters in Plant Membranes

    Energy Technology Data Exchange (ETDEWEB)

    Sze, Heven

    1998-04-01

    The overall objectives of the proposal submitted in 6/90 was to understand how Ca was transported across plant membranes, and how these transport pathways were regulated. Ca participates in many cellular processes, including the transduction of hormonal and environmental signals, secretion, and protein folding. These processes depend on the coordination of passive Ca fluxes via channels and active Ca pumps; however these transport pathways are poorly understood in plants. We had, therefore, proposed to identify and characterize Ca transport proteins, such as the inositol-1 ,4,5-trisphosphate (IP3)-sensitive Ca channels and Ca pumps. We have had difficulties characterizing and cloning the IP3-sensitive Ca channel, but have made considerable progress on the biochemical characterization, and partial purification of a 120 kD Ca-pumping ATPase. We have begun to determine the structure of Ca pumps by molecular cloning and have already obtained a partial cDNA with features characteristic of Ca pumps.

  11. Dynamic properties of calcium-activated chloride currents in Xenopus laevis oocytes.

    Science.gov (United States)

    M De la Fuente, Ildefonso; Malaina, Iker; Pérez-Samartín, Alberto; Boyano, María Dolores; Pérez-Yarza, Gorka; Bringas, Carlos; Villarroel, Álvaro; Fedetz, María; Arellano, Rogelio; Cortes, Jesus M; Martínez, Luis

    2017-02-13

    Chloride is the most abundant permeable anion in the cell, and numerous studies in the last two decades highlight the great importance and broad physiological role of chloride currents mediated anion transport. They participate in a multiplicity of key processes, as for instance, the regulation of electrical excitability, apoptosis, cell cycle, epithelial secretion and neuronal excitability. In addition, dysfunction of Cl(-) channels is involved in a variety of human diseases such as epilepsy, osteoporosis and different cancer types. Historically, chloride channels have been of less interest than the cation channels. In fact, there seems to be practically no quantitative studies of the dynamics of chloride currents. Here, for the first time, we have quantitatively studied experimental calcium-activated chloride fluxes belonging to Xenopus laevis oocytes, and the main results show that the experimental Cl(-) currents present an informational structure characterized by highly organized data sequences, long-term memory properties and inherent "crossover" dynamics in which persistent correlations arise at short time intervals, while anti-persistent behaviors become dominant in long time intervals. Our work sheds some light on the understanding of the informational properties of ion currents, a key element to elucidate the physiological functional coupling with the integrative dynamics of metabolic processes.

  12. Microdamage induced calcium efflux from bone matrix activates intracellular calcium signaling in osteoblasts via L-type and T-type voltage-gated calcium channels.

    Science.gov (United States)

    Jung, Hyungjin; Best, Makenzie; Akkus, Ozan

    2015-07-01

    Mechanisms by which bone microdamage triggers repair response are not completely understood. It has been shown that calcium efflux ([Ca(2+)]E) occurs from regions of bone undergoing microdamage. Such efflux has also been shown to trigger intracellular calcium signaling ([Ca(2+)]I) in MC3T3-E1 cells local to damaged regions. Voltage-gated calcium channels (VGCCs) are implicated in the entry of [Ca(2+)]E to the cytoplasm. We investigated the involvement of VGCC in the extracellular calcium induced intracellular calcium response (ECIICR). MC3T3-E1 cells were subjected to one dimensional calcium efflux from their basal aspect which results in an increase in [Ca(2+)]I. This increase was concomitant with membrane depolarization and it was significantly reduced in the presence of Bepridil, a non-selective VGCC inhibitor. To identify specific type(s) of VGCC in ECIICR, the cells were treated with selective inhibitors for different types of VGCC. Significant changes in the peak intensity and the number of [Ca(2+)]I oscillations were observed when L-type and T-type specific VGCC inhibitors (Verapamil and NNC55-0396, respectively) were used. So as to confirm the involvement of L- and T-type VGCC in the context of microdamage, cells were seeded on devitalized notched bone specimen, which were loaded to induce microdamage in the presence and absence of Verapamil and NNC55-0396. The results showed significant decrease in [Ca(2+)]I activity of cells in the microdamaged regions of bone when L- and T-type blockers were applied. This study demonstrated that extracellular calcium increase in association with damage depolarizes the cell membrane and the calcium ions enter the cell cytoplasm by L- and T-type VGCCs. Copyright © 2015 Elsevier Inc. All rights reserved.

  13. Anoctamin Calcium-Activated Chloride Channels May Modulate Inhibitory Transmission in the Cerebellar Cortex.

    Directory of Open Access Journals (Sweden)

    Weiping Zhang

    Full Text Available Calcium-activated chloride channels of the anoctamin (alias TMEM16 protein family fulfill critical functions in epithelial fluid transport, smooth muscle contraction and sensory signal processing. Little is known, however, about their contribution to information processing in the central nervous system. Here we examined the recent finding that a calcium-dependent chloride conductance impacts on GABAergic synaptic inhibition in Purkinje cells of the cerebellum. We asked whether anoctamin channels may underlie this chloride conductance. We identified two anoctamin channel proteins, ANO1 and ANO2, in the cerebellar cortex. ANO1 was expressed in inhibitory interneurons of the molecular layer and the granule cell layer. Both channels were expressed in Purkinje cells but, while ANO1 appeared to be retained in the cell body, ANO2 was targeted to the dendritic tree. Functional studies confirmed that ANO2 was involved in a calcium-dependent mode of ionic plasticity that reduces the efficacy of GABAergic synapses. ANO2 channels attenuated GABAergic transmission by increasing the postsynaptic chloride concentration, hence reducing the driving force for chloride influx. Our data suggest that ANO2 channels are involved in a Ca2+-dependent regulation of synaptic weight in GABAergic inhibition. Thus, in balance with the chloride extrusion mechanism via the co-transporter KCC2, ANO2 appears to regulate ionic plasticity in the cerebellum.

  14. Quasi-equilibrium channel model of an constant current arc

    OpenAIRE

    Gerasimov Alexander V.; Kirpichnikov Alexander P.

    2003-01-01

    The rather simple method of calculation of electronic and gas temperature in the channel of arc of plasma generator is offered. This method is based on self-consistent two-temperature channel model of an electric arc. The method proposed enables to obtain radial allocation of gas and electronic temperatures in a non-conducting zone of an constant current arc, for prescribed parameters of discharge (current intensity and power of the discharge), with enough good precision. The results obtained...

  15. Mechanism of magnesium activation of calcium-activated potassium channels.

    Science.gov (United States)

    Shi, Jingyi; Krishnamoorthy, Gayathri; Yang, Yanwu; Hu, Lei; Chaturvedi, Neha; Harilal, Dina; Qin, Jun; Cui, Jianmin

    2002-08-22

    Large-conductance (BK type) Ca(2+)-dependent K(+) channels are essential for modulating muscle contraction and neuronal activities such as synaptic transmission and hearing. BK channels are activated by membrane depolarization and intracellular Ca(2+) and Mg(2+) (refs 6-10). The energy provided by voltage, Ca(2+) and Mg(2+) binding are additive in activating the channel, suggesting that these signals open the activation gate through independent pathways. Here we report a molecular investigation of a Mg(2+)-dependent activation mechanism. Using a combined site-directed mutagenesis and structural analysis, we demonstrate that a structurally new Mg(2+)-binding site in the RCK/Rossman fold domain -- an intracellular structural motif that immediately follows the activation gate S6 helix -- is responsible for Mg(2+)-dependent activation. Mutations that impair or abolish Mg(2+) sensitivity do not affect Ca(2+) sensitivity, and vice versa. These results indicate distinct structural pathways for Mg(2+)- and Ca(2+)-dependent activation and suggest a possible mechanism for the coupling between Mg(2+) binding and channel opening.

  16. Functional and pharmacological consequences of the distribution of voltage-gated calcium channels in the renal blood vessels.

    Science.gov (United States)

    Hansen, P B L

    2013-04-01

    Calcium channel blockers are widely used to treat hypertension because they inhibit voltage-gated calcium channels that mediate transmembrane calcium influx in, for example, vascular smooth muscle and cardiomyocytes. The calcium channel family consists of several subfamilies, of which the L-type is usually associated with vascular contractility. However, the L-, T- and P-/Q-types of calcium channels are present in the renal vasculature and are differentially involved in controlling vascular contractility, thereby contributing to regulation of kidney function and blood pressure. In the preglomerular vascular bed, all the three channel families are present. However, the T-type channel is the only channel in cortical efferent arterioles which is in contrast to the juxtamedullary efferent arteriole, and that leads to diverse functional effects of L- and T-type channel inhibition. Furthermore, by different mechanisms, T-type channels may contribute to both constriction and dilation of the arterioles. Finally, P-/Q-type channels are involved in the regulation of human intrarenal arterial contractility. The calcium blockers used in the clinic affect not only L-type but also P-/Q- and T-type channels. Therefore, the distinct effect obtained by inhibiting a given subtype or set of channels under experimental settings should be considered when choosing a calcium blocker for treatment. T-type channels seem to be crucial for regulating the GFR and the filtration fraction. Use of blockers is expected to lead to preferential efferent vasodilation, reduction of glomerular pressure and proteinuria. Therefore, renovascular T-type channels might provide novel therapeutic targets, and may have superior renoprotective effects compared to conventional calcium blockers. Acta Physiologica © 2013 Scandinavian Physiological Society.

  17. Quasi-equilibrium channel model of an constant current arc

    Directory of Open Access Journals (Sweden)

    Gerasimov Alexander V.

    2003-01-01

    Full Text Available The rather simple method of calculation of electronic and gas temperature in the channel of arc of plasma generator is offered. This method is based on self-consistent two-temperature channel model of an electric arc. The method proposed enables to obtain radial allocation of gas and electronic temperatures in a non-conducting zone of an constant current arc, for prescribed parameters of discharge (current intensity and power of the discharge, with enough good precision. The results obtained can be used in model and engineering calculations to estimate gas and electronic temperatures in the channel of an arc plasma generator.

  18. Eugenol dilates rat cerebral arteries by inhibiting smooth muscle cell voltage-dependent calcium channels.

    Science.gov (United States)

    Peixoto-Neves, Dieniffer; Leal-Cardoso, Jose Henrique; Jaggar, Jonathan H

    2014-11-01

    Plants high in eugenol, a phenylpropanoid compound, are used as folk medicines to alleviate diseases including hypertension. Eugenol has been demonstrated to relax conduit and ear arteries and reduce systemic blood pressure, but mechanisms involved are unclear. Here, we studied eugenol regulation of resistance-size cerebral arteries that control regional brain blood pressure and flow and investigated mechanisms involved. We demonstrate that eugenol dilates arteries constricted by either pressure or membrane depolarization (60 mM K) in a concentration-dependent manner. Experiments performed using patch-clamp electrophysiology demonstrated that eugenol inhibited voltage-dependent calcium (Ca) currents, when using Ba as a charge carrier, in isolated cerebral artery smooth muscle cells. Eugenol inhibition of voltage-dependent Ca currents involved pore block, a hyperpolarizing shift (∼-10 mV) in voltage-dependent inactivation, an increase in the proportion of steady-state inactivating current, and acceleration of inactivation rate. In summary, our data indicate that eugenol dilates cerebral arteries by means of multimodal inhibition of voltage-dependent Ca channels.

  19. Single Ca(2+)-activated Cl(-) channel currents recorded from toad olfactory cilia.

    Science.gov (United States)

    Delgado, Ricardo; Mura, Casilda V; Bacigalupo, Juan

    2016-04-25

    Odor transduction, occurring in the chemosensory cilia of vertebrate olfactory sensory neurons, is triggered by guanosine triphosphate-coupled odor receptors and mediated by a cyclic adenosine monophosphate (cAMP) signaling cascade, where cAMP opens cationic non-selective cyclic nucleotide-gated (CNG) channels. Calcium enters through CNG gates Ca(2+)-activated Cl(-) channels, allowing a Cl(-) inward current that enhances the depolarization initiated by the CNG-dependent inward current. The anoctamin channel 2, ANO2, is considered the main Ca(2+)-activated Cl(-) channel of olfactory transduction. Although Ca(2+)-activated Cl(-) channel-dependent currents in olfactory sensory neurons were reported to be suppressed in ANO2-knockout mice, field potentials from their olfactory epithelium were only modestly diminished and their smell-dependent behavior was unaffected, suggesting the participation of additional Ca(2+)-activated Cl(-) channel types. The Bestrophin channel 2, Best2, was also detected in mouse olfactory cilia and ClCa4l, belonging to the ClCa family of Ca(2+)-activated Cl(-) channels, were found in rat cilia. Best2 knock-out mice present no electrophysiological or behavioral impairment, while the ClCa channels have not been functionally studied; therefore, the overall participation of all these channels in olfactory transduction remains unresolved. We explored the presence of detectable Ca(2+)-activated Cl(-) channels in toad olfactory cilia by recording from inside-out membrane patches excised from individual cilia and detected unitary Cl(-) current events with a pronounced Ca(2+) dependence, corresponding to 12 and 24 pS conductances, over tenfold higher than the aforementioned channels, and a approx. fivefold higher Ca(2+) affinity (K0.5 = 0.38 µM). Remarkably, we observed immunoreactivity to anti-ClCa and anti-ANO2 antibodies in the olfactory cilia, suggesting a possible cooperative function of both channel type in chemotransduction. These results

  20. Sarcoplasmic Reticulum Calcium Release Channels in Ventricles of Older Adult Hamsters

    Science.gov (United States)

    Nicholl, Peter A.; Howlett, Susan E.

    2006-01-01

    Whether the density of sarcoplasmic reticulum (SR) calcium release channels/ryanodine receptors in the heart declines with age is not clear. We investigated age-related changes in the density of [3H]-ryanodine receptors in crude ventricular homogenates, which contained all ligand binding sites in heart and in isolated junctional SR membranes.…

  1. The ethanol withdrawal syndrome: A role for dihydropyridine-sensitive calcium channels in neuronal hyperexcitability states

    Energy Technology Data Exchange (ETDEWEB)

    Whittington, M.A.

    1990-01-01

    This project investigated the effects of dihydropyridine calcium channel blockers on behavioral and electrophysiological aspects of ethanol withdrawal. The effects of the dihydropyridine (+)-PN 200-110, on changes in neuronal function during ethanol withdrawal, were compared with effects on changes caused by the GABAergic convulsant drug bicuculline. Behavioral correlates of ethanol withdrawal were measured in two strains of mice using a rating of handling-induced convulsions. Concurrent chronic treatment with ethanol and the dihydropyridine calcium channel blockers ([plus minus])-nitrendipine, ([plus minus])-nimodipine or ([plus minus])-PN 200-110 prevented withdrawal-induced increased in convulsive behavior. This effect was dose dependent. The duration of chronic treatment with calcium channel blocker affected the degree of protection against increases in convulsive behavior seen during ethanol withdrawal. Concurrent chronic treatment with ethanol, and the mixed calcium channel activator/blocker ([plus minus])-BAY K 8644, prevented ethanol withdrawal-induced increases in convulsive behavior. Single acute injections of nitrendipine immediately on cessation of chronic treatment with ethanol, or 2h later, reduced withdrawal-induced increases in convulsive behavior in a dose-dependent manner throughout the 12h test period. Slices isolated from mice after chronic ethanol treatment showed a complex, time-dependent pattern of changes in the above measurements, culminating in epileptiform discharges seen from 4h to 7h into withdrawal.

  2. [Expression of L-type calcium channel alpha1C subunit in adult rat heart].

    Science.gov (United States)

    Ou, Yan; Niu, Xiao-lin; Ren, Fu-xian; Zhang, Ying; Ling, Feng-dong

    2005-11-01

    To investigate the expression and distribution of L-type calcium channel alpha1C subunits in adult rat heart. HE staining was applied on the frozen sections of adult rat heart to identify the sinoatrial node (SAN), atrioventricular node (AVN), and posterior nodal extension (PNE). The protein expression of L-type calcium channel alpha1C in adult rat heart and its cellular localization were examined by Western blotting and immunohistochemistry, respectively. L-type calcium channel alpha1C subunit was immunolocalized on the membrane of the myocardial cells, and its expression increased gradually in the SAN, AVN, PNE, right atrium and right ventricle. The protein level of L-type calcium channel alpha1C in the AVN was similar to that in the PNE (P>0.05), and its level in the right atrium and ventricle were significantly higher than those in the SAN and AVN (Pchannel alpha1C subunit may play a role in the electrophysiological functions of the heart.

  3. The α2δ subunit and absence epilepsy: Beyond calcium channels?

    NARCIS (Netherlands)

    Celli, R.; Santolini, I.; Guiducci, M.; Luijtelaar, E.L.J.M. van; Parisi, P.; Striano, P.; Gradini, R.; Battaglia, G.; Ngomba, R.T.; Nicoletti, F.

    2017-01-01

    Spike-wave discharges, underlying absence seizures, are generated within a cortico-thalamo-cortical network that involves the somatosensory cortex, the reticular thalamic nucleus, and the ventrobasal thalamic nuclei. Activation of T-type voltage-sensitive calcium channels (VSCCs) contributes to the

  4. A cyclic GMP-dependent calcium-activated chloride current in smooth-muscle cells from rat mesenteric resistance arteries

    DEFF Research Database (Denmark)

    Matchkov, Vladimir; Aalkjær, Christian; Nilsson, Holger

    2004-01-01

    M) in the pipette solution. The current was found to be a calcium-activated chloride current with an absolute requirement for cyclic GMP (EC50 6.4 microM). The current could be activated by the constitutively active subunit of PKG. Current activation was blocked by the protein kinase G antagonist Rp-8-Br-PET...... no voltage or time dependence. It was inhibited by nickel and zinc ions in the micromolar range, but was unaffected by cobalt and had a low sensitivity to inhibition by the chloride channel blockers niflumic acid, DIDS, and IAA-94. The properties of this current in mesenteric artery smooth-muscle cells...

  5. Absence epilepsy in tottering mutant mice is associated with calcium channel defects.

    Science.gov (United States)

    Fletcher, C F; Lutz, C M; O'Sullivan, T N; Shaughnessy, J D; Hawkes, R; Frankel, W N; Copeland, N G; Jenkins, N A

    1996-11-15

    Mutations at the mouse tottering (tg) locus cause a delayed-onset, recessive neurological disorder resulting in ataxia, motor seizures, and behavioral absence seizures resembling petit mal epilepsy in humans. A more severe allele, leaner (tg(la)), also shows a slow, selective degeneration of cerebellar neurons. By positional cloning, we have identified an alpha1A voltage-sensitive calcium channel gene that is mutated in tg and tg(la) mice. The alpha1A gene is widely expressed in the central nervous system with prominent, uniform expression in the cerebellum. alpha1A expression does not mirror the localized pattern of cerebellar degeneration observed in tg(la) mice, providing evidence for regional differences in biological function of alpha1A channels. These studies define the first mutations in a mammalian central nervous system-specific voltage-sensitive calcium channel and identify the first gene involved in absence epilepsy.

  6. Reporting sodium channel activity using calcium flux: pharmacological promiscuity of cardiac Nav1.5.

    Science.gov (United States)

    Zhang, Hongkang; Zou, Beiyan; Du, Fang; Xu, Kaiping; Li, Min

    2015-02-01

    Voltage-gated sodium (Nav) channels are essential for membrane excitability and represent therapeutic targets for treating human diseases. Recent reports suggest that these channels, e.g., Nav1.3 and Nav1.5, are inhibited by multiple structurally distinctive small molecule drugs. These studies give reason to wonder whether these drugs collectively target a single site or multiple sites in manifesting such pharmacological promiscuity. We thus investigate the pharmacological profile of Nav1.5 through systemic analysis of its sensitivity to diverse compound collections. Here, we report a dual-color fluorescent method that exploits a customized Nav1.5 [calcium permeable Nav channel, subtype 5 (SoCal5)] with engineered-enhanced calcium permeability. SoCal5 retains wild-type (WT) Nav1.5 pharmacological profiles. WT SoCal5 and SoCal5 with the local anesthetics binding site mutated (F1760A) could be expressed in separate cells, each with a different-colored genetically encoded calcium sensor, which allows a simultaneous report of compound activity and site dependence. The pharmacological profile of SoCal5 reveals a hit rate (>50% inhibition) of around 13% at 10 μM, comparable to that of hERG. The channel activity is susceptible to blockage by known drugs and structurally diverse compounds. The broad inhibition profile is highly dependent on the F1760 residue in the inner cavity, which is a residue conserved among all nine subtypes of Nav channels. Both promiscuity and dependence on F1760 seen in Nav1.5 were replicated in Nav1.4. Our evidence of a broad inhibition profile of Nav channels suggests a need to consider off-target effects on Nav channels. The site-dependent promiscuity forms a foundation to better understand Nav channels and compound interactions. Copyright © 2014 by The American Society for Pharmacology and Experimental Therapeutics.

  7. Calcium channels and pumps in cancer: changes and consequences.

    Science.gov (United States)

    Monteith, Gregory R; Davis, Felicity M; Roberts-Thomson, Sarah J

    2012-09-14

    Increases in intracellular free Ca(2+) play a major role in many cellular processes. The deregulation of Ca(2+) signaling is a feature of a variety of diseases, and modulators of Ca(2+) signaling are used to treat conditions as diverse as hypertension to pain. The Ca(2+) signal also plays a role in processes important in cancer, such as proliferation and migration. Many studies in cancer have identified alterations in the expression of proteins involved in the movement of Ca(2+) across the plasma membrane and subcellular organelles. In some cases, these Ca(2+) channels or pumps are potential therapeutic targets for specific cancer subtypes or correlate with prognosis.

  8. Calcium Channels and Pumps in Cancer: Changes and Consequences*

    Science.gov (United States)

    Monteith, Gregory R.; Davis, Felicity M.; Roberts-Thomson, Sarah J.

    2012-01-01

    Increases in intracellular free Ca2+ play a major role in many cellular processes. The deregulation of Ca2+ signaling is a feature of a variety of diseases, and modulators of Ca2+ signaling are used to treat conditions as diverse as hypertension to pain. The Ca2+ signal also plays a role in processes important in cancer, such as proliferation and migration. Many studies in cancer have identified alterations in the expression of proteins involved in the movement of Ca2+ across the plasma membrane and subcellular organelles. In some cases, these Ca2+ channels or pumps are potential therapeutic targets for specific cancer subtypes or correlate with prognosis. PMID:22822055

  9. Calcium-activated SK channels control firing regularity by modulating sodium channel availability in midbrain dopamine neurons.

    Science.gov (United States)

    Iyer, Rajeshwari; Ungless, Mark A; Faisal, Aldo A

    2017-07-12

    Dopamine neurons in the substantia nigra pars compacta and ventral tegmental area regulate behaviours such as reward-related learning, and motor control. Dysfunction of these neurons is implicated in Schizophrenia, addiction to drugs, and Parkinson's disease. While some dopamine neurons fire single spikes at regular intervals, others fire irregular single spikes interspersed with bursts. Pharmacological inhibition of calcium-activated potassium (SK) channels increases the variability in their firing pattern, sometimes also increasing the number of spikes fired in bursts, indicating that SK channels play an important role in maintaining dopamine neuron firing regularity and burst firing. However, the exact mechanisms underlying these effects are still unclear. Here, we develop a biophysical model of a dopamine neuron incorporating ion channel stochasticity that enabled the analysis of availability of ion channels in multiple states during spiking. We find that decreased firing regularity is primarily due to a significant decrease in the AHP that in turn resulted in a reduction in the fraction of available voltage-gated sodium channels due to insufficient recovery from inactivation. Our model further predicts that inhibition of SK channels results in a depolarisation of action potential threshold along with an increase in its variability.

  10. Putative calcium-binding domains of the Caenorhabditis elegans BK channel are dispensable for intoxication and ethanol activation

    Science.gov (United States)

    Davis, S. J.; Scott, L. L.; Ordemann, G.; Philpo, A.; Cohn, J.; Pierce-Shimomura, J. T.

    2016-01-01

    Alcohol modulates the highly conserved, voltage- and calcium-activated potassium (BK) channel, which contributes to alcohol-mediated behaviors in species from worms to humans. Previous studies have shown that the calcium-sensitive domains, RCK1 and the Ca2+ bowl, are required for ethanol activation of the mammalian BK channel in vitro. In the nematode Caenorhabditis elegans, ethanol activates the BK channel in vivo, and deletion of the worm BK channel, SLO-1, confers strong resistance to intoxication. To determine if the conserved RCK1 and calcium bowl domains were also critical for intoxication and basal BK channel-dependent behaviors in C. elegans, we generated transgenic worms that express mutated SLO-1 channels predicted to have the RCK1, Ca2+ bowl or both domains rendered insensitive to calcium. As expected, mutating these domains inhibited basal function of SLO-1 in vivo as neck and body curvature of these mutants mimicked that of the BK null mutant. Unexpectedly, however, mutating these domains singly or together in SLO-1 had no effect on intoxication in C. elegans. Consistent with these behavioral results, we found that ethanol activated the SLO-1 channel in vitro with or without these domains. By contrast, in agreement with previous in vitro findings, C. elegans harboring a human BK channel with mutated calcium-sensing domains displayed resistance to intoxication. Thus, for the worm SLO-1 channel, the putative calcium-sensitive domains are critical for basal in vivo function but unnecessary for in vivo ethanol action. PMID:26113050

  11. Expression of calcium channel CaV1.3 in cat spinal cord: light and electron microscopic immunohistochemical study

    DEFF Research Database (Denmark)

    Zhang, Mengliang; Møller, Morten; Broman, Jonas

    2008-01-01

    In spinal neurons, plateau potentials serve to amplify neuronal input signals. To a large extent, the underlying persistent inward current is mediated by a subtype of the L-type calcium channel (Ca(V)1.3). In the present investigation, we have studied its distribution and cellular localization...... enlargements and the phrenic nucleus in cervical, Clarke's nucleus in lower thoracic and upper lumbar, and Onuf's nucleus in upper sacral segments. At the ultrastructural level, Ca(V)1.3-immunoreactive products were found in neuronal somata and dendrites of different sizes. In the soma, they were predominantly...

  12. Effects of low-dose ionising radiation on pituitary adenoma: is there a role for L-type calcium channel?

    Energy Technology Data Exchange (ETDEWEB)

    Soares, Marcella Araugio; Santos, Raquel Gouvea dos [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN), Belo Horizonte, MG (Brazil). Lab. de Radiobiologia]. E-mail: santosr@cdtn.br

    2005-10-15

    Pituitary adenomas constitute about 6-18% of brain tumours in adults. Activation of voltage gated calcium currents can account for growth hormone over secretion in some GH-secreting pituitary adenomas that produce an acromegaly appearance and increase mortality. Ca{sup 2+} ions, as mediators of intracellular signalling, are crucial for the development of apoptosis. However, the role of [Ca{sup 2+}] in the development of apoptosis is ambiguous. In this study, the effects of low-dose ionising gamma radiation ({sup 60} Co) on rat pituitary adenoma cells survival and proliferation and the role of calcium channels on the apoptosis radio-induced were evaluated. Doses as low as 3 Gy were found to inhibit GH3 cell proliferation. Even though there was a significant number of live cells,168 hours following irradiation, they were not able to proliferate. The results indicate that the blockade of extracellular calcium influx through these channels does not interfere in the radiation-induced apoptosis in GH3 cells. (author)

  13. Seeing the forest through the trees: towards a unified view on physiological calcium regulation of voltage-gated sodium channels.

    Science.gov (United States)

    Van Petegem, Filip; Lobo, Paolo A; Ahern, Christopher A

    2012-12-05

    Voltage-gated sodium channels (Na(V)s) underlie the upstroke of the action potential in the excitable tissues of nerve and muscle. After opening, Na(V)s rapidly undergo inactivation, a crucial process through which sodium conductance is negatively regulated. Disruption of inactivation by inherited mutations is an established cause of lethal cardiac arrhythmia, epilepsy, or painful syndromes. Intracellular calcium ions (Ca(2+)) modulate sodium channel inactivation, and multiple players have been suggested in this process, including the cytoplasmic Na(V) C-terminal region including two EF-hands and an IQ motif, the Na(V) domain III-IV linker, and calmodulin. Calmodulin can bind to the IQ domain in both Ca(2+)-bound and Ca(2+)-free conditions, but only to the DIII-IV linker in a Ca(2+)-loaded state. The mechanism of Ca(2+) regulation, and its composite effect(s) on channel gating, has been shrouded in much controversy owing to numerous apparent experimental inconsistencies. Herein, we attempt to summarize these disparate data and propose a novel, to our knowledge, physiological mechanism whereby calcium ions promote sodium current facilitation due to Ca(2+) memory at high-action-potential frequencies where Ca(2+) levels may accumulate. The available data suggest that this phenomenon may be disrupted in diseases where cytoplasmic calcium ion levels are chronically high and where targeted phosphorylation may decouple the Ca(2+) regulatory machinery. Many Na(V) disease mutations associated with electrical dysfunction are located in the Ca(2+)-sensing machinery and misregulation of Ca(2+)-dependent channel modulation is likely to contribute to disease phenotypes. Copyright © 2012 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  14. Activation of L-type calcium channel in twitch skeletal muscle fibres of the frog.

    Science.gov (United States)

    Francini, F; Bencini, C; Squecco, R

    1996-07-01

    1. The activation of the L-type calcium current (ICa) was studied in normally polarized (-100 mV) cut skeletal muscle fibres of the frog with the double Vaseline-gap voltage-clamp technique. Both external and internal solutions were Ca2+ buffered. Solutions were made in order to minimize all but the Ca2+ current. 2. The voltage-dependent components of the time course of activation were determined by two procedures: fast and slow components were evaluated by multiexponential fitting to current traces elicited by long voltage pulses (5 s) after removing inactivation; fast components were also determined by short voltage pulses having different duration (0.5-70 ms). 3. The components of deactivation were evaluated after removing the charge-movement current from the total tail current by the difference between two short (50 and 70 ms) voltage pulses to 10 mV, moving the same intramembrane charge. Two exponential components, fast and slow (time constants, 6 +/- 0.3 and 90 +/- 7 ms at -100 mV; n = 26), were found. 4. The time onset of ICa was evaluated either by multiexponential fitting to the ICa activation or by pulses of different duration to test the beginning of the 'on' and 'off' inequality. This was at about 2 ms, denoting that it was very early. 5. The time constant vs. voltage plots indicated the presence of four voltage-dependent components in the activation pathway. Various kinetic models are discussed. Models with independent transitions, like a Hodgkin-Huxley scheme, were excluded. Suitable models were a five-state sequential and a four-state cyclic with a branch scheme. The latter gave the best simulation of the data. 6. The steady-state activation curve saturated at high potentials. It had a half-voltage value of 1 +/- 0.2 mV and the opening probability was only 0.82 +/- 0.2 at 20 mV (n = 32). This result implies a larger number of functional calcium channels than was previously supposed and is in agreement with the number of dihydropyridine (DHP

  15. Regulation of calcium signalling by docosahexaenoic acid in human T-cells. Implication of CRAC channels.

    Science.gov (United States)

    Bonin, A; Khan, N A

    2000-02-01

    We elucidated the role of docosahexaenoic acid (DHA) on the increases in free intracellular calcium concentrations, [Ca(2+)]i, in human (Jurkat) T-cell lines. DHA evoked an increase in [Ca(2+)]i in a dose-dependent manner in these cells. Anti-CD3 antibody, known to stimulate increases in Ca(2+) from endoplasmic reticulum (ER) via the production of inositol trisphosphate, also evoked increases in [Ca(2+)]i in Jurkat T-cells. We also used thapsigargin which inhibits Ca(2+)-ATPase of the ER and, therefore, increases Ca(2+) in the cytosol. Interestingly, addition of DHA during the thapsigargin-induced peak response exerted an additive effect on the increases in [Ca(2+)]i in human T-cells, indicating that the mechanisms of action of these two agents are different. However, the DHA-induced calcium response was not observed when this agent was added during the anti-CD3-induced calcium peak, though its addition resulted in a prolonged and sustained calcium response as a function of time, suggesting that DHA recruits calcium, in part, from the ER pool and the prolonged response may be due to Ca(2+) influx. In the medium containing 0% Ca(2+), the DHA-evoked response on the increases in [Ca(2+)]i was significantly curtailed as compared to that in 100% Ca(2+) medium, supporting the notion that the response of the DHA is also due, in part, to the opening of calcium channels. Furthermore, preincubation of cells with tyrphostin A9, an inhibitor of Ca(2+) release-activated Ca(2+) (CRAC) channels also significantly curtailed the DHA-induced sustained response on the increases in [Ca(2+)]i in these cells. These results suggest that DHA induces an increase in [Ca(2+)]i via the ER pool and the opening of CRAC channels in human T-cells.

  16. Ryanodine receptor/calcium release channel PKA phosphorylation: A critical mediator of heart failure progression

    Science.gov (United States)

    Wehrens, Xander H. T.; Lehnart, Stephan E.; Reiken, Steven; Vest, John A.; Wronska, Anetta; Marks, Andrew R.

    2006-01-01

    Defective regulation of the cardiac ryanodine receptor (RyR2)/calcium release channel, required for excitation-contraction coupling in the heart, has been linked to cardiac arrhythmias and heart failure. For example, diastolic calcium “leak” via RyR2 channels in the sarcoplasmic reticulum has been identified as an important factor contributing to impaired contractility in heart failure and ventricular arrhythmias that cause sudden cardiac death. In patients with heart failure, chronic activation of the “fight or flight” stress response leads to protein kinase A (PKA) hyperphosphorylation of RyR2 at Ser-2808. PKA phosphorylation of RyR2 Ser-2808 reduces the binding affinity of the channel-stabilizing subunit calstabin2, resulting in leaky RyR2 channels. We developed RyR2-S2808A mice to determine whether Ser-2808 is the functional PKA phosphorylation site on RyR2. Furthermore, mice in which the RyR2 channel cannot be PKA phosphorylated were relatively protected against the development of heart failure after myocardial infarction. Taken together, these data show that PKA phosphorylation of Ser-2808 on the RyR2 channel appears to be a critical mediator of progressive cardiac dysfunction after myocardial infarction. PMID:16407108

  17. Accelerated inactivation of the L-type calcium current due to a mutation in CACNB2b underlies Brugada syndrome

    DEFF Research Database (Denmark)

    Cordeiro, Jonathan M; Marieb, Mark; Pfeiffer, Ryan

    2009-01-01

    S in which loss of function is caused by accelerated inactivation of I(Ca). The proband, a 32 year old male, displayed a Type I ST segment elevation in two right precordial ECG leads following a procainamide challenge. EP study was positive with induction of polymorphic VT/VF. Interrogation of implanted ICD...... significantly faster in mutant channels between 0 and + 20 mV. Action potential voltage clamp experiments showed that total charge was reduced by almost half compared to WT. We report the first BrS mutation in CaCNB2b resulting in accelerated inactivation of L-type calcium channel current. Our results suggest...

  18. Clofazimine inhibits human Kv1.3 potassium channel by perturbing calcium oscillation in T lymphocytes.

    Directory of Open Access Journals (Sweden)

    Yunzhao R Ren

    Full Text Available The Kv1.3 potassium channel plays an essential role in effector memory T cells and has been implicated in several important autoimmune diseases including multiple sclerosis, psoriasis and type 1 diabetes. A number of potent small molecule inhibitors of Kv1.3 channel have been reported, some of which were found to be effective in various animal models of autoimmune diseases. We report herein the identification of clofazimine, a known anti-mycobacterial drug, as a novel inhibitor of human Kv1.3. Clofazimine was initially identified as an inhibitor of intracellular T cell receptor-mediated signaling leading to the transcriptional activation of human interleukin-2 gene in T cells from a screen of the Johns Hopkins Drug Library. A systematic mechanistic deconvolution revealed that clofazimine selectively blocked the Kv1.3 channel activity, perturbing the oscillation frequency of the calcium-release activated calcium channel, which in turn led to the inhibition of the calcineurin-NFAT signaling pathway. These effects of clofazimine provide the first line of experimental evidence in support of a causal relationship between Kv1.3 and calcium oscillation in human T cells. Furthermore, clofazimine was found to be effective in blocking human T cell-mediated skin graft rejection in an animal model in vivo. Together, these results suggest that clofazimine is a promising immunomodulatory drug candidate for treating a variety of autoimmune disorders.

  19. Iron overload and apoptosis of HL-1 cardiomyocytes: effects of calcium channel blockade.

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    Mei-pian Chen

    Full Text Available Iron overload cardiomyopathy that prevails in some forms of hemosiderosis is caused by excessive deposition of iron into the heart tissue and ensuing damage caused by a raise in labile cell iron. The underlying mechanisms of iron uptake into cardiomyocytes in iron overload condition are still under investigation. Both L-type calcium channels (LTCC and T-type calcium channels (TTCC have been proposed to be the main portals of non-transferrinic iron into heart cells, but controversies remain. Here, we investigated the roles of LTCC and TTCC as mediators of cardiac iron overload and cellular damage by using specific Calcium channel blockers as potential suppressors of labile Fe(II and Fe(III ingress in cultured cardiomyocytes and ensuing apoptosis.Fe(II and Fe(III uptake was assessed by exposing HL-1 cardiomyocytes to iron sources and quantitative real-time fluorescence imaging of cytosolic labile iron with the fluorescent iron sensor calcein while iron-induced apoptosis was quantitatively measured by flow cytometry analysis with Annexin V. The role of calcium channels as routes of iron uptake was assessed by cell pretreatment with specific blockers of LTCC and TTCC.Iron entered HL-1 cardiomyocytes in a time- and dose-dependent manner and induced cardiac apoptosis via mitochondria-mediated caspase-3 dependent pathways. Blockade of LTCC but not of TTCC demonstrably inhibited the uptake of ferric but not of ferrous iron. However, neither channel blocker conferred cardiomyocytes with protection from iron-induced apoptosis.Our study implicates LTCC as major mediators of Fe(III uptake into cardiomyocytes exposed to ferric salts but not necessarily as contributors to ensuing apoptosis. Thus, to the extent that apoptosis can be considered a biological indicator of damage, the etiopathology of cardiosiderotic damage that accompanies some forms of hemosiderosis would seem to be unrelated to LTCC or TTCC, but rather to other routes of iron ingress present in

  20. Potentiation of Opioid-Induced Analgesia by L-Type Calcium Channel Blockers: Need for Clinical Trial in Cancer Pain

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    S Basu Ray

    2008-01-01

    Full Text Available Previous reports indicate that the analgesic effect of opioids is due to both closure of specific voltage-gated calcium channels (N- and P/Q-types and opening of G protein-coupled inwardly rectifying potassium channels (GIRKs in neurons concerned with transmission of pain. However, administration of opioids leads to unacceptable levels of side effects, particularly at high doses. Thus, current research is directed towards simultaneously targeting other voltage-gated calcium channels (VGCCs like the L-type VGCCs or even other cell signaling mechanisms, which would aug-ment opioid-mediated analgesic effect without a concurrent increase in the side effects. Unfortunately, the results of these studies are often conflicting considering the different experimental paradigms (variable drug selection and their doses and also the specific pain test used for studying analgesia adopted by researchers. The present review focuses on some of the interesting findings regarding the analgesic effect of Opioids + L-VGCC blockers and suggests that time has come for a clinical trial of this combination of drugs in the treatment of cancer pain.

  1. Mechanical Augmentation Channel Design for Turbine Current Generators

    Directory of Open Access Journals (Sweden)

    E. García

    2014-04-01

    Full Text Available We present the design and analysis of augmentation channels to increase the efficiency of shrouded marine current turbines in conditions of low intensity flows. These turbines are part of a prototype of a floating device composed of wind and marine current generators for generating renewable energy. It intends to exploit renewable energy resources in an integrated manner using wind and current turbines in offshore plants optimizing the economic investment.

  2. GABA(A) Increases Calcium in Subventricular Zone Astrocyte-Like Cells Through L- and T-Type Voltage-Gated Calcium Channels

    DEFF Research Database (Denmark)

    Young, Stephanie Z; Platel, Jean-Claude; Nielsen, Jakob V

    2010-01-01

    induced Ca(2+) increases in 40-50% of SVZ astrocytes. GABA(A)-induced Ca(2+) increases were prevented with nifedipine and mibefradil, blockers of L- and T-type voltage-gated calcium channels (VGCC). The L-type Ca(2+) channel activator BayK 8644 increased the percentage of GABA(A)-responding astrocyte...

  3. Aluminium and hydrogen ions inhibit a mechanosensory calcium-selective cation channel

    Science.gov (United States)

    Ding, J. P.; Pickard, B. G.

    1993-01-01

    The tension-dependent activity of mechanosensory calcium-selective cation channels in excised plasmalemmal patches from onion bulb scale epidermis is modulated by pH in the physiologically meaningful range between 4.5 and 7.2. It is rapidly lowered by lowering pH and rapidly raised by raising pH. Channel activity is effectively inhibited by low levels of aluminium ions and activity can be partially restored by washing for a few minutes. We suggest that under normal conditions the sensitivity of the mechanosensory channels to pH of the wall free space plays important roles in regulation of plant activities such as growth. We further suggest that, when levels of acid and aluminium ions in the soil solution are high, they might inhibit similar sensory channels in cells of the root tip, thus contributing critically to the acid soil syndrome.

  4. L-type calcium channel blockers, morphine and pain: Newer insights

    Directory of Open Access Journals (Sweden)

    Rakesh Kumar

    2010-01-01

    Full Text Available Earlier, we had reported that co-administration of opioids and L-type calcium channel blockers (L-CCBs like diltiazem could prove useful in the treatment of cancer pain. Much of this report was based upon earlier published work involving animal models of pain exposed to brief periods of noxious radiant heat without any tissue injury. However, pain in clinical situations usually result from tissue injury. Thus, the aim of the current investigation was to study the analgesic effect of this combination of drugs in the rat formalin test which is associated with actual tissue injury. Wistar rats (n=60 received either L-CCB (nifedipine/nimodipine/verapamil/diltiazem i.p. or morphine (s.c. or both drugs. The formalin test was done 30 min after morphine or placebo injection. The naloxone reversal test was also done. Administration of L-CCBs alone, particularly diltiazem, increased pain in the formalin test. In contrast, co-administration of these L-CCBs with morphine led to decreased pain response, though statistically significant decrease was noted only with nimodipine + morphine. Naloxone reversed this analgesic effect, indicating that it was primarily an opioid-mediated effect. The results show that administration of L-CCBs alone may prove counterproductive in the therapeutic management of pain (anti-analgesic effect. However, co-administration of both drugs (morphine and nimodipine in quick succession could lead to adequate pain relief.

  5. Endothelin induces two types of contractions of rat uterus: phasic contractions by way of voltage-dependent calcium channels and developing contractions through a second type of calcium channels

    Energy Technology Data Exchange (ETDEWEB)

    Kozuka, M.; Ito, T.; Hirose, S.; Takahashi, K.; Hagiwara, H.

    1989-02-28

    Effects of endothelin on nonvascular smooth muscle have been examined using rat uterine horns and two modes of endothelin action have been revealed. Endothelin (0.3 nM) caused rhythmic contractions of isolated uterus in the presence of extracellular calcium. The rhythmic contractions were completely inhibited by calcium channel antagonists. These characteristics of endothelin-induced contractions were very similar to those induced by oxytocin. Binding assays using /sup 125/I-endothelin showed that endothelin and the calcium channel blockers did not compete for the binding sites. However, endothelin was unique in that it caused, in addition to rhythmic contractions, a slowly developing monophasic contraction that was insensitive to calcium channel blockers. This developing contraction became dominant at higher concentrations of endothelin and was also calcium dependent.

  6. Calcium signaling in lymphocytes and ELF fields. Evidence for an electric field metric and a site of interaction involving the calcium ion channel.

    Science.gov (United States)

    Liburdy, R P

    1992-04-13

    Calcium influx increased during mitogen-activated signal transduction in thymic lymphocytes exposed to a 22 mT, 60 Hz magnetic field (E induced = 1.7 mV/cm, 37 degrees C, 60 min). To distinguish between an electric or a magnetic field dependence a special multi-ring annular cell culture plate based on Faraday's Law of Induction was employed. Studies show a dependence on the strength of the induced electric field at constant magnetic flux density. Moreover, exposure to a pure 60 Hz electric field or to a magnetically-induced electric field of identical strength resulted in similar changes in calcium transport. The first real-time monitoring of [Ca2+]i during application of a 60 Hz electric field revealed an increase in [Ca2+]i observed 100 s after mitogen stimulation; this suggests that the plateau phase rather than the early phase of calcium signaling was influenced. The hypothesis was tested by separating, in time, the early release of calcium from intracellular stores from the influx of extracellular calcium. In calcium-free buffer, 60 Hz field exerted little influence on the early release of calcium from intracellular stores. In contrast, addition of extracellular calcium during exposure enhanced calcium influx through the plasma membrane. Alteration of the plateau phase of calcium signaling implicates the calcium channel as a site of field interaction. In addition, an electric field exposure metric is mechanistically consistent with a cell-surface interaction site.

  7. A combined role of calcium channel blockers and angiotensin receptor blockers in stroke prevention

    Directory of Open Access Journals (Sweden)

    Ji-Guang Wang

    2009-07-01

    Full Text Available Ji-Guang WangCentre for Epidemiological Studies and Clinical Trials, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, ChinaAbstract: Stroke is a leading cause of death and disability worldwide. The importance of lowering blood pressure for reducing the risk of stroke is well established. However, not all the benefits of antihypertensive treatments in stroke can be accounted for by reductions in BP and there may be differences between antihypertensive classes as to which provides optimal protection. Dihydropyridine calcium channel blockers, such as amlodipine, and angiotensin receptor blockers, such as valsartan, represent the two antihypertensive drug classes with the strongest supportive data for the prevention of stroke. Therefore, when combination therapy is required, a combination of these two antihypertensive classes represents a logical approach.Keywords: stroke, angiotensin, calcium channel, cerebrovascular, hypertension, blood pressure

  8. Do calcium-dependent ionic currents mediate ischemic ventricular fibrillation?

    Science.gov (United States)

    Clusin, W T; Bristow, M R; Karagueuzian, H S; Katzung, B G; Schroeder, J S

    1982-02-18

    Calcium ions mediate the adverse effects of myocardial ischemia and have been implicated in the genesis of arrhythmias. Calcium influx blocking drugs protect against early ventricular arrhythmias during experimental coronary occlusion, and recent studies suggest that this effect is at least partly due to inhibition of myocardial cell calcium influx. Most of the pharmacologic maneuvers used to simulate acute ischemic arrhythmias in vivo also produce intracellular calcium overload. Production of calcium overload in small myocardial cell clusters causes fibrillatory electrical and mechanical activity similar to that recorded from fibrillating hearts. Fibrillation in these cell clusters is mediated not by reentrant conduction, but by the same subcellular processes that give rise to depolarizing afterpotentials and abnormal automaticity. Agents favoring calcium influx, such as beta adrenergic agonists, accentuate these processes, while agents that depress calcium influx inhibit them. Although the relation of these experimental models to clinical ischemic arrhythmias has not been fully delineated, calcium influx blocking drugs may prove useful in reducing the incidence of sudden cardiac death.

  9. Regulation of Spinal Substance P Release by Intrathecal Calcium Channel Blockade

    Science.gov (United States)

    Takasusuki, Toshifumi; Yaksh, Tony L.

    2012-01-01

    Background We investigated the role of different voltage sensitive calcium channels expressed at presynaptic afferent terminals in substance P release and on nociceptive behavior evoked by intraplantar formalin by examining the effects of intrathecally delivered N- (ziconotide), T- (mibefradil) and L-type voltage sensitive calcium channels blockers (diltiazem and verapamil). Methods Rats received intrathecal pretreatment with saline or doses of morphine, ziconotide, mibefradil, diltiazem or verapamil. The effect of these injections upon flinching evoked by intraplantar formalin (5%, 50μl) was quantified. To assess substance P release, the incidence of neurokinin 1 receptor internalization in the ipsilateral and contralateral lamina I was determined in immunofluorescent stained tissues. Results Intrathecal morphine (20μg), ziconotide (0.3, 0.6 and 1μg), mibefradil (100μg, but not 50μg), diltiazem (500μg, but not 300μg) and verapamil (200μg, but not 50 and 100μg) reduced paw flinching in phase 2 as compared to vehicle control (P Ziconotide (0.3, 0.6 and 1μg) and morphine (20μg) significantly inhibited neurokinin 1 receptor internalization (P < 0.05), but mibefradil, diltiazem and verapamil at the highest doses had no effect. Conclusion These results emphasize the role in vivo of N-, but not T- and L-type voltage sensitive calcium channels in mediating the stimulus evoked substance P release from small primary afferents and suggest that T- and L-type voltage sensitive calcium channels blockers exert antihyperalgesic effects by an action on other populations of afferents or mechanisms involving post synaptic excitability. PMID:21577088

  10. [Results of an intervention to reduce potentially inappropriate prescriptions of beta blockers and calcium channel blockers].

    Science.gov (United States)

    Machado-Alba, J E; Giraldo-Giraldo, C; Aguirre Novoa, A

    2016-01-01

    To determine the frequency of simultaneous prescription of β-blockers and calcium channel blockers, notify the cardiovascular risk of these patients to the health care professionals in charge of them, and achieve a reduction in the number of those who use them. Quasi-experimental, prospective study by developing an intervention on medical prescriptions of patients older than 65 years treated between January 1 and July 30, 2014, affiliated to the Health System in 101 cities in Colombia. A total of 43,180 patients received a β-blocker each month, and 14,560 receiving a calcium channel blocker were identified. Educational interventions were performed and an evaluation was made, using sociodemographic and pharmacological variables, on the number of patients that stopped taking any of the two drugs in the following three months. A total of 535 patients, with a mean age 75.8±6.7 years received concomitant β-blockers plus calcium channel blockers. Modification of therapy was achieved in 235 patients (43.9% of users) after 66 educational interventions. In 209 cases (88.9%) one of the two drugs was suspended, and 11.1% changed to other antihypertensive drugs. The variable of being more than 85 years old (OR: 1.93; 95% CI: 1.07-3.50), and receiving concomitant medication with inhibitors of the renin-angiotensin system (OR: 2.16; 95% CI: 1.28-3.65) were associated with increased risk of their doctor changing or stopping the prescription. An improved adherence to recommendations for appropriate use of β-blockers and calcium channel blockers by health service providers was achieved. Intervention programs that reduce potentially inappropriate prescriptions for patients treated for cardiovascular disease should be used more frequently. Copyright © 2015 SECA. Published by Elsevier Espana. All rights reserved.

  11. Calcium Channels: Structure and Function (Annals of the New York Academy of Sciences. Volume 560)

    Science.gov (United States)

    1989-06-26

    of the Calcium-Channel Agonist CGP 28392 on Transmitter Release at Mouse Neuromuscular Junctions. By J. BURGES and D . W .-W RAY...for example, CGP 28392 (most likely (S)- CGP 28392, see Refs. 12 and 13), (S)-(+)-202-791, or (- )-Bay K 8644 are always inhibitory." Interestingly...electric organ synapse in an elasmobranch is reversibly blocked by wCgTX," whereas synapses in amphibia, |2 reptiles , and birds (D.Y., unpublished) are

  12. Effects of Calcium Channel Blockers on Antidepressant Action of Alprazolam and Imipramine

    Directory of Open Access Journals (Sweden)

    Gorash ZM

    2007-01-01

    Full Text Available Alprazolam is effective as an anxiolytic and in the adjunct treatment of depression. In this study, the effects of calcium channel antagonists on the antidepressant action of alprazolam and imipramine were investigated. A forced swimming maze was used to study behavioral despair in albino mice. Mice were divided into nine groups (n = 7 per group. One group received a single dose of 1% Tween 80; two groups each received a single dose of the antidepressant alone (alprazolam or imipramine; two groups each received a single dose of the calcium channel blocker (nifedipine or verapamil; four groups each received a single dose of the calcium channel blocker followed by a single dose of the antidepressant (with same doses used for either in the previous four groups. Drug administration was performed concurrently on the nine groups. Our data confirmed the antidepressant action of alprazolam and imipramine. Both nifedipine and verapamil produced a significant antidepressant effect (delay the onset of immobility when administered separately. Verapamil augmented the antidepressant effects of alprazolam and imipramine (additive antidepressant effect. This may be due to the possibility that verapamil might have antidepressant-like effect through different mechanism. Nifedipine and imipramine combined led to a delay in the onset of immobility greater than their single use but less than the sum of their independent administration. This may be due to the fact that nifedipine on its own might act as an antidepressant but blocks one imipramine mechanism that depends on L-type calcium channel activation. Combining nifedipine with alprazolam produced additional antidepressant effects, which indicates that they exert antidepressant effects through different mechanisms.

  13. An expert protocol for immunofluorescent detection of calcium channels in tsA-201 cells.

    Science.gov (United States)

    Koch, Peter; Herzig, Stefan; Matthes, Jan

    Pore-forming subunits of voltage gated calcium channels (VGCC) are large membrane proteins (260kDa) containing 24 transmembrane domains. Despite transfection with viral promoter driven vectors, biochemical analysis of VGCC is often hampered by rather low expression levels in heterologous systems rendering VGCC challenging targets. Especially in immunofluorescent detection, calcium channels are demanding proteins. We provide an expert step-by-step protocol with adapted conditions for handling procedures (tsA-201 cell culture, transient transfection, incubation time and temperature at 28°C or 37°C and immunostaining) to address the L-type calcium-channel pore Cav1.2 in an immunofluorescent approach. We performed immunocytochemical analysis of Cav1.2 expression at single-cell level in combination with detection of different markers for cellular organelles. We show confluency levels and shapes of tsA-201 cells at different time points during an experiment. Our experiments reveal sufficient levels of Cav1.2 protein and a correct Cav1.2 expression pattern in polygonal shaped cells already 12h after transfection. A sequence of elaborated protocol modifications allows subcellular localization analysis of Cav1.2 in an immunocytochemical approach. We provide a protocol that may be used to achieve insights into physiological and pathophysiological processes involving voltage gated calcium channels. Our protocol may be used for expression analysis of other challenging proteins and efficient overexpression may be exploited in related biochemical techniques requiring immunolabels. Copyright © 2016 Elsevier Inc. All rights reserved.

  14. Interactions between calcium channel blockers and the anticonvulsants carbamazepine and phenytoin.

    Science.gov (United States)

    Bahls, F H; Ozuna, J; Ritchie, D E

    1991-05-01

    We describe a retrospective analysis of the frequency of adverse interactions between calcium channel blockers and anticonvulsant drugs (phenytoin and carbamazepine) in a series of 43 patients. Ten patients receiving carbamazepine and three patients receiving phenytoin exhibited symptoms or signs of toxicity. Toxicity occurred with both diltiazem and verapamil, but not with nifedipine. These results emphasize the need for careful clinical and laboratory monitoring of patients receiving both classes of medication.

  15. Calcium channel TRPV6 as a potential therapeutic target in estrogen receptor-negative breast cancer.

    Science.gov (United States)

    Peters, Amelia A; Simpson, Peter T; Bassett, Johnathon J; Lee, Jane M; Da Silva, Leonard; Reid, Lynne E; Song, Sarah; Parat, Marie-Odile; Lakhani, Sunil R; Kenny, Paraic A; Roberts-Thomson, Sarah J; Monteith, Gregory R

    2012-10-01

    Calcium signaling is a critical regulator of cell proliferation. Elevated expression of calcium channels and pumps is a characteristic of some cancers, including breast cancer. We show that the plasma membrane calcium channel TRPV6, which is highly selective for Ca(2+), is overexpressed in some breast cancer cell lines. Silencing of TRPV6 expression in a breast cancer cell line with increased endogenous TRPV6 expression leads to a reduction in basal calcium influx and cellular proliferation associated with a reduction in DNA synthesis. TRPV6 gene amplification was identified as one mechanism of TRPV6 overexpression in a subset of breast cancer cell lines and breast tumor samples. Analysis of two independent microarray expression datasets from breast tumor samples showed that increased TRPV6 expression is a feature of estrogen receptor (ER)-negative breast tumors encompassing the basal-like molecular subtype, as well as HER2-positive tumors. Breast cancer patients with high TRPV6 levels had decreased survival compared with patients with low or intermediate TRPV6 expression. Our findings suggest that inhibitors of TRPV6 may offer a novel therapeutic strategy for the treatment of ER-negative breast cancers.

  16. Calcium-dependent inhibition of T-type calcium channels by TRPV1 activation in rat sensory neurons.

    Science.gov (United States)

    Comunanza, Valentina; Carbone, Emilio; Marcantoni, Andrea; Sher, Emanuele; Ursu, Daniel

    2011-11-01

    We studied the inhibitory effects of transient receptor potential vanilloid-1 (TRPV1) activation by capsaicin on low-voltage-activated (LVA, T-type) Ca(2+) channel and high-voltage-activated (HVA; L, N, P/Q, R) currents in rat DRG sensory neurons, as a potential mechanism underlying capsaicin-induced analgesia. T-type and HVA currents were elicited in whole-cell clamped DRG neurons using ramp commands applied before and after 30-s exposures to 1 μM capsaicin. T-type currents were estimated at the first peak of the I-V characteristics and HVA at the second peak, occurring at more positive potentials. Small and medium-sized DRG neurons responded to capsaicin producing transient inward currents of variable amplitudes, mainly carried by Ca(2+). In those cells responding to capsaicin with a large Ca(2+) influx (59% of the total), a marked inhibition of both T-type and HVA Ca(2+) currents was observed. The percentage of T-type and HVA channel inhibition was prevented by replacing Ca(2+) with Ba(2+) during capsaicin application or applying high doses of intracellular BAPTA (20 mM), suggesting that TRPV1-mediated inhibition of T-type and HVA channels is Ca(2+)-dependent and likely confined to membrane nano-microdomains. Our data are consistent with the idea that TRPV1-induced analgesia may derive from indirect inhibition of both T-type and HVA channels which, in turn, would reduce the threshold of nociceptive signals generation (T-type channel inhibition) and nociceptive synaptic transmission (HVA-channels inhibition).

  17. Alzheimer disease amyloid beta protein forms calcium channels in bilayer membranes: blockade by tromethamine and aluminum.

    Science.gov (United States)

    Arispe, N; Rojas, E; Pollard, H B

    1993-01-15

    Amyloid beta protein (A beta P) is the 40- to 42-residue polypeptide implicated in the pathogenesis of Alzheimer disease. We have incorporated this peptide into phosphatidylserine liposomes and then fused the liposomes with a planar bilayer. When incorporated into bilayers the A beta P forms channels, which generate linear current-voltage relationships in symmetrical solutions. A permeability ratio, PK/PCl, of 11 for the open A beta P channel was estimated from the reversal potential of the channel current in asymmetrical KCl solutions. The permeability sequence for different cations, estimated from the reversal potential of the A beta P-channel current for each system of asymmetrical solutions, is Pcs > PLi > PCa > or = PK > PNa. A beta P-channel current (either CS+ or Ca2+ as charge carriers) is blocked reversibly by tromethamine (millimolar range) and irreversibly by Al3+ (micromolar range). The inhibition of the A beta P-channel current by these two substances depends on transmembrane potential, suggesting that the mechanism of blockade involves direct interaction between tromethamine (or Al3+) and sites within the A beta P channel. Hitherto, A beta P has been presumed to be neurotoxic. On the basis of the present data we suggest that the channel activity of the polypeptide may be responsible for some or all of its neurotoxic effects. We further propose that a useful strategy for drug discovery for treatment of Alzheimer disease may include screening compounds for their ability to block or otherwise modify A beta P channels.

  18. Chemical analysis and calcium channel blocking activity of the essential oil of Perovskia abrotanoides.

    Science.gov (United States)

    Shah, Abdul Jabbar; Rasheed, Munawwer; Jabeen, Qaiser; Ahmed, Amir; Tareen, Rasool Bakhsh; Gilani, Anwarul Hassan; Nadir, Muhammad; Ahmad, Viqar Uddin

    2013-11-01

    The aim of this study was to investigate the chemical composition and provide a pharmacological base for the medicinal use of the essential oil of Perovskia abrotanoides (Pa.Oil) in gastrointestinal disorders, such as colic. The chemical investigation resulted in the identification of 26 compounds, of which tricyclene, beta-trans-ocimene, terpinene-4-acetate, terpinen-4-ol, caran-3beta-ol, linalyl acetate, beta-caryophyllene oxide and alpha-elemene had not previously been reported from P. abrotanoides. Major constituents were 1,8-cineol and delta-3-carene, which constituting 50% of the oil. In the isolated rabbit jejunum preparation Pa.Oil caused inhibition of spontaneous and high K+ (80 mM)-induced contractions, with respective EC50 values of 0.13 (0.08-0.20; n = 4) and 0.90 mg/mL (0.50-1.60; n = 5), thus showing that spasmolytic activity is mediated possibly through calcium channel blockade (CCB). The CCB activity was confirmed when pre-treatment of the tissue with Pa.Oil (0.03-0.1 mg/mL) caused a rightward shift in the Ca++ concentration-response curves, similar to that caused by verapamil, a standard calcium channel blocker. These data indicate that the essential oil of P. abrotanoides possesses spasmolytic activity mediated possibly through inhibition of voltage-dependent calcium channels, which may explain its medicinal use in colic and possibly diarrhea.

  19. Unexpected Effect of Calcium Channel Blockers on the Optic Nerve Compartment Syndrome.

    Science.gov (United States)

    Konieczka, K; Todorova, M G; Bojinova, R I; Binggeli, T; Chackathayil, T N; Flammer, J

    2016-04-01

    The optic nerve compartment syndrome is a pathological condition in which cerebrospinal fluid of the subarachnoid space surrounding the optic nerve is partly or totally segregated from the cerebrospinal fluid of the intracranial subarachnoid space, leading - inter alia - to an increase in the diameter of the optic nerve sheath. The pathogenesis of this condition remains unclear. We have observed clinically that optic nerve compartment syndrome often occurs in normal tension glaucoma patients with Flammer syndrome. To treat Flammer syndrome, some glaucoma patients received a low dose of a calcium channel blocker and we analysed whether this treatment also had an effect on the optic nerve compartment syndrome. We retrospectively analysed the data of 10 eyes of seven patients suffering from a combination of primary open angle glaucoma, optic nerve compartment syndrome, and Flammer syndrome. We included subjects who had eye socket echography before and after a few months of therapy with a calcium channel blocker. All patients received a low dose of a calcium channel blocker (nifedipine or amlodipine) to treat Flammer syndrome. As expected, the symptoms of Flammer syndrome were mitigated. To our surprise, the optic nerve compartment syndrome also improved in eight of the 10 eyes (80 %), but remained unchanged in the remainder. To some extent, the optic nerve compartment syndrome is related to the combination of primary open angle glaucoma and Flammer syndrome. On the basis of our results, we hypothesise that treatment of Flammer syndrome may also improve the optic nerve compartment syndrome. Georg Thieme Verlag KG Stuttgart · New York.

  20. The effect of calcium channel blockers on prevention of preeclampsia in pregnant women with chronic hypertension.

    Science.gov (United States)

    Jiang, N; Liu, Q; Liu, L; Yang, W W; Zeng, Y

    2015-01-01

    Pregnant women with chronic hypertension are at increased risk for complications. This study aims to investigate whether calcium channel blockers plus low dosage aspirin therapy can reduce the incidence of complications during pregnancy with chronic hypertension and improve the prognosis of neonates. From March 2011 to June 2013, 33 patients were selected to join this trial according to the chronic hypertension criteria set by the Preface Bulletin of American College of Obstetricians and Gynecologists, (ACOG). Patients were administrated calcium channel blockers plus low-dosage aspirin and vitamin C. The statistic data of baseline and prognosis from the patients were retrospectively reviewed and compared. Blood pressure of patients was controlled by these medicines with average systolic pressure from 146.3 to 148.7 mmHg and average diastolic pressure from 93.8 to 97.9 mmHg; 39.4% patients complicated mild preeclampsia; however, none of them developed severe preeclampsia or eclampsia, or complicate placental abruption. 30.3% patients delivered at preterm labour; 84.8% patients underwent cesarean section. The neonatal average weight was 3,008 ± 629.6 g, in which seven neonatal weights were less than 2,500 g. All of the neonatal Apgar scores were 9 to 10 at one to five minutes. Small for gestational age (SGA) occurred in five (15%). Calcium channel blockers can improve the outcome of pregnancy women with chronic hypertension to avoid the occurrence of severe pregnancy complication or neonatal morbidity.

  1. Long-Term Blocking of Calcium Channels in mdx Mice Results in Differential Effects on Heart and Skeletal Muscle

    DEFF Research Database (Denmark)

    Jørgensen, Louise Helskov; Blain, Alison; Greally, Elizabeth

    2011-01-01

    calcium ions to enter the cell. The objective of this study was to investigate the effect of chronically blocking calcium channels with the aminoglycoside antibiotic streptomycin from onset of disease in the mdx mouse model of Duchenne muscular dystrophy (DMD). Treatment in utero onwards delayed onset......The disease mechanisms underlying dystrophin-deficient muscular dystrophy are complex, involving not only muscle membrane fragility, but also dysregulated calcium homeostasis. Specifically, it has been proposed that calcium channels directly initiate a cascade of pathological events by allowing...... in older mice. However, streptomycin treatment did not show positive effects in diaphragm or heart muscle, and heart pathology was worsened. Thus, blocking calcium channels even before disease onset does not prevent dystrophy, making this an unlikely treatment for DMD. These findings highlight...

  2. The effect of calcium hardness on hatching success of channel catfish x blue catfish hybrid catfish eggs

    Science.gov (United States)

    The present study was designed to determine the optimal level of calcium hardness in hatching waters to incubate channel catfish Ictalurus punctatus ' x blue catfish I. furcatus ' hybrid catfish eggs. Hatching success of hybrid catfish eggs was higher (phardness (C...

  3. Efficacy and safety of calcium channel blockers in heart failure : Focus on recent trials with second-generation dihydropyridines

    NARCIS (Netherlands)

    de Vries, RJM; van Veldhuisen, DJ; Dunselman, PHJM

    Background Chronic heart failure (CHF) has high morbidity and mortality rates despite treatment with angiotensin-converting-enzyme inhibitors, diuretics, and digoxin. Adjunctive-vasodilation through calcium channel blockade has been suggested as potentially useful, However, the first-generation

  4. Design and Synthesis of a Conformationally Rigid Mimic of the Dihydropyrimidine Calcium Channel Modulator SQ 32,926

    Directory of Open Access Journals (Sweden)

    Birgit Jauk

    2000-03-01

    Full Text Available A conformationally rigid polyheterocycle (3 which mimics the putative receptorbound conformation of dihydropyridine-type calcium channel modulators is prepared in a seven-step reaction sequence based on a Biginelli-type cyclocondensation reaction.

  5. Design and Synthesis of a Conformationally Rigid Mimic of the Dihydropyrimidine Calcium Channel Modulator SQ 32,926

    OpenAIRE

    Birgit Jauk; Tetiana Pernat; Oliver Kappe, C.

    2000-01-01

    A conformationally rigid polyheterocycle (3) which mimics the putative receptorbound conformation of dihydropyridine-type calcium channel modulators is prepared in a seven-step reaction sequence based on a Biginelli-type cyclocondensation reaction.

  6. [Nonuniform distribution and contribution of the P- and P/Q-type calcium channels to short-term inhibitory synaptic transmission in cultured hippocampal neurons].

    Science.gov (United States)

    Mizerna, O P; Fedulova, S A; Veselovs'kyĭ, M S

    2010-01-01

    In the present study, we investigated the sensitivity of GABAergic short-term plasticity to the selective P- and P/Q-type calcium channels blocker omega-agatoxin-IVA. To block the P-type channels we used 30 nM of this toxin and 200 nM of the toxin was used to block the P/Q channel types. The evoked inhibitory postsynaptic currents (eIPSC) were studied using patch-clamp technique in whole-cell configuration in postsynaptic neuron and local extracellular stimulation of single presynaptic axon by rectangular pulse. The present data show that the contribution of P- and P/Q-types channels to GABAergic synaptic transmission in cultured hippocampal neurons are 30% and 45%, respectively. It was shown that the mediate contribution of the P- and P/Q-types channels to the amplitudes of eIPSC is different to every discovered neuron. It means that distribution of these channels is non-uniform. To study the short-term plasticity of inhibitory synaptic transmission, axons of presynaptic neurons were paired-pulse stimulated with the interpulse interval of 150 ms. Neurons demonstrated both the depression and facilitation. The application of 30 nM and 200 nM of the blocker decreased the depression and increased facilitation to 8% and 11%, respectively. In addition, we found that the mediate contribution of the P- and P/Q-types channels to realization of synaptic transmission after the second stimuli is 4% less compared to that after the first one. Therefore, blocking of both P- and P/Q-types calcium channels can change the efficiency of synaptic transmission. In this instance it facilitates realization of the transmission via decreased depression or increased facilitation. These results confirm that the P- and P/Q-types calcium channels are involved in regulation of the short-term inhibitory synaptic plasticity in cultured hippocampal neurons.

  7. Aberrant Splicing Induced by Dysregulated Rbfox2 Produces Enhanced Function of CaV1.2 Calcium Channel and Vascular Myogenic Tone in Hypertension.

    Science.gov (United States)

    Zhou, Yingying; Fan, Jia; Zhu, Huayuan; Ji, Li; Fan, Wenyong; Kapoor, Isha; Wang, Yue; Wang, Yuan; Zhu, Guoqing; Wang, Juejin

    2017-12-01

    Calcium influx from activated voltage-gated calcium channel Ca V 1.2 in vascular smooth muscle cells is indispensable for maintaining myogenic tone and blood pressure. The function of Ca V 1.2 channel can be optimized by alternative splicing, one of post-transcriptional modification mechanisms. The splicing factor Rbfox2 is known to regulate the Ca V 1.2 pre-mRNA alternative splicing events during neuronal development. However, Rbfox2's roles in modulating the key function of vascular Ca V 1.2 channel and in the pathogenesis of hypertension remain elusive. Here, we report that the proportion of Ca V 1.2 channels with alternative exon 9* is increased by 10.3%, whereas that with alternative exon 33 is decreased by 10.5% in hypertensive arteries. Surprisingly, the expression level of Rbfox2 is increased ≈3-folds, presumably because of the upregulation of a dominant-negative isoform of Rbfox2. In vascular smooth muscle cells, we find that knockdown of Rbfox2 dynamically increases alternative exon 9*, whereas decreases exon 33 inclusion of Ca V 1.2 channels. By patch-clamp studies, we show that diminished Rbfox2-induced alternative splicing shifts the steady-state activation and inactivation curves of vascular Ca V 1.2 calcium channel to hyperpolarization, which makes the window current potential to more negative. Moreover, siRNA-mediated knockdown of Rbfox2 increases the pressure-induced vascular myogenic tone of rat mesenteric artery. Taken together, our data indicate that Rbfox2 modulates the functions of vascular Ca V 1.2 calcium channel by dynamically regulating the expressions of alternative exons 9* and 33, which in turn affects the vascular myogenic tone. Therefore, our work suggests a key role for Rbfox2 in hypertension, which provides a rational basis for designing antihypertensive therapies. © 2017 American Heart Association, Inc.

  8. The involvement of the Mid1/Cch1/Yvc1 calcium channels in Aspergillus fumigatus virulence.

    Directory of Open Access Journals (Sweden)

    Patrícia Alves de Castro

    Full Text Available Aspergillus fumigatus is a major opportunistic pathogen and allergen of mammals. Calcium homeostasis and signaling is essential for numerous biological processes and also influences A. fumigatus pathogenicity. The presented study characterized the function of the A. fumigatus homologues of three Saccharomyces cerevisiae calcium channels, voltage-gated Cch1, stretch-activated Mid1 and vacuolar Yvc1. The A. fumigatus calcium channels cchA, midA and yvcA were regulated at transcriptional level by increased calcium levels. The YvcA::GFP fusion protein localized to the vacuoles. Both ΔcchA and ΔmidA mutant strains showed reduced radial growth rate in nutrient-poor minimal media. Interestingly, this growth defect in the ΔcchA strain was rescued by the exogenous addition of CaCl2. The ΔcchA, ΔmidA, and ΔcchA ΔmidA strains were also sensitive to the oxidative stress inducer, paraquat. Restriction of external Ca(2+ through the addition of the Ca(2+-chelator EGTA impacted upon the growth of the ΔcchA and ΔmidA strains. All the A. fumigatus ΔcchA, ΔmidA, and ΔyvcA strains demonstrated attenuated virulence in a neutropenic murine model of invasive pulmonary aspergillosis. Infection with the parental strain resulted in a 100% mortality rate at 15 days post-infection, while the mortality rate of the ΔcchA, ΔmidA, and ΔyvcA strains after 15 days post-infection was only 25%. Collectively, this investigation strongly indicates that CchA, MidA, and YvcA play a role in A. fumigatus calcium homeostasis and virulence.

  9. FM dyes enter via a store-operated calcium channel and modify calcium signaling of cultured astrocytes

    Science.gov (United States)

    Li, Dongdong; Hérault, Karine; Oheim, Martin; Ropert, Nicole

    2009-01-01

    The amphiphilic fluorescent styryl pyridinium dyes FM1-43 and FM4-64 are used to probe activity-dependent synaptic vesicle cycling in neurons. Cultured astrocytes can internalize FM1-43 and FM4-64 inside vesicles but their uptake is insensitive to the elevation of cytosolic calcium (Ca2+) concentration and the underlying mechanism remains unclear. Here we used total internal reflection fluorescence microscopy and pharmacological tools to study the mechanisms of FM4-64 uptake into cultured astrocytes from mouse neocortex. Our data show that: (i) endocytosis is not a major route for FM4-64 uptake into astrocytes; (ii) FM4-64 enters astrocytes through an aqueous pore and strongly affects Ca2+ homeostasis; (iii) partitioning of FM4-64 into the outer leaflet of the plasma membrane results in a facilitation of store-operated Ca2+ entry (SOCE) channel gating; (iv) FM4-64 permeates and competes with Ca2+ for entry through a SOCE channel; (v) intracellular FM4-64 mobilizes Ca2+ from the endoplasmic reticulum stores, conveying a positive feedback to activate SOCE and to sustain dye uptake into astrocytes. Our study demonstrates that FM dyes are not markers of cycling vesicles in astrocytes and calls for a careful interpretation of FM fluorescence. PMID:20007370

  10. Ziconotide, an intrathecally administered N-type calcium channel antagonist for the treatment of chronic pain.

    Science.gov (United States)

    Wermeling, Daniel P

    2005-08-01

    Ziconotide is a novel peptide that blocks the entry of calcium into neuronal N-type voltage-sensitive calcium channels, preventing the conduction of nerve signals. N-type calcium channels are present in the superficial laminae of the dorsal horn of the spinal cord. In various animal models of pain, intrathecal administration of ziconotide blocked nerve transmission and nociception. The United States Food and Drug Administration recently approved ziconotide intrathecal infusion for the management of severe chronic pain in patients who require intrathecal therapy and who are intolerant of or refractory to other treatment, such as systemic analgesics, adjunctive therapies, or intrathecal morphine. The drug has a narrow therapeutic window and a lag time for the onset and offset of analgesia and adverse events. In early clinical trials, frequent and severe psychiatric and central nervous system adverse effects were associated with rapid intrathecal infusion (0.4 microg/hr) and frequent up-titration (every 12 hrs). Therefore, patients with psychiatric symptoms are not candidates for this drug. Drug trials of external intrathecal catheters and microinfusion devices demonstrated a 3% risk of meningitis. A low initial infusion rate of 0.1 microg/hour and limiting infusion rate increases to 2-3 times/week are now recommended. Patients responsive to intrathecal ziconotide require an implanted infusion system to receive long-term therapy.

  11. Enigma homolog 1 scaffolds protein kinase D1 to regulate the activity of the cardiac L-type voltage-gated calcium channel.

    Science.gov (United States)

    Maturana, Andrés D; Wälchli, Sébastien; Iwata, Miki; Ryser, Stephan; Van Lint, Johannes; Hoshijima, Masahiko; Schlegel, Werner; Ikeda, Yasuhiro; Tanizawa, Katsuyuki; Kuroda, Shun'ichi

    2008-06-01

    In cardiomyocytes, protein kinase D1 (PKD1) plays a central role in the response to stress signals. From a yeast two-hybrid assay, we have identified Enigma Homolog 1 (ENH1) as a new binding partner of PKD1. Since in neurons, ENH1, associated with protein kinase Cepsilon, was shown to modulate the activity of N-type calcium channels, and the pore-forming subunit of the cardiac L-type voltage-gated calcium channel, alpha1C, possesses a potential phosphorylation site for PKD1, we studied here a possible role of ENH1 and PKD1 in the regulation of the cardiac L-type voltage-gated calcium channel. PKD1-interacting proteins were searched by yeast two-hybrid screening. In vivo protein interactions in cardiomyocytes isolated from heart ventricles of newborn rats were tested by co-immunoprecipitation. Small interfering RNA and a dominant negative mutant of PKD1 were delivered into cardiomyocytes by use of an adenovirus. Calcium currents were measured by the patch-clamp technique. Both ENH1 and PKD1 interact with alpha1C in cardiomyocytes. This interaction is increased upon stimulation. Silencing of ENH1 prevented the binding of PKD1 to alpha1C. Moreover, a dominant negative mutant of PKD1 or the silencing of ENH1 inhibited the alpha-adrenergic-induced increase of L-type calcium currents. We found a new binding partner, ENH1, and a new target, alpha1C, for PKD1 in neonatal rat cardiomyocytes. We propose a model where ENH1 scaffolds PKD1 to alpha1C in order to form a signalling complex that regulates the activity of cardiac L-type voltage-gated Ca(2+) channels.

  12. Small-conductance calcium-activated potassium (SK) channels contribute to action potential repolarization in human atria

    DEFF Research Database (Denmark)

    Skibsbye, Lasse; Poulet, Claire; Diness, Jonas Goldin

    2014-01-01

    AIMS: Small-conductance calcium-activated potassium (SK) channels are expressed in the heart of various species, including humans. The aim of the present study was to address whether SK channels play a functional role in human atria. METHODS AND RESULTS: Quantitative real-time PCR analyses showed...

  13. Putative calcium-binding domains of the Caenorhabditis elegans BK channel are dispensable for intoxication and ethanol activation.

    Science.gov (United States)

    Davis, S J; Scott, L L; Ordemann, G; Philpo, A; Cohn, J; Pierce-Shimomura, J T

    2015-07-01

    Alcohol modulates the highly conserved, voltage- and calcium-activated potassium (BK) channel, which contributes to alcohol-mediated behaviors in species from worms to humans. Previous studies have shown that the calcium-sensitive domains, RCK1 and the Ca(2+) bowl, are required for ethanol activation of the mammalian BK channel in vitro. In the nematode Caenorhabditis elegans, ethanol activates the BK channel in vivo, and deletion of the worm BK channel, SLO-1, confers strong resistance to intoxication. To determine if the conserved RCK1 and calcium bowl domains were also critical for intoxication and basal BK channel-dependent behaviors in C. elegans, we generated transgenic worms that express mutated SLO-1 channels predicted to have the RCK1, Ca(2+) bowl or both domains rendered insensitive to calcium. As expected, mutating these domains inhibited basal function of SLO-1 in vivo as neck and body curvature of these mutants mimicked that of the BK null mutant. Unexpectedly, however, mutating these domains singly or together in SLO-1 had no effect on intoxication in C. elegans. Consistent with these behavioral results, we found that ethanol activated the SLO-1 channel in vitro with or without these domains. By contrast, in agreement with previous in vitro findings, C. elegans harboring a human BK channel with mutated calcium-sensing domains displayed resistance to intoxication. Thus, for the worm SLO-1 channel, the putative calcium-sensitive domains are critical for basal in vivo function but unnecessary for in vivo ethanol action. © 2015 John Wiley & Sons Ltd and International Behavioural and Neural Genetics Society.

  14. The concentration of adrenaline and noradrenaline in the serum of dogs under the influence of calcium channels blockers

    Directory of Open Access Journals (Sweden)

    Milanović Tamara

    2015-01-01

    Full Text Available The most important characteristic of calcium channels is selective regulation of slow incoming stream of calcium into the cell tissue providing the slow increasement of action potential. Such tissues include smooth muscles of blood vessels, cardiocytes and heart noduses (AV and SA node. Different calcium antagonists have different effects on previous tissues due to their different chemical formula. Verapamile, Nifedipin and Diltiazem are the most frequently used of all. Their commonest characteristic is blocking the calcium channels causing vasodilatation of blood vessels as well as negative inotropic and chronotropic influence. By blocking the incoming calcium through slow channels of myofibrils of smooth muscles, the antagonists of calcium decrease the quantity of available calcium for contraction which causes vasodilatation. The most famous and most frequently used calcium antagonist is Verapamile. In terms of electrophysiology, Verapamile inhibits action potentials of heart noduses, especially the AV node, where the slow incoming of calcium is the most important for depolarization. Prolongation of the efective refractory period of SA node causes the heart frequency decreasement while prolongation of the effective refractory period of AV node slows down the work of chambers in case of flater and fibrillation of atriums. The molecules of calcium-bonding protein called kalmodulin are located in synaptic endings. Each kalmodulin can bond four calcium ions providing transfer into active calcium-kalmodulin complex which activates the kinase protein. Activated kinase protein starts the exocytosis of neurotransmitters into synaptic gap. Apart from activating kinase protein, calcium-kalmodulin complex also starts the activity of calcium pump presynaptic membrane which pumps calcium out of presynaptic ending stopping the further exocytosis of neurotransmitters into synaptic gap. Taking into consideration the fact that opening the calcium channels on

  15. Large conductance, calcium- and voltage-gated potassium (BK) channels: regulation by cholesterol.

    Science.gov (United States)

    Dopico, Alejandro M; Bukiya, Anna N; Singh, Aditya K

    2012-08-01

    Cholesterol (CLR) is an essential component of eukaryotic plasma membranes. CLR regulates the membrane physical state, microdomain formation and the activity of membrane-spanning proteins, including ion channels. Large conductance, voltage- and Ca²⁺-gated K⁺ (BK) channels link membrane potential to cell Ca²⁺ homeostasis. Thus, they control many physiological processes and participate in pathophysiological mechanisms leading to human disease. Because plasmalemma BK channels cluster in CLR-rich membrane microdomains, a major driving force for studying BK channel-CLR interactions is determining how membrane CLR controls the BK current phenotype, including its pharmacology, channel sorting, distribution, and role in cell physiology. Since both BK channels and CLR tissue levels play a pathophysiological role in human disease, identifying functional and structural aspects of the CLR-BK channel interaction may open new avenues for therapeutic intervention. Here, we review the studies documenting membrane CLR-BK channel interactions, dissecting out the many factors that determine the final BK current response to changes in membrane CLR content. We also summarize work in reductionist systems where recombinant BK protein is studied in artificial lipid bilayers, which documents a direct inhibition of BK channel activity by CLR and builds a strong case for a direct interaction between CLR and the BK channel-forming protein. Bilayer lipid-mediated mechanisms in CLR action are also discussed. Finally, we review studies of BK channel function during hypercholesterolemia, and underscore the many consequences that the CLR-BK channel interaction brings to cell physiology and human disease. Copyright © 2012 Elsevier Inc. All rights reserved.

  16. Nitric oxide regulates neuronal activity via calcium-activated potassium channels.

    Directory of Open Access Journals (Sweden)

    Lei Ray Zhong

    Full Text Available Nitric oxide (NO is an unconventional membrane-permeable messenger molecule that has been shown to play various roles in the nervous system. How NO modulates ion channels to affect neuronal functions is not well understood. In gastropods, NO has been implicated in regulating the feeding motor program. The buccal motoneuron, B19, of the freshwater pond snail Helisoma trivolvis is active during the hyper-retraction phase of the feeding motor program and is located in the vicinity of NO-producing neurons in the buccal ganglion. Here, we asked whether B19 neurons might serve as direct targets of NO signaling. Previous work established NO as a key regulator of growth cone motility and neuronal excitability in another buccal neuron involved in feeding, the B5 neuron. This raised the question whether NO might modulate the electrical activity and neuronal excitability of B19 neurons as well, and if so whether NO acted on the same or a different set of ion channels in both neurons. To study specific responses of NO on B19 neurons and to eliminate indirect effects contributed by other cells, the majority of experiments were performed on single cultured B19 neurons. Addition of NO donors caused a prolonged depolarization of the membrane potential and an increase in neuronal excitability. The effects of NO could mainly be attributed to the inhibition of two types of calcium-activated potassium channels, apamin-sensitive and iberiotoxin-sensitive potassium channels. NO was found to also cause a depolarization in B19 neurons in situ, but only after NO synthase activity in buccal ganglia had been blocked. The results suggest that NO acts as a critical modulator of neuronal excitability in B19 neurons, and that calcium-activated potassium channels may serve as a common target of NO in neurons.

  17. Calcium Channel Blockers and Esophageal Sclerosis: Should We Expect Exacerbation of Interstitial Lung Disease

    Directory of Open Access Journals (Sweden)

    Charalampos Seretis

    2012-01-01

    Full Text Available Esophageal sclerosis is the most common visceral manifestation of systemic sclerosis, resulting in impaired esophageal clearance and retention of ingested food; in addition, co-existence of lung fibrosis with esophageal scleroderma is not uncommon. Both the progression of generalized connective tissue disorders and the damaging effect of chronic aspiration due to esophageal dysmotility appear to be involved in this procedure of interstitial fibrosis. Nifedipine is a widely prescribed calcium antagonist in a significant percentage of rheumatologic patients suffering from Raynaud syndrome, in order to inhibit peripheral vasospasm. Nevertheless, blocking calcium channels has proven to contribute to exacerbation of gastroesophageal reflux, which consequently can lead to chronic aspiration. We describe the case of severe exacerbation of interstitial lung disease in a 76-year-old female with esophageal sclerosis who was treated with oral nifedipine for Raynaud syndrome.

  18. A functional tandem between transient receptor potential canonical channels 6 and calcium-dependent chloride channels in human epithelial cells.

    Science.gov (United States)

    Bertrand, Johanna; Dannhoffer, Luc; Antigny, Fabrice; Vachel, Laura; Jayle, Christophe; Vandebrouck, Clarisse; Becq, Frédéric; Norez, Caroline

    2015-10-15

    TRPC6 plays important human physiological functions, notably in artery and arterioles constriction, in regulation of vascular volume and in bronchial muscle constriction. It is implicated in pulmonary hypertension, cardiovascular disease, and focal segmental glomerulosclerosis and seems to play a role in cancer development. Previously, we identified Guanabenz, an α2-adrenergic agonist used for hypertension treatment (Wytensin®), as an activator of calcium-dependent chloride channels (CaCC) in human Cystic Fibrosis (CF) nasal epithelial cells by transiently increasing [Ca2+]i via an influx of extracellular Ca2+. In this study, using assays to measure chloride channel activity, we show that guanabenz is an activator of CaCC in freshly dissociated human bronchial epithelial cells from three CF patients with various genotypes (F508del/F508del, F508del/R1066C, F508del/H1085R). We further characterised the effect of guanabenz and show that it is independent of α-adrenergic receptors, is inhibited by the TRPC family inhibitor SKF-96365 but not by the TRPV family inhibitor ruthenium red. Using western-blotting, Ca2+ measurements and iodide efflux assay, we found that TRPC1 siRNA has no effect on guanabenz induced responses whereas TRPC6 siRNA prevented the guanabenz-dependent Ca2+ influx and the CaCC-dependent activity stimulated by guanabenz. In conclusion, we show that TRPC6 channel is pivotal for the activation of CaCC by guanabenz through a α2-adrenergic-independent pathway in human airway epithelial cells. We suggest propose a functional coupling between TRPC6 and CaCC and guanabenz as a potential TRPC6 activator for exploring TRPC6 and CaCC channel functions and corresponding channelopathies. Copyright © 2015 Elsevier B.V. All rights reserved.

  19. New Conotoxin SO-3 Targeting N-type Voltage-Sensitive Calcium Channels

    Directory of Open Access Journals (Sweden)

    Lei Wen

    2006-04-01

    Full Text Available Selective blockers of the N-type voltage-sensitive calcium (CaV channels are useful in the management of severe chronic pain. Here, the structure and function characteristics of a novel N-type CaV channel blocker, SO-3, are reviewed. SO-3 is a 25-amino acid conopeptide originally derived from the venom of Conus striatus, and contains the same 4-loop, 6-cysteine framework (C-C-CC-C-C as O-superfamily conotoxins. The synthetic SO-3 has high analgesic activity similar to ω-conotoxin MVIIA (MVIIA, a selective N-type CaV channel blocker approved in the USA and Europe for the alleviation of persistent pain states. In electrophysiological studies, SO-3 shows more selectivity towards the N-type CaV channels than MVIIA. The dissimilarity between SO-3 and MVIIA in the primary and tertiary structures is further discussed in an attempt to illustrate the difference in selectivity of SO-3 and MVIIA towards N-type CaV channels.

  20. Dendritic and Axonal L-Type Calcium Channels Cooperate to Enhance Motoneuron Firing Output duringDrosophilaLarval Locomotion.

    Science.gov (United States)

    Kadas, Dimitrios; Klein, Aylin; Krick, Niklas; Worrell, Jason W; Ryglewski, Stefanie; Duch, Carsten

    2017-11-08

    Behaviorally adequate neuronal firing patterns are critically dependent on the specific types of ion channel expressed and on their subcellular localization. This study combines in situ electrophysiology with genetic and pharmacological intervention in larval Drosophila melanogaster of both sexes to address localization and function of L-type like calcium channels in motoneurons. We demonstrate that Dmca1D (Ca v 1 homolog) L-type like calcium channels localize to both the somatodendritic and the axonal compartment of larval crawling motoneurons. In situ patch-clamp recordings in genetic mosaics reveal that Dmca1D channels increase burst duration and maximum intraburst firing frequencies during crawling-like motor patterns in semi-intact animals. Genetic and acute pharmacological manipulations suggest that prolonged burst durations are caused by dendritically localized Dmca1D channels, which activate upon cholinergic synaptic input and amplify EPSPs, thus indicating a conserved function of dendritic L-type channels from Drosophila to vertebrates. By contrast, maximum intraburst firing rates require axonal calcium influx through Dmca1D channels, likely to enhance sodium channel de-inactivation via a fast afterhyperpolarization through BK channel activation. Therefore, in unmyelinated Drosophila motoneurons different functions of axonal and dendritic L-type like calcium channels likely operate synergistically to maximize firing output during locomotion. SIGNIFICANCE STATEMENT Nervous system function depends on the specific excitabilities of different types of neurons. Excitability is largely shaped by different combinations of voltage-dependent ion channels. Despite a high degree of conservation, the huge diversity of ion channel types and their differential localization pose challenges in assigning distinct functions to specific channels across species. We find a conserved role, from fruit flies to mammals, for L-type calcium channels in augmenting motoneuron

  1. α-SNAP regulates dynamic, on-site assembly and calcium selectivity of Orai1 channels.

    Science.gov (United States)

    Li, Peiyao; Miao, Yong; Dani, Adish; Vig, Monika

    2016-08-15

    Orai1 forms a highly calcium-selective pore of the calcium release activated channel, and α-SNAP is necessary for its function. Here we show that α-SNAP regulates on-site assembly of Orai1 dimers into calcium-selective multimers. We find that Orai1 is a dimer in resting primary mouse embryonic fibroblasts but displays variable stoichiometry in the plasma membrane of store-depleted cells. Remarkably, α-SNAP depletion induces formation of higher-order Orai1 oligomers, which permeate significant levels of sodium via Orai1 channels. Sodium permeation in α-SNAP-deficient cells cannot be corrected by tethering multiple Stim1 domains to Orai1 C-terminal tail, demonstrating that α-SNAP regulates functional assembly and calcium selectivity of Orai1 multimers independently of Stim1 levels. Fluorescence nanoscopy reveals sustained coassociation of α-SNAP with Stim1 and Orai1, and α-SNAP-depleted cells show faster and less constrained mobility of Orai1 within ER-PM junctions, suggesting Orai1 and Stim1 coentrapment without stable contacts. Furthermore, α-SNAP depletion significantly reduces fluorescence resonance energy transfer between Stim1 and Orai1 N-terminus but not C-terminus. Taken together, these data reveal a unique role of α-SNAP in the on-site functional assembly of Orai1 subunits and suggest that this process may, in part, involve enabling crucial low-affinity interactions between Orai1 N-terminus and Stim1. © 2016 Li, Miao, et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

  2. Calcium

    Science.gov (United States)

    ... Turn to calcium-fortified (or "calcium-set") tofu, soy milk, tempeh, soy yogurt, and cooked soybeans (edamame). Calcium-fortified foods. Look for calcium-fortified orange juice, soy or rice milk, breads, and cereal. Beans. You can get decent ...

  3. Presynaptic Localization and Possible Function of Calcium-Activated Chloride Channel Anoctamin 1 in the Mammalian Retina.

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    Ji Hyun Jeon

    Full Text Available Calcium (Ca(2+-activated chloride (Cl(- channels (CaCCs play a role in the modulation of action potentials and synaptic responses in the somatodendritic regions of central neurons. In the vertebrate retina, large Ca(2+-activated Cl(- currents (ICl(Ca regulate synaptic transmission at photoreceptor terminals; however, the molecular identity of CaCCs that mediate ICl(Ca remains unclear. The transmembrane protein, TMEM16A, also called anoctamin 1 (ANO1, has been recently validated as a CaCC and is widely expressed in various secretory epithelia and nervous tissues. Despite the fact that tmem16a was first cloned in the retina, there is little information on its cellular localization and function in the mammalian retina. In this study, we found that ANO1 was abundantly expressed as puncta in 2 synaptic layers. More specifically, ANO1 immunoreactivity was observed in the presynaptic terminals of various retinal neurons, including photoreceptors. ICl(Ca was first detected in dissociated rod bipolar cells expressing ANO1. ICl(Ca was abolished by treatment with the Ca(2+ channel blocker Co(2+, the L-type Ca(2+ channel blocker nifedipine, and the Cl(- channel blockers 5-nitro-2-(3-phenylpropylamino benzoic acid (NPPB and niflumic acid (NFA. More specifically, a recently discovered ANO1-selective inhibitor, T16Ainh-A01, and a neutralizing antibody against ANO1 inhibited ICl(Ca in rod bipolar cells. Under a current-clamping mode, the suppression of ICl(Ca by using NPPB and T16Ainh-A01 caused a prolonged Ca(2+ spike-like depolarization evoked by current injection in dissociated rod bipolar cells. These results suggest that ANO1 confers ICl(Ca in retinal neurons and acts as an intrinsic regulator of the presynaptic membrane potential during synaptic transmission.

  4. A genetic screen for dihydropyridine (DHP)-resistant worms reveals new residues required for DHP-blockage of mammalian calcium channels.

    Science.gov (United States)

    Kwok, Trevor C Y; Hui, Kwokyin; Kostelecki, Wojciech; Ricker, Nicole; Selman, Guillermo; Feng, Zhong-Ping; Roy, Peter John

    2008-05-09

    Dihydropyridines (DHPs) are L-type calcium channel (Ca(v)1) blockers prescribed to treat several diseases including hypertension. Ca(v)1 channels normally exist in three states: a resting closed state, an open state that is triggered by membrane depolarization, followed by a non-conducting inactivated state that is triggered by the influx of calcium ions, and a rapid change in voltage. DHP binding is thought to alter the conformation of the channel, possibly by engaging a mechanism similar to voltage dependent inactivation, and locking a calcium ion in the pore, thereby blocking channel conductance. As a Ca(v)1 channel crystal structure is lacking, the current model of DHP action has largely been achieved by investigating the role of candidate Ca(v)1 residues in mediating DHP-sensitivity. To better understand DHP-block and identify additional Ca(v)1 residues important for DHP-sensitivity, we screened 440,000 randomly mutated Caenorhabditis elegans genomes for worms resistant to DHP-induced growth defects. We identified 30 missense mutations in the worm Ca(v)1 pore-forming (alpha(1)) subunit, including eleven in conserved residues known to be necessary for DHP-binding. The remaining polymorphisms are in eight conserved residues not previously associated with DHP-sensitivity. Intriguingly, all of the worm mutants that we analyzed phenotypically exhibited increased channel activity. We also created orthologous mutations in the rat alpha(1C) subunit and examined the DHP-block of current through the mutant channels in culture. Six of the seven mutant channels examined either decreased the DHP-sensitivity of the channel and/or exhibited significant residual current at DHP concentrations sufficient to block wild-type channels. Our results further support the idea that DHP-block is intimately associated with voltage dependent inactivation and underscores the utility of C. elegans as a screening tool to identify residues important for DHP interaction with mammalian Ca(v)1

  5. POSITIONS OF CALCIUM CHANNEL BLOCKER LERCANIDIPINE ACCORDING TO EVIDENCE BASED CARDIOLOGY

    Directory of Open Access Journals (Sweden)

    Yu. V. Lukina

    2010-01-01

    Full Text Available Data of evidence based cardiology including results of international clinical trials on efficacy and safety of the modern calcium channel blocker (CCB, lercanidipine, are presented. Results of these trials show the firm position of lercanidipine in the modern cardiology and confirm that treatment with lercanidipine leads to significant reduction of systolic and diastolic blood pressure (BP with no effect on heart rate (HR. Peripheral edema (the common side effect of CCBs occurs rarer with lercanidipine treatment than this with any other CCB treatment. Lercanidipine can be recommended to patients with concomitant diseases due to its additional features.

  6. Current challenges in distribution channels of cultural goods and services

    Directory of Open Access Journals (Sweden)

    Razieh Fayaz

    2016-06-01

    Full Text Available Nowadays, one product that has a well qualified design will not have expected utility if it cannot be available at the appropriate time and place to its buyers. Thus, marketing managers and official sales always try to find the more efficient and modern methods of distribution through investigating the transfer methods of goods. Appropriate decision will lead to the enhancement of transfer speed, convenience of customers, and reduction of costs. One of the main tools of marketing is the efficient distribution system. Since cultural products have a determining role in conveyance of thoughts, values, and social norms and transmit cultural values and messages with themselves, their distribution has a great importance. This study aimed to investigate the current challenges in distribution channels of cultural goods and services. Some of these challenges were being traditional, the length of the channel, and the number of intermediaries.

  7. Expression of the alpha(2)delta subunit interferes with prepulse facilitation in cardiac L-type calcium channels.

    Science.gov (United States)

    Platano, D; Qin, N; Noceti, F; Birnbaumer, L; Stefani, E; Olcese, R

    2000-06-01

    We investigated the role of the accessory alpha(2)delta subunit on the voltage-dependent facilitation of cardiac L-type Ca(2+) channels (alpha(1C)). alpha(1C) Channels were coexpressed in Xenopus oocytes with beta(3) and alpha(2)delta calcium channel subunits. In alpha(1C) + beta(3), the amplitude of the ionic current (measured during pulses to 10 mV) was in average approximately 1.9-fold larger after the application of a 200-ms prepulse to +80 mV. This phenomenon, commonly referred to as voltage-dependent facilitation, was not observed when alpha(2)delta was coexpressed with alpha(1C) + beta(3). In alpha(1C) + beta(3), the prepulse produced a left shift ( approximately 40 mV) of the activation curve. Instead, the activation curve for alpha(1C) + beta(3) + alpha(2)delta was minimally affected by the prepulse and had a voltage dependence very similar to the G-V curve of the alpha(1C) + beta(3) channel facilitated by the prepulse. Coexpression of alpha(2)delta with alpha(1C) + beta(3) seems to mimic the prepulse effect by shifting the activation curve toward more negative potentials, leaving little room for facilitation. The facilitation of alpha(1C) + beta(3) was associated with an increase of the charge movement. In the presence of alpha(2)delta, the charge remained unaffected after the prepulse. Coexpression of alpha(2)delta seems to set all the channels in a conformational state from where the open state can be easily reached, even without prepulse.

  8. Calcium Activated K+ Channels in The Electroreceptor of the Skate Confirmed by Cloning. Details of Subunits and Splicing

    Science.gov (United States)

    King, Benjamin L.; Shi, Ling Fang; Kao, Peter; Clusin, William T.

    2015-01-01

    Elasmobranchs detect small potentials using excitable cells of the ampulla of Lorenzini which have calcium-activated K+ channels, first described in l974. A distinctive feature of the outward current in voltage clamped ampullae is its apparent insensitivity to voltage. The sequence of a BK channel α isoform expressed in the ampulla of the skate was characterized. A signal peptide is present at the beginning of the gene. When compared to human isoform 1 (the canonical sequence), the largest difference was absence of a 59 amino acid region from the S8-S9 intracellular linker that contains the strex regulatory domain. The ampulla isoform was also compared with the isoform predicted˜ in late skate embryos where strex was also absent. The BK voltage sensors were conserved in both skate isoforms. Differences between the skate and human BK channel included alternative splicing. Alternative splicing occurs at seven previously defined sites that are characteristic for BK channels in general and hair cells in particular. Skate BK sequences were highly similar to the Australian ghost shark and several other vertebrate species. Based on alignment of known BK sequences with the skate genome and transcriptome, there are at least two isoforms of Kcnma1α expressed in the skate. One of the β subunits (β4), which is known to decrease voltage sensitivity, was also identified in the skate genome and transcriptome and in the ampulla. These studies advance our knowledge of BK channels and suggest further studies in the ampulla and other excitable tissues. PMID:26687710

  9. Calcium activated K⁺ channels in the electroreceptor of the skate confirmed by cloning. Details of subunits and splicing.

    Science.gov (United States)

    King, Benjamin L; Shi, Ling Fang; Kao, Peter; Clusin, William T

    2016-03-01

    Elasmobranchs detect small potentials using excitable cells of the ampulla of Lorenzini which have calcium-activated K(+) channels, first described in 1974. A distinctive feature of the outward current in voltage clamped ampullae is its apparent insensitivity to voltage. The sequence of a BK channel α isoform expressed in the ampulla of the skate was characterized. A signal peptide is present at the beginning of the gene. When compared to human isoform 1 (the canonical sequence), the largest difference was absence of a 59 amino acid region from the S8-S9 intra-cellular linker that contains the strex regulatory domain. The ampulla isoform was also compared with the isoform predicted in late skate embryos where strex was also absent. The BK voltage sensors were conserved in both skate isoforms. Differences between the skate and human BK channel included alternative splicing. Alternative splicing occurs at seven previously defined sites that are characteristic for BK channels in general and hair cells in particular. Skate BK sequences were highly similar to the Australian ghost shark and several other vertebrate species. Based on alignment of known BK sequences with the skate genome and transcriptome, there are at least two isoforms of Kcnma1α expressed in the skate. One of the β subunits (β4), which is known to decrease voltage sensitivity, was also identified in the skate genome and transcriptome and in the ampulla. These studies advance our knowledge of BK channels and suggest further studies in the ampulla and other excitable tissues. Copyright © 2015 Elsevier B.V. All rights reserved.

  10. Effects of thymol on calcium and potassium currents in canine and human ventricular cardiomyocytes

    Science.gov (United States)

    Magyar, János; Szentandrássy, Norbert; Bányász, Tamás; Fülöp, László; Varró, András; Nánási, Péter P

    2002-01-01

    Concentration-dependent effects of thymol (1–1000 μM) was studied on action potential configuration and ionic currents in isolated canine ventricular cardiomyocytes using conventional microelectrode and patch clamp techniques.Low concentration of thymol (10 μM) removed the notch of the action potential, whereas high concentrations (100 μM or higher) caused an additional shortening of action potential duration accompanied by progressive depression of plateau and reduction of Vmax.In the canine cells L-type Ca current (ICa) was decreased by thymol in a concentration-dependent manner (EC50: 158±7 μM, Hill coeff.: 2.96±0.43). In addition, thymol (50–250 μM) accelerated the inactivation of ICa, increased the time constant of recovery from inactivation, shifted the steady-state inactivation curve of ICa leftwards, but voltage dependence of activation remained unaltered. Qualitatively similar results were obtained with thymol in ventricular myocytes isolated from healthy human hearts.Thymol displayed concentration-dependent suppressive effects on potassium currents: the transient outward current, Ito (EC50: 60.6±11.4 μM, Hill coeff.: 1.03±0.11), the rapid component of the delayed rectifier, IKr (EC50: 63.4±6.1 μM, Hill coeff.: 1.29±0.15), and the slow component of the delayed rectifier, IKs (EC50: 202±11 μM, Hill coeff.: 0.72±0.14), however, K channel kinetics were not much altered by thymol. These effects on Ca and K currents developed rapidly (within 0.5 min) and were readily reversible.In conclusion, thymol suppressed cardiac ionic channels in a concentration-dependent manner, however, both drug-sensitivities as well as the mechanism of action seems to be different when blocking calcium and potassium channels. PMID:12010783

  11. Altered voltage-gated calcium channels in rat inferior colliculus neurons contribute to alcohol withdrawal seizures

    Science.gov (United States)

    N’Gouemo, Prosper

    2015-01-01

    We have previously reported that enhanced susceptibility to alcohol withdrawal seizures (AWS) parallels the enhancement of the current density of high-threshold voltage-gated Ca2+ (CaV) channels in rat inferior colliculus (IC) neurons. However, whether this increased current density is a cause or consequence of AWS is unclear. Here, I report changes in the current density of CaV channels in IC neurons during the course of alcohol withdrawal and the potential anticonvulsant effect of intra-IC infusions of L- and P-type CaV channel antagonists. Whole-cell currents were activated by depolarizing pulses using barium as the charge carrier. Currents and seizure susceptibility were evaluated in control animals 3 h after alcohol intoxication, as well as 3 h (before AWS), 24 h (when AWS susceptibility is maximal), and 48 h (when AWS susceptibility is no longer present) after alcohol withdrawal. Nifedipine, nimodipine (L-type antagonists) or ω-agatoxin TK (P-type antagonist) were infused intra-IC to probe the role of CaV channels in the pathogenesis of AWS. CaV current density and conductance in IC neurons were significantly increased 3 and 24 h after alcohol withdrawal compared with the control group or the group tested 3 h following ethanol intoxication. Blockade of L-type CaV channels within the IC completely suppressed AWS, and inhibition of P-type channels reduced AWS severity. These findings suggest that the enhancement of CaV currents in IC neurons occurs prior to AWS onset and that alterations in L- and P-type CaV channels in these neurons may underlie the pathogenesis of AWS. PMID:25914156

  12. Bradykinin-evoked changes in cytosolic calcium and membrane currents in cultured bovine pulmonary artery endothelial cells.

    Science.gov (United States)

    Cannell, M B; Sage, S O

    1989-12-01

    1. Cultured bovine pulmonary artery endothelial cells were voltage clamped using a single microelectrode while cytosolic free calcium concentration ([Ca2+]i) was simultaneously measured using the fluorescent calcium indicator, Indo-1. 2. The resting current-voltage relationship was non-linear and exhibited marked inward rectification near the resting potential. In about 60% of cells examined, superfusion of saline resulted in a hyperpolarization and decrease in inward current. This result did not depend on the presence of agonist and is consistent with the presence of extracellular potassium accumulation in restricted spaces around the cell and the known dependence of the inward rectifier. In other cells there was no effect. 3. Resting [Ca2+]i was sensitive to membrane potential, decreasing continuously with membrane depolarization over the range -70 to +60 mV. This result is consistent with a simple pump-leak model and suggests that voltage-dependent calcium channels are not present in these cells. 4. Bradykinin (10 microM) increased [Ca2+]i after a delay of approximately 3 s. [Ca2+]i reached a peak after a further 3 s and declined over several minutes. 5. During the rise in [Ca2+]i evoked by application of bradykinin, there were no changes in the current-voltage relationship of the cell. These results question the role of a receptor-operated non-selective cation channel in mediating the increase in [Ca2+]i. This observation, coupled with the observed delay in the agonist-evoked response suggests that a second messenger system is involved in mediating the increase in [Ca2+]i. 6. Changes in the current-voltage relation started to occur about 30 s after the application of agonist. These changes could be explained by the activation of large-conductance potassium and non-selective cation channels with a reversal potential near 0 mV. The latter channels may mediate the plateau phase of the agonist-evoked response. 7. The results are discussed with respect to the

  13. Calcium cooperativity of exocytosis as a measure of Ca²+ channel domain overlap.

    Science.gov (United States)

    Matveev, Victor; Bertram, Richard; Sherman, Arthur

    2011-06-29

    The number of Ca(2+) channels contributing to the exocytosis of a single neurotransmitter vesicle in a presynaptic terminal has been a question of significant interest and debate, and is important for a full understanding of localized Ca(2+) signaling in general, and synaptic physiology in particular. This is usually estimated by measuring the sensitivity of the neurotransmitter release rate to changes in the synaptic Ca(2+) current, which is varied using appropriate voltage-clamp protocols or via pharmacological Ca(2+) channel block under the condition of constant single-channel Ca(2+) current. The slope of the resulting log-log plot of transmitter release rate versus presynaptic Ca(2+) current is termed Ca(2+)current cooperativity of exocytosis, and provides indirect information about the underlying presynaptic morphology. In this review, we discuss the relationship between the Ca(2+) current cooperativity and the average number of Ca(2+) channels participating in the exocytosis of a single vesicle, termed the Ca(2+)channel cooperativity. We relate these quantities to the morphology of the presynaptic active zone. We also review experimental studies of Ca(2+) current cooperativity and its modulation during development in different classes of synapses. Copyright © 2011. Published by Elsevier B.V.

  14. Calcium Cooperativity of Exocytosis as a Measure of Ca2+ Channel Domain Overlap

    Science.gov (United States)

    Matveev, Victor; Bertram, Richard; Sherman, Arthur

    2011-01-01

    The number of Ca2+ channels contributing to the exocytosis of a single neurotransmitter vesicle in a presynaptic terminal has been a question of significant interest and debate, and is important for a full understanding of localized Ca2+ signaling in general, and synaptic physiology in particular. This is usually estimated by measuring the sensitivity of the neurotransmitter release rate to changes in the synaptic Ca2+ current, which is varied using appropriate voltage-clamp protocols or via pharmacological Ca2+ channel block under the condition of constant single-channel Ca2+ current. The slope of the resulting log-log plot of transmitter release rate versus presynaptic Ca2+ current is termed Ca2+ current cooperativity of exocytosis, and provides indirect information about the underlying presynaptic morphology. In this review, we discuss the relationship between the Ca2+ current cooperativity and the average number of Ca2+ channels participating in the exocytosis of a single vesicle, termed the Ca2+ channel cooperativity. We relate these quantities to the morphology of the presynaptic active zone. We also review experimental studies of Ca2+ current cooperativity and its modulation during development in different classes of synapses. PMID:21621748

  15. Simultaneous mapping of membrane voltage and calcium in zebrafish heart in vivo reveals chamber-specific developmental transitions in ionic currents

    Directory of Open Access Journals (Sweden)

    Jennifer H Hou

    2014-09-01

    Full Text Available The cardiac action potential (AP and the consequent cytosolic Ca2+ transient are key indicators of cardiac function. Natural developmental processes, as well as many drugs and pathologies change the waveform, propagation, or variability (between cells or over time of these parameters. Here we apply a genetically encoded dual-function calcium and voltage reporter (CaViar to study the development of the zebrafish heart in vivo between 1.5 and 4 days post fertilization (dpf. We developed a high-sensitivity spinning disk confocal microscope and associated software for simultaneous three-dimensional optical mapping of voltage and calcium. We produced a transgenic zebrafish line expressing CaViar under control of the heart-specific cmlc2 promoter, and applied ion channel blockers at a series of developmental stages to map the maturation of the action potential in vivo. Early in development, the AP initiated via a calcium current through L-type calcium channels. Between 90 – 102 hours post fertilization (hpf, the ventricular AP switched to a sodium-driven upswing, while the atrial AP remained calcium driven. In the adult zebrafish heart, a sodium current drives the AP in both the atrium and ventricle. Simultaneous voltage and calcium imaging with genetically encoded reporters provides a new approach for monitoring cardiac development, and the effects of drugs on cardiac function.

  16. Postsynaptic GABABRs Inhibit L-Type Calcium Channels and Abolish Long-Term Potentiation in Hippocampal Somatostatin Interneurons.

    Science.gov (United States)

    Booker, Sam A; Loreth, Desiree; Gee, Annabelle L; Watanabe, Masahiko; Kind, Peter C; Wyllie, David J A; Kulik, Ákos; Vida, Imre

    2018-01-02

    Inhibition provided by local GABAergic interneurons (INs) activates ionotropic GABAA and metabotropic GABAB receptors (GABABRs). Despite GABABRs representing a major source of inhibition, little is known of their function in distinct IN subtypes. Here, we show that, while the archetypal dendritic-inhibitory somatostatin-expressing INs (SOM-INs) possess high levels of GABABR on their somato-dendritic surface, they fail to produce significant postsynaptic inhibitory currents. Instead, GABABRs selectively inhibit dendritic CaV1.2 (L-type) Ca2+ channels on SOM-IN dendrites, leading to reduced calcium influx and loss of long-term potentiation at excitatory input synapses onto these INs. These data provide a mechanism by which GABABRs can contribute to disinhibition and control the efficacy of extrinsic inputs to hippocampal networks. Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.

  17. Distribution of high-conductance calcium-activated potassium channels in rat vestibular epithelia.

    Science.gov (United States)

    Schweizer, Felix E; Savin, David; Luu, Cindy; Sultemeier, David R; Hoffman, Larry F

    2009-11-10

    Voltage- and calcium-activated potassium channels (BK) are important regulators of neuronal excitability. BK channels seem to be crucial for frequency tuning in nonmammalian vestibular and auditory hair cells. However, there are a paucity of data concerning BK expression in mammalian vestibular hair cells. We therefore investigated the localization of BK channels in mammalian vestibular hair cells, specifically in rat vestibular neuroepithelia. We find that only a subset of hair cells in the utricle and the crista ampullaris express BK channels. BK-positive hair cells are located mainly in the medial striolar region of the utricle, where they constitute at most 12% of hair cells, and in the central zone of the horizontal crista. A majority of BK-positive hair cells are encapsulated by a calretinin-positive calyx defining them as type I cells. The remainder are either type I cells encapsulated by a calretinin-negative calyx or type II hair cells. Surprisingly, the number of BK-positive hair cells in the utricle peaks in juvenile rats and declines in early adulthood. BK channels were not found in vestibular afferent dendrites or somata. Our data indicate that BK channel expression in the mammalian vestibular system differs from the expression pattern in the mammalian auditory and the nonmammalian vestibular system. The molecular diversity of vestibular hair cells indicates a functional diversity that has not yet been fully characterized. The predominance of BK-positive hair cells within the medial striola of juvenile animals suggests that they contribute to a scheme of highly lateralized coding of linear head movements during late development.

  18. Actions of Calcium Channel Blockers on Vascular Proteoglycan Synthesis: Relationship to Atherosclerosis

    Science.gov (United States)

    Survase, Soniya; Ivey, Melanie E; Nigro, Julie; Osman, Narin; Little, Peter J

    2005-01-01

    Calcium channel blockers (CCBs) are a widely used group of antihypertensive agents. CCBs are efficacious in the reduction of blood pressure but the extent to which they manifest beneficial effects on cardiovascular disease is variable. Clinical studies indicate that pleiotropic actions make significant contributions to the efficacy of agents aimed at preventing atherosclerosis. The “response to retention” hypothesis implicates the binding and retention of lipoproteins by glycosaminoglycan chains on proteoglycans as an initiating step in atherogenesis. Atherogenic factors act as agonists and several classes of drugs including peroxisome proliferating-activated receptor (PPAR)-α and -γ ligands act as antagonists in this model. Initial data have demonstrated that high concentrations of CCBs inhibit proteoglycan synthesis. Newer preliminary data show that the action is very modest at reasonable concentrations and appears to be independent of calcium channel blocking activity. We have reviewed the role of cardiovascular drugs acting on vascular smooth muscle proteoglycan synthesis and considered the potential action of CCBs in this model. We conclude that the inhibition of proteoglycan synthesis by CCBs does not play a role in the attenuation of atherosclerosis; however, the antihypertensive efficacy and alternative beneficial actions provide support for the use of CCBs in the therapy of cardiovascular disease. PMID:17319105

  19. Synergistic Effect of Fluconazole and Calcium Channel Blockers against Resistant Candida albicans.

    Directory of Open Access Journals (Sweden)

    Shuyuan Liu

    Full Text Available Candidiasis has increased significantly recently that threatens patients with low immunity. However, the number of antifungal drugs on the market is limited in comparison to the number of available antibacterial drugs. This fact, coupled with the increased frequency of fungal resistance, makes it necessary to develop new therapeutic strategies. Combination drug therapy is one of the most widely used and effective strategy to alleviate this problem. In this paper, we were aimed to evaluate the combined antifungal effects of four CCBs (calcium channel blockers, amlodipine (AML, nifedipine (NIF, benidipine (BEN and flunarizine (FNZ with fluconazole against C. albicans by checkerboard and time-killing method. In addition, we determined gene (CCH1, MID1, CNA1, CNB1, YVC1, CDR1, CDR2 and MDR1 expression by quantitative PCR and investigated the efflux pump activity of resistant candida albicans by rhodamine 6G assay to reveal the potential mechanisms. Finally, we concluded that there was a synergy when fluconazole combined with the four tested CCBs against resistant strains, with fractional inhibitory concentration index (FICI <0.5, but no interaction against sensitive strains (FICI = 0.56 ~ 2. The mechanism studies revealed that fluconazole plus amlodipine caused down-regulating of CNA1, CNB1 (encoding calcineurin and YVC1 (encoding calcium channel protein in vacuole membrane.

  20. Stereoselective inhibition of thromboxane-induced coronary vasoconstriction by 1,4-dihydropyridine calcium channel antagonists

    Energy Technology Data Exchange (ETDEWEB)

    Eltze, M.; Boer, R.; Sanders, K.H.; Boss, H.; Ulrich, W.R.; Flockerzi, D. (Byk Gulden Pharmaceuticals, Konstanz (Germany F.R.))

    1990-01-01

    The biological activity of the (+)-S- and (-)-R-enantiomers of niguldipine, of the (-)-S- and (+)-R-enantiomers of felodipine and nitrendipine, and of rac-nisoldipine and rac-nimodipine was investigated in vitro and in vivo. Inhibition of coronary vasoconstriction due to the thromboxane A2 (TxA2)-mimetic U-46619 in guinea pig Langendorff hearts, displacement of (+)-({sup 3}H)isradipine from calcium channel binding sites of guinea pig skeletal muscle T-tubule membranes, and blood pressure reduction in spontaneously hypertensive rats were determined. The enantiomers were obtained by stereoselective synthesis. Cross-contamination was less than 0.5% for both S- and R-enantiomers of niguldipine and nitrendipine and less than 1% for those of felodipine. From the doses necessary for a 50% inhibition of coronary vasoconstriction, stereoselectivity ratios for (+)-(S)-/(-)-(R)-niguldipine, (-)-(S)-/(+)-(R)-felodipine, and (-)-(S)-/(+)-(R)-nitrendipine of 28, 13, and 7, respectively, were calculated. The potency ratio rac-nisoldipine/rac-nimodipine was 3.5. Ratios obtained from binding experiments and antihypertensive activity were (+)-(S)-/(-)-(R)-niguldipine = 45 and 35, (-)-(S)-/(+)-(R)-felodipine = 12 and 13, (-)-(S)-/(+)-(R)-nitrendipine = 8 and 8, and rac-nisoldipine/rac-nimodipine = 8 and 7, respectively. Highly significant correlations were found between the in vitro potency of the substances to prevent U-46619-induced coronary vasoconstriction and their affinity for calcium channel binding sites as well as their antihypertensive activity.

  1. Synergistic Effect of Fluconazole and Calcium Channel Blockers against Resistant Candida albicans

    Science.gov (United States)

    Liu, Shuyuan; Yue, Longtao; Gu, Wenrui; Li, Xiuyun; Zhang, Liuping; Sun, Shujuan

    2016-01-01

    Candidiasis has increased significantly recently that threatens patients with low immunity. However, the number of antifungal drugs on the market is limited in comparison to the number of available antibacterial drugs. This fact, coupled with the increased frequency of fungal resistance, makes it necessary to develop new therapeutic strategies. Combination drug therapy is one of the most widely used and effective strategy to alleviate this problem. In this paper, we were aimed to evaluate the combined antifungal effects of four CCBs (calcium channel blockers), amlodipine (AML), nifedipine (NIF), benidipine (BEN) and flunarizine (FNZ) with fluconazole against C. albicans by checkerboard and time-killing method. In addition, we determined gene (CCH1, MID1, CNA1, CNB1, YVC1, CDR1, CDR2 and MDR1) expression by quantitative PCR and investigated the efflux pump activity of resistant candida albicans by rhodamine 6G assay to reveal the potential mechanisms. Finally, we concluded that there was a synergy when fluconazole combined with the four tested CCBs against resistant strains, with fractional inhibitory concentration index (FICI) fluconazole plus amlodipine caused down-regulating of CNA1, CNB1 (encoding calcineurin) and YVC1 (encoding calcium channel protein in vacuole membrane). PMID:26986478

  2. Castration prevents calcium channel blocker-induced gingival hyperplasia in beagle dogs.

    Science.gov (United States)

    Dayan, D; Kozlovsky, A; Tal, H; Kariv, N; Shemesh, M; Nyska, A

    1998-07-01

    1. The purpose of this study was to investigate testosterone's role on the calcium channel antagonist oxodipine-inducing gingival hyperplasia in a dog model. 2. Two experiments were conducted using castrated and intact male dogs. Oxodipine was administered orally for 90 days, at a dose of 24 mg/kg/day. In the first experiment, the occurrence of gingival hyperplasia was evaluated. In the second, the gingival index (GI) and gingival hyperplasia index (GHI) were recorded and correlated with serum levels of testosterone. 3. A significant positive correlation between GI, GHI and plasma testosterone was noted. Castrated dogs were injected with testosterone, 4 months after the start of oxodipine treatment, while in the non-castrated dogs, administration of oxodipine was stopped. Castration correlated with lack of GH, while testosterone injection to the same dogs was associated with an increase of GI and GHI. 4. Since it is known that testosterone receptors are present in the gingiva, it is proposed that oxodipine-induced gingival hyperplasia could be mediated by the calcium channel blocker on plasma testosterone levels.

  3. Modulation of the N-type calcium channel gene expression by the alpha subunit of Go.

    Science.gov (United States)

    Kim, Bum-Jun; Ghil, Sung-Ho; Kim, Min-Ji; Yun Park, So; Kim, Dong-Sun; Hwan Kim, Sung; Chin, Hemin; Birnbaumer, Lutz; Jiang, Meisheng; Hong, Sung Youl; Suh-Kim, Haeyoung; Lee, Young-Don

    2003-04-10

    Go, a heterotrimeric G-protein, is enriched in brain and neuronal growth cones. Although several reports suggest that Go may be involved in modulation of neuronal differentiation, the precise role of Go is not clear. To investigate the function of Go in neuronal differentiation, we determined the effect of Goalpha, the alpha subunit of Go, on the expression of Ca(v)2.2, the pore-forming unit of N-type calcium channels, at the transcription level. Treatment with cyclic AMP (cAMP), which triggers neurite outgrowth in neuroblastoma F11 cells, increased the mRNA level and the promoter activity of the Ca(v)2.2 gene. Overexpression of Goalpha inhibited neurite extension in F11 cells and simultaneously repressed the stimulatory effect of cAMP on the Ca(v)2.2 gene expression to the basal level. Targeted mutation of the Goalpha gene also increased the level of Ca(v)2.2 in the brain. These results suggest that Go may regulate neuronal differentiation through modulation of gene expression of target genes such as N-type calcium channels.

  4. Alzheimer disease amyloid beta protein forms calcium channels in bilayer membranes: blockade by tromethamine and aluminum.

    OpenAIRE

    Arispe, N.; Rojas, E.; Pollard, H B

    1993-01-01

    Amyloid beta protein (A beta P) is the 40- to 42-residue polypeptide implicated in the pathogenesis of Alzheimer disease. We have incorporated this peptide into phosphatidylserine liposomes and then fused the liposomes with a planar bilayer. When incorporated into bilayers the A beta P forms channels, which generate linear current-voltage relationships in symmetrical solutions. A permeability ratio, PK/PCl, of 11 for the open A beta P channel was estimated from the reversal potential of the c...

  5. Understanding alternative splicing of Cav1.2 calcium channels for a new approach towards individualized medicine

    Science.gov (United States)

    Liao, Ping; Soong, Tuck Wah

    2010-01-01

    Calcium channel blockers (CCBs) are widely used to treat cardiovascular diseases such as hypertension, angina pectoris, hypertrophic cardiomyopathy, and supraventricular tachycardia. CCBs selectively inhibit the inward flow of calcium ions through voltage-gated calcium channels, particularly Cav1.2, that are expressed in the cardiovascular system. Changes to the molecular structure of Cav1.2 channels could affect sensitivity of the channels to blockade by CCBs. Recently, extensive alternative splicing was found in Cav1.2 channels that generated wide phenotypic variations. Cardiac and smooth muscles express slightly different, but functionally important Cav1.2 splice variants. Alternative splicing could also modulate the gating properties of the channels and giving rise to different responses to inhibition by CCBs. Importantly, alternative splicing of Cav1.2 channels may play an important role to influence the outcome of many cardiovascular disorders. Therefore, the understanding of how alternative splicing impacts Cav1.2 channels pharmacology in various diseases and different organs may provide the possibility for individualized therapy with minimal side effects. PMID:23554629

  6. Role of calcium influx through voltage-operated calcium channels and of calcium mobilization in the physiology of Schistosoma mansoni muscle contractions.

    Science.gov (United States)

    Mendonça-Silva, D L; Novozhilova, E; Cobbett, P J R; Silva, C L M; Noël, F; Totten, M I J; Maule, A G; Day, T A

    2006-07-01

    We tested the hypothesis that voltage-operated Ca2+ channels mediate an extracellular Ca2+ influx in muscle fibres from the human parasite Schistosoma mansoni and, along with Ca2+ mobilization from the sarcoplasmic reticulum, contribute to muscle contraction. Indeed, whole-cell voltage clamp revealed voltage-gated inward currents carried by divalent ions with a peak current elicited by steps to +20 mV (from a holding potential of -70 mV). Depolarization of the fibres by elevated extracellular K+ elicited contractions that were completely dependent on extracellular Ca2+ and inhibited by nicardipine (half inhibition at 4.1 microM). However these contractions were not very sensitive to other classical blockers of voltage-gated Ca2+ channels, indicating that the schistosome muscle channels have an atypical pharmacology when compared to their mammalian counterparts. Futhermore, the contraction induced by 5 mM caffeine was inhibited after depletion of the sarcoplasmic reticulum either with thapsigargin (10 microM) or ryanodine (10 microM). These data suggest that voltage-operated Ca2+ channels do contribute to S. mansoni contraction as does the mobilization of stored Ca2+, despite the small volume of sarcoplasmic reticulum in schistosome smooth muscles.

  7. The β1 Subunit Enhances Oxidative Regulation of Large-Conductance Calcium-activated K+ Channels

    Science.gov (United States)

    Santarelli, Lindsey Ciali; Chen, Jianguo; Heinemann, Stefan H.; Hoshi, Toshinori

    2004-01-01

    Oxidative stress may alter the functions of many proteins including the Slo1 large conductance calcium-activated potassium channel (BKCa). Previous results demonstrated that in the virtual absence of Ca2+, the oxidant chloramine-T (Ch-T), without the involvement of cysteine oxidation, increases the open probability and slows the deactivation of BKCa channels formed by human Slo1 (hSlo1) α subunits alone. Because native BKCa channel complexes may include the auxiliary subunit β1, we investigated whether β1 influences the oxidative regulation of hSlo1. Oxidation by Ch-T with β1 present shifted the half-activation voltage much further in the hyperpolarizing direction (−75 mV) as compared with that with α alone (−30 mV). This shift was eliminated in the presence of high [Ca2+]i, but the increase in open probability in the virtual absence of Ca2+ remained significant at physiologically relevant voltages. Furthermore, the slowing of channel deactivation after oxidation was even more dramatic in the presence of β1. Oxidation of cysteine and methionine residues within β1 was not involved in these potentiated effects because expression of mutant β1 subunits lacking cysteine or methionine residues produced results similar to those with wild-type β1. Unlike the results with α alone, oxidation by Ch-T caused a significant acceleration of channel activation only when β1 was present. The β1 M177 mutation disrupted normal channel activation and prevented the Ch-T–induced acceleration of activation. Overall, the functional effects of oxidation of the hSlo1 pore-forming α subunit are greatly amplified by the presence of β1, which leads to the additional increase in channel open probability and the slowing of deactivation. Furthermore, M177 within β1 is a critical structural determinant of channel activation and oxidative sensitivity. Together, the oxidized BKCa channel complex with β1 has a considerable chance of being open within the physiological voltage

  8. Lotus japonicus CASTOR and POLLUX are ion channels essential for perinuclear calcium spiking in legume root endosymbiosis.

    Science.gov (United States)

    Charpentier, Myriam; Bredemeier, Rolf; Wanner, Gerhard; Takeda, Naoya; Schleiff, Enrico; Parniske, Martin

    2008-12-01

    The mechanism underlying perinuclear calcium spiking induced during legume root endosymbioses is largely unknown. Lotus japonicus symbiosis-defective castor and pollux mutants are impaired in perinuclear calcium spiking. Homology modeling suggested that the related proteins CASTOR and POLLUX might be ion channels. Here, we show that CASTOR and POLLUX form two independent homocomplexes in planta. CASTOR reconstituted in planar lipid bilayers exhibited ion channel activity, and the channel characteristics were altered in a symbiosis-defective mutant carrying an amino acid replacement close to the selectivity filter. Permeability ratio determination and competition experiments reveled a weak preference of CASTOR for cations such as potassium over anions. POLLUX has an identical selectivity filter region and complemented a potassium transport-deficient yeast mutant, suggesting that POLLUX is also a potassium-permeable channel. Immunogold labeling localized the endogenous CASTOR protein to the nuclear envelope of Lotus root cells. Our data are consistent with a role of CASTOR and POLLUX in modulating the nuclear envelope membrane potential. They could either trigger the opening of calcium release channels or compensate the charge release during the calcium efflux as counter ion channels.

  9. Lavender oil-potent anxiolytic properties via modulating voltage dependent calcium channels.

    Directory of Open Access Journals (Sweden)

    Anita M Schuwald

    Full Text Available Recent clinical data support the clinical use of oral lavender oil in patients suffering from subsyndromal anxiety. We identified the molecular mechanism of action that will alter the perception of lavender oil as a nonspecific ingredient of aromatherapy to a potent anxiolytic inhibiting voltage dependent calcium channels (VOCCs as highly selective drug target. In contrast to previous publications where exorbitant high concentrations were used, the effects of lavender oil in behavioral, biochemical, and electrophysiological experiments were investigated in physiological concentrations in the nanomolar range, which correlate to a single dosage of 80 mg/d in humans that was used in clinical trials. We show for the first time that lavender oil bears some similarities with the established anxiolytic pregabalin. Lavender oil inhibits VOCCs in synaptosomes, primary hippocampal neurons and stably overexpressing cell lines in the same range such as pregabalin. Interestingly, Silexan does not primarily bind to P/Q type calcium channels such as pregabalin and does not interact with the binding site of pregabalin, the α2δ subunit of VOCCs. Lavender oil reduces non-selectively the calcium influx through several different types of VOCCs such as the N-type, P/Q-type and T-type VOCCs. In the hippocampus, one brain region important for anxiety disorders, we show that inhibition by lavender oil is mainly mediated via N-type and P/Q-type VOCCs. Taken together, we provide a pharmacological and molecular rationale for the clinical use of the oral application of lavender oil in patients suffering from anxiety.

  10. Late sodium current in the pathophysiology of cardiovascular disease: consequences of sodium–calcium overload

    OpenAIRE

    Noble, D; Noble, P J

    2006-01-01

    Late sodium current in cardiac cells is very small compared with the fast component, but as it flows throughout the action potential it may make a substantial contribution to sodium loading during each cardiac cycle. Late sodium current may contribute to triggering arrhythmia in two ways: by causing repolarisation failure (early afterdepolarisations); and by triggering late afterdepolarisations attributable to calcium oscillations in sodium–calcium overload conditions. Reduction of late sodiu...

  11. Stability of high-dose insulin in normal saline bags for treatment of calcium channel blocker and beta blocker overdose.

    Science.gov (United States)

    Laskey, Dayne; Vadlapatla, Rajesh; Hart, Katherine

    2016-11-01

    High-dose insulin has become a first-line therapy for treating severe calcium channel blocker and beta blocker toxicity. Insulin infusions used to treat other conditions (e.g., diabetic ketoacidosis) may be used, but this may lead to pulmonary compromise due to fluid volume overload. An obvious solution would be to use a more concentrated insulin infusion; however, data describing the stability of insulin in polyvinyl chloride bags at concentrations >1 unit/mL are not readily available. To determine the stability of insulin at 16 units/mL in 0.9% saline solution. Eight-hundred units of regular insulin (8 mL from a stock vial containing 100 units/mL) were added to 42 mL of 0.9% saline solution in a polyvinyl chloride bag to make a final concentration of 16 units/mL. Two bags were stored at 4 °C (refrigerated) and two at 25 °C (room temperature). Samples were withdrawn and tested for insulin concentration periodically over 14 days. Concentrated regular insulin in a polyvinyl chloride bag remained within 90% of equilibrium concentration at all time points, indicating the 16 units/mL concentration was sufficiently stable both refrigerated and at room temperature for 14 days. Administration of high-dose insulin can cause fluid volume overload when using traditional insulin formulations. The 16 units/mL concentration allows for the treatment of a patient with severe calcium channel blocker or beta blocker toxicity for a reasonable period of time without administering excessive fluid. Insulin at a concentration of 16 units/mL is stable for 14 days, the maximum timeframe currently allowed under US Pharmacopeia rules for compounding of sterile preparations. This stability data will allow institutions to issue beyond-use dating for intravenous fluids containing concentrated insulin and used for treating beta blocker and calcium channel blocker toxicity.

  12. Evaluating state dependence and subtype selectivity of calcium channel modulators in automated electrophysiology assays.

    Science.gov (United States)

    Kuryshev, Yuri A; Brown, Arthur M; Duzic, Emir; Kirsch, Glenn E

    2014-03-01

    Voltage-gated Ca2+ channels play essential roles in control of neurosecretion and muscle contraction. The pharmacological significance of Cav channels stem from their identification as the molecular targets of calcium blockers used in the treatment of cardiovascular diseases, such as hypertension, angina, and arrhythmia, and neurologic diseases, such as pain and seizure. It has been proposed that state-dependent Cav inhibitors, that is, those that preferentially bind to channels in open or inactivated states, may improve the therapeutic window over relatively state-independent Cav inhibitors. High-throughput fluorescent-based functional assays have been useful in screening chemical libraries to identify Cav inhibitors. However, hit confirmation, mechanism of action, and subtype selectivity are better suited to automated patch clamp assays that have sufficient capacity to handle the volume of compounds identified during screening, even of modest sized libraries (≤500,000 compounds), and the flexible voltage control that allows evaluation of state-dependent drug blocks. IonWorks Barracuda (IWB), the newest generation of IonWorks instruments, provides the opportunity to accelerate the Cav drug discovery studies in an automated patch clamp platform in 384-well format capable of medium throughput screening and profiling studies. We have validated hCav1.2, hCav2.1, hCav2.2, and hCav3.2 channels assays on the IWB platform (population patch clamp mode) and demonstrated that the biophysical characteristics of the channels (activation, inactivation, and steady-state inactivation) obtained with the IWB system are consistent with known subtype-specific characteristics. Using standard reference compounds (nifedipine, BAY K8644, verapamil, mibefradil, and pimozide), we demonstrated subtype-selective and state- and use-dependent characteristics of drug-channel interactions. Here we describe the design and validation of novel robust high-throughput Cav channel assays on the IWB

  13. Turtle Flexion Reflex Motor Patterns Show Windup, Mediated Partly by L-type Calcium Channels

    Directory of Open Access Journals (Sweden)

    Keith P. Johnson

    2017-10-01

    Full Text Available Windup is a form of multisecond temporal summation in which identical stimuli, delivered seconds apart, trigger increasingly strong neuronal responses. L-type Ca2+ channels have been shown to play an important role in the production of windup of spinal cord neuronal responses, initially in studies of turtle spinal cord and later in studies of mammalian spinal cord. L-type Ca2+ channels have also been shown to contribute to windup of limb withdrawal reflex (flexion reflex in rats, but flexion reflex windup has not previously been described in turtles and its cellular mechanisms have not been studied. We studied windup of flexion reflex motor patterns, evoked with weak mechanical and electrical stimulation of the dorsal hindlimb foot skin and assessed via a hip flexor (HF nerve recording, in spinal cord-transected and immobilized turtles in vivo. We found that an L-type Ca2+ channel antagonist, nifedipine, applied at concentrations of 50 μM or 100 μM to the hindlimb enlargement spinal cord, significantly reduced windup of flexion reflex motor patterns, while lower concentrations of nifedipine had no such effect. Nifedipine similarly reduced the amplitude of an individual flexion reflex motor pattern evoked by a stronger mechanical stimulus, in a dose-dependent manner, suggesting that L-type Ca2+ channels contribute to each flexion reflex as well as to multisecond summation of flexion reflex responses in turtles. We also found that we could elicit flexion reflex windup consistently using a 4-g von Frey filament, which is not usually considered a nociceptive stimulus. Thus, it may be that windup can be evoked by a wide range of tactile stimuli and that L-type calcium channels contribute to multisecond temporal summation of diverse tactile stimuli across vertebrates.

  14. Calcium-activated potassium (BK) channels are encoded by duplicate slo1 genes in teleost fishes.

    Science.gov (United States)

    Rohmann, Kevin N; Deitcher, David L; Bass, Andrew H

    2009-07-01

    Calcium-activated, large conductance potassium (BK) channels in tetrapods are encoded by a single slo1 gene, which undergoes extensive alternative splicing. Alternative splicing generates a high level of functional diversity in BK channels that contributes to the wide range of frequencies electrically tuned by the inner ear hair cells of many tetrapods. To date, the role of BK channels in hearing among teleost fishes has not been investigated at the molecular level, although teleosts account for approximately half of all extant vertebrate species. We identified slo1 genes in teleost and nonteleost fishes using polymerase chain reaction and genetic sequence databases. In contrast to tetrapods, all teleosts examined were found to express duplicate slo1 genes in the central nervous system, whereas nonteleosts that diverged prior to the teleost whole-genome duplication event express a single slo1 gene. Phylogenetic analyses further revealed that whereas other slo1 duplicates were the result of a single duplication event, an independent duplication occurred in a basal teleost (Anguilla rostrata) following the slo1 duplication in teleosts. A third, independent slo1 duplication (autotetraploidization) occurred in salmonids. Comparison of teleost slo1 genomic sequences to their tetrapod orthologue revealed a reduced number of alternative splice sites in both slo1 co-orthologues. For the teleost Porichthys notatus, a focal study species that vocalizes with maximal spectral energy in the range electrically tuned by BK channels in the inner ear, peripheral tissues show the expression of either one (e.g., vocal muscle) or both (e.g., inner ear) slo1 paralogues with important implications for both auditory and vocal physiology. Additional loss of expression of one slo1 paralogue in nonneural tissues in P. notatus suggests that slo1 duplicates were retained via subfunctionalization. Together, the results predict that teleost fish achieve a diversity of BK channel subfunction via

  15. Conotoxins as Tools to Understand the Physiological Function of Voltage-Gated Calcium (CaV Channels

    Directory of Open Access Journals (Sweden)

    David Ramírez

    2017-10-01

    Full Text Available Voltage-gated calcium (CaV channels are widely expressed and are essential for the completion of multiple physiological processes. Close regulation of their activity by specific inhibitors and agonists become fundamental to understand their role in cellular homeostasis as well as in human tissues and organs. CaV channels are divided into two groups depending on the membrane potential required to activate them: High-voltage activated (HVA, CaV1.1–1.4; CaV2.1–2.3 and Low-voltage activated (LVA, CaV3.1–3.3. HVA channels are highly expressed in brain (neurons, heart, and adrenal medulla (chromaffin cells, among others, and are also classified into subtypes which can be distinguished using pharmacological approaches. Cone snails are marine gastropods that capture their prey by injecting venom, “conopeptides”, which cause paralysis in a few seconds. A subset of conopeptides called conotoxins are relatively small polypeptides, rich in disulfide bonds, that target ion channels, transporters and receptors localized at the neuromuscular system of the animal target. In this review, we describe the structure and properties of conotoxins that selectively block HVA calcium channels. We compare their potency on several HVA channel subtypes, emphasizing neuronal calcium channels. Lastly, we analyze recent advances in the therapeutic use of conotoxins for medical treatments.

  16. Diabetes-Induced Inhibition of Voltage-Dependent Calcium Channels in the Retinal Microvasculature: Role of Spermine

    Science.gov (United States)

    Matsushita, Kenji; Fukumoto, Masanori; Kobayashi, Takatoshi; Kobayashi, Masato; Ishizaki, Eisuke; Minami, Masahiro; Katsumura, Kozo; Liao, Sophie D.; Wu, David M.; Zhang, Ting

    2010-01-01

    Purpose. Although decentralized control of blood flow is particularly important in the retina, knowledge of the functional organization of the retinal microvasculature is limited. Here, the authors characterized the distribution and regulation of L-type voltage-dependent calcium channels (VDCCs) within the most decentralized operational complex of the retinal vasculature—the feeder vessel/capillary unit—which consists of a capillary network plus the vessel linking it with a myocyte-encircled arteriole. Methods. Perforated-patch recordings, calcium-imaging, and time-lapse photography were used to assess VDCC-dependent changes in ionic currents, intracellular calcium, abluminal cell contractility, and lumen diameter, in microvascular complexes freshly isolated from the rat retina. Results. Topographical heterogeneity was found in the distribution of functional VDCCs; VDCC activity was markedly greater in feeder vessels than in capillaries. Experiments showed that this topographical distribution occurs, in large part, because of the inhibition of capillary VDCCs by a mechanism dependent on the endogenous polyamine spermine. An operational consequence of functional VDCCs predominantly located in the feeder vessels is that voltage-driven vasomotor responses are generated chiefly in this portion of the feeder vessel/capillary unit. However, early in the course of diabetes, this ability to generate voltage-driven vasomotor responses becomes profoundly impaired because of the inhibition of feeder vessel VDCCs by a spermine-dependent mechanism. Conclusions. The regulation of VDCCs by endogenous spermine not only plays a critical role in establishing the physiological organization of the feeder vessel/capillary unit, but also may contribute to dysfunction of this decentralized operational unit in the diabetic retina. PMID:20484578

  17. Stimulation of NOX2 in isolated hearts reversibly sensitizes RyR2 channels to activation by cytoplasmic calcium.

    Science.gov (United States)

    Donoso, Paulina; Finkelstein, José Pablo; Montecinos, Luis; Said, Matilde; Sánchez, Gina; Vittone, Leticia; Bull, Ricardo

    2014-03-01

    The response of ryanodine receptor (RyR) channels to cytoplasmic free calcium concentration ([Ca(2+)]) is redox sensitive. Here, we report the effects of a mild oxidative stress on cardiac RyR (RyR2) channels in Langendorff perfused rat hearts. Single RyR2 channels from control ventricles displayed the same three responses to Ca(2+) reported in other mammalian tissues, characterized by low, moderate, or high maximal activation. A single episode of 5 min of global ischemia, followed by 1 min of reperfusion, enhanced 2.3-fold the activity of NOX2 compared to controls and changed the frequency distribution of the different responses of RyR2 channels to calcium, favoring the more active ones: high activity response increased and low activity response decreased with respect to controls. This change was fully prevented by perfusion with apocynin or VAS 2870 before ischemia and totally reversed by the extension of the reperfusion period to 15 min. In vitro activation of NOX2 in control SR vesicles mimicked the effect of the ischemia/reperfusion episode on the frequencies of emergence of single RyR2 channel responses to [Ca(2+)] and increased 2.2-fold the rate of calcium release in Ca(2+)-loaded SR vesicles. In vitro changes were reversed at the single channel level by DTT and in isolated SR vesicles by glutaredoxin. Our results indicate that in whole hearts a mild oxidative stress enhances the response of cardiac RyR2 channels to calcium via NOX2 activation, probably by S-glutathionylation of RyR2 protein. This change is transitory and fully reversible, suggesting a possible role of redox modification in the physiological response of cardiac RyR2 to cellular calcium influx. Copyright © 2014 Elsevier Ltd. All rights reserved.

  18. Consequences of activating the calcium-permeable ion channel TRPV1 in breast cancer cells with regulated TRPV1 expression.

    Science.gov (United States)

    Wu, Tina T L; Peters, Amelia A; Tan, Ping T; Roberts-Thomson, Sarah J; Monteith, Gregory R

    2014-08-01

    Increased expression of specific calcium channels in some cancers and the role of calcium signaling in proliferation and invasion have led to studies assessing calcium channel inhibitors as potential therapies for some cancers. The use of channel activators to promote death of cancer cells has been suggested, but the risk of activators promoting cancer cell proliferation and the importance of the degree of channel over-expression is unclear. We developed an MCF-7 breast cancer cell line with inducible TRPV1 overexpression and assessed the role of TRPV1 levels on cell death mediated by the TRPV1 activator capsaicin and the potential for submaximal activation to promote proliferation. The TRPV1 level was a determinant of cell death induced by capsaicin. A concentration response curve with varying TRPV1 expression levels identified the minimum level of TRPV1 required for capsaicin induced cell death. At no level of TRPV1 over-expression or capsaicin concentration did TRPV1 activation enhance proliferation. Cell death induced by capsaicin was necrotic and associated with up-regulation of c-Fos and RIP3. These studies suggest that activators of specific calcium channels may be an effective way to induce necrosis and that this approach may not always be associated with enhancement of cancer cell proliferation. Copyright © 2014 Elsevier Ltd. All rights reserved.

  19. TRPV6 calcium channel translocates to the plasma membrane via Orai1-mediated mechanism and controls cancer cell survival.

    Science.gov (United States)

    Raphaël, Maylis; Lehen'kyi, V'yacheslav; Vandenberghe, Matthieu; Beck, Benjamin; Khalimonchyk, Sergiy; Vanden Abeele, Fabien; Farsetti, Leonardo; Germain, Emmanuelle; Bokhobza, Alexandre; Mihalache, Adriana; Gosset, Pierre; Romanin, Christoph; Clézardin, Philippe; Skryma, Roman; Prevarskaya, Natalia

    2014-09-16

    Transient receptor potential vanilloid subfamily member 6 (TRPV6) is a highly selective calcium channel that has been considered as a part of store-operated calcium entry (SOCE). Despite its first discovery in the early 2000s, the role of this channel in prostate cancer (PCa) remained, until now, obscure. Here we show that TRPV6 mediates calcium entry, which is highly increased in PCa due to the remodeling mechanism involving the translocation of the TRPV6 channel to the plasma membrane via the Orai1/TRPC1-mediated Ca(2+)/Annexin I/S100A11 pathway, partially contributing to SOCE. The TRPV6 calcium channel is expressed de novo by the PCa cell to increase its survival by enhancing proliferation and conferring apoptosis resistance. Xenografts in nude mice and bone metastasis models confirmed the remarkable aggressiveness of TRPV6-overexpressing tumors. Immunohistochemical analysis of these demonstrated the increased expression of clinical markers such as Ki-67, prostate specific antigen, synaptophysin, CD31, and CD56, which are strongly associated with a poor prognosis. Thus, the TRPV6 channel acquires its oncogenic potential in PCa due to the remodeling mechanism via the Orai1-mediated Ca(2+)/Annexin I/S100A11 pathway.

  20. TRPV6 calcium channel translocates to the plasma membrane via Orai1-mediated mechanism and controls cancer cell survival

    Science.gov (United States)

    Raphaël, Maylis; Lehen’kyi, V’yacheslav; Vandenberghe, Matthieu; Beck, Benjamin; Khalimonchyk, Sergiy; Vanden Abeele, Fabien; Farsetti, Leonardo; Germain, Emmanuelle; Bokhobza, Alexandre; Mihalache, Adriana; Gosset, Pierre; Romanin, Christoph; Clézardin, Philippe; Skryma, Roman; Prevarskaya, Natalia

    2014-01-01

    Transient receptor potential vanilloid subfamily member 6 (TRPV6) is a highly selective calcium channel that has been considered as a part of store-operated calcium entry (SOCE). Despite its first discovery in the early 2000s, the role of this channel in prostate cancer (PCa) remained, until now, obscure. Here we show that TRPV6 mediates calcium entry, which is highly increased in PCa due to the remodeling mechanism involving the translocation of the TRPV6 channel to the plasma membrane via the Orai1/TRPC1-mediated Ca2+/Annexin I/S100A11 pathway, partially contributing to SOCE. The TRPV6 calcium channel is expressed de novo by the PCa cell to increase its survival by enhancing proliferation and conferring apoptosis resistance. Xenografts in nude mice and bone metastasis models confirmed the remarkable aggressiveness of TRPV6-overexpressing tumors. Immunohistochemical analysis of these demonstrated the increased expression of clinical markers such as Ki-67, prostate specific antigen, synaptophysin, CD31, and CD56, which are strongly associated with a poor prognosis. Thus, the TRPV6 channel acquires its oncogenic potential in PCa due to the remodeling mechanism via the Orai1-mediated Ca2+/Annexin I/S100A11 pathway. PMID:25172921

  1. [Low conductivity calcium channels in the plasmatic membrane of macrophages: activation with inositol 1,4,5-triphosphate].

    Science.gov (United States)

    Semenova, S B; Kiselev, K I; Mozhaeva, G N

    1998-01-01

    Using patch-clamp technique we have shown that the plasma membrane of mouse macrophages contains calcium channels that are activated by inositol (1, 4, 5)-trisphosphate (IP3) and blocked by heparine. Their conductivity properties strongly differentiate them from IP3-activated channels of endoplasmic reticulum, but make it possible to include them to the ICRAC family. By the other hand, properties of the IP3 receptor (IP3R) of our channels are similar to those of endoplasmic IP3R. Basing on these data we suggest that IP3R could be located out of the plasma membrane, and by some conformational changes transduces the signal to the high selective Ca2+ channel in the plasma membrane. This model well conforms with the known in the literature "coupling model" of calcium signalling [1].

  2. Gynura procumbens Merr. decreases blood pressure in rats by vasodilatation via inhibition of calcium channels

    Directory of Open Access Journals (Sweden)

    See-Ziau Hoe

    2011-01-01

    Full Text Available INTRODUCTION: Gynura procumbens has been shown to decrease blood pressure via inhibition of the angiotensinconverting enzyme. However, other mechanisms that may contribute to the hypotensive effect have not been studied. OBJECTIVES: To investigate the cardiovascular effects of a butanolic fraction of Gynura procumbens in rats. METHODS: Anaesthetized rats were given intravenous bolus injections of butanolic fraction at doses of 2.5-20 mg/kg in vivo. The effect of butanolic fraction on vascular reactivity was recorded in isolated rat aortic rings in vitro. RESULTS: Intravenous administrations of butanolic fraction elicited significant (p<0.001 and dose-dependent decreases in the mean arterial pressure. However, a significant (p<0.05 decrease in the heart rate was observed only at the higher doses (10 and 20 mg/kg. In isolated preparations of rat aortic rings, phenylephrine (1×10-6 M- or potassium chloride (8×10-2 M-precontracted endothelium-intact and -denuded tissue; butanolic fraction (1×10-6-1×10-1 g/ml induced similar concentration-dependent relaxation of the vessels. In the presence of 2.5×10-3 and 5.0×10-3 g/ml butanolic fraction, the contractions induced by phenylephrine (1×10-9-3×10-5 M and potassium chloride (1×10-2-8×10-2 M were significantly antagonized. The calcium-induced vasocontractions (1×10-4-1×10-2 M were antagonized by butanolic fraction concentration-dependently in calcium-free and high potassium (6×10-2 M medium, as well as in calcium- and potassium-free medium containing 1×10-6 M phenylephrine. However, the contractions induced by noradrenaline (1×10-6 M and caffeine (4.5×10-2 M were not affected by butanolic fraction. CONCLUSION: Butanolic fraction contains putative hypotensive compounds that appear to inhibit calcium influx via receptor-operated and/or voltage-dependent calcium channels to cause vasodilation and a consequent fall in blood pressure.

  3. It takes two T to shape immunity: emerging role for T-type calcium channels in immune cells

    Czech Academy of Sciences Publication Activity Database

    Lacinová, L.; Weiss, Norbert

    2016-01-01

    Roč. 35, č. 4 (2016), s. 393-396 ISSN 0231-5882 R&D Projects: GA ČR GA15-13556S; GA MŠk 7AMB15FR015 Institutional support: RVO:61388963 Keywords : calcium channel * T-type channel * Ca(v)3.1 * immune cells Subject RIV: CE - Biochemistry Impact factor: 1.170, year: 2016

  4. Orai and TRPC channel characterization in FcεRI-mediated calcium signaling and mediator secretion in human mast cells.

    Science.gov (United States)

    Wajdner, Hannah E; Farrington, Jasmine; Barnard, Claire; Peachell, Peter T; Schnackenberg, Christine G; Marino, Joseph P; Xu, Xiaoping; Affleck, Karen; Begg, Malcolm; Seward, Elizabeth P

    2017-03-01

    Inappropriate activation of mast cells via the FcεRI receptor leads to the release of inflammatory mediators and symptoms of allergic disease. Calcium influx is a critical regulator of mast cell signaling and is required for exocytosis of preformed mediators and for synthesis of eicosanoids, cytokines and chemokines. Studies in rodent and human mast cells have identified Orai calcium channels as key contributors to FcεRI-initiated mediator release. However, until now the role of TRPC calcium channels in FcεRI-mediated human mast cell signaling has not been published. Here, we show evidence for the expression of Orai 1,2, and 3 and TRPC1 and 6 in primary human lung mast cells and the LAD2 human mast cell line but, we only find evidence of functional contribution of Orai and not TRPC channels to FcεRI-mediated calcium entry. Calcium imaging experiments, utilizing an Orai selective antagonist (Synta66) showed the contribution of Orai to FcεRI-mediated signaling in human mast cells. Although, the use of a TRPC3/6 selective antagonist and agonist (GSK-3503A and GSK-2934A, respectively) did not reveal evidence for TRPC6 contribution to FcεRI-mediated calcium signaling in human mast cells. Similarly, inactivation of STIM1-regulated TRPC1 in human mast cells (as tested by transfecting cells with STIM1-KK684-685EE - TRPC1 gating mutant) failed to alter FcεRI-mediated calcium signaling in LAD2 human mast cells. Mediator release assays confirm that FcεRI-mediated calcium influx through Orai is necessary for histamine and TNFα release but is differentially involved in the generation of cytokines and eicosanoids. © 2017 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.

  5. Differential effects of voltage-gated calcium channel blockers on calcium channel alpha-2-delta-1 subunit protein-mediated nociception.

    Science.gov (United States)

    Chang, E; Chen, X; Kim, M; Gong, N; Bhatia, S; Luo, Z D

    2015-05-01

    Overexpression of the voltage-gated calcium channel (VGCC) alpha-2-delta1 subunit protein (Cav α2 δ1 ) has been shown to cause pain states. However, whether VGCC are involved in pain states driven by abnormal Cav α2 δ1 expression is not known. Intrathecal injection of N-, P/Q- and L-type VGCC blockers were tested in two models: a transgenic neuronal Cav α2 δ1 overexpression (TG) model with behavioural hypersensitivity and a spinal nerve ligation (SNL) model with Cav α2 δ1 overexpression in sensory pathways and neuropathy pain states. The nociceptive response to mechanical stimuli was significantly attenuated in both models with ω-conotoxin GVIA (an N-type VGCC blocker) and nifedipine (an L-type VGCC blocker), in which ω-conotoxin GVIA appeared more potent than nifedipine. Treatments with ω-agatoxin IVA (P-VGCC blocker), but not ω-conotoxin MVIIC (Q-VGCC blocker) had similar potency in the TG model as the N-type VGCC blocker, while both ω-agatoxin IVA and ω-conotoxin MVIIC had minimal effects in the SNL model compared with controls. These findings suggest that, at the spinal level, N- and L-type VGCC are likely involved in behavioural hypersensitivity states driven by Cav α2 δ1 overexpression. Q-type VGCC has minimal effects in both models. The anti-nociceptive effects of P-type VGCC blocker in the Cav α2 δ1 TG mice, but minimally at the SNL model with presynaptic Cav α2 δ1 up-regulation, suggest that its potential action site(s) is at the post-synaptic and/or supraspinal level. These findings support that N-, L- and P/Q-type VGCC have differential contributions to behavioural hypersensitivity modulated by Cav α2 δ1 dysregulation at the spinal cord level. © 2014 European Pain Federation - EFIC®

  6. Use of clopidogrel and calcium channel blockers and risk of major adverse cardiovascular events

    DEFF Research Database (Denmark)

    Schmidt, Morten; Johansen, Martin B; Robertson, Douglas J

    2012-01-01

    Eur J Clin Invest 2011 ABSTRACT: Background  The CYP3A4 inhibition by calcium channel blockers (CCBs) may attenuate the effectiveness of clopidogrel. Using time-varying drug exposure ascertainment, we examined whether CCB use modified the association between clopidogrel use and major adverse......-month follow-up, we tracked the use of clopidogrel and CCBs and the rate of MACE (composite of myocardial infarction, ischaemic stroke, stent thrombosis, target lesion revascularization, or cardiac death). We used Cox regression to compute hazard ratios, controlling for potential confounders. Results......  Overall, the 12-month risk for MACE was 14·5%. The rate was 130 per 1000 person years for concomitant clopidogrel and CCB use, 106 for clopidogrel without CCB use, 213 for CCB without clopidogrel use, and 248 for no use of either drug. The adjusted hazard ratio for MACE comparing clopidogrel use...

  7. Anti-Convulsant Activity of Boerhaavia diffusa: Plausible Role of Calcium Channel Antagonism

    Directory of Open Access Journals (Sweden)

    Mandeep Kaur

    2011-01-01

    Full Text Available “Ethnopharmacological” use of roots of Boerhaavia diffusa (B. diffusa in the treatment of epilepsy in Nigerian folk medicine and reports showing the presence of a calcium channel antagonistic compound “liriodendrin” in its roots, led us to undertake the present study. The study was designed to investigate the methanolic root extract of B. diffusa and its different fractions including liriodendrin-rich fraction for exploring the possible role of liriodendrin in its anti-convulsant activity. Air-dried roots of B. diffusa were extracted with methanol by cold maceration. The methanol soluble fraction of extract thus obtained was successively extracted to obtain liriodendrin-rich fraction and two side fractions, that is, chloroform fraction and phenolic compound fraction. Anti-convulsant activity of methanolic extract (1000, 1500 and 2000 mg kg-1, intraperitoneally (i.p. and its different fractions, that is, liriodendrin-rich fraction (10, 20 and 40 mg kg-1, i.p., chloroform fraction (20 mg kg-1, i.p. and phenolic compound fraction (1 mg kg-1, i.p. were studied in pentylenetetrazol (PTZ-induced seizures (75 mg kg-1, i.p.. The crude methanolic extract of B. diffusa and only its liriodendrin-rich fraction showed a dose-dependent protection against PTZ-induced convulsions. The liriodendrin-rich fraction also showed significant protection against seizures induced by BAY k-8644. These findings reiterated the anti-convulsant activity of methanolic extract of B. diffusa roots. Furthermore, it can be concluded that the observed anti-convulsant activity was due to its calcium channel antagonistic action as this activity was retained only in the liodendrin-rich fraction, which has additionally been confirmed by significant anti-convulsant activity of liriodendrin-rich fraction in BAY k-8644-induced seizures.

  8. Reversal of acute theophylline toxicity by calcium channel blockers in dogs and rats.

    Science.gov (United States)

    Whitehurst, V E; Joseph, X; Vick, J A; Alleva, F R; Zhang, J; Balazs, T

    1996-06-17

    Theophylline, widely used in the treatment of pulmonary diseases, has a narrow therapeutic index; the recommended plasma levels being 10-20 micrograms/ml in humans. The misuse or abuse of theophylline can cause life-threatening central nervous system and cardiovascular effects. Increased intracellular Ca2+ levels are thought to play an important role in theophylline toxicity and death. The objective of this study was to determine whether Ca2+ channel blockers, e.g. verapamil, nifedipine, or diltiazem, prevent sudden death caused by theophylline treatment in rats and dogs. Groups of Sprague-Dawley rats were treated with theophylline alone (150 mg/kg i.p.) or with theophylline pretreatment followed by administration of verapamil (0.25 to 0.5 mg/kg i.p.), nifedipine (0.25 to 1.0 mg/kg i.p.), or diltiazem (0.5 to 1.0 mg/kg i.p.), 2.5 to 15 min later. The rats were observed for toxic signs and survival over a period of 15 days. All three calcium channel blockers significantly reduced the theophylline-induced sudden death in rats. In a separate study, neither verapamil (0.5 mg/kg i.p.) nor nifedipine (1.0 mg/kg i.p.) prevented the theophylline-induced myocardial necrosis in the rat. In beagle dogs, verapamil (0.5 mg/kg i.v.) prevented theophylline (15 mg/kg/min i.v. for 10 min)-induced hypotension, arrhythmias, and sudden death. Our results support previously reported findings that calcium plays a major role in theophylline-induced toxicity and death.

  9. Cloning, chromosomal localization, and functional expression of the alpha 1 subunit of the L-type voltage-dependent calcium channel from normal human heart

    NARCIS (Netherlands)

    Schultz, D; Mikala, G; Yatani, A; Engle, D B; Iles, D E; Segers, B; Sinke, R J; Weghuis, D O; Klöckner, U; Wakamori, M

    1993-01-01

    A unique structural variant of the cardiac L-type voltage-dependent calcium channel alpha 1 subunit cDNA was isolated from libraries derived from normal human heart mRNA. The deduced amino acid sequence shows significant homology to other calcium channel alpha 1 subunits. However, differences from

  10. Severe beta blocker and calcium channel blocker overdose: Role of high dose insulin.

    Science.gov (United States)

    Seegobin, Karan; Maharaj, Satish; Deosaran, Ansuya; Reddy, Pramod

    2018-01-10

    A 54-year-old female presented after taking an overdose of an unknown amount of hydrochlorothiazide, doxazocin, atenolol and amlodipine. She was initially refractory to treatment with conventional therapy (intravenous fluids, activated charcoal, glucagon 5 mg followed with glucagon drip, calcium gluconate 10%, and atropine). Furthermore, insulin at 4 U/kg was not effective in improving her hemodynamics. Shortly after high dose insulin was achieved with 10 U/kg, there was dramatic improvement in hemodynamics resulting in three of five vasopressors being weaned off in 8 h. She was subsequently off all vasopressors after six additional hours. The role of high dose insulin has been documented in prior cases, however it is generally recommended after other conventional therapies have failed. However, there are other reports that suggest it as initial therapy. Our patient failed conventional therapies and responded well only with maximum dose of insulin. Physicians should consider high dose insulin early in severe beta blocker or calcium channel blocker overdose for improvement in hemodynamics. This leads to early discontinuation of vasopressors. It is important that emergency physicians be aware of the beneficial effects of high dose insulin when initiated early as opposed to waiting for conventional therapy to fail; as these patients often present first to the emergency department. Early initiation in the emergency department can be beneficial in these patients. Copyright © 2018. Published by Elsevier Inc.

  11. Antimicrobial, anti-oxidant and calcium channel blocking activities of Amberboa divaricata

    Directory of Open Access Journals (Sweden)

    Shahid Muhammad Iqbal

    2014-03-01

    Full Text Available Traditional healers in Pakistan use the herb Amberboa divaricata as tonic, aperiant, deobstruent, febrifuge, anti-diarrheal, antiperiodic, antipyretic, anti-cough and in skin disorders. In vitro tissue experiments were carried out on rabbit jejunum to elucidate the possible mechanism of its prescribed effects on gastrointestinal tract, while antibacterial and antioxidant experiments were performed to provide pharmacological evidence of its traditional use in skin disorders. The 70%methanolic crude extract of A. divaricata produced dose dependent relaxation in isolated rabbit jejunum tissue in a concentration range of 0.1–3.0 mg/mL (n=5. Calcium response curves were constructed at concen-tration of 0.03 and 0.1 mg/mL (n=5, which produced rightward shift in a pattern similar to that of verapamil, confirming the calcium channel blocking activity. Agar disc diffusion assay at a concentration of 10 mg crude extract/disc showed clear zones of inhibition.

  12. Calcium current inactivation in identified neurones of Helix aspersa.

    Science.gov (United States)

    Plant, T D; Standen, N B

    1981-01-01

    1. A two-electrode voltage clamp method was used to study Ca inward currents in identified Helix aspersa neurones bathed in 25 mM-Ca, Na-free saline with TEA and 4-AP. 2. Inward currents were blocked by CdCl2. In Cd delayed outward currents appeared at +30 mV. When two identical depolarizations were separated by a gap inward current turned off to the same level during the two pulses up to +20 mV; above this potential the records cross over. 3. The turn-off of inward current at potentials up to +20 mV was not affected by 0.2 mM-quinine, which reduced outward currents at more depolarized potentials. Inward currents declined exponentially over the first 100 msec with a time constant around 60 msec at 0 mV. Double-pulse experiments gave the same time course of turn-off. 4. When Ca inward current was reduced by lowering [Ca]o or by partial block by Cd the rate and extent of turn-off was reduced. 5. The inactivation curve (obtained using a double pulse with gap method) was U-shaped. The curve was not significantly changed by addition of quinine (0.2 mM) or by changing test pulse size. 6. Recovery of inward currents after a depolarizing prepulse was a double-exponential process, with time constants of 120 msec and 9.4 sec at 10--11 degrees C. 7. Our results are discussed in terms of possible Ca-dependent Ca inactivation and in terms of the possibility of development of an outward Ca-dependent K current. PMID:7338811

  13. Turbidity current hydraulics and sediment deposition in erodible sinuous channels: Laboratory experiments and numerical simulations

    NARCIS (Netherlands)

    Janocko, M.; Cartigny, M.J.B.; Nemec, W.; Hansen, E.W.M.

    2013-01-01

    This study explores the relationship between the hydraulics of turbidity currents in erodible sinuous channels and the resulting intra-channel sediment depocentres (channel bars). Four factors are considered to exert critical control on sedimentation in sinuous submarine channels: (1) the

  14. Effects of low-dose ionising radiation on pituitary adenoma: is there a role for L-type calcium channel?

    Directory of Open Access Journals (Sweden)

    Marcella Araugio Soares

    2005-10-01

    Full Text Available Pituitary adenomas constitute about 6-18% of brain tumours in adults. Activation of voltage gated calcium currents can account for growth hormone oversecretion in some GH-secreting pituitary adenomas that produce an acromegaly appearance and increase mortality. Ca2+ ions, as mediators of intracellular signalling, are crucial for the development of apoptosis. However, the role of [Ca2+] in the development of apoptosis is ambiguous. In this study, the effects of low-dose ionising gamma radiation (60Co on rat pituitary adenoma cells survival and proliferation and the role of calcium channels on the apoptosis radio-induced were evaluated. Doses as low as 3 Gy were found to inhibit GH3 cell proliferation. Even though there was a significant number of live cells,168 hours following irradiation, they were not able to proliferate. The results indicate that the blockade of extracellular calcium influx through these channels does not interfere in the radiation-induced apoptosis in GH3 cells.Adenomas de pituitária constituem cerca de 6-18% dos tumores cerebrais em adultos. A ativação de correntes de cálcio dependentes de voltagem podem levar à super-excreção de hormônio do crescimento produzindo acromegalia e aumentando a mortalidade. Íons Ca2+ como mediadores de sinalização intracelular são cruciais no desenvolvimento da apoptose. No entanto, o papel da [Ca 2+] no desenvolvimento da apoptose é ambíguo. Neste estudo nós avaliamos os efeitos de baixas doses de radiação gama (60Co na sobrevivência e proliferação de células de adenoma de pituitária de rato e o papel do cálcio na apoptose radio-induzida. Nossos resultados mostraram que a dose de 3Gy foi suficiente para inibir a proliferação das células GH3. Apesar de existir um número significativo de células vivas após 168 horas do tratamento com radiação, elas não estavam aptas a proliferar. Nossos resultados também indicaram que bloqueio do influxo de cálcio extracelular n

  15. CO, Pb++ and SO2 effects on L-type calcium channel and action potential in human atrial myocytes. In silico study

    Directory of Open Access Journals (Sweden)

    Diana C. Pachajoa

    2017-09-01

    Full Text Available Exposure to air pollutants like carbon monoxide (CO, lead (Pb++ and sulfur dioxide (SO2 promotes the occurrence of cardiovascular diseases. Experimental studies have shown that CO, Pb++ and SO2 block L-type calcium channels, reducing the calcium current (ICaL and the action potential duration (APD, which favors the initiation of atrial arrhythmias. The goal is to study the effects of CO, Pb++ and SO2 at different concentrations on ICaL and action potential using computational simulation. For this purpose, models of the effects of the air pollutants on the atrial L-type calcium channel were developed and were incorporated into a mathematical model of a human atrial cell. The results suggest that CO, Pb++ and SO2 block the ICaL current in a fraction that increases along with the concentration, generating an APD shortening. These results are consistent with experimental studies. The combined effect of the three air pollutants produced an APD shortening, which is considered to be a pro-arrhythmic effect.

  16. Role of calcium-activated potassium channels with small conductance in bradykinin-induced vasodilation of porcine retinal arterioles

    DEFF Research Database (Denmark)

    Dalsgaard, Thomas; Kroigaard, Christel; Bek, Toke

    2009-01-01

    PURPOSE: Endothelial dysfunction and impaired vasodilation may be involved in the pathogenesis of retinal vascular diseases. In the present study, the mechanisms underlying bradykinin vasodilation were examined and whether calcium-activated potassium channels of small (SK(Ca)) and intermediate (I...

  17. Dopamine Induces LTP Differentially in Apical and Basal Dendrites through BDNF and Voltage-Dependent Calcium Channels

    Science.gov (United States)

    Navakkode, Sheeja; Sajikumar, Sreedharan; Korte, Martin; Soong, Tuck Wah

    2012-01-01

    The dopaminergic modulation of long-term potentiation (LTP) has been studied well, but the mechanism by which dopamine induces LTP (DA-LTP) in CA1 pyramidal neurons is unknown. Here, we report that DA-LTP in basal dendrites is dependent while in apical dendrites it is independent of activation of L-type voltage-gated calcium channels (VDCC).…

  18. The calcium-activated potassium channel KCa3.1 is an important modulator of hepatic injury

    DEFF Research Database (Denmark)

    Møller, Linda Maria Sevelsted; Fialla, Annette Dam; Schierwagen, Robert

    2016-01-01

    The calcium-activated potassium channel KCa3.1 controls different cellular processes such as proliferation and volume homeostasis. We investigated the role of KCa3.1 in experimental and human liver fibrosis. KCa3.1 gene expression was investigated in healthy and injured human and rodent liver. Ef...

  19. Antagonism of T-type calcium channels inhibits high-fat diet-induced weight gain in mice.

    Science.gov (United States)

    Uebele, Victor N; Gotter, Anthony L; Nuss, Cindy E; Kraus, Richard L; Doran, Scott M; Garson, Susan L; Reiss, Duane R; Li, Yuxing; Barrow, James C; Reger, Thomas S; Yang, Zhi-Qiang; Ballard, Jeanine E; Tang, Cuyue; Metzger, Joseph M; Wang, Sheng-Ping; Koblan, Kenneth S; Renger, John J

    2009-06-01

    The epidemics of obesity and metabolic disorders have well-recognized health and economic burdens. Pharmacologic treatments for these diseases remain unsatisfactory with respect to both efficacy and side-effect profiles. Here, we have identified a potential central role for T-type calcium channels in regulating body weight maintenance and sleep. Previously, it was shown that mice lacking CaV3.1 T-type calcium channels have altered sleep/wake activity. We found that these mice were also resistant to high-fat diet-induced weight gain, without changes in food intake or sensitivity to high-fat diet-induced disruptions of diurnal rhythm. Administration of a potent and selective antagonist of T-type calcium channels, TTA-A2, to normal-weight animals prior to the inactive phase acutely increased sleep, decreased body core temperature, and prevented high-fat diet-induced weight gain. Administration of TTA-A2 to obese rodents reduced body weight and fat mass while concurrently increasing lean muscle mass. These effects likely result from better alignment of diurnal feeding patterns with daily changes in circadian physiology and potentially an increased metabolic rate during the active phase. Together, these studies reveal what we believe to be a previously unknown role for T-type calcium channels in the regulation of sleep and weight maintenance and suggest the potential for a novel therapeutic approach to treating obesity.

  20. Calcium channel blockade limits cardiac remodeling and improves cardiac function in myocardial infarction-induced heart failure in rats

    NARCIS (Netherlands)

    Sandmann, S.; Claas, R.; Cleutjens, J. P.; Daemen, M. J.; Unger, T.

    2001-01-01

    Calcium channel antagonists (CCAs) have been proposed to prevent cardiac events after myocardial infarction (MI). However, unwanted effects, such as negative inotropy, limit their use in many cases. The aim of this study was to compare the effects of long-term treatment with the CCAs, mibefradil,

  1. Calcium

    Science.gov (United States)

    ... and blood vessels contract and expand, to secrete hormones and enzymes and to send messages through the nervous system. It is important to get plenty of calcium in the foods you eat. Foods rich in calcium include Dairy products such as milk, cheese, and yogurt Leafy, green vegetables Fish with ...

  2. Inactivation kinetics and pharmacology distinguish two calcium currents in mouse pancreatic B-cells

    Energy Technology Data Exchange (ETDEWEB)

    Hopkins, W.F.; Satin, L.S.; Cook, D.L. (Univ. of Washington School of Medicine, Seattle (USA))

    1991-02-01

    Voltage-dependent calcium currents were studied in cultured adult mouse pancreatic B-cells using the whole-cell voltage-clamp technique. When calcium currents were elicited with 10-sec depolarizing command pulses, the time course of inactivation was well fit by the sum of two exponentials. The more rapidly-inactivating component had a time constant of 75 +/- 5 msec at 0 mV and displayed both calcium influx- and voltage-dependent inactivation, while the more slowly-inactivating component had a time constant of 2750 +/- 280 msec at 0 mV and inactivated primarily via voltage. The fast component was subject to greater steady-state inactivation at holding potentials between -100 and -40 mV and activated at a lower voltage threshold. This component was also significantly reduced by nimodipine (0.5 microM) when a holding potential of -100 mV was used, whereas the slow component was unaffected. In contrast, the slow component was greatly increased by replacing external calcium with barium, while the fast component was unchanged. Cadmium (1-10 microM) displayed a voltage-dependent block of calcium currents consistent with a greater effect on the high-threshold, more-slowly inactivating component. Taken together, the data suggest that cultured mouse B-cells, as with other insulin-secreting cells we have studied, possess at least two distinct calcium currents. The physiological significance of two calcium currents having distinct kinetic and steady-state inactivation characteristics for B-cell burst firing and insulin secretion is discussed.

  3. [Distribution diversity of integrins and calcium channels on major human and mouse host cells of Leptospira species].

    Science.gov (United States)

    Li, Cheng-xue; Zhao, Xin; Qian, Jing; Yan, Jie

    2012-07-01

    To determine the distribution of integrins and calcium channels on major human and mouse host cells of Leptospira species. The expression of β1, β2 and β3 integrins was detected with immunofluorescence assay on the surface of human monocyte line THP-1, mouse mononuclear-macrophage-like cell line J774A.1, human vascular endothelial cell line HUVEC, mouse vascular endothelial cell EOMA, human hepatocyte line L-02, mouse hepatocyte line Hepa1-6, human renal tubular epithelial cell line HEK-293, mouse glomerular membrane epithelial cell line SV40-MES13, mouse collagen blast line NIH/3T3, human and mouse platelets. The distribution of voltage gate control calcium channels Cav3.1, Cav3.2, Cav3.3 and Cav2.3, and receptor gate calcium channels P(2)X(1), P(2)2X(2), P(2)X(3), P(2)X(4), P(2)X(5), P(2)X(6) and P(2)X(7) were determined with Western blot assay. β1 integrin proteins were positively expressed on the membrane surface of J774A.1, THP-1, HUVEC, EOMA, L-02, Hepa1-6 and HEK-239 cells as well as human and mouse platelets. β2 integrin proteins were expressed on the membrane surface of J774A.1, THP-1, HUVEC, EOMA, and NIH/3T3 cells. β3 integrin proteins were expressed on the membrane surface of J774A.1, THP-1, HUVEC, EOMA, Hepa1-6, HEK-239 and NIH/3T3 cells as well as human and mouse platelets. P(2)X(1) receptor gate calcium channel was expressed on the membrane surface of human and mouse platelets, while P(2)X(5) receptor gate calcium channel was expressed on the membrane surface of J774A.1, THP-1, L-02, Hepa1-6, HEK-239 and HUVEC cells. However, the other calcium channels were not detected on the tested cell lines or platelets. There is a large distribution diversity of integrins and calcium channel proteins on the major human and mouse host cells of Leptospira species, which may be associated with the differences of leptospira-induced injury in different host cells.

  4. Numerical Simulation of Density Current Evolution in a Diverging Channel

    Directory of Open Access Journals (Sweden)

    Mitra Javan

    2012-01-01

    Full Text Available When a buoyant inflow of higher density enters a reservoir, it sinks below the ambient water and forms an underflow. Downstream of the plunge point, the flow becomes progressively diluted due to the fluid entrainment. This study seeks to explore the ability of 2D width-averaged unsteady Reynolds-averaged Navier-Stokes (RANS simulation approach for resolving density currents in an inclined diverging channel. 2D width-averaged unsteady RANS equations closed by a buoyancy-modified − turbulence model are integrated in time with a second-order fractional step approach coupled with a direct implicit method and discretized in space on a staggered mesh using a second-order accurate finite volume approach incorporating a high-resolution semi-Lagrangian technique for the convective terms. A series of 2D width-averaged unsteady simulations is carried out for density currents. Comparisons with the experimental measurements and the other numerical simulations show that the predictions of velocity and density field are with reasonable accuracy.

  5. Establishing homology between mitochondrial calcium uniporters, prokaryotic magnesium channels and chlamydial IncA proteins.

    Science.gov (United States)

    Lee, Andre; Vastermark, Ake; Saier, Milton H

    2014-08-01

    Mitochondrial calcium uniporters (MCUs) (TC no. 1.A.77) are oligomeric channel proteins found in the mitochondrial inner membrane. MCUs have two well-conserved transmembrane segments (TMSs), connected by a linker, similar to bacterial MCU homologues. These proteins and chlamydial IncA proteins (of unknown function; TC no. 9.B.159) are homologous to prokaryotic Mg(2+) transporters, AtpI and AtpZ, based on comparison scores of up to 14.5 sds. A phylogenetic tree containing all of these proteins showed that the AtpZ proteins cluster coherently as a subset within the large and diverse AtpI cluster, which branches separately from the MCUs and IncAs, both of which cluster coherently. The MCUs and AtpZs share the same two TMS topology, but the AtpIs have four TMSs, and IncAs can have either two (most frequent) or four (less frequent) TMSs. Binary alignments, comparison scores and motif analyses showed that TMSs 1 and 2 align with TMSs 3 and 4 of the AtpIs, suggesting that the four TMS AtpI proteins arose via an intragenic duplication event. These findings establish an evolutionary link interconnecting eukaryotic and prokaryotic Ca(2+) and Mg(2+) transporters with chlamydial IncAs, and lead us to suggest that all members of the MCU superfamily, including IncAs, function as divalent cation channels. © 2014 The Authors.

  6. Fetal calcium regulates branching morphogenesis in the developing human and mouse lung: involvement of voltage-gated calcium channels.

    Directory of Open Access Journals (Sweden)

    Sarah C Brennan

    Full Text Available Airway branching morphogenesis in utero is essential for optimal postnatal lung function. In the fetus, branching morphogenesis occurs during the pseudoglandular stage (weeks 9-17 of human gestation, embryonic days (E11.5-16.5 in mouse in a hypercalcaemic environment (~1.7 in the fetus vs. ~1.1-1.3 mM for an adult. Previously we have shown that fetal hypercalcemia exerts an inhibitory brake on branching morphogenesis via the calcium-sensing receptor. In addition, earlier studies have shown that nifedipine, a selective blocker of L-type voltage-gated Ca(2+ channels (VGCC, inhibits fetal lung growth, suggesting a role for VGCC in lung development. The aim of this work was to investigate the expression of VGCC in the pseudoglandular human and mouse lung, and their role in branching morphogenesis. Expression of L-type (CaV1.2 and CaV1.3, P/Q type (CaV2.1, N-type (CaV2.2, R-type (CaV2.3, and T-type (CaV3.2 and CaV3.3 VGCC was investigated in paraffin sections from week 9 human fetal lungs and E12.5 mouse embryos. Here we show, for the first time, that Cav1.2 and Cav1.3 are expressed in both the smooth muscle and epithelium of the developing human and mouse lung. Additionally, Cav2.3 was expressed in the lung epithelium of both species. Incubating E12.5 mouse lung rudiments in the presence of nifedipine doubled the amount of branching, an effect which was partly mimicked by the Cav2.3 inhibitor, SNX-482. Direct measurements of changes in epithelial cell membrane potential, using the voltage-sensitive fluorescent dye DiSBAC2(3, demonstrated that cyclic depolarisations occur within the developing epithelium and coincide with rhythmic occlusions of the lumen, driven by the naturally occurring airway peristalsis. We conclude that VGCC are expressed and functional in the fetal human and mouse lung, where they play a role in branching morphogenesis. Furthermore, rhythmic epithelial depolarisations evoked by airway peristalsis would allow for branching to

  7. The calcium channel β2 (CACNB2 subunit repertoire in teleosts

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    Mueller Rachel

    2008-04-01

    Full Text Available Abstract Background Cardiomyocyte contraction is initiated by influx of extracellular calcium through voltage-gated calcium channels. These oligomeric channels utilize auxiliary β subunits to chaperone the pore-forming α subunit to the plasma membrane, and to modulate channel electrophysiology 1. Several β subunit family members are detected by RT-PCR in the embryonic heart. Null mutations in mouse β2, but not in the other three β family members, are embryonic lethal at E10.5 due to defects in cardiac contractility 2. However, a drawback of the mouse model is that embryonic heart rhythm is difficult to study in live embryos due to their intra-uterine development. Moreover, phenotypes may be obscured by secondary effects of hypoxia. As a first step towards developing a model for contributions of β subunits to the onset of embryonic heart rhythm, we characterized the structure and expression of β2 subunits in zebrafish and other teleosts. Results Cloning of two zebrafish β2 subunit genes (β2.1 and β2.2 indicated they are membrane-associated guanylate kinase (MAGUK-family genes. Zebrafish β2 genes show high conservation with mammals within the SH3 and guanylate kinase domains that comprise the "core" of MAGUK proteins, but β2.2 is much more divergent in sequence than β2.1. Alternative splicing occurs at the N-terminus and within the internal HOOK domain. In both β2 genes, alternative short ATG-containing first exons are separated by some of the largest introns in the genome, suggesting that individual transcript variants could be subject to independent cis-regulatory control. In the Tetraodon nigrovidis and Fugu rubripes genomes, we identified single β2 subunit gene loci. Comparative analysis of the teleost and human β2 loci indicates that the short 5' exon sequences are highly conserved. A subset of 5' exons appear to be unique to teleost genomes, while others are shared with mammals. Alternative splicing is temporally and

  8. The Need for a Rational Approach to Vasoconstrictive Syndromes: Transcranial Doppler and Calcium Channel Blockade in Reversible Cerebral Vasoconstriction Syndrome

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    Elisabeth B. Marsh

    2016-07-01

    Full Text Available Introduction: Reversible cerebral vasoconstriction syndrome (RCVS typically affects young patients and left untreated can result in hemorrhage or ischemic stroke. Though the disorder has been well characterized in the literature, the most appropriate way to diagnose, treat, and evaluate therapeutic response remains unclear. In previous studies, transcranial Doppler ultrasound (TCD has shown elevated velocities indicative of vasospasm. This imaging modality is noninvasive and inexpensive; an attractive option for diagnosis and therapeutic monitoring if it is sensitive enough to detect changes in the acute setting given that RCVS often affects the distal vessels early in the course of disease. There is also limited data that calcium channel blockade may be effective in treating vasospasm secondary to RCVS, though the agent of choice, formulation, and dose are unclear. Methods: We report a small cohort of seven patients presenting with thunderclap headache whose vascular imaging was consistent with RCVS. All were treated with calcium channel blockade and monitored with TCD performed every 1–2 days. Results: On presentation, TCD correlated with standard neuroimaging findings of vasospasm (on MR, CT, and conventional angiography. TCD was also able to detect improvement in velocities in the acute setting that correlated well with initiation of calcium channel blockade. Long-acting verapamil appeared to have the greatest effect on velocities compared to nimodipine and shorter-acting calcium channel blockers. Conclusion: Though small, our cohort demonstrates potential utility of TCD to monitor RCVS, and relative superiority of extended-release verapamil over other calcium channel blockers, illustrating the need for larger randomized trials.

  9. Sociability impairments in Genetic Absence Epilepsy Rats from Strasbourg: Reversal by the T-type calcium channel antagonist Z944.

    Science.gov (United States)

    Henbid, Mark T; Marks, Wendie N; Collins, Madeline J; Cain, Stuart M; Snutch, Terrance P; Howland, John G

    2017-10-01

    Childhood absence epilepsy (CAE) is associated with interictal co-morbid symptoms including abnormalities in social behaviour. Genetic Absence Epilepsy Rats from Strasbourg (GAERS) is a model of CAE that exhibits physiological and behavioural alterations characteristic of the human disorder. However, it is unknown if GAERS display the social deficits often observed in CAE. Sociability in rodents is thought to be mediated by neural circuits densely populated with T-type calcium channels and GAERS contain a missense mutation in the Cav3.2 T-type calcium channel gene. Thus, the objective of this study was to examine the effects of the clinical stage pan-T-type calcium channel blocker, Z944, on sociability behaviour in male and female GAERS and non-epileptic control (NEC) animals. Female GAERS showed reduced sociability in a three-chamber sociability task whereas male GAERS, male NECs, and female NECs all showed a preference for the chamber containing a stranger rat. In drug trials, pre-treatment with 5mg/kg of Z944 normalized sociability in female GAERS. In contrast, female NECs showed impaired sociability following Z944 treatment. Dose-dependent decreases in locomotor activity were noted following Z944 treatment in both strains. Treatment with 10mg/kg of Z944 altered exploration such that only 8 of the 16 rats tested explored both sides of the testing chamber. In those that explored the chamber, significant preference for the stranger rat was observed in GAERS but not NECs. Overall, the data suggest that T-type calcium channels are critical in regulating sociability in both GAERS and NEC animals. Future research should focus on T-type calcium channels in the treatment of sociability deficits observed in disorders such as CAE. Copyright © 2017 Elsevier Inc. All rights reserved.

  10. High affinity complexes of pannexin channels and L-type calcium channel splice-variants in human lung: Possible role in clevidipine-induced dyspnea relief in acute heart failure

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    Gerhard P. Dahl

    2016-08-01

    Research in Context: Clevidipine lowers blood pressure by inhibiting calcium channels in vascular smooth muscle. In patients with acute heart failure, clevidipine was shown to relieve breathing problems. This was only partially related to the blood pressure lowering actions of clevidipine and not conferred by another calcium channel inhibitor. We here found calcium channel variants in human lung that are more selectively inhibited by clevidipine, especially when associated with pannexin channels. This study gives a possible mechanism for clevidipine's relief of breathing problems and supports future clinical trials testing the role of clevidipine in the treatment of acute heart failure.

  11. Expression and cellular localization of the voltage-gated calcium channel α2δ3 in the rodent retina

    Science.gov (United States)

    Müller, Luis Pérez de Sevilla; Sargoy, Allison; Fernández-Sánchez, Laura; Rodriguez, Allen; Liu, Janelle; Cuenca, Nicolás; Brecha, Nicholas

    2015-01-01

    High voltage activated calcium channels are hetero-oligomeric protein complexes that mediate multiple cellular processes including the influx of extracellular Ca2+, neurotransmitter release, gene transcription and synaptic plasticity. These channels consist of a primary α1 pore-forming subunit, which is associated with an extracellular α2δ subunit and an intracellular β auxiliary subunit, which alter the gating properties and trafficking of the calcium channel. The cellular localization of the α2δ3 subunit in the mouse and rat retina is unknown. In this study, using RT-PCR a single band at ~305 bp corresponding to the predicted size of the α2δ3 subunit fragment was in mouse and rat retina and brain homogenates. Western blotting of rodent retina and brain homogenates showed a single 123 kDa band. Immunohistochemistry using an affinity purified antibody to the α2δ3 subunit revealed immunoreactive cell bodies in the ganglion cell layer (GCL) and inner nuclear layer (INL), and immunoreactive processes in the inner plexiform layer (IPL) and the outer plexiform layer (OPL). α2δ3 immunoreactivity was localized to multiple cell types, including ganglion, amacrine and bipolar cells, and photoreceptors, but not by horizontal cells. The expression of the α2δ3 calcium channel subunit to multiple cell types suggests this subunit participates widely in Ca channel-mediated signaling in the retina. PMID:25631988

  12. Involvement of the Calcium Inward Current in Cardiac Impulse Propagation

    Science.gov (United States)

    Rohr, Stephan; Kucera, Jan P.

    1997-01-01

    In general, the fast sodium inward current (INa) is regarded as the main inward current ensuring fast and safe excitation of the normally polarized working myocardium. However, under conditions of locally delayed excitation in the millisecond range, the slow inward current (ICa) might additionally contribute to the success of impulse propagation. This hypothesis was tested in patterned growth cultures of neonatal rat ventricular myocytes, which consisted of narrow cell strands connected to large rectangular cell monolayers, where INa or ICa could be modified in the narrow cell strand adjacent to the expansion by a microsuperfusion system. As assessed during antegrade (strand → expansion) propagation under control conditions using a system for multiple site optical recording of transmembrane voltage (MSORTV), this cell pattern gave either rise to local activation delays at the expansion ranging from 0.5 to 4 ms (dcontrol), or it induced undirectional conduction blocks (UCBs) in the antegrade direction. Irrespective of the size of dcontrol, suppression of the sodium current with tetrodotoxin confined to the cell strand adjacent to the expansion invariably induced UCB in the antegrade direction. If dcontrol was >1 ms, UCB could also be elicited by suppression of ICa alone with nifedipine. Conversely, if UCB was present under control conditions, the inclusion of Bay K 8644 in the microsuperfusion established successful bidirectional conduction. These results suggest that ICa can be critically important for the success of impulse propagation across abrupt expansions of excitable tissue even if INa is not concurrently depressed. ImagesFIGURE 1FIGURE 2FIGURE 3FIGURE 4FIGURE 5 PMID:9017201

  13. Accessory subunit KChIP2 modulates the cardiac L-type calcium current

    DEFF Research Database (Denmark)

    Thomsen, Morten B; Wang, Chaojian; Ozgen, Nazira

    2009-01-01

    Complex modulation of voltage-gated Ca2+ currents through the interplay among Ca2+ channels and various Ca(2+)-binding proteins is increasingly being recognized. The K+ channel interacting protein 2 (KChIP2), originally identified as an auxiliary subunit for K(V)4.2 and a component of the transie...

  14. Calcium

    Science.gov (United States)

    ... from dietary supplements are linked to a greater risk of kidney stones, especially among older adults. But calcium from foods does not appear to cause kidney stones. For most people, other factors (such as not drinking enough fluids) probably have ...

  15. Calcium Cooperativity of Exocytosis as a Measure of Ca2+ Channel Domain Overlap

    OpenAIRE

    Matveev, Victor; Bertram, Richard; Sherman, Arthur

    2011-01-01

    The number of Ca2+ channels contributing to the exocytosis of a single neurotransmitter vesicle in a presynaptic terminal has been a question of significant interest and debate, and is important for a full understanding of localized Ca2+ signaling in general, and synaptic physiology in particular. This is usually estimated by measuring the sensitivity of the neurotransmitter release rate to changes in the synaptic Ca2+ current, which is varied using appropriate voltage-clamp protocols or via ...

  16. Calcium transient and sodium-calcium exchange current in human versus rabbit sinoatrial node pacemaker cells

    NARCIS (Netherlands)

    Verkerk, Arie O.; van Borren, Marcel M. G. J.; Wilders, Ronald

    2013-01-01

    There is an ongoing debate on the mechanism underlying the pacemaker activity of sinoatrial node (SAN) cells, focusing on the relative importance of the "membrane clock" and the "Ca(2+) clock" in the generation of the small net membrane current that depolarizes the cell towards the action potential

  17. Direct Anandamide Activation of TRPV1 Produces Divergent Calcium and Current Responses

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    Axel J. Fenwick

    2017-06-01

    Full Text Available In the brainstem nucleus of the solitary tract (NTS, primary vagal afferent neurons express the transient receptor potential vanilloid subfamily member 1 (TRPV1 at their central terminals where it contributes to quantal forms of glutamate release. The endogenous membrane lipid anandamide (AEA is a putative TRPV1 agonist in the brain, yet the extent to which AEA activation of TRPV1 has a neurophysiological consequence is not well established. We investigated the ability of AEA to activate TRPV1 in vagal afferent neurons in comparison to capsaicin (CAP. Using ratiometric calcium imaging and whole-cell patch clamp recordings we confirmed that AEA excitatory activity requires TRPV1, binds competitively at the CAP binding site, and has low relative affinity. While AEA-induced increases in peak cytosolic calcium were similar to CAP, AEA-induced membrane currents were significantly smaller. Removal of bath calcium increased the AEA current with no change in peak CAP currents revealing a calcium sensitive difference in specific ligand activation of TRPV1. Both CAP- and AEA-activated TRPV1 currents maintained identical reversal potentials, arguing against a major difference in ion selectivity to resolve the AEA differences in signaling. In contrast with CAP, AEA did not alter spontaneous glutamate release at NTS synapses. We conclude: (1 AEA activation of TRPV1 is markedly different from CAP and produces different magnitudes of calcium influx from whole-cell current; and (2 exogenous AEA does not alter spontaneous glutamate release onto NTS neurons. As such, AEA may convey modulatory changes to calcium-dependent processes, but does not directly facilitate glutamate release.

  18. Congenital heart block maternal sera autoantibodies target an extracellular epitope on the α1G T-type calcium channel in human fetal hearts.

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    Linn S Strandberg

    Full Text Available BACKGROUND: Congenital heart block (CHB is a transplacentally acquired autoimmune disease associated with anti-Ro/SSA and anti-La/SSB maternal autoantibodies and is characterized primarily by atrioventricular (AV block of the fetal heart. This study aims to investigate whether the T-type calcium channel subunit α1G may be a fetal target of maternal sera autoantibodies in CHB. METHODOLOGY/PRINCIPAL FINDINGS: We demonstrate differential mRNA expression of the T-type calcium channel CACNA1G (α1G gene in the AV junction of human fetal hearts compared to the apex (18-22.6 weeks gestation. Using human fetal hearts (20-22 wks gestation, our immunoprecipitation (IP, Western blot analysis and immunofluorescence (IF staining results, taken together, demonstrate accessibility of the α1G epitope on the surfaces of cardiomyocytes as well as reactivity of maternal serum from CHB affected pregnancies to the α1G protein. By ELISA we demonstrated maternal sera reactivity to α1G was significantly higher in CHB maternal sera compared to controls, and reactivity was epitope mapped to a peptide designated as p305 (corresponding to aa305-319 of the extracellular loop linking transmembrane segments S5-S6 in α1G repeat I. Maternal sera from CHB affected pregnancies also reacted more weakly to the homologous region (7/15 amino acids conserved of the α1H channel. Electrophysiology experiments with single-cell patch-clamp also demonstrated effects of CHB maternal sera on T-type current in mouse sinoatrial node (SAN cells. CONCLUSIONS/SIGNIFICANCE: Taken together, these results indicate that CHB maternal sera antibodies readily target an extracellular epitope of α1G T-type calcium channels in human fetal cardiomyocytes. CHB maternal sera also show reactivity for α1H suggesting that autoantibodies can target multiple fetal targets.

  19. Calcium-Activated Chloride Channels (CaCCs) Regulate Action Potential and Synaptic Response in Hippocampal Neurons

    Science.gov (United States)

    Huang, Wendy C.; Xiao, Shaohua; Huang, Fen; Harfe, Brian D.; Jan, Yuh Nung; Jan, Lily Yeh

    2012-01-01

    SUMMARY Central neurons respond to synaptic inputs from other neurons by generating synaptic potentials. Once the summated synaptic potentials reach threshold for action potential firing, the signal propagates leading to transmitter release at the synapse. The calcium influx accompanying such signaling opens calcium-activated ion channels for feedback regulation. Here we report a novel mechanism for modulating hippocampal neuronal signaling that involves calcium-activated chloride channels (CaCCs). We present the first evidence that CaCCs reside in hippocampal neurons and are in close proximity of calcium channels and NMDA receptors to shorten action potential duration, dampen excitatory synaptic potentials, impede temporal summation, and raise the threshold for action potential generation by synaptic potential. Having recently identified TMEM16A and TMEM16B as CaCCs, we further show that TMEM16B but not TMEM16A is important for hippocampal CaCC, laying the groundwork for deciphering the dynamic CaCC modulation of neuronal signaling in neurons important for learning and memory. PMID:22500639

  20. Single calcium channel domain gating of synaptic vesicle fusion at fast synapses; analysis by graphic modeling

    Science.gov (United States)

    Stanley, Elise F

    2015-01-01

    At fast-transmitting presynaptic terminals Ca2+ enter through voltage gated calcium channels (CaVs) and bind to a synaptic vesicle (SV) -associated calcium sensor (SV-sensor) to gate fusion and discharge. An open CaV generates a high-concentration plume, or nanodomain of Ca2+ that dissipates precipitously with distance from the pore. At most fast synapses, such as the frog neuromuscular junction (NMJ), the SV sensors are located sufficiently close to individual CaVs to be gated by single nanodomains. However, at others, such as the mature rodent calyx of Held (calyx of Held), the physiology is more complex with evidence that CaVs that are both close and distant from the SV sensor and it is argued that release is gated primarily by the overlapping Ca2+ nanodomains from many CaVs. We devised a 'graphic modeling' method to sum Ca2+ from individual CaVs located at varying distances from the SV-sensor to determine the SV release probability and also the fraction of that probability that can be attributed to single domain gating. This method was applied first to simplified, low and high CaV density model release sites and then to published data on the contrasting frog NMJ and the rodent calyx of Held native synapses. We report 3 main predictions: the SV-sensor is positioned very close to the point at which the SV fuses with the membrane; single domain-release gating predominates even at synapses where the SV abuts a large cluster of CaVs, and even relatively remote CaVs can contribute significantly to single domain-based gating. PMID:26457441

  1. Involvement of Potassium Channels and Calcium-Independent Mechanisms in Hydrogen Sulfide-Induced Relaxation of Rat Mesenteric Small Arteries.

    Science.gov (United States)

    Hedegaard, Elise R; Gouliaev, Anja; Winther, Anna K; Arcanjo, Daniel D R; Aalling, Mathilde; Renaltan, Nirthika S; Wood, Mark E; Whiteman, Matthew; Skovgaard, Nini; Simonsen, Ulf

    2016-01-01

    Endogenous hydrogen sulfide (H2S) is involved in the regulation of vascular tone. We hypothesized that the lowering of calcium and opening of potassium (K) channels as well as calcium-independent mechanisms are involved in H2S-induced relaxation in rat mesenteric small arteries. Amperometric recordings revealed that free [H2S] after addition to closed tubes of sodium hydrosulfide (NaHS), Na2S, and GYY4137 [P-(4-methoxyphenyl)-P-4-morpholinyl-phosphinodithioic acid] were, respectively, 14%, 17%, and 1% of added amount. The compounds caused equipotent relaxations in isometric myographs, but based on the measured free [H2S], GYY4137 caused more relaxation in relation to released free H2S than NaHS and Na2S in rat mesenteric small arteries. Simultaneous measurements of [H2S] and tension showed that 15 µM of free H2S caused 61% relaxation in superior mesenteric arteries. Simultaneous measurements of smooth muscle calcium and tension revealed that NaHS lowered calcium and caused relaxation of NE-contracted arteries, while high extracellular potassium reduced NaHS relaxation without corresponding calcium changes. In NE-contracted arteries, NaHS (1 mM) lowered the phosphorylation of myosin light chain, while phosphorylation of myosin phosphatase target subunit 1 remained unchanged. Protein kinase A and G, inhibitors of guanylate cyclase, failed to reduce NaHS relaxation, whereas blockers of voltage-gated KV7 channels inhibited NaHS relaxation, and blockers of mitochondrial complex I and III abolished NaHS relaxation. Our findings suggest that low micromolar concentrations of free H2S open K channels followed by lowering of smooth muscle calcium, and by another mechanism involving mitochondrial complex I and III leads to uncoupling of force, and hence vasodilation. Copyright © 2015 by The American Society for Pharmacology and Experimental Therapeutics.

  2. Use of calcium channel blockers in cardiovascular risk reduction: issues in Latin America.

    Science.gov (United States)

    Alcocer, Luis; Bendersky, Mario; Acosta, Julio; Urina-Triana, Miguel

    2010-01-01

    Cardiovascular disease (CVD) is a continuum that begins with the presence of several risk factors for CVD, including smoking, hypertension, obesity, diabetes mellitus, and high levels of cholesterol, and if unaddressed can result in premature death, ischemic heart disease, stroke, congestive heart failure, and end-stage renal disease. Hypertension is associated with a significant increase in cardiovascular (CV) morbidity and mortality, raising the risk of stroke, myocardial infarction, heart failure, kidney disease, and peripheral arterial disease. In Latin America, the prevalence of hypertension and other CV risk factors has become similar to that seen in more developed countries, increasing the proportion of the population at high risk for CVD and congestive heart failure; however, it is hypertension that is a key driving force behind CV risk in Latin America. Despite the existence of a wide range of antihypertensive agents, BP control and reductions in CV risk remain poor in Latin America and in Hispanics living in the US. Ethnic differences in treatment rates and disease awareness have been well documented. Studies have shown that calcium channel blockers (CCBs; calcium channel antagonists) are at least as effective in reducing BP and improving the CV risk profile as other classes of antihypertensive agents when administered as monotherapy. CCBs have also been shown to be effective when administered as part of combination therapy in both low- and high-risk hypertensive patients, suggesting that CCBs can easily be combined with other antihypertensive classes in order to achieve BP control and CV risk reduction. In patients with hypertension, coronary artery disease, and high cholesterol, CCBs have been associated with beneficial effects on a range of other aspects of the CV continuum, including the vasculature, coronary calcification, and progression of atherosclerosis. CCBs have also been shown to preserve renal function. Unlike diuretics and beta

  3. Spasmolytic activity of Rosmarinus officinalis L. involves calcium channels in the guinea pig ileum.

    Science.gov (United States)

    Ventura-Martínez, Rosa; Rivero-Osorno, Oscar; Gómez, Claudia; González-Trujano, María Eva

    2011-10-11

    Rosmarinus officinalis L. is a plant used around the world for its properties to cure pain in several conditions, such as arthritic and abdominal pain or as an antispasmodic; however, there are no scientific studies demonstrating its spasmolytic activity. Therefore, the aim of the present study was to investigate the effect of an ethanol extract from Rosmarinus officinalis aerial parts and the possible mechanism involved by using rings from the isolated guinea pig ileum (IGPI). The IGPI rings were pre-contracted with potassium chloride (KCl; 60 mM), acetylcholine (ACh; 1 × 10(-9) to 1 × 10(-5)M) or electrical field stimulation (EFS; 0.3 Hz of frequency, 3.0 ms of duration and 14 V intensity) and tested in the presence of the Rosmarinus officinalis ethanol extract (150, 300, 600 and 1 200 μg/mL) or a referenced smooth muscle relaxant (papaverine, 30 μM). In addition, the possible mechanism of action was analyzed in the presence of hexametonium (a ganglionic blocker), indomethacine (an inhibitor of prostaglandins), l-NAME (a selective inhibitor of the nitric oxide synthase) and nifedipine (a calcium channel blocker). Rosmarinus officinalis ethanol extract exhibited a significant and concentration-dependent spasmolytic activity on the contractions induced by KCl (CI(50) = 661.06 ± 155.91 μg/mL); ACh (CI(50) = 464.05 ± 16.85 μg/mL) and EFS (CI(50) = 513.72 ± 34.13 μg/mL). Spasmolytic response of Rosmarinus officinalis (600 μg/mL) was reverted in the presence of nifedipine 1 μM, but not in the presence of hexamethonium 0.5mM, indomethacine 1 μM or L-NAME 100 μM. The present results reinforce the use of Rosmarinus officinalis as antispasmodic in folk medicine. Moreover, it is demonstrated the involvement of calcium channels in this activity, but not the participation of nicotinic receptors, prostaglandins or nitric oxide. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

  4. Alcohol Dependence Disrupts Amygdalar L-Type Voltage-Gated Calcium Channel Mechanisms.

    Science.gov (United States)

    Varodayan, Florence P; de Guglielmo, Giordano; Logrip, Marian L; George, Olivier; Roberto, Marisa

    2017-04-26

    L-type voltage-gated calcium channels (LTCCs) are implicated in several psychiatric disorders that are comorbid with alcoholism and involve amygdala dysfunction. Within the amygdala, the central nucleus (CeA) is critical in acute alcohol's reinforcing actions, and its dysregulation in human alcoholics drives their negative emotional state and motivation to drink. Here we investigated the specific role of CeA LTCCs in the effects of acute alcohol at the molecular, cellular physiology, and behavioral levels, and their potential neuroadaptation in alcohol-dependent rats. Alcohol increases CeA activity (neuronal firing rates and GABA release) in naive rats by engaging LTCCs, and intra-CeA LTCC blockade reduces alcohol intake in nondependent rats. Alcohol dependence reduces CeA LTCC membrane abundance and disrupts this LTCC-based mechanism; instead, corticotropin-releasing factor type 1 receptors (CRF1s) mediate alcohol's effects on CeA activity and drive the escalated alcohol intake of alcohol-dependent rats. Collectively, our data indicate that alcohol dependence functionally alters the molecular mechanisms underlying the CeA's response to alcohol (from LTCC- to CRF1-driven). This mechanistic switch contributes to and reflects the prominent role of the CeA in the negative emotional state that drives excessive drinking.SIGNIFICANCE STATEMENT The central amygdala (CeA) plays a critical role in the development of alcohol dependence. As a result, much preclinical alcohol research aims to identify relevant CeA neuroadaptions that promote the transition to dependence. Here we report that acute alcohol increases CeA neuronal activity in naive rats by engaging L-type calcium channels (LTCCs) and that intra-CeA LTCC blockade reduces alcohol intake in nondependent rats. Alcohol dependence disrupts this LTCC-based mechanism; instead, corticotropin-releasing factor type 1 receptors (CRF1s) mediate alcohol's effects on CeA activity and drive the escalated alcohol intake of alcohol

  5. S-acylation dependent post-translational cross-talk regulates large conductance calcium- and voltage- activated potassium (BK channels

    Directory of Open Access Journals (Sweden)

    Michael J Shipston

    2014-08-01

    Full Text Available Mechanisms that control surface expression and/or activity of large conductance calcium-activated potassium (BK channels are important determinants of their (pathophysiological function. Indeed, BK channel dysfunction is associated with major human disorders ranging from epilepsy to hypertension and obesity. S-acylation (S-palmitoylation represents a major reversible, post-translational modification controlling the properties and function of many proteins including ion channels. Recent evidence reveals that both pore-forming and regulatory subunits of BK channels are S-acylated and control channel trafficking and regulation by AGC-family protein kinases. The pore-forming α-subunit is S-acylated at two distinct sites within the N- and C-terminus, each site being regulated by different palmitoyl acyl transferases (zDHHCs and acyl thioesterases. (APTs. S-acylation of the N-terminus controls channel trafficking and surface expression whereas S-acylation of the C-terminal domain determines regulation of channel activity by AGC-family protein kinases. S-acylation of the regulatory β4-subunit controls ER exit and surface expression of BK channels but does not affect ion channel kinetics at the plasma membrane. Furthermore, a significant number of previously identified BK-channel interacting proteins have been shown, or are predicted to be, S-acylated. Thus, the BK channel multi-molecular signalling complex may be dynamically regulated by this fundamental post-translational modification and thus S-acylation likely represents an important determinant of BK channel physiology in health and disease.

  6. IgG from amyotrophic lateral sclerosis affects tubular calcium channels of skeletal muscle.

    Science.gov (United States)

    Delbono, O; García, J; Appel, S H; Stefani, E

    1991-06-01

    Amyotrophic lateral sclerosis (ALS) is a devastating human disease of upper and lower motoneurons. We studied the action of the immunoglobulin G (IgG) from ALS and disease control patients on dihydropyridine (DHP)-sensitive Ca2+ channels in single mammalian skeletal muscle fibers with the double Vaseline gap technique. The peak of the Ca2+ current (ICa) and the charge movement were reduced when the fibers were incubated in ALS IgG. These effects were lost when the IgG was boiled or adsorbed with skeletal tubular membranes. ALS IgG reduced skeletal muscle ICa in a similar fashion as nifedipine; the ICa blockade was voltage dependent, and the associated charge movement was reduced. These observations suggest that IgG from ALS patients reacts with the skeletal muscle DHP-sensitive Ca2+ channels or some associated regulatory moiety.

  7. Anti-neuroinflammatory effects of the calcium channel blocker nicardipine on microglial cells: implications for neuroprotection.

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    Bor-Ren Huang

    Full Text Available BACKGROUND/OBJECTIVE: Nicardipine is a calcium channel blocker that has been widely used to control blood pressure in severe hypertension following events such as ischemic stroke, traumatic brain injury, and intracerebral hemorrhage. However, accumulating evidence suggests that inflammatory processes in the central nervous system that are mediated by microglial activation play important roles in neurodegeneration, and the effect of nicardipine on microglial activation remains unresolved. METHODOLOGY/PRINCIPAL FINDINGS: In the present study, using murine BV-2 microglia, we demonstrated that nicardipine significantly inhibits microglia-related neuroinflammatory responses. Treatment with nicardipine inhibited microglial cell migration. Nicardipine also significantly inhibited LPS plus IFN-γ-induced release of nitric oxide (NO, and the expression of inducible nitric oxide synthase (iNOS and cyclooxygenase-2 (COX-2. Furthermore, nicardipine also inhibited microglial activation by peptidoglycan, the major component of the Gram-positive bacterium cell wall. Notably, nicardipine also showed significant anti-neuroinflammatory effects on microglial activation in mice in vivo. CONCLUSION/SIGNIFICANCE: The present study is the first to report a novel inhibitory role of nicardipine on neuroinflammation and provides a new candidate agent for the development of therapies for inflammation-related neurodegenerative diseases.

  8. Genetic analysis of hyperemesis gravidarum reveals association with intracellular calcium release channel (RYR2).

    Science.gov (United States)

    Fejzo, Marlena Schoenberg; Myhre, Ronny; Colodro-Conde, Lucía; MacGibbon, Kimber W; Sinsheimer, Janet S; Reddy, M V Prasad Linga; Pajukanta, Päivi; Nyholt, Dale R; Wright, Margaret J; Martin, Nicholas G; Engel, Stephanie M; Medland, Sarah E; Magnus, Per; Mullin, Patrick M

    2017-01-05

    Hyperemesis Gravidarum (HG), severe nausea/vomiting in pregnancy (NVP), can cause poor maternal/fetal outcomes. Genetic predisposition suggests the genetic component is essential in discovering an etiology. We performed whole-exome sequencing of 5 families followed by analysis of variants in 584 cases/431 controls. Variants in RYR2 segregated with disease in 2 families. The novel variant L3277R was not found in any case/control. The rare variant, G1886S was more common in cases (p = 0.046) and extreme cases (p = 0.023). Replication of G1886S using Norwegian/Australian data was supportive. Common variants rs790899 and rs1891246 were significantly associated with HG and weight loss. Copy-number analysis revealed a deletion in a patient. RYR2 encodes an intracellular calcium release channel involved in vomiting, cyclic-vomiting syndrome, and is a thyroid hormone target gene. Additionally, RYR2 is a downstream drug target of Inderal, used to treat HG and CVS. Thus, herein we provide genetic evidence for a pathway and therapy for HG. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  9. Effect of Calcium Channel Blockers on Lower Urinary Tract Symptoms: A Systematic Review

    Directory of Open Access Journals (Sweden)

    Muhammad Salman

    2017-01-01

    Full Text Available Background. Numerous medications are known to be associated with the development of lower urinary tract symptoms (LUTS. One such medication group is calcium channel blockers (CCB. Objective. To critically examine the literature regarding the involvement of CCB in manifestation of LUTS in humans. Methods. A systematic literature search was conducted on PubMed, SciELO, Scopus, and OpenGrey databases to find all potentially relevant research studies before August 2016. Results. Five studies met the inclusion criteria and were included in this review. Three out of five studies stated that CCB were involved in either precipitation or exacerbation of LUTS. As for the remaining two studies, one study found out that only the monotherapy of CCB was associated with increased prevalence of nocturia and voiding symptoms in young females, whereas the other study reported an inverse association of CCB with LUTS. The methodological quality of studies was considered high for four studies and low for one study. Conclusion. Healthcare providers should make efforts for an earlier identification of the individuals at risk of LUTS prior to the commencement of CCB therapy. Moreover, patients should be counselled to notify their healthcare provider if they notice urinary symptoms after the initiation of CCB.

  10. Differential effects of calcium channel blockers on size selectivity of proteinuria in diabetic glomerulopathy.

    Science.gov (United States)

    Smith, A C; Toto, R; Bakris, G L

    1998-09-01

    Calcium channel blockers (CCBs) are known to have differential effects on both changes in proteinuria as well as progression of diabetic nephropathy. No clinical study, however, has evaluated whether the differential antiproteinuric effects of CCBs may be explained by their effect on glomerular membrane permeability. We, therefore, tested the hypothesis that certain subclasses of CCBs reduce proteinuria by changing size selectivity of the glomerular membrane, hence changing its permeability. Twenty-one patients with type 2 diabetes and the presence of nephropathy with hypertension were randomized to receive either diltiazem CD or nifedipine GITS after baseline data for mean systolic and diastolic pressure, urinary protein excretion, glomerular filtration rate, renal plasma flow, neutral dextran and IgG clearances were obtained. Glomerular filtration rate, renal plasma flow, neutral dextran and IgG clearance were measured every three months, arterial pressure and heart rate every month. Patients were followed for 21 months. At 21 months, both patient groups had similar levels of blood pressure control, however, only the diltiazem group had a change in proteinuria (4+/-10%delta, nifedipine vs. -57+/-18%delta, diltiazem; P proteinuria do so, in part, by improving glomerular size permselectivity.

  11. The effect of the molecular properties of calcium channel blockers on their elimination route

    Directory of Open Access Journals (Sweden)

    Trbojević-Stanković Jasna B.

    2015-01-01

    Full Text Available Calcium channel blockers (CCBs are among the most widely used drugs in cardiovascular medicine. In this study, nine CCBs (amlodipine, felodipine, isradipine, nicardipine, nifedipine, nimodipine, nisoldipine, verapamil and diltiazem were investigated to assess the relationship between their molecular properties and elimination data obtained from literature. The descriptors of the molecular properties of CCBs were calculated using three software packages. The relationship between computed molecular properties and elimination data collected from relevant literature, initially investigated with simple linear regression analysis, showed poor correlation (R2 <0.25. Application of molecular weight or volume data as additional independent variable, multiple linear regression (MLR revealed better correlations (R2 ~ 0.38 between CCB renal and fecal elimination data and their lipophilicity. Excluding nimodipine from the calculations resulted in more acceptable correlations. The best correlations were established after computed lipophilicity descriptor and molecular weight were applied (R2 = 0.66 with acceptable probability value. [Projekat Ministarstva nauke Republike Srbije, br. TR34031

  12. The Low-Threshold Calcium Channel Cav3.2 Determines Low-Threshold Mechanoreceptor Function

    Directory of Open Access Journals (Sweden)

    Amaury François

    2015-01-01

    Full Text Available The T-type calcium channel Cav3.2 emerges as a key regulator of sensory functions, but its expression pattern within primary afferent neurons and its contribution to modality-specific signaling remain obscure. Here, we elucidate this issue using a unique knockin/flox mouse strain wherein Cav3.2 is replaced by a functional Cav3.2-surface-ecliptic GFP fusion. We demonstrate that Cav3.2 is a selective marker of two major low-threshold mechanoreceptors (LTMRs, Aδ- and C-LTMRs, innervating the most abundant skin hair follicles. The presence of Cav3.2 along LTMR-fiber trajectories is consistent with critical roles at multiple sites, setting their strong excitability. Strikingly, the C-LTMR-specific knockout uncovers that Cav3.2 regulates light-touch perception and noxious mechanical cold and chemical sensations and is essential to build up that debilitates allodynic symptoms of neuropathic pain, a mechanism thought to be entirely A-LTMR specific. Collectively, our findings support a fundamental role for Cav3.2 in touch/pain pathophysiology, validating their critic pharmacological relevance to relieve mechanical and cold allodynia.

  13. eNOS-dependent antisenscence effect of a calcium channel blocker in human endothelial cells.

    Directory of Open Access Journals (Sweden)

    Toshio Hayashi

    Full Text Available Senescence of vascular endothelial cells is an important contributor to the pathogenesis of age-associated vascular disorders such as atherosclerosis. We investigated the effects of antihypertensive agents on high glucose-induced cellular senescence in human umbilical venous endothelial cells (HUVECs. Exposure of HUVECs to high glucose (22 mM for 3 days increased senescence-associated- β-galactosidase (SA-β-gal activity, a senescence marker, and decreased telomerase activity, a replicative senescence marker. The calcium channel blocker nifedipine, but not the β1-adrenergic blocking agent atenolol or the angiotensin-converting enzyme inhibitor perindopril, reduced SA-β-gal positive cells and prevented a decrease in telomerase activity in a high-glucose environment. This beneficial effect of nifedipine was associated with reduced reactive oxygen species (ROS and increased endothelial nitric oxide synthase (eNOS activity. Thus, nifedipine prevented high glucose-induced ROS generation and increased basal eNOS phosphorylation level at Ser-1177. Treatment with N (G-nitro-L-arginine (L-NAME and transfection of small interfering RNA (siRNA targeting eNOS eliminated the anti-senscence effect of nifedipine. These results demonstrate that nifedipine can prevent endothelial cell senescence in an eNOS-dependent manner. The anti-senescence action of nifedipine may represent a novel mechanism by which it protects against atherosclerosis.

  14. Amlodipine, a long-acting calcium channel blocker, attenuates morning blood pressure rise in hypertensive patients.

    Science.gov (United States)

    Ishimitsu, T; Minami, J; Kawano, Y; Numabe, A; Takishita, S; Matsuoka, H

    1999-07-01

    1. The effects of once-daily calcium channel blockers with different plasma half-lives on diurnal blood pressure changes were examined in hypertensive patients. 2. Patients with essential hypertension, nine men and 13 women aged 61 +/- 2 years, were treated with amlodipine or nitrendipine in a random cross-over design for 12-16 weeks each. The study drugs were given once daily as monotherapy (n = 8) or in combination with other classes of antihypertensive drugs (n = 14). The plasma half-life of amlodipine is as long as 36 h, while that of nitrendipine is 10 h. At the end of each treatment period, 24 h ambulatory blood pressure and pulse rate were monitored. 3. Average office blood pressure was comparably controlled below 140/90 mmHg by either amlodipine or nitrendipine, both in the monotherapy and the combination therapy groups; however, pulse rate was greater in nitrendipine than in amlodipine either in the monotherapy (by 6 b.p.m., P morning (05.30-09.00 h) blood pressure was higher in nitrendipine than in amlodipine by 6/4 mmHg in the monotherapy (P morning blood pressure and mitigating reflex activation of the sympathetic nervous system.

  15. Calcium-dependent expression of transient receptor potential canonical type 3 channels in patients with chronic kidney disease

    DEFF Research Database (Denmark)

    Liu, Ying; Krueger, Katharina; Hovsepian, Anahit

    2011-01-01

    It is unknown whether extracellular calcium may regulate the expression of transient receptor potential canonical type 3 (TRPC3) channels in patients with chronic kidney disease. Using quantitative in-cell Western assay we compared the expression of TRPC3 channel protein in monocytes from 20...... patients with chronic kidney disease and 19 age- and sex-matched healthy control subjects. TRPC3 channels were identified by immunoblotting using specific antibodies and TRPC3 protein was further confirmed by mass spectrometry. We observed a significant increase of TRPC3 channel protein expression...... in patients with chronic kidney disease compared to healthy control subjects (normalized expression, 0.42±0.06 vs. 0.19±0.03; p...

  16. Targeting voltage-gated calcium channels: developments in peptide and small-molecule inhibitors for the treatment of neuropathic pain

    Science.gov (United States)

    Vink, S; Alewood, PF

    2012-01-01

    Chronic pain affects approximately 20% of people worldwide and places a large economic and social burden on society. Despite the availability of a range of analgesics, this condition is inadequately treated, with complete alleviation of symptoms rarely occurring. In the past 30 years, the voltage-gated calcium channels (VGCCs) have been recognized as potential targets for analgesic development. Although the majority of the research has been focused on Cav2.2 in particular, other VGCC subtypes such as Cav3.2 have recently come to the forefront of analgesic research. Venom peptides from marine cone snails have been proven to be a valuable tool in neuroscience, playing a major role in the identification and characterization of VGCC subtypes and producing the first conotoxin-based drug on the market, the ω-conotoxin, ziconotide. This peptide potently and selectively inhibits Cav2.2, resulting in analgesia in chronic pain states. However, this drug is only available via intrathecal administration, and adverse effects and a narrow therapeutic window have limited its use in the clinic. Other Cav2.2 inhibitors are currently in development and offer the promise of an improved route of administration and safety profile. This review assesses the potential of targeting VGCCs for analgesic development, with a main focus on conotoxins that block Cav2.2 and the developments made to transform them into therapeutics. PMID:22725651

  17. Nimodipine, a calcium channel blocker, delays the spontaneous LH surge in women with regular menstrual cycles: a prospective pilot study.

    Science.gov (United States)

    Nayot, Dan; Klachook, Shany; Casper, Robert F

    2013-02-07

    Currently GnRH analogue injections are used to prevent premature LH surges in women undergoing assisted reproductive technology. This was a pilot study to determine the safety and effectiveness of nimodipine, an oral calcium channel blocker, to delay the mid-cycle spontaneous LH surge in women with regular menstrual cycles. Eight women with regular menstrual cycles self-monitored three consecutive cycles for the day of an LH surge by daily urine assay. The first and third cycles were observatory. In the second cycle, subjects took nimodipine 60 mg by mouth three times daily for four days, starting two days prior to the expected LH surge day based on cycle one. The LH surge day in cycle 2 (nimodipine) was significantly delayed in comparison to both observatory cycle 1 (15.5+/-3.4 vs 14.0+/-2.8 days; p=0.033) and cycle 3 (15.1+/-3.5 vs 13.1+/-2.4 days; p=0.044). There was no difference in the LH surge day between the two observatory cycles (13.4+/-2.4 vs 13.1+/-2.4 days; p=0.457). Three patients experienced a mild headache. There was a statistically significant delay in the spontaneous LH surge day in the treatment cycle in comparison to both observatory cycles. Nimopidine should be further investigated as an oral alternative to delay a spontaneous LH surge.

  18. Calcium Channel α2δ1 Proteins Mediate Trigeminal Neuropathic Pain States Associated with Aberrant Excitatory Synaptogenesis*

    Science.gov (United States)

    Li, Kang-Wu; Yu, Yanhui Peter; Zhou, Chunyi; Kim, Doo-Sik; Lin, Bin; Sharp, Kelli; Steward, Oswald; Luo, Z. David

    2014-01-01

    To investigate a potential mechanism underlying trigeminal nerve injury-induced orofacial hypersensitivity, we used a rat model of chronic constriction injury to the infraorbital nerve (CCI-ION) to study whether CCI-ION caused calcium channel α2δ1 (Cavα2δ1) protein dysregulation in trigeminal ganglia and associated spinal subnucleus caudalis and C1/C2 cervical dorsal spinal cord (Vc/C2). Furthermore, we studied whether this neuroplasticity contributed to spinal neuron sensitization and neuropathic pain states. CCI-ION caused orofacial hypersensitivity that correlated with Cavα2δ1 up-regulation in trigeminal ganglion neurons and Vc/C2. Blocking Cavα2δ1 with gabapentin, a ligand for the Cavα2δ1 proteins, or Cavα2δ1 antisense oligodeoxynucleotides led to a reversal of orofacial hypersensitivity, supporting an important role of Cavα2δ1 in orofacial pain processing. Importantly, increased Cavα2δ1 in Vc/C2 superficial dorsal horn was associated with increased excitatory synaptogenesis and increased frequency, but not the amplitude, of miniature excitatory postsynaptic currents in dorsal horn neurons that could be blocked by gabapentin. Thus, CCI-ION-induced Cavα2δ1 up-regulation may contribute to orofacial neuropathic pain states through abnormal excitatory synapse formation and enhanced presynaptic excitatory neurotransmitter release in Vc/C2. PMID:24459143

  19. Short-term exposure to L-type calcium channel blocker, verapamil, alters the expression pattern of calcium-binding proteins in the brain of goldfish, Carassius auratus.

    Science.gov (United States)

    Palande, Nikhil V; Bhoyar, Rahul C; Biswas, Saikat P; Jadhao, Arun G

    2015-01-01

    The influx of calcium ions (Ca(2+)) is responsible for various physiological events including neurotransmitter release and synaptic modulation. The L-type voltage dependent calcium channels (L-type VDCCs) transport Ca(2+) across the membrane. Calcium-binding proteins (CaBPs) bind free cytosolic Ca(2+) and prevent excitotoxicity caused by sudden increase in cytoplasmic Ca(2+). The present study was aimed to understand the regulation of expression of neuronal CaBPs, namely, calretinin (CR) and parvalbumin (PV) following blockade of L-type VDCCs in the CNS of Carassius auratus. Verapamil (VRP), a potent L-type VDCC blocker, selectively blocks Ca(2+) entry at the plasma membrane level. VRP present in the aquatic environment at a very low residual concentration has shown ecotoxicological effects on aquatic animals. Following acute exposure for 96h, median lethal concentration (LC50) for VRP was found to be 1.22mg/L for goldfish. At various doses of VRP, the behavioral alterations were observed in the form of respiratory difficulty and loss of body balance confirming the cardiovascular toxicity caused by VRP at higher doses. In addition to affecting the cardiovascular system, VRP also showed effects on the nervous system in the form of altered expression of PV. When compared with controls, the pattern of CR expression did not show any variations, while PV expression showed significant alterations in few neuronal populations such as the pretectal nucleus, inferior lobes, and the rostral corpus cerebellum. Our result suggests possible regulatory effect of calcium channel blockers on the expression of PV. Copyright © 2015 Elsevier Inc. All rights reserved.

  20. Effect of glycerol treatment on the calcium current of frog skeletal muscle.

    Science.gov (United States)

    Siri, L N; Sánchez, J A; Stefani, E

    1980-08-01

    1. Current and voltage clamp experiments were carried out on frog skeletal muscle fibres. For voltage clamp, the three micro-electrode technique near the fibre end was used. 2. Calcium spikes and currents were recorded in TEA sulphate saline. The addition of 400 mM-glycerol did not appreciably modify them. 3. Muscle fibers were detubulated with the glycerol method. They showed sodium propagating action potentials, with sodium and potassium currents of expected amplitudes. 4. Calcium spikes and currents were reduced or abolished in detubulated muscle fibres. 5. An analysis of fibre capacitance showed a linear correlation between the remaining ICa and the degree of electric discontinuity between the transverse tubular system and the surface membrane. 6. These results indicate that ICa is mainly located in the transverse tubular system. This localization is compatible with some role during mechanical activation.

  1. A high-throughput assay for evaluating state dependence and subtype selectivity of Cav2 calcium channel inhibitors.

    Science.gov (United States)

    Dai, Ge; Haedo, Rodolfo J; Warren, Vivien A; Ratliff, Kevin S; Bugianesi, Randal M; Rush, Alison; Williams, Mark E; Herrington, James; Smith, McHardy M; McManus, Owen B; Swensen, Andrew M

    2008-04-01

    Cav2.2 channels play a critical role in pain signaling by controlling synaptic transmission between dorsal root ganglion neurons and dorsal horn neurons. The Cav2.2-selective peptide blocker ziconotide (Prialt, Elan Pharmaceuticals, Dublin, Ireland) has proven efficacious in pain relief, but has a poor therapeutic index and requires intrathecal administration. This has provided impetus for finding an orally active, state-dependent Cav2.2 inhibitor with an improved safety profile. Members of the Cav2 subfamily of calcium channels are the main contributors to central and peripheral synaptic transmission, but the pharmacological effects of blocking each subtype is not yet defined. Here we describe a high-throughput fluorescent assay using a fluorometric imaging plate reader (FLIPR [Molecular Devices, Sunnyvale, CA]) designed to quickly evaluate the state dependence and selectivity of inhibitors across the Cav2 subfamily. Stable cell lines expressing functional Cav2 channels (Ca(V)alpha, beta(3), and alpha(2)delta subunits) were co-transfected with an inward rectifier (Kir2.3) so that membrane potential, and therefore channel state, could be controlled by external potassium concentration. Following cell incubation in drug with varying concentrations of potassium, a high potassium trigger was added to elicit calcium influx through available, unblocked channels. State-dependent inhibitors that preferentially bind to channels in the open or inactivated state can be identified by their increased potency at higher potassium concentrations, where cells are depolarized and channels are biased towards these states. Although the Cav2 channel subtypes differ in their voltage dependence of inactivation, by adjusting pre-trigger potassium concentrations, the degree of steady-state inactivation can be more closely matched across Cav2 subtypes to assess molecular selectivity.

  2. Fragile X mental retardation protein controls synaptic vesicle exocytosis by modulating N-type calcium channel density

    Science.gov (United States)

    Ferron, Laurent; Nieto-Rostro, Manuela; Cassidy, John S.; Dolphin, Annette C.

    2014-04-01

    Fragile X syndrome (FXS), the most common heritable form of mental retardation, is characterized by synaptic dysfunction. Synaptic transmission depends critically on presynaptic calcium entry via voltage-gated calcium (CaV) channels. Here we show that the functional expression of neuronal N-type CaV channels (CaV2.2) is regulated by fragile X mental retardation protein (FMRP). We find that FMRP knockdown in dorsal root ganglion neurons increases CaV channel density in somata and in presynaptic terminals. We then show that FMRP controls CaV2.2 surface expression by targeting the channels to the proteasome for degradation. The interaction between FMRP and CaV2.2 occurs between the carboxy-terminal domain of FMRP and domains of CaV2.2 known to interact with the neurotransmitter release machinery. Finally, we show that FMRP controls synaptic exocytosis via CaV2.2 channels. Our data indicate that FMRP is a potent regulator of presynaptic activity, and its loss is likely to contribute to synaptic dysfunction in FXS.

  3. First direct electron microscopic visualization of a tight spatial coupling between GABAA-receptors and voltage-sensitive calcium channels

    DEFF Research Database (Denmark)

    Hansen, G H; Belhage, B; Schousboe, A

    1992-01-01

    Using cerebellar granule neurons in culture it was demonstrated that exposure of the cells to the GABAA receptor agonist 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol (THIP) leads to an increase in the number of voltage-gated calcium channels as revealed by quantitative preembedding indirect imm...... of THIP-treated cultures. This suggests that primarily low affinity GABAA-receptors are closely associated with Ca2+ channels and this may be important for the ability of these receptors to mediate an inhibitory action on transmitter release even under extreme depolarizing conditions....

  4. Electromagnetic fields act via activation of voltage-gated calcium channels to produce beneficial or adverse effects

    OpenAIRE

    Pall, Martin L

    2013-01-01

    The direct targets of extremely low and microwave frequency range electromagnetic fields (EMFs) in producing non-thermal effects have not been clearly established. However, studies in the literature, reviewed here, provide substantial support for such direct targets. Twenty-three studies have shown that voltage-gated calcium channels (VGCCs) produce these and other EMF effects, such that the L-type or other VGCC blockers block or greatly lower diverse EMF effects. Furthermore, the voltage-gat...

  5. Amyloid Beta Peptides Block New Synapse Assembly by Nogo Receptor-Mediated Inhibition of T-Type Calcium Channels.

    Science.gov (United States)

    Zhao, Yanjun; Sivaji, Sivaprakash; Chiang, Michael C; Ali, Haadi; Zukowski, Monica; Ali, Sareen; Kennedy, Bryan; Sklyar, Alex; Cheng, Alice; Guo, Zihan; Reed, Alexander K; Kodali, Ravindra; Borowski, Jennifer; Frost, Georgia; Beukema, Patrick; Wills, Zachary P

    2017-10-11

    Compelling evidence links amyloid beta (Aβ) peptide accumulation in the brains of Alzheimer's disease (AD) patients with the emergence of learning and memory deficits, yet a clear understanding of the events that drive this synaptic pathology are lacking. We present evidence that neurons exposed to Aβ are unable to form new synapses, resulting in learning deficits in vivo. We demonstrate the Nogo receptor family (NgR1-3) acts as Aβ receptors mediating an inhibition of synapse assembly, plasticity, and learning. Live imaging studies reveal Aβ activates NgRs on the dendritic shaft of neurons, triggering an inhibition of calcium signaling. We define T-type calcium channels as a target of Aβ-NgR signaling, mediating Aβ's inhibitory effects on calcium, synapse assembly, plasticity, and learning. These studies highlight deficits in new synapse assembly as a potential initiator of cognitive pathology in AD, and pinpoint calcium dysregulation mediated by NgRs and T-type channels as key components. VIDEO ABSTRACT. Copyright © 2017 Elsevier Inc. All rights reserved.

  6. Structure-function of proteins interacting with the α1 pore-forming subunit of high-voltage-activated calcium channels

    Science.gov (United States)

    Neely, Alan; Hidalgo, Patricia

    2014-01-01

    Openings of high-voltage-activated (HVA) calcium channels lead to a transient increase in calcium concentration that in turn activate a plethora of cellular functions, including muscle contraction, secretion and gene transcription. To coordinate all these responses calcium channels form supramolecular assemblies containing effectors and regulatory proteins that couple calcium influx to the downstream signal cascades and to feedback elements. According to the original biochemical characterization of skeletal muscle Dihydropyridine receptors, HVA calcium channels are multi-subunit protein complexes consisting of a pore-forming subunit (α1) associated with four additional polypeptide chains β, α2, δ, and γ, often referred to as accessory subunits. Twenty-five years after the first purification of a high-voltage calcium channel, the concept of a flexible stoichiometry to expand the repertoire of mechanisms that regulate calcium channel influx has emerged. Several other proteins have been identified that associate directly with the α1-subunit, including calmodulin and multiple members of the small and large GTPase family. Some of these proteins only interact with a subset of α1-subunits and during specific stages of biogenesis. More strikingly, most of the α1-subunit interacting proteins, such as the β-subunit and small GTPases, regulate both gating and trafficking through a variety of mechanisms. Modulation of channel activity covers almost all biophysical properties of the channel. Likewise, regulation of the number of channels in the plasma membrane is performed by altering the release of the α1-subunit from the endoplasmic reticulum, by reducing its degradation or enhancing its recycling back to the cell surface. In this review, we discuss the structural basis, interplay and functional role of selected proteins that interact with the central pore-forming subunit of HVA calcium channels. PMID:24917826

  7. Structure-function of proteins interacting with the alpha1 pore-forming subunit of high voltage-activated calcium channel

    Directory of Open Access Journals (Sweden)

    Alan eNeely

    2014-06-01

    Full Text Available Openings of high-voltage-activated calcium channels lead to a transient increase in calcium concentration that in turn activate a plethora of cellular functions, including muscle contraction, secretion and gene transcription. To coordinate all these responses calcium channels form supramolecular assemblies containing effectors and regulatory proteins that couple calcium influx to the downstream signal cascades and to feedback elements. According to the original biochemical characterization of skeletal muscle Dihydropyridine receptors, high-voltage-activated calcium channels are multi-subunit protein complexes consisting of a pore-forming subunit (α1 associated with four additional polypeptide chains β, α2, δ and γ, often referred to as accessory subunits. Twenty-five years after the first purification of a high-voltage calcium channel, the concept of a flexible stoichiometry to expand the repertoire of mechanisms that regulate calcium channel influx has emerged. Several other proteins have been identified that associate directly with the α1-subunit, including calmodulin and multiple members of the small and large GTPase family. Some of these proteins only interact with a subset of α1-subunits and during specific stages of biogenesis. More strikingly, most of the α1-subunit interacting proteins, such as the β-subunit and small GTPases, regulate both gating and trafficking through a variety of mechanisms. Modulation of channel activity covers almost all biophysical properties of the channel. Likewise, regulation of the number of channels in the plasma membrane is performed by altering the release of the α1-subunit from the endoplasmic reticulum, by reducing its degradation or enhancing its recycling back to the cell surface. In this review, we discuss the structural basis, interplay and functional role of selected proteins that interact with the central pore-forming subunit of high-voltage-activated calcium channels.

  8. Clinical features of neuromuscular disorders in patients with N-type voltage-gated calcium channel antibodies

    Directory of Open Access Journals (Sweden)

    Andreas Totzeck

    2016-09-01

    Full Text Available Neuromuscular junction disorders affect the pre- or postsynaptic nerve to muscle transmission due to autoimmune antibodies. Members of the group like myasthenia gravis and Lambert-Eaton syndrome have pathophysiologically distinct characteristics. However, in practice, distinction may be difficult. We present a series of three patients with a myasthenic syndrome, dropped-head syndrome, bulbar and respiratory muscle weakness and positive testing for anti-N-type voltage-gated calcium channel antibodies. In two cases anti-acetylcholin receptor antibodies were elevated, anti-P/Q-type voltage-gated calcium channel antibodies were negative. All patients initially responded to pyridostigmine with a non-response in the course of the disease. While one patient recovered well after treatment with intravenous immunoglobulins, 3,4-diaminopyridine, steroids and later on immunosuppression with mycophenolate mofetil, a second died after restriction of treatment due to unfavorable cancer diagnosis, the third patient declined treatment. Although new antibodies causing neuromuscular disorders were discovered, clinical distinction has not yet been made. Our patients showed features of pre- and postsynaptic myasthenic syndrome as well as severe dropped-head syndrome and bulbar and axial muscle weakness, but only anti-N-type voltage-gated calcium channel antibodies were positive. When administered, one patient benefited from 3,4-diaminopyridine. We suggest that this overlap-syndrome should be considered especially in patients with assumed seronegative myasthenia gravis and lack of improvement under standard therapy.

  9. Effect of MCI-176, a new calcium channel blocker, on large and small coronary arteries in dogs.

    Science.gov (United States)

    Ishibashi, T; Nakazawa, M; Imai, S

    1989-04-01

    MCI-176, a new calcium channel blocker, increases coronary blood flow and may improve perfusion in ischaemic areas. Its vasodilating effects on large conductive coronary arteries and the resistive arterioles were therefore compared with those of diltiazem, nifedipine, glyceryl trinitrate and adenosine in anaesthetised open chest beagle dogs. Intracoronary injection of these compounds caused dose dependent increases in coronary flow associated with decreases in the resistance of resistive arterioles, and the rank order of potency was nifedipine greater than adenosine greater than MCI-176 greater than diltiazem greater than glyceryl trinitrate. The resistance of the large conductive vessels was likewise reduced by these agents, except for adenosine. Glyceryl trinitrate showed the highest selectivity to the large conductive vessels, while adenosine showed the lowest and calcium channel blockers were intermediate. Among three calcium channel blockers, MCI-176 had the highest selectivity to the large conductive vessels, while the duration of action was the longest with diltiazem; the duration of action of MCI-176 was intermediate. Thus, MCI-176 is a coronary vasodilator, the potency of which is intermediate between nifedipine and diltiazem, but it has the highest selectivity to the large conductive vessels among these three compounds.

  10. Small-cell lung cancer with voltage-gated calcium channel antibody-positive paraneoplastic limbic encephalitis: a case report.

    Science.gov (United States)

    Kaira, Kyoichi; Okamura, Takashi; Takahashi, Hiroki; Horiguchi, Norio; Sunaga, Noriaki; Hisada, Takeshi; Yamada, Masanobu

    2014-04-08

    Paraneoplastic limbic encephalitis is a rare neurological syndrome and clinically characterized by cognitive dysfunction, memory impairment, seizures and psychiatric symptoms. Paraneoplastic limbic encephalitis is most frequently found in small-cell lung cancer, among various malignancies, and antineuronal antibodies are related to the autoimmune mechanism. We experienced a rare case of a patient with small-cell lung cancer with anti-voltage-gated calcium channel antibody-positive paraneoplastic limbic encephalitis. A 61-year-old Japanese man with a history of smoking cigarettes presented with seizure, confusion and personality change in acute onset. Brain magnetic resonance imaging showed high signal intensity on T2-weighted image in his right temporal lobe, suggestive of limbic encephalitis. A mediastinoscopy of the lymph node revealed small-cell lung carcinoma, and he was staged as having limited stage disease. Antibodies against P/Q-type and N-type voltage-gated calcium channel were positive and Hu antibody was negative. He was started on chemotherapy of carboplatin plus etoposide with concurrent thoracic radiotherapy. Neurological symptoms were gradually improved after systemic chemotherapy. We should be alert to the potential of malignant neoplasms associated with paraneoplastic limbic encephalitis when we examine a patient with cancer with neurological disorders such as personality change, disorientation, unconsciousness and memory loss. A clinical marker such as voltage-gated calcium channel antibody may help our diagnosis in clinical practice.

  11. Calcium channel blockers shorten the periodicity of ultradian variation in blood pressure in patients with essential hypertension.

    Science.gov (United States)

    Kawamura, H; Mitsubayashi, H; Saito, T; Kanmatsuse, K; Saito, N

    1998-09-01

    We studied ultradian and circadian variations in blood pressure (BP) in patients with essential hypertension who were receiving antihypertensive agents. No patient had previously received antihypertensive agents before this study began. After a 2-wk control period, we performed ambulatory blood pressure monitoring (ABPM) in 86 patients with essential hypertension (WHO stages I or II). The patients were then given a long-acting angiotensin converting enzyme inhibitor (ACEI) (captopril or imidapril), a beta-receptor blocker (arotinolol or bisoprolol), or a calcium channel blocker (nisoldipine or benidipine) twice daily to control BP. We evaluated the patients' BP once every 2 wk to ensure optimal control. After 12 wk, ultradian and circadian variations in BP were analyzed by the maximum entropy method (MEM). All antihypertensive agents decreased office systolic BP (SBP), office diastolic BP (DBP), 24-h SBP, and 24-h DBP. ACEI did not change office, 24-h, daytime, or nighttime pulse rate (PR). Arotinolol and bisoprolol decreased 24-h PR. All antihypertensive agents decreased 24-h, daytime, and nighttime pressure rate product. MEM showed that no antihypertensive agent affected the circadian variation in the 1st peak (24-h periodicity) of SBP, DBP, or PR. However, calcium channel blockers shortened the periodicity of circadian variations in the 2nd peak (12-h periodicity) of SBP and the 3rd peak (8 to 6 h periodicity) of SBP. Therefore, ultradian variations in BP should be carefully monitored in hypertensive patients treated with calcium channel blockers.

  12. Synthesis and Effects of Novel Dihydropyridines as Dual Calcium Channel Blocker and Angiotensin Antagonist on Isolated Rat Aorta

    Directory of Open Access Journals (Sweden)

    Farzin Hadizadeh

    2010-01-01

    Full Text Available Four novel losartan analogues 5a-d were synthesized by connecting a dihydropyridine nucleus to imidazole ring. The effects of 5a and 5b on angiotensin receptors (AT1 and L-type calcium channels were investigated on isolated rat aorta. Materials and MethodsAortic rings were pre-contracted with 1 µM Angiotensin II or 80 mM KCl and relaxant effects of losartan, nifedipine, 5a and 5b were evaluated by cumulative addition of these drugs to the bath solution.ResultsThe results showed that compounds 5a and 5b have both L-type calcium channel and AT1 receptor blocking activity. Their effects on AT1 receptors are 1000 and 100,000 times more than losartan respectively. The activity of compound 5b on L-type calcium channel is significantly less than nifedipine but compound 5a has comparable effect with nifedipine. ConclusionFinally we concluded that these two new Compounds can be potential candidates to be used as effective antihypertensive agents.

  13. Amino acid substitutions in the FXYD motif enhance phospholemman-induced modulation of cardiac L-type calcium channels.

    Science.gov (United States)

    Guo, Kai; Wang, Xianming; Gao, Guofeng; Huang, Congxin; Elmslie, Keith S; Peterson, Blaise Z

    2010-11-01

    We have found that phospholemman (PLM) associates with and modulates the gating of cardiac L-type calcium channels (Wang et al., Biophys J 98: 1149-1159, 2010). The short 17 amino acid extracellular NH(2)-terminal domain of PLM contains a highly conserved PFTYD sequence that defines it as a member of the FXYD family of ion transport regulators. Although we have learned a great deal about PLM-dependent changes in calcium channel gating, little is known regarding the molecular mechanisms underlying the observed changes. Therefore, we investigated the role of the PFTYD segment in the modulation of cardiac calcium channels by individually replacing Pro-8, Phe-9, Thr-10, Tyr-11, and Asp-12 with alanine (P8A, F9A, T10A, Y11A, D12A). In addition, Asp-12 was changed to lysine (D12K) and cysteine (D12C). As expected, wild-type PLM significantly slows channel activation and deactivation and enhances voltage-dependent inactivation (VDI). We were surprised to find that amino acid substitutions at Thr-10 and Asp-12 significantly enhanced the ability of PLM to modulate Ca(V)1.2 gating. T10A exhibited a twofold enhancement of PLM-induced slowing of activation, whereas D12K and D12C dramatically enhanced PLM-induced increase of VDI. The PLM-induced slowing of channel closing was abrogated by D12A and D12C, whereas D12K and T10A failed to impact this effect. These studies demonstrate that the PFXYD motif is not necessary for the association of PLM with Ca(V)1.2. Instead, since altering the chemical and/or physical properties of the PFXYD segment alters the relative magnitudes of opposing PLM-induced effects on Ca(V)1.2 channel gating, PLM appears to play an important role in fine tuning the gating kinetics of cardiac calcium channels and likely plays an important role in shaping the cardiac action potential and regulating Ca(2+) dynamics in the heart.

  14. Short-channel drain current model for asymmetric heavily / lightly ...

    Indian Academy of Sciences (India)

    PRADIPTA DUTTA

    2017-07-29

    Jul 29, 2017 ... transistors (MOSFETs) is a good practice for semicon- ductor industry to achieve higher packing density and better circuit performance. But down-scaling has some disadvantages also. These small scaled devices suffer from various types of short channel effects like veloc- ity saturation, drain-induced ...

  15. A blocker of N- and T-type voltage-gated calcium channels attenuates ethanol-induced intoxication, place preference, self-administration, and reinstatement.

    Science.gov (United States)

    Newton, Philip M; Zeng, Lily; Wang, Victoria; Connolly, Jacklyn; Wallace, Melisa J; Kim, Chanki; Shin, Hee-Sup; Belardetti, Francesco; Snutch, Terrance P; Messing, Robert O

    2008-11-05

    There is a clear need for new therapeutics to treat alcoholism. Here, we test our hypothesis that selective inhibitors of neuronal calcium channels will reduce ethanol consumption and intoxication, based on our previous studies using knock-out mice and cell culture systems. We demonstrate that pretreatment with the novel mixed N-type and T-type calcium channel antagonist 1-(6,6-bis(4-fluorophenyl)hexyl)-4-(3,4,5-trimethoxybenzyl)piperazine (NP078585) reduced ethanol intoxication. NP078585 also attenuated the reinforcing and rewarding properties of ethanol, measured by operant self-administration and the expression of an ethanol conditioned place preference, and abolished stress-induced reinstatement of ethanol seeking. NP078585 did not affect alcohol responses in mice lacking N-type calcium channels. These results suggest that selective calcium channel inhibitors may be useful in reducing acute ethanol intoxication and alcohol consumption by human alcoholics.

  16. Role of the T-type calcium channel CaV3.2 in the chronotropic action of corticosteroids in isolated rat ventricular myocytes.

    Science.gov (United States)

    Maturana, Andrés; Lenglet, Sébastien; Python, Magaly; Kuroda, Shun'ichi; Rossier, Michel F

    2009-08-01

    The mineralocorticoid receptor is involved in the development of several cardiac dysfunctions, including lethal ventricular arrhythmias associated with heart failure or hyperaldosteronism, but the molecular mechanisms responsible for these effects remain to be clarified. Reexpression of low voltage-activated T-type calcium channels in ventricular myocytes together with other fetal genes during cardiac pathologies could confer automaticity to these cells and would represent a pro-arrhythmogenic condition if occurring in vivo. In the present study, we demonstrated that in isolated neonatal rat ventricular myocytes, corticosteroids selectively induced the expression of a particular isoform of T channel, Ca(V)3.2/alpha1H. This response was accompanied by an increase of the Ca(V)3.2 T-type current, identified with the patch clamp technique by its sensitivity to nickel, and a concomitant acceleration of the myocyte spontaneous contractions. Silencing Ca(V)3.2 expression markedly reduced the chronotropic response to steroids. Moreover, modulation of the frequency of cell contractions by different redox agents was independent of channel expression but involved a direct regulation of channel activity. Although oxidants increased both Ca(V)3.2 current amplitude and beating frequency, they decreased L-type channel activity. Reducing agents had the opposite effect on these parameters. In conclusion, the acceleration of ventricular myocyte spontaneous contractions induced by corticosteroids in vitro appears dependent on the expression of the Ca(V)3.2 T channel isoform and modulated by the redox potential of the cells. These results provide a molecular model that could explain the high incidence of arrhythmias observed in patients upon combination of inappropriate activation of the mineralocorticoid receptor and oxidative stress.

  17. Scoring of coronary artery calcium scans: history, assumptions, current limitations, and future directions.

    Science.gov (United States)

    Alluri, Krishna; Joshi, Parag H; Henry, Travis S; Blumenthal, Roger S; Nasir, Khurram; Blaha, Michael J

    2015-03-01

    Coronary artery calcium (CAC) scanning is a reliable, noninvasive technique for estimating overall coronary plaque burden and for identifying risk for future cardiac events. Arthur Agatston and Warren Janowitz published the first technique for scoring CAC scans in 1990. Given the lack of available data correlating CAC with burden of coronary atherosclerosis at that time, their scoring algorithm was remarkable, but somewhat arbitrary. Since then, a few other scoring techniques have been proposed for the measurement of CAC including the Volume score and Mass score. Yet despite new data, little in this field has changed in the last 15 years. The main focus of our paper is to review the implications of the current approach to scoring CAC scans in terms of correlation with the central disease - coronary atherosclerosis. We first discuss the methodology of each available scoring system, describing how each of these scores make important indirect assumptions in the way they account (or do not account) for calcium density, location of calcium, spatial distribution of calcium, and microcalcification/emerging calcium that might limit their predictive power. These assumptions require further study in well-designed, large event-driven studies. In general, all of these scores are adequate and are highly correlated with each other. Despite its age, the Agatston score remains the most extensively studied and widely accepted technique in both the clinical and research settings. After discussing CAC scoring in the era of contrast enhanced coronary CT angiography, we discuss suggested potential modifications to current CAC scanning protocols with respect to tube voltage, tube current, and slice thickness which may further improve the value of CAC scoring. We close with a focused discussion of the most important future directions in the field of CAC scoring. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  18. Lessons learned from a novel calcium-channel protagonist and person.

    Science.gov (United States)

    Dillon, Margaret

    2015-11-15

    A long time ago (circa 1976), David C. Triggle was Chair of the Department of Biochemical Pharmacology at S.U.N.Y. Buffalo where he led the faculty and staff in the education and mentoring of countless pharmacy and graduate students who passed through the hallowed halls of the University. Trained as a chemist, David spent his days synthesizing new and improved calcium channel blockers in a cramped, makeshift organic chemistry lab while a lab full of aspiring pharmacologists measured their effects on contractile responses of various smooth muscle preparations. I was a graduate student fortunate enough to land in David's laboratory, and thanks to him, I successfully navigated out with a Ph.D. in hand. That being said, his influence was less through his role as thesis advisor and more by the example he set in his simple, everyday life in Buffalo, N.Y: his love for - and dedication to - his family, his concern for the environment and his health, his perseverance in that tiny organic chemistry closet, his command of the English language, his unbridled honesty and cynicism, and his quiet pursuit of excellence. This article chronicles student life during that particular time period and provides a glimpse into David's unique personality and lifestyle that made him a role model to me and others. Interwoven is my own circuitous career path both before and after leaving S.U.N.Y. Buffalo that culminated in a productive career at the opposite end of the drug development process from where it all started in pharmacology. Copyright © 2015. Published by Elsevier Inc.

  19. Enhancement of Tissue Expansion by Calcium Channel Blocker: A preliminary study

    Directory of Open Access Journals (Sweden)

    Aktas Alper

    2003-10-01

    Full Text Available Abstract Background Reconstruction of the defects after surgical resection of tumors is one of the important issues in surgical oncology. It is essential that the defect should be covered with a tissue quite similar to the original one and is best achieved by harvesting tissue from an area adjacent to the defect. Tissue expansion is one of the most frequently used reconstructive techniques. A number of studies evaluated blood circulation, capsule formation, tissue tolerance, histomorphological changes and complications of expander placement. However, only a few attempted to enhance tissue expansion. This study we aimed to evaluate verapamil, a calcium channel blocker, to enhance tissue expansion. Material and method Twelve New Zealand rabbits weighing between 900 gm and 1200 gm were assigned into study and control groups. High volume expanders (100, 200 or 300 cc were placed into the subcutaneous tissue. Rabbits in the study group received verapamil. Expanders in the control group were inflated every three days to achieve same pressure as the study group. The size of the flaps was assessed by applying pressure on tip of the flap to demonstrate the contraction. Histopathological examinations were performed. Results By administering liquid earlier and more quickly less flap retraction was observed in the study group. In the control group expanders were exposed in two rabbits while no complication occurred in the study group. Following extraction of the expanders, the flaps were elevated and less retraction was observed in the study group compared to controls. Conclusion Verapamil is safe when used topically and provides less retracted flaps. It can be suggested that verapamil acts on the myofibroblasts in the capsule around tissue expanders and thus increases efficiency of the expanders.

  20. Effect of a calcium channel blocker and antispasmodic in diarrhoea-predominant irritable bowel syndrome.

    Science.gov (United States)

    Lu, C L; Chen, C Y; Chang, F Y; Chang, S S; Kang, L J; Lu, R H; Lee, S D

    2000-08-01

    Irritable bowel syndrome (IBS) is a colonic function disorder. Both pinaverlum bromide (a selective calcium channel blocker) and mebeverine (an antispasmodic) are reported to be effective in the long-term (12-16 weeks) treatment of IBS patients. Their efficacy in the short-term treatment of IBS patients and colonic transit time is unclear. Furthermore, substance P and neuropeptide Y have either excitatory or inhibitory effects on colonic motility. Whether the efficacy of both drugs is mediated through these neuropeptides remains unknown. A clinical trial was conducted with 91 patients with diarrhoea-predominant IBS. After basal measurement of the total colonic transit time, IBS patients were randomized to receive either pinaverlum bromide (50 mg, t.i.d.) or mebeverine (100 mg, t.i.d.) for 2 weeks. The symptomatic scores regarding defaecation, total colonic transit time and serum levels of substance P and neuropeptide Y were measured before and after treatments. The daily defaecation frequency was markedly decreased after treatment (pinaverlum bromide, 2.9+/-1.2 vs 2.0+/-1.0, Pmebeverine, 2.7+/-1.1 vs 2.1+/-1.0, Pmebeverine 73.4 vs 71.8%, P> 0.05). The total colonic transit time was significantly prolonged only after pinaverlum bromide treatment (21.4+/-15.5 vs 30.8+/-14.8 h, Pmebeverine have similar therapeutic efficacies on diarrhoea-predominant IBS patients. Prolonged colonic transit time may be one of the factors responsible for the efficacy of pinaverlum bromide on the IBS patients. Substance P and neuropeptideY appear less important in the pathogenesis of diarrhoea-predominant IBS.

  1. Alternative Splicing of L-type CaV1.2 Calcium Channels: Implications in Cardiovascular Diseases

    Directory of Open Access Journals (Sweden)

    Zhenyu Hu

    2017-11-01

    Full Text Available L-type Cav1.2 calcium channels are the major pathway for Ca2+ influx to initiate the contraction of smooth and cardiac muscles. Alteration of Cav1.2 channel function has been implicated in multiple cardiovascular diseases, such as hypertension and cardiac hypertrophy. Alternative splicing is a post-transcriptional mechanism that expands Cav1.2 channel structures to modify function, pharmacological and biophysical property such as calcium/voltage-dependent inactivation (C/VDI, or to influence its post-translational modulation by interacting proteins such as Galectin-1. Alternative splicing has generated functionally diverse Cav1.2 isoforms that can be developmentally regulated in the heart, or under pathophysiological conditions such as in heart failure. More importantly, alternative splicing of certain exons of Cav1.2 has been reported to be regulated by splicing factors such as RNA-binding Fox-1 homolog 1/2 (Rbfox 1/2, polypyrimidine tract-binding protein (PTBP1 and RNA-binding motif protein 20 (RBM20. Understanding how Cav1.2 channel function is remodelled in disease will provide better information to guide the development of more targeted approaches to discover therapeutic agents for cardiovascular diseases.

  2. Alternative Splicing of L-type CaV1.2 Calcium Channels: Implications in Cardiovascular Diseases.

    Science.gov (United States)

    2017-11-24

    L-type Cav1.2 calcium channels are the major pathway for Ca2+ influx to initiate the contraction of smooth and cardiac muscles. Alteration of Cav1.2 channel function has been implicated in multiple cardiovascular diseases, such as hypertension and cardiac hypertrophy. Alternative splicing is a post-transcriptional mechanism that expands Cav1.2 channel structures to modify function, pharmacological and biophysical property such as calcium/voltage-dependent inactivation (C/VDI), or to influence its post-translational modulation by interacting proteins such as Galectin-1. Alternative splicing has generated functionally diverse Cav1.2 isoforms that can be developmentally regulated in the heart, or under pathophysiological conditions such as in heart failure. More importantly, alternative splicing of certain exons of Cav1.2 has been reported to be regulated by splicing factors such as RNA-binding Fox-1 homolog 1/2 (Rbfox 1/2), polypyrimidine tract-binding protein (PTBP1) and RNA-binding motif protein 20 (RBM20). Understanding how Cav1.2 channel function is remodelled in disease will provide better information to guide the development of more targeted approaches to discover therapeutic agents for cardiovascular diseases.

  3. The effect of verapamil and diltiazem on cardiac stimulant effect of adrenaline and calcium chloride on isolated frog heart

    OpenAIRE

    Lakhavat Sudhakar, Naveen Kumar T, Tadvi NA, Venkata Rao Y

    2013-01-01

    Background: Calcium channel blockers block voltage dependent L-type of calcium channel and thus reduce the frequency of opening of these channels in response to depolarization. The result is a marked decrease in transmembrane calcium current associated with long lasting relaxation of vascular smooth muscle, reduction in contractility in cardiac muscle, decrease in pacemaker activity in the SA node and decrease in conduction velocity in the AV node. Among Calcium channel blockers verapamil, ...

  4. L-type calcium channels and MAP kinase contribute to thyrotropin-releasing hormone-induced depolarization in thalamic paraventricular nucleus neurons.

    Science.gov (United States)

    Kolaj, Miloslav; Zhang, Li; Renaud, Leo P

    2016-06-01

    In rat paraventricular thalamic nucleus (PVT) neurons, activation of thyrotropin-releasing hormone (TRH) receptors enhances neuronal excitability via concurrent decrease in a G protein-coupled inwardly rectifying K (GIRK)-like conductance and opening of a cannabinoid receptor-sensitive transient receptor potential canonical (TRPC)-like conductance. Here, we investigated the calcium (Ca(2+)) contribution to the components of this TRH-induced response. TRH-induced membrane depolarization was reduced in the presence of intracellular BAPTA, also in media containing nominally zero [Ca(2+)]o, suggesting a critical role for both intracellular Ca(2+) release and Ca(2+) influx. TRH-induced inward current was unchanged by T-type Ca(2+) channel blockade, but was decreased by blockade of high-voltage-activated Ca(2+) channels (HVACCs). Both the pharmacologically isolated GIRK-like and the TRPC-like components of the TRH-induced response were decreased by nifedipine and increased by BayK8644, implying Ca(2+) influx via L-type Ca(2+) channels. Only the TRPC-like conductance was reduced by either thapsigargin or dantrolene, suggesting a role for ryanodine receptors and Ca(2+)-induced Ca(2+) release in this component of the TRH-induced response. In pituitary and other cell lines, TRH stimulates MAPK. In PVT neurons, only the GIRK-like component of the TRH-induced current was selectively decreased in the presence of PD98059, a MAPK inhibitor. Collectively, the data imply that TRH-induced depolarization and inward current in PVT neurons involve both a dependency on extracellular Ca(2+) influx via opening of L-type Ca(2+) channels, a sensitivity of a TRPC-like component to intracellular Ca(2+) release via ryanodine channels, and a modulation by MAPK of a GIRK-like conductance component. Copyright © 2016 the American Physiological Society.

  5. Inhibition of CaV3.2 T-type calcium channels in peripheral sensory neurons contributes to analgesic properties of epipregnanolone.

    Science.gov (United States)

    Ayoola, Christine; Hwang, Sung Mi; Hong, Sung Jun; Rose, Kirstin E; Boyd, Christopher; Bozic, Neda; Park, Ji-Yong; Osuru, Hari Prasad; DiGruccio, Michael R; Covey, Douglas F; Jevtovic-Todorovic, Vesna; Todorovic, Slobodan M

    2014-09-01

    T-type calcium channels (T-channels) play an important role in controlling excitability of nociceptors. We have previously shown that a synthetic series of 5β-reduced steroids induce a voltage-dependent blockade of T-currents in rat dorsal root ganglia (DRG) cells in vitro and induce potent analgesia to thermal stimuli in rats in vivo (Mol Pharmacol 66:1223-1235, 2004). Here, we investigated the effects of the endogenous 5β-reduced neuroactive steroid molecule, epipregnanolone [(3β,5β)-3-hydroxypregnan-20-one], on peripheral nociception. We used acutely dissociated DRG cells in vitro from adult rats as well as in vivo pain studies in mice and rats to investigate the effects of epipregnanolone on DRG T-channels. We found that epipregnanolone reversibly blocked DRG T-currents with a half-maximal inhibitory concentration (IC50) of 2 μM and stabilized the channel in the inactive state. However, sodium, potassium, and gamma-aminobutyric acid (GABA)-gated ionic currents were not sensitive to the blocking effects of epipregnanolone even at 10 μM. In ensuing in vivo studies, we found that intraplantar (i.pl.) injections of epipregnanolone directly into peripheral receptive fields reduced responses to nociceptive heat stimuli in rats in a dose-dependent fashion. Furthermore, i.pl. epipregnanolone injections effectively reduced responses to peripheral nociceptive thermal and mechanical stimuli in wild-type mice but had no effect on the responses of CaV3.2 knockout mice. We conclude that the inhibition of peripheral CaV3.2 T-channels contributes to the potent analgesic effect of the endogenous steroid epipregnanolone.

  6. Activation of MrgC receptor inhibits N-type calcium channels in small-diameter primary sensory neurons in mice.

    Science.gov (United States)

    Li, Zhe; He, Shao-Qiu; Xu, Qian; Yang, Fei; Tiwari, Vinod; Liu, Qin; Tang, Zongxiang; Han, Liang; Chu, Yu-Xia; Wang, Yun; Hin, Niyada; Tsukamoto, Takashi; Slusher, Barbara; Guan, Xiaowei; Wei, Feng; Raja, Srinivasa N; Dong, Xinzhong; Guan, Yun

    2014-08-01

    Mas-related G-protein-coupled receptor subtype C (mouse MrgC11 and rat rMrgC), expressed specifically in small-diameter primary sensory neurons, may constitute a novel pain inhibitory mechanism. We have shown previously that intrathecal administration of MrgC-selective agonists can strongly attenuate persistent pain in various animal models. However, the underlying mechanisms for MrgC agonist-induced analgesia remain elusive. Here, we conducted patch-clamp recordings to test the effect of MrgC agonists on high-voltage-activated (HVA) calcium current in small-diameter dorsal root ganglion (DRG) neurons. Using pharmacological approaches, we show for the first time that an MrgC agonist (JHU58) selectively and dose-dependently inhibits N-type, but not L- or P/Q-type, HVA calcium channels in mouse DRG neurons. Activation of HVA calcium channels is important to neurotransmitter release and synaptic transmission. Patch-clamp recordings in spinal cord slices showed that JHU58 attenuated the evoked excitatory postsynaptic currents in substantia gelatinosa (SG) neurons in wild-type mice, but not in Mrg knockout mice, after peripheral nerve injury. These findings indicate that activation of endogenously expressed MrgC receptors at central terminals of primary sensory fibers may decrease peripheral excitatory inputs onto SG neurons. Together, these results suggest potential cellular and molecular mechanisms that may contribute to intrathecal MrgC agonist-induced analgesia. Because MrgC shares substantial genetic homogeneity with human MrgX1, our findings may suggest a rationale for developing intrathecally delivered MrgX1 receptor agonists to treat pathological pain in humans and provide critical insight regarding potential mechanisms that may underlie its analgesic effects. Copyright © 2014 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.

  7. [Gentamicin on inner hair cells ribbon synapses CaV1.3 calcium ion channel protein expression].

    Science.gov (United States)

    Sun, Jianhua; Wang, Xuefeng; Liu, Ke

    2014-02-01

    To learn the influence the gentamycin on C57BL/6J mice hear and cochlear hair cell ribbon synapses CaV1.3 calcium protein amount. To explore the relationship between hear loss and its dosage correlation change and significance. The fixed amino glucoside to C57BL/6J mice was used to make abdominal cavity injection mold every day. The auditory brain-stem response ABR was used to measure the hear of mice in 7th, 14th, 28th after the injection. Immunofluorescence method was used to observe cochlear basement membrane of hair ribbon synapse CaV1.3 calcium channel proteins in the distribution and expression. Inner hair cells synaptic membrane was immune fluorescent tags with CtbP2 and CaV1. 3. With the growth of the injected drugs, ABR threshold increased,but all the hair cells and shape had no obvious change. However the amount of hair rib bon synapse CaV1.3 calcium ion channel proteins in the expression had significant differences (P < 0.01). CaV1.3 calcium ion channel proteins increased slightly lower than normal at 7th day, significantly decreased at 14th day, had increased, increased quantity compare with 14th day, but at 28th day after intraperitoneal injection of gentamicin. The increasing,decreasing and increasing trend of cochlear hair cells CaV1.3 proteins in the environment of amino glucoside drug toxicity showed that the increase of hair ribbon synapse CaV1.3 proteins may have a compensatory effect on the drug toxicity. With the increase of the drug toxicity effect, this kind of decompensated function could be the listening decline, which may be one of the mechanism of damage to hearing.

  8. Impact of phosphomimetic and non-phosphorylatable mutations of phospholemman on L-type calcium channels gating in HEK 293T cells.

    Science.gov (United States)

    Guo, Kai; Wang, Yue-Peng; Zhou, Zhi-Wen; Jiang, Yi-Bo; Li, Wei; Chen, Xiao-Meng; Li, Yi-Gang

    2015-03-01

    Phospholemman (PLM) is an important phosphorylation substrate for protein kinases A and C in the heart. Until now, the association between PLM phosphorylation status and L-type calcium channels (LTCCs) gating has not been fully understood. We investigated the kinetics of LTCCs in HEK 293T cells expressing phosphomimetic or nonphosphorylatable PLM mutants. The LTCCs gating was measured in HEK 293T cells transfected with LTCC and wild-type (WT) PLM, phosphomimetic or nonphosphorylatable PLM mutants: 6263AA, 6869AA, AAAA, 6263DD, 6869DD or DDDD. WT PLM significantly slowed LTCCs activation and deactivation while enhanced voltage-dependent inactivation (VDI). PLM mutants 6869DD and DDDD significantly increased the peak of the currents. 6263DD accelerated channel activation, while 6263AA slowed it more than WT PLM. 6869DD significantly enhanced PLM-induced increase of VDI. AAAA slowed the channel activation more than 6263AA, and DDDD accelerated the channel VDI more than 6869DD. Our results demonstrate that phosphomimetic PLM could stimulate LTCCs and alter their dynamics, while PLM nonphosphorylatable mutant produced the opposite effects. © 2015 The Authors. Journal of Cellular and Molecular Medicine published by John Wiley & Sons Ltd and Foundation for Cellular and Molecular Medicine.

  9. Physiology and Evolution of Voltage-Gated Calcium Channels in Early Diverging Animal Phyla: Cnidaria, Placozoa, Porifera and Ctenophora

    Science.gov (United States)

    Senatore, Adriano; Raiss, Hamad; Le, Phuong

    2016-01-01

    Voltage-gated calcium (Cav) channels serve dual roles in the cell, where they can both depolarize the membrane potential for electrical excitability, and activate transient cytoplasmic Ca2+ signals. In animals, Cav channels play crucial roles including driving muscle contraction (excitation-contraction coupling), gene expression (excitation-transcription coupling), pre-synaptic and neuroendocrine exocytosis (excitation-secretion coupling), regulation of flagellar/ciliary beating, and regulation of cellular excitability, either directly or through modulation of other Ca2+-sensitive ion channels. In recent years, genome sequencing has provided significant insights into the molecular evolution of Cav channels. Furthermore, expanded gene datasets have permitted improved inference of the species phylogeny at the base of Metazoa, providing clearer insights into the evolution of complex animal traits which involve Cav channels, including the nervous system. For the various types of metazoan Cav channels, key properties that determine their cellular contribution include: Ion selectivity, pore gating, and, importantly, cytoplasmic protein-protein interactions that direct sub-cellular localization and functional complexing. It is unclear when these defining features, many of which are essential for nervous system function, evolved. In this review, we highlight some experimental observations that implicate Cav channels in the physiology and behavior of the most early-diverging animals from the phyla Cnidaria, Placozoa, Porifera, and Ctenophora. Given our limited understanding of the molecular biology of Cav channels in these basal animal lineages, we infer insights from better-studied vertebrate and invertebrate animals. We also highlight some apparently conserved cellular functions of Cav channels, which might have emerged very early on during metazoan evolution, or perhaps predated it. PMID:27867359

  10. Physiology and evolution of voltage-gated calcium channels in early diverging animal phyla: Cnidaria, Placozoa, Porifera and Ctenophora

    Directory of Open Access Journals (Sweden)

    Adriano Senatore

    2016-11-01

    Full Text Available Voltage-gated calcium (Cav channels serve dual roles in the cell, where they can both depolarize the membrane potential for electrical excitability, and activate transient cytoplasmic Ca2+ signals. In animals, Cav channels play crucial roles including driving muscle contraction (excitation-contraction coupling, gene expression (excitation-transcription coupling, pre-synaptic and neuroendocrine exocytosis (excitation-secretion coupling, regulation of flagellar/ciliary beating, and regulation of cellular excitability, either directly or through modulation of other Ca2+-sensitive ion channels. In recent years, genome sequencing has provided significant insights into the molecular evolution of Cav channels. Furthermore, expanded gene datasets have permitted improved inference of the species phylogeny at the base of Metazoa, providing clearer insights into the evolution of complex animal traits which involve Cav channels, including the nervous system. For the various types of metazoan Cav channels, key properties that determine their cellular contribution include: ion selectivity, pore gating, and, importantly, cytoplasmic protein-protein interactions that direct sub-cellular localization and functional complexing. It is unclear when many of these defining features, many of which are essential for nervous system function, evolved. In this review, we highlight some experimental observations that implicate Cav channels in the physiology and behavior of the most early-diverging animals from the phyla Cnidaria, Placozoa, Porifera and Ctenophora. Given our limited understanding of the molecular biology of Cav channels in these basal animal lineages, we infer insights from better-studied vertebrate and invertebrate animals. We also highlight some apparently conserved cellular functions of Cav channels, which might have emerged very early on during metazoan evolution, or perhaps predated it.

  11. Physiology and Evolution of Voltage-Gated Calcium Channels in Early Diverging Animal Phyla: Cnidaria, Placozoa, Porifera and Ctenophora.

    Science.gov (United States)

    Senatore, Adriano; Raiss, Hamad; Le, Phuong

    2016-01-01

    Voltage-gated calcium (Cav) channels serve dual roles in the cell, where they can both depolarize the membrane potential for electrical excitability, and activate transient cytoplasmic Ca(2+) signals. In animals, Cav channels play crucial roles including driving muscle contraction (excitation-contraction coupling), gene expression (excitation-transcription coupling), pre-synaptic and neuroendocrine exocytosis (excitation-secretion coupling), regulation of flagellar/ciliary beating, and regulation of cellular excitability, either directly or through modulation of other Ca(2+)-sensitive ion channels. In recent years, genome sequencing has provided significant insights into the molecular evolution of Cav channels. Furthermore, expanded gene datasets have permitted improved inference of the species phylogeny at the base of Metazoa, providing clearer insights into the evolution of complex animal traits which involve Cav channels, including the nervous system. For the various types of metazoan Cav channels, key properties that determine their cellular contribution include: Ion selectivity, pore gating, and, importantly, cytoplasmic protein-protein interactions that direct sub-cellular localization and functional complexing. It is unclear when these defining features, many of which are essential for nervous system function, evolved. In this review, we highlight some experimental observations that implicate Cav channels in the physiology and behavior of the most early-diverging animals from the phyla Cnidaria, Placozoa, Porifera, and Ctenophora. Given our limited understanding of the molecular biology of Cav channels in these basal animal lineages, we infer insights from better-studied vertebrate and invertebrate animals. We also highlight some apparently conserved cellular functions of Cav channels, which might have emerged very early on during metazoan evolution, or perhaps predated it.

  12. Anti-addiction drug ibogaine inhibits voltage-gated ionic currents: A study to assess the drug's cardiac ion channel profile

    Energy Technology Data Exchange (ETDEWEB)

    Koenig, Xaver; Kovar, Michael; Rubi, Lena; Mike, Agnes K.; Lukacs, Peter; Gawali, Vaibhavkumar S.; Todt, Hannes [Center for Physiology and Pharmacology, Department of Neurophysiology and -pharmacology, Medical University of Vienna, 1090 Vienna (Austria); Hilber, Karlheinz, E-mail: karlheinz.hilber@meduniwien.ac.at [Center for Physiology and Pharmacology, Department of Neurophysiology and -pharmacology, Medical University of Vienna, 1090 Vienna (Austria); Sandtner, Walter [Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, 1090 Vienna (Austria)

    2013-12-01

    The plant alkaloid ibogaine has promising anti-addictive properties. Albeit not licenced as a therapeutic drug, and despite hints that ibogaine may perturb the heart rhythm, this alkaloid is used to treat drug addicts. We have recently reported that ibogaine inhibits human ERG (hERG) potassium channels at concentrations similar to the drugs affinity for several of its known brain targets. Thereby the drug may disturb the heart's electrophysiology. Here, to assess the drug's cardiac ion channel profile in more detail, we studied the effects of ibogaine and its congener 18-Methoxycoronaridine (18-MC) on various cardiac voltage-gated ion channels. We confirmed that heterologously expressed hERG currents are reduced by ibogaine in low micromolar concentrations. Moreover, at higher concentrations, the drug also reduced human Na{sub v}1.5 sodium and Ca{sub v}1.2 calcium currents. Ion currents were as well reduced by 18-MC, yet with diminished potency. Unexpectedly, although blocking hERG channels, ibogaine did not prolong the action potential (AP) in guinea pig cardiomyocytes at low micromolar concentrations. Higher concentrations (≥ 10 μM) even shortened the AP. These findings can be explained by the drug's calcium channel inhibition, which counteracts the AP-prolonging effect generated by hERG blockade. Implementation of ibogaine's inhibitory effects on human ion channels in a computer model of a ventricular cardiomyocyte, on the other hand, suggested that ibogaine does prolong the AP in the human heart. We conclude that therapeutic concentrations of ibogaine have the propensity to prolong the QT interval of the electrocardiogram in humans. In some cases this may lead to cardiac arrhythmias. - Highlights: • We study effects of anti-addiction drug ibogaine on ionic currents in cardiomyocytes. • We assess the cardiac ion channel profile of ibogaine. • Ibogaine inhibits hERG potassium, sodium and calcium channels. • Ibogaine’s effects on

  13. Role for voltage gated calcium channels in calcitonin gene-related peptide release in the rat trigeminovascular system

    DEFF Research Database (Denmark)

    Amrutkar, D V; Ploug, K B; Olesen, J

    2011-01-01

    Clinical and genetic studies have suggested a role for voltage gated calcium channels (VGCCs) in the pathogenesis of migraine. Release of calcitonin gene-related peptide (CGRP) from trigeminal neurons has also been implicated in migraine. The VGCCs are located presynaptically on neurons and are i......Clinical and genetic studies have suggested a role for voltage gated calcium channels (VGCCs) in the pathogenesis of migraine. Release of calcitonin gene-related peptide (CGRP) from trigeminal neurons has also been implicated in migraine. The VGCCs are located presynaptically on neurons...... and are involved in the release of these peptides to different stimuli. We have examined the presence and importance of VGCCs in controlling the CGRP release from rat dura mater, freshly isolated trigeminal ganglion (TG) and trigeminal nucleus caudalis (TNC). Each of the four VGCCs, P/Q-, N-, and L- and T...... the potassium induced CGRP release. In the absence of calcium ions (Ca2+) and in the presence of a cocktail of blockers, the stimulated CGRP release from dura mater was reduced almost to the same level as basal CGRP release. In the TG ¿-conotoxin GVIA inhibited the potassium induced CGRP release significantly...

  14. Role for voltage gated calcium channels in calcitonin gene-related peptide release in the rat trigeminovascular system

    DEFF Research Database (Denmark)

    Amrutkar, D V; Ploug, K B; Olesen, J

    2011-01-01

    Clinical and genetic studies have suggested a role for voltage gated calcium channels (VGCCs) in the pathogenesis of migraine. Release of calcitonin gene-related peptide (CGRP) from trigeminal neurons has also been implicated in migraine. The VGCCs are located presynaptically on neurons and are i......Clinical and genetic studies have suggested a role for voltage gated calcium channels (VGCCs) in the pathogenesis of migraine. Release of calcitonin gene-related peptide (CGRP) from trigeminal neurons has also been implicated in migraine. The VGCCs are located presynaptically on neurons...... and are involved in the release of these peptides to different stimuli. We have examined the presence and importance of VGCCs in controlling the CGRP release from rat dura mater, freshly isolated trigeminal ganglion (TG) and trigeminal nucleus caudalis (TNC). Each of the four VGCCs, P/Q-, N-, and L- and T...... the potassium induced CGRP release. In the absence of calcium ions (Ca2+) and in the presence of a cocktail of blockers, the stimulated CGRP release from dura mater was reduced almost to the same level as basal CGRP release. In the TG ω-conotoxin GVIA inhibited the potassium induced CGRP release significantly...

  15. Anti-Epileptic Drugs Delay Age-Related Loss of Spiral Ganglion Neurons via T-type Calcium Channel

    Science.gov (United States)

    Lei, Debin; Gao, Xia; Perez, Philip; Ohlemiller, Kevin K; Chen, Chien-Chang; Campbell, Kevin P.; Hood, Aizhen Yang; Bao, Jianxin

    2011-01-01

    Loss of spiral ganglion neurons is a major cause of age-related hearing loss (presbycusis). Despite being the third most prevalent condition afflicting elderly persons, there are no known medications to prevent presbycusis. Because calcium signaling has long been implicated in age-related neuronal death, we investigated T-type calcium channels. This family is comprised of three members (Cav3.1, Cav3.2, and Cav3.3), based on their respective main pore-forming alpha subunits: α1G, α1H, and α1I. In the present study, we report a significant delay of age-related loss of cochlear function and preservation of spiral ganglion neurons in α1H null and heterozygous mice, clearly demonstrating an important role for Cav3.2 in age-related neuronal loss. Furthermore, we show that anticonvulsant drugs from a family of T-type calcium channel blockers can significantly preserve spiral ganglion neurons during aging. To our knowledge, this is the first report of drugs capable of diminishing age-related loss of spiral ganglion neurons. PMID:21640179

  16. Anion-sensitive regions of L-type CaV1.2 calcium channels expressed in HEK293 cells.

    Directory of Open Access Journals (Sweden)

    Norbert Babai

    2010-01-01

    Full Text Available L-type calcium currents (I(Ca are influenced by changes in extracellular chloride, but sites of anion effects have not been identified. Our experiments showed that CaV1.2 currents expressed in HEK293 cells are strongly inhibited by replacing extracellular chloride with gluconate or perchlorate. Variance-mean analysis of I(Ca and cell-attached patch single channel recordings indicate that gluconate-induced inhibition is due to intracellular anion effects on Ca(2+ channel open probability, not conductance. Inhibition of CaV1.2 currents produced by replacing chloride with gluconate was reduced from approximately 75%-80% to approximately 50% by omitting beta subunits but unaffected by omitting alpha(2delta subunits. Similarly, gluconate inhibition was reduced to approximately 50% by deleting an alpha1 subunit N-terminal region of 15 residues critical for beta subunit interactions regulating open probability. Omitting beta subunits with this mutant alpha1 subunit did not further diminish inhibition. Gluconate inhibition was unchanged with expression of different beta subunits. Truncating the C terminus at AA1665 reduced gluconate inhibition from approximately 75%-80% to approximately 50% whereas truncating it at AA1700 had no effect. Neutralizing arginines at AA1696 and 1697 by replacement with glutamines reduced gluconate inhibition to approximately 60% indicating these residues are particularly important for anion effects. Expressing CaV1.2 channels that lacked both N and C termini reduced gluconate inhibition to approximately 25% consistent with additive interactions between the two tail regions. Our results suggest that modest changes in intracellular anion concentration can produce significant effects on CaV1.2 currents mediated by changes in channel open probability involving beta subunit interactions with the N terminus and a short C terminal region.

  17. Sigma-1 receptor agonist increases axon outgrowth of hippocampal neurons via voltage-gated calcium ions channels.

    Science.gov (United States)

    Li, Dong; Zhang, Shu-Zhuo; Yao, Yu-Hong; Xiang, Yun; Ma, Xiao-Yun; Wei, Xiao-Li; Yan, Hai-Tao; Liu, Xiao-Yan

    2017-12-01

    Sigma-1 receptors (Sig-1Rs) are unique endoplasmic reticulum proteins that have been implicated in both neurodegenerative and ischemic diseases, such as Alzheimer's disease and stroke. Accumulating evidence has suggested that Sig-1R plays a role in neuroprotection and axon outgrowth. The underlying mechanisms of Sig-1R-mediated neuroprotection have been well elucidated. However, the mechanisms underlying the effects of Sig-1R on axon outgrowth are not fully understood. To clarify this issue, we utilized immunofluorescence to compare the axon lengths of cultured naïve hippocampal neurons before and after the application of the Sig-1R agonist, SA4503. Then, electrophysiology and immunofluorescence were used to examine voltage-gated calcium ion channel (VGCCs) currents in the cell membranes and growth cones. We found that Sig-1R activation dramatically enhanced the axonal length of the naïve hippocampal neurons. Application of the Sig-1R antagonist NE100 and gene knockdown techniques both demonstrated the effects of Sig-1R. The growth-promoting effect of SA4503 was accompanied by the inhibition of voltage-gated Ca2+ influx and was recapitulated by incubating the neurons with the L-type, N-type, and P/Q-type VGCC blockers, nimodipine, MVIIA and ω-agatoxin IVA, respectively. This effect was unrelated to glial cells. The application of SA4503 transformed the growth cone morphologies from complicated to simple, which favored axon outgrowth. Sig-1R activation can enhance axon outgrowth and may have a substantial influence on neurogenesis and neurodegenerative diseases. © 2017 John Wiley & Sons Ltd.

  18. Nimodipine, a calcium channel blocker, delays the spontaneous LH surge in women with regular menstrual cycles: a prospective pilot study

    Science.gov (United States)

    2013-01-01

    Background Currently GnRH analogue injections are used to prevent premature LH surges in women undergoing assisted reproductive technology. This was a pilot study to determine the safety and effectiveness of nimodipine, an oral calcium channel blocker, to delay the mid-cycle spontaneous LH surge in women with regular menstrual cycles. Methods Eight women with regular menstrual cycles self-monitored three consecutive cycles for the day of an LH surge by daily urine assay. The first and third cycles were observatory. In the second cycle, subjects took nimodipine 60 mg by mouth three times daily for four days, starting two days prior to the expected LH surge day based on cycle one. Results The LH surge day in cycle 2 (nimodipine) was significantly delayed in comparison to both observatory cycle 1 (15.5+/−3.4 vs 14.0+/−2.8 days; p = 0.033) and cycle 3 (15.1+/−3.5 vs 13.1+/−2.4 days; p = 0.044). There was no difference in the LH surge day between the two observatory cycles (13.4+/−2.4 vs 13.1+/−2.4 days; p = 0.457). Three patients experienced a mild headache. Conclusions There was a statistically significant delay in the spontaneous LH surge day in the treatment cycle in comparison to both observatory cycles. Nimopidine should be further investigated as an oral alternative to delay a spontaneous LH surge. PMID:23391256

  19. Nimodipine, a calcium channel blocker, delays the spontaneous LH surge in women with regular menstrual cycles: a prospective pilot study

    Directory of Open Access Journals (Sweden)

    Nayot Dan

    2013-02-01

    Full Text Available Abstract Background Currently GnRH analogue injections are used to prevent premature LH surges in women undergoing assisted reproductive technology. This was a pilot study to determine the safety and effectiveness of nimodipine, an oral calcium channel blocker, to delay the mid-cycle spontaneous LH surge in women with regular menstrual cycles. Methods Eight women with regular menstrual cycles self-monitored three consecutive cycles for the day of an LH surge by daily urine assay. The first and third cycles were observatory. In the second cycle, subjects took nimodipine 60 mg by mouth three times daily for four days, starting two days prior to the expected LH surge day based on cycle one. Results The LH surge day in cycle 2 (nimodipine was significantly delayed in comparison to both observatory cycle 1 (15.5+/−3.4 vs 14.0+/−2.8 days; p = 0.033 and cycle 3 (15.1+/−3.5 vs 13.1+/−2.4 days; p = 0.044. There was no difference in the LH surge day between the two observatory cycles (13.4+/−2.4 vs 13.1+/−2.4 days; p = 0.457. Three patients experienced a mild headache. Conclusions There was a statistically significant delay in the spontaneous LH surge day in the treatment cycle in comparison to both observatory cycles. Nimopidine should be further investigated as an oral alternative to delay a spontaneous LH surge.

  20. ω-Tbo-IT1-New Inhibitor of Insect Calcium Channels Isolated from Spider Venom.

    Science.gov (United States)

    Mikov, Alexander N; Fedorova, Irina M; Potapieva, Natalia N; Maleeva, Ekaterina E; Andreev, Yaroslav A; Zaitsev, Alexey V; Kim, Kira K; Bocharov, Eduard V; Bozin, Timur N; Altukhov, Dmitry A; Lipkin, Alexey V; Kozlov, Sergey A; Tikhonov, Denis B; Grishin, Eugene V

    2015-11-27

    Novel disulfide-containing polypeptide toxin was discovered in the venom of the Tibellus oblongus spider. We report on isolation, spatial structure determination and electrophysiological characterization of this 41-residue toxin, called ω-Tbo-IT1. It has an insect-toxic effect with LD50 19 μg/g in experiments on house fly Musca domestica larvae and with LD50 20 μg/g on juvenile Gromphadorhina portentosa cockroaches. Electrophysiological experiments revealed a reversible inhibition of evoked excitatory postsynaptic currents in blow fly Calliphora vicina neuromuscular junctions, while parameters of spontaneous ones were not affected. The inhibition was concentration dependent, with IC50 value 40 ± 10 nM and Hill coefficient 3.4 ± 0.3. The toxin did not affect frog neuromuscular junctions or glutamatergic and GABAergic transmission in rat brains. Ca(2+) currents in Calliphora vicina muscle were not inhibited, whereas in Periplaneta americana cockroach neurons at least one type of voltage gated Ca(2+) current was inhibited by ω-Tbo-IT1. Thus, the toxin apparently acts as an inhibitor of presynaptic insect Ca(2+) channels. Spatial structure analysis of the recombinant ω-Tbo-IT1 by NMR spectroscopy in aqueous solution revealed that the toxin comprises the conventional ICK fold containing an extended β-hairpin loop and short β-hairpin loop which are capable of making "scissors-like mutual motions".

  1. Modulatory effects of the fruits of Tribulus terrestris L. on the function of atopic dermatitis-related calcium channels, Orai1 and TRPV3

    Directory of Open Access Journals (Sweden)

    Joo Hyun Nam

    2016-07-01

    Conclusions: Our results suggest that T. terrestris extract may have a therapeutic potential for recovery of abnormal skin barrier pathologies in atopic dermatitis through modulating the activities of calcium ion channels, Orai1 and TRPV3. This is the first study to report the modulatory effect of a medicinal plant on the function of ion channels in skin barrier.

  2. High glucose enhances transient receptor potential channel canonical type 6-dependent calcium influx in human platelets via phosphatidylinositol 3-kinase-dependent pathway

    DEFF Research Database (Denmark)

    Liu, Daoyan; Maier, Alexandra; Scholze, Alexandra

    2008-01-01

    Transient receptor potential canonical type 6 (TRPC6) channels mediating 1-oleoyl-2-acetyl-sn-glycerol (OAG)-induced calcium entry have been identified on human platelets. In the present study we tested the hypothesis that hyperglycemia increases the expression of TRPC6 channels....

  3. Aberrant Splicing Promotes Proteasomal Degradation of L-type Ca v 1.2 Calcium Channels by Competitive Binding for CaV β Subunits in Cardiac Hypertrophy

    NARCIS (Netherlands)

    Hu, Zhenyu; Wang, Jiong Wei; Yu, Dejie; Soon, Jia Lin; De Kleijn, Dominique P V|info:eu-repo/dai/nl/30481489X; Foo, Roger; Liao, Ping; Colecraft, Henry M.; Soong, Tuck Wah

    2016-01-01

    Decreased expression and activity of Ca V1.2 calcium channels has been reported in pressure overload-induced cardiac hypertrophy and heart failure. However, the underlying mechanisms remain unknown. Here we identified in rodents a splice variant of Ca V1.2 channel, named Ca V1.2 e21+22, that

  4. Insulin reduces neuronal excitability by turning on GABA(A channels that generate tonic current.

    Directory of Open Access Journals (Sweden)

    Zhe Jin

    Full Text Available Insulin signaling to the brain is important not only for metabolic homeostasis but also for higher brain functions such as cognition. GABA (γ-aminobutyric acid decreases neuronal excitability by activating GABA(A channels that generate phasic and tonic currents. The level of tonic inhibition in neurons varies. In the hippocampus, interneurons and dentate gyrus granule cells normally have significant tonic currents under basal conditions in contrast to the CA1 pyramidal neurons where it is minimal. Here we show in acute rat hippocampal slices that insulin (1 nM "turns on" new extrasynaptic GABA(A channels in CA1 pyramidal neurons resulting in decreased frequency of action potential firing. The channels are activated by more than million times lower GABA concentrations than synaptic channels, generate tonic currents and show outward rectification. The single-channel current amplitude is related to the GABA concentration resulting in a single-channel GABA affinity (EC(50 in intact CA1 neurons of 17 pM with the maximal current amplitude reached with 1 nM GABA. They are inhibited by GABA(A antagonists but have novel pharmacology as the benzodiazepine flumazenil and zolpidem are inverse agonists. The results show that tonic rather than synaptic conductances regulate basal neuronal excitability when significant tonic conductance is expressed and demonstrate an unexpected hormonal control of the inhibitory channel subtypes and excitability of hippocampal neurons. The insulin-induced new channels provide a specific target for rescuing cognition in health and disease.

  5. Sodium channels gone wild: resurgent current from neuronal and muscle channelopathies

    OpenAIRE

    Cannon, Stephen C.; Bean, Bruce P.

    2009-01-01

    Voltage-dependent sodium channels are the central players in the excitability of neurons, cardiac muscle, and skeletal muscle. Hundreds of mutations in sodium channels have been associated with human disease, particularly genetic forms of epilepsy, arrhythmias, myotonia, and periodic paralysis. In this issue of the JCI, Jarecki and colleagues present evidence suggesting that many such mutations alter the gating of sodium channels to produce resurgent sodium current, an unusual form of gating ...

  6. A promoter in the coding region of the calcium channel gene CACNA1C generates the transcription factor CCAT.

    Directory of Open Access Journals (Sweden)

    Natalia Gomez-Ospina

    Full Text Available The C-terminus of the voltage-gated calcium channel Cav1.2 encodes a transcription factor, the calcium channel associated transcriptional regulator (CCAT, that regulates neurite extension and inhibits Cav1.2 expression. The mechanisms by which CCAT is generated in neurons and myocytes are poorly understood. Here we show that CCAT is produced by activation of a cryptic promoter in exon 46 of CACNA1C, the gene that encodes CaV1.2. Expression of CCAT is independent of Cav1.2 expression in neuroblastoma cells, in mice, and in human neurons derived from induced pluripotent stem cells (iPSCs, providing strong evidence that CCAT is not generated by cleavage of CaV1.2. Analysis of the transcriptional start sites in CACNA1C and immune-blotting for channel proteins indicate that multiple proteins are generated from the 3' end of the CACNA1C gene. This study provides new insights into the regulation of CACNA1C, and provides an example of how exonic promoters contribute to the complexity of mammalian genomes.

  7. Antagonism of Lidocaine Inhibition by Open-Channel Blockers That Generate Resurgent Na Current

    Science.gov (United States)

    Bant, Jason S.; Aman, Teresa K.; Raman, Indira M.

    2013-01-01

    Na channels that generate resurgent current express an intracellular endogenous open-channel blocking protein, whose rapid binding upon depolarization and unbinding upon repolarization minimizes fast and slow inactivation. Na channels also bind exogenous compounds, such as lidocaine, which functionally stabilize inactivation. Like the endogenous blocking protein, these use-dependent inhibitors bind most effectively at depolarized potentials, raising the question of how lidocaine-like compounds affect neurons with resurgent Na current. We therefore recorded lidocaine inhibition of voltage-clamped, tetrodotoxin-sensitive Na currents in mouse Purkinje neurons, which express a native blocking protein, and in mouse hippocampal CA3 pyramidal neurons with and without a peptide from the cytoplasmic tail of NaVβ4 (the β4 peptide), which mimics endogenous open-channel block. To control channel states during drug exposure, lidocaine was applied with rapid-solution exchange techniques during steps to specific voltages. Inhibition of Na currents by lidocaine was diminished by either the β4 peptide or the native blocking protein. In peptide-free CA3 cells, prolonging channel opening with a site-3 toxin, anemone toxin II, reduced lidocaine inhibition; this effect was largely occluded by open-channel blockers, suggesting that lidocaine binding is favored by inactivation but prevented by open-channel block. In constant 100 μM lidocaine, current-clamped Purkinje cells continued to fire spontaneously. Similarly, the β4 peptide reduced lidocaine-dependent suppression of spiking in CA3 neurons in slices. Thus, the open-channel blocking protein responsible for resurgent current acts as a natural antagonist of lidocaine. Neurons with resurgent current may therefore be less susceptible to use-dependent Na channel inhibitors used as local anesthetic, antiarrhythmic, and anticonvulsant drugs. PMID:23486968

  8. Scientific research related to calcium channel blockers poisoning: Bibliometric analysis in Scopus, 1968-2012.

    Science.gov (United States)

    Zyoud, S H; Al-Jabi, S W; Sweileh, W M; Waring, W S

    2015-11-01

    Calcium channel blockers (CCBs) were the most common agents associated with a significant morbidity and mortality rate. The main objective of this study was to examine the publication pattern related to CCBs poisoning at the global level using bibliometric analysis of articles published in SciVerse Scopus online database. Data were searched for documents that contained specific words regarding CCB poisoning as keywords in the title. No time period limitations were specified in the search regarding the starting year. The ending date of the search was 31 December 2012. The criteria were met by 713 publications from 53 countries. The largest number of articles associated with CCBs was from the United States (30%), followed by the United Kingdom (7.4%), Japan (6%), and Germany (5.6%). No data related to CCBs were published from 159 (75%) of 212 countries registered in World Bank online database. There was no correlation between the number of published articles in the country and its population size (r = 0.03, p > 0.926). United Kingdom and Australia were the leading countries in terms of number of CCBs publications per million inhabitants (0.83 and 0.82 articles per million inhabitants, respectively), followed by the United States (0.68). Countries with a large population, such as India, tended to rank relatively low (0.01 articles per million inhabitants). The total number of citations at the time of data analysis (23 October 2014) was 6462, with an average of 9.1 citations per document. The highest median (interquartile range) number of citations was 8 (8-18) for the United States, followed by 6 (1-21) for Australia, 5 (1-15) for the United Kingdom, and 5 (1-24) for Canada. The h-index of the retrieved documents was 37. Scientific production on CCBs poisoning is increasing; nonetheless, the international collaboration is still rare. The amount of CCBs-based research activity was low or not available in most countries. More regional epidemiological studies are

  9. Antihypertensive and vasorelaxant activities of Laelia autumnalis are mainly through calcium channel blockade.

    Science.gov (United States)

    Vergara-Galicia, Jorge; Ortiz-Andrade, Rolffy; Castillo-España, Patricia; Ibarra-Barajas, Maximiliano; Gallardo-Ortiz, Itzell; Villalobos-Molina, Rafael; Estrada-Soto, Samuel

    2008-07-01

    The aim of the present study was to evaluate the possible mechanism of the vasorelaxant action of methanol extract from Laelia autumnalis (MELa) in isolated rat aortic rings, and to establish its antihypertensive activity in vivo. MELa (0.15-->50 microg/mL) induced relaxation in aortic rings pre-contracted with KCl (80 mM), showing an IC50 value of 34.61+/-1.41 microg/mL and E max value of 85.0+/-4.38% (in endothelium-intact rings) and an IC50 value of 45.11+/-4.17 microg/mL and E max value of 80.0+/-12.1% (in endothelium-denuded rings). Serotonin (5-HT, 1 x 10(-4) M) provoked sustained contraction, which was markedly inhibited by MELa (0.15-->50 microg/mL) in a concentration-dependent and endothelium-independent manner. Pretreatment with MELa (15, 46, 150, 300 and 1500 microg/mL) also inhibited contractile responses to norepinephrine (NE 1 x 10(-11) M to 1 x 10(-5.5) M). In endothelium-denuded rings, the vasorelaxant effect of MELa was reduced partially by ODQ (1 microM), but not by tetraethylammonium (5 microM), glibenclamide (10 microM), and 2-aminopyridine (100 microM). The extract also reduced NE-induced transient contraction in Ca2+-free solution, and inhibited contraction induced by increasing external calcium in Ca2+-free medium plus high KCl (80 mM). The antihypertensive effect of MELa was determined in spontaneously hypertensive rats (SHR). A single oral administration of the extract (100 mg/kg) exhibited a significant decrease in systolic and diastolic blood pressure and heart rate (p<0.05) in SHR rats. Our results suggest that MELa induces relaxation in rat aortic rings through an endothelium-independent pathway, involving blockade of Ca2+ channels and a possible cGMP enhanced concentrations and also causes an antihypertensive effect.

  10. Efficacy of Methylene Blue in an Experimental Model of Calcium Channel Blocker Induced Shock

    Science.gov (United States)

    Jang, David H.; Donovan, Sean; Nelson, Lewis S.; Bania, Theodore C.; Hoffman, Robert S.; Chu, Jason

    2014-01-01

    BACKGROUND Calcium channel blocker poisonings account for a substantial number of reported deaths from cardiovascular drugs. While supportive care is the mainstay of treatment, experimental therapies such as high dose insulin-euglycemia and lipid emulsion have been studied in animal models and used in humans. In the most severe cases even aggressive care is inadequate and deaths occur. In both experimental models and clinical cases of vasodilatory shock, methylene blue improves hemodynamic measures. Methylene blue acts as both a nitric oxide scavenger and inhibits guanylate cyclase that is responsible for the production of cGMP. Excessive cGMP production is associated with refractory vasodilatory shock in sepsis and anaphylaxis. The aim of this study was to determine the efficacy of methylene blue in an animal model of amlodipine-induced shock. METHODS Sprague-Dawley rats were anesthetized, ventilated and instrumented for continuous blood pressure and heart rate monitoring. The dose of amlodipine that produced death within 60 minutes was 17 mg/kg/hour (LD50). Rats were divided into 2 groups: amlodipine followed by methylene blue or amlodipine followed by normal saline (NS) with 15 rats in each group. Rats received methylene blue at 2 mg/kg over 5 mins or an equivalent amount of NS in three intervals from the start of the protocol: Minute 5, 30, and 60. The animals were observed for a total of 2 hours after the start of the protocol. Mortality risk and survival time were analyzed using Fisher’s exact test and Kaplan Meier survival analysis with the log rank test. RESULTS Overall, 1/15 (7%) rats in the saline-treated group survived to 120 minutes compared with 5/15 (33%) rats in the methylene blue-treated group (difference −26%, 95% CI –54%, 0.3%). The median survival time for the NS group was 42 min (95% CI, 28.1,55.9) and the methylene blue group was 109 min (95% CI, 93.9,124.1). Heart rate and MAP differences between groups were analyzed until 60 minutes

  11. Ursodeoxycholic acid prevents ventricular conduction slowing and arrhythmia by restoring T-type calcium current in fetuses during cholestasis.

    Directory of Open Access Journals (Sweden)

    Oladipupo Adeyemi

    Full Text Available Increased maternal serum bile acid concentrations in intrahepatic cholestasis of pregnancy (ICP are associated with fetal cardiac arrhythmias. Ursodeoxycholic acid (UDCA has been shown to demonstrate anti-arrhythmic properties via preventing ICP-associated cardiac conduction slowing and development of reentrant arrhythmias, although the cellular mechanism is still being elucidated.High-resolution fluorescent optical mapping of electrical activity and electrocardiogram measurements were used to characterize effects of UDCA on one-day-old neonatal and adult female Langendorff-perfused rat hearts. ICP was modelled by perfusion of taurocholic acid (TC, 400μM. Whole-cell calcium currents were recorded from neonatal rat and human fetal cardiomyocytes.TC significantly prolonged the PR interval by 11.0±3.5% (P<0.05 and slowed ventricular conduction velocity (CV by 38.9±5.1% (P<0.05 exclusively in neonatal and not in maternal hearts. A similar CV decline was observed with the selective T-type calcium current (ICa,T blocker mibefradil 1μM (23.0±6.2%, P<0.05, but not with the L-type calcium current (ICa,L blocker nifedipine 1μM (6.9±6.6%, NS. The sodium channel blocker lidocaine (30μM reduced CV by 60.4±4.5% (P<0.05. UDCA co-treatment was protective against CV slowing induced by TC and mibefradil, but not against lidocaine. UDCA prevented the TC-induced reduction in the ICa,T density in both isolated human fetal (-10.2±1.5 versus -5.5±0.9 pA/pF, P<0.05 and neonatal rat ventricular myocytes (-22.3±1.1 versus -9.6±0.8 pA/pF, P<0.0001, whereas UDCA had limited efficacy on the ICa,L.Our findings demonstrate that ICa,T plays a significant role in ICP-associated fetal cardiac conduction slowing and arrhythmogenesis, and is an important component of the fetus-specific anti-arrhythmic activity of UDCA.

  12. Ursodeoxycholic acid prevents ventricular conduction slowing and arrhythmia by restoring T-type calcium current in fetuses during cholestasis.

    Science.gov (United States)

    Adeyemi, Oladipupo; Alvarez-Laviada, Anita; Schultz, Francisca; Ibrahim, Effendi; Trauner, Michael; Williamson, Catherine; Glukhov, Alexey V; Gorelik, Julia

    2017-01-01

    Increased maternal serum bile acid concentrations in intrahepatic cholestasis of pregnancy (ICP) are associated with fetal cardiac arrhythmias. Ursodeoxycholic acid (UDCA) has been shown to demonstrate anti-arrhythmic properties via preventing ICP-associated cardiac conduction slowing and development of reentrant arrhythmias, although the cellular mechanism is still being elucidated. High-resolution fluorescent optical mapping of electrical activity and electrocardiogram measurements were used to characterize effects of UDCA on one-day-old neonatal and adult female Langendorff-perfused rat hearts. ICP was modelled by perfusion of taurocholic acid (TC, 400μM). Whole-cell calcium currents were recorded from neonatal rat and human fetal cardiomyocytes. TC significantly prolonged the PR interval by 11.0±3.5% (P<0.05) and slowed ventricular conduction velocity (CV) by 38.9±5.1% (P<0.05) exclusively in neonatal and not in maternal hearts. A similar CV decline was observed with the selective T-type calcium current (ICa,T) blocker mibefradil 1μM (23.0±6.2%, P<0.05), but not with the L-type calcium current (ICa,L) blocker nifedipine 1μM (6.9±6.6%, NS). The sodium channel blocker lidocaine (30μM) reduced CV by 60.4±4.5% (P<0.05). UDCA co-treatment was protective against CV slowing induced by TC and mibefradil, but not against lidocaine. UDCA prevented the TC-induced reduction in the ICa,T density in both isolated human fetal (-10.2±1.5 versus -5.5±0.9 pA/pF, P<0.05) and neonatal rat ventricular myocytes (-22.3±1.1 versus -9.6±0.8 pA/pF, P<0.0001), whereas UDCA had limited efficacy on the ICa,L. Our findings demonstrate that ICa,T plays a significant role in ICP-associated fetal cardiac conduction slowing and arrhythmogenesis, and is an important component of the fetus-specific anti-arrhythmic activity of UDCA.

  13. AHR-16303B, a novel antagonist of 5-HT2 receptors and voltage-sensitive calcium channels

    Energy Technology Data Exchange (ETDEWEB)

    Barrett, R.J.; Appell, K.C.; Kilpatrick, B.F.; Proakis, A.G.; Nolan, J.C.; Walsh, D.A. (A. H. Robins Research Labs., Richmond, VA (USA))

    1991-01-01

    In vivo and in vitro methods were used to characterize AHR-16303B, a novel compound with antagonistic action at 5-HT2 receptors and voltage-sensitive calcium channels. The 5-HT2 receptor-antagonistic properties of AHR-16303B were demonstrated by inhibition of (a) (3H)ketanserin binding to rat cerebral cortical membranes (IC50 = 165 nM); (b) 5-hydroxytryptamine (5-HT)-induced foot edema in rats (minimum effective dose, (MED) = 0.32 mg/kg orally, p.o.); (c) 5-HT-induced vasopressor responses in spontaneously hypertensive rats (SHR) (ID50 = 0.18 mg/kg intravenously (i.v.), 1.8 mg/kg p.o.), (d) 5-HT-induced antidiuresis in rats (MED = 1 mg/kg p.o.), and (e) platelet aggregation induced by 5-HT + ADP (IC50 = 1.5 mM). The calcium antagonist properties of AHR-16303B were demonstrated by inhibition of (a) (3H)nimodipine binding to voltage-sensitive calcium channels on rabbit skeletal muscle membranes (IC50 = 15 nM), (b) KCl-stimulated calcium flux into cultured PC12 cells (IC50 = 81 nM), and (c) CaCl2-induced contractions of rabbit thoracic aortic strips (pA2 = 8.84). AHR-16303B had little or no effect on binding of radioligands to dopamine2 (DA2) alpha 1, alpha 2, H1, 5-HT1 alpha, beta 2, muscarinic M1, or sigma opioid receptors; had no effect on 5-HT3 receptor-mediated vagal bradycardia; and had only minor negative inotropic, chronotropic, and dromotropic effects on isolated guinea pig atria. In conscious SHR, 30 mg/kg p.o. AHR-16303B completely prevented the vasopressor responses to i.v. 5-HT, and decreased blood pressure (BP) by 24% 3 h after dosing.

  14. Lung adenocarcinoma with Lambert–Eaton myasthenic syndrome indicated by voltage-gated calcium channel: a case report

    Directory of Open Access Journals (Sweden)

    Arai Hiromasa

    2012-09-01

    Full Text Available Abstract Introduction Lambert–Eaton myasthenic syndrome is a rare disorder and it is known as a paraneoplastic neurological syndrome. Small cell lung cancer often accompanies this syndrome. Lambert–Eaton myasthenic syndrome associated with lung adenocarcinoma is extremely rare; there are only a few reported cases worldwide. Case presentation A 75-year-old Japanese man with a past history of chronic rheumatoid arthritis and Sjögren syndrome was diagnosed with Lambert–Eaton myasthenic syndrome by electromyography and serum anti-P/Q-type voltage-gated calcium channel antibody level preceding the diagnosis of lung cancer. A chest computed tomography to screen for malignant lesions revealed an abnormal shadow in the lung. Although a histopathological examination by bronchoscopic study could not reveal the malignancy, lung cancer was mostly suspected after the results of a chest computed tomography and [18F]-fluorodeoxyglucose positron emission tomography. An intraoperative diagnosis based on the frozen section obtained by tumor biopsy was adenocarcinoma so the patient underwent a lobectomy of the right lower lobe and lymph node dissection with video-assisted thoracoscopic surgery. The permanent pathological examination was the same as the frozen diagnosis (pT2aN1M0: Stage IIa: TNM staging 7th edition. Immunohistochemistry revealed that most of the cancer cells were positive for P/Q-type voltage-gated calcium channel. Conclusions Our case is a rare combination of Lambert–Eaton myasthenic syndrome associated with lung adenocarcinoma, rheumatoid arthritis and Sjögren syndrome, and to the best of our knowledge it is the first report that indicates the presence of voltage-gated calcium channel in lung adenocarcinoma by immunostaining.

  15. Modulation of Tonic GABA Currents by Anion Channel and Connexin Hemichannel Antagonists.

    Science.gov (United States)

    Ransom, Christopher B; Ye, Zucheng; Spain, William J; Richerson, George B

    2017-04-12

    Anion channels and connexin hemichannels are permeable to amino acid neurotransmitters. It is hypothesized that these conductive pathways release GABA, thereby influencing ambient GABA levels and tonic GABAergic inhibition. To investigate this, we measured the effects of anion channel/hemichannel antagonists on tonic GABA currents of rat hippocampal neurons. In contrast to predictions, blockade of anion channels and hemichannels with NPPB potentiated tonic GABA currents of neurons in culture and acute hippocampal slices. In contrast, the anion channel/hemichannel antagonist carbenoxolone (CBX) inhibited tonic currents. These findings could result from alterations of ambient GABA concentration or direct effects on GABAA receptors. To test for effects on GABAA receptors, we measured currents evoked by exogenous GABA. Coapplication of NPPB with GABA potentiated GABA-evoked currents. CBX dose-dependently inhibited GABA-evoked currents. These results are consistent with direct effects of NPPB and CBX on GABAA receptors. GABA release from hippocampal cell cultures was directly measured using HPLC. Inhibition of anion channels with NPPB or CBX did not affect GABA release from cultured hippocampal neurons. NPPB reduced GABA release from pure astrocytic cultures by 21%, but the total GABA release from astrocytes was small compared to that of mixed cultures. These data indicate that drugs commonly used to antagonize anion channels and connexin hemichannels may affect tonic currents via direct effects on GABAA receptors and have negligible effects on ambient GABA concentrations. Interpretation of experiments using NPPB or CBX should include consideration of their effects on tonic GABA currents.

  16. Localization of large conductance calcium-activated potassium channels and their effect on calcitonin gene-related peptide release in the rat trigemino-neuronal pathway

    DEFF Research Database (Denmark)

    Wulf-Johansson, H.; Amrutkar, D.V.; Hay-Schmidt, Anders

    2010-01-01

    Large conductance calcium-activated potassium (BK(Ca)) channels are membrane proteins contributing to electrical propagation through neurons. Calcitonin gene-related peptide (CGRP) is a neuropeptide found in the trigeminovascular system (TGVS). Both BK(Ca) channels and CGRP are involved in migraine...... pathophysiology. Here we study the expression and localization of BK(Ca) channels and CGRP in the rat trigeminal ganglion (TG) and the trigeminal nucleus caudalis (TNC) as these structures are involved in migraine pain. Also the effect of the BK(Ca) channel blocker iberiotoxin and the BK(Ca) channel opener NS...

  17. Mitochondrial dysfunction in oxidative stress : On the impact of neuronal KCa channels & calcium signaling in neurodegeneration

    NARCIS (Netherlands)

    Honrath, Birgit

    2017-01-01

    Mitochondriale dysfunctie in oxidatieve stress – over de impact van neuronale KCa kanalen en calcium signalering in neurodegeneratie (246 words) Neurodegeneratieve ziektes, zoals de ziekte van Alzheimer of Parkinson, worden gekarakteriseerd door een verlies van neuronen in verschillende

  18. Calcium regulation by temperature-sensitive transient receptor potential channels in human uveal melanoma cells.

    Science.gov (United States)

    Mergler, Stefan; Derckx, Raissa; Reinach, Peter S; Garreis, Fabian; Böhm, Arina; Schmelzer, Lisa; Skosyrski, Sergej; Ramesh, Niraja; Abdelmessih, Suzette; Polat, Onur Kerem; Khajavi, Noushafarin; Riechardt, Aline Isabel

    2014-01-01

    Uveal melanoma (UM) is both the most common and fatal intraocular cancer among adults worldwide. As with all types of neoplasia, changes in Ca(2+) channel regulation can contribute to the onset and progression of this pathological condition. Transient receptor potential channels (TRPs) and cannabinoid receptor type 1 (CB1) are two different types of Ca(2+) permeation pathways that can be dysregulated during neoplasia. We determined in malignant human UM and healthy uvea and four different UM cell lines whether there is gene and functional expression of TRP subtypes and CB1 since they could serve as drug targets to either prevent or inhibit initiation and progression of UM. RT-PCR, Ca(2+) transients, immunohistochemistry and planar patch-clamp analysis probed for their gene expression and functional activity, respectively. In UM cells, TRPV1 and TRPM8 gene expression was identified. Capsaicin (CAP), menthol or icilin induced Ca(2+) transients as well as changes in ion current behavior characteristic of TRPV1 and TRPM8 expression. Such effects were blocked with either La(3+), capsazepine (CPZ) or BCTC. TRPA1 and CB1 are highly expressed in human uvea, but TRPA1 is not expressed in all UM cell lines. In UM cells, the CB1 agonist, WIN 55,212-2, induced Ca(2+) transients, which were suppressed by La(3+) and CPZ whereas CAP-induced Ca(2+) transients could also be suppressed by CB1 activation. Identification of functional TRPV1, TRPM8, TRPA1 and CB1 expression in these tissues may provide novel drug targets for treatment of this aggressive neoplastic disease. © 2013.

  19. Current-voltage curve of sodium channels and concentration dependence of sodium permeability in frog skin

    DEFF Research Database (Denmark)

    Fuchs, W; Larsen, Erik Hviid; Lindemann, B

    1977-01-01

    transport through open Na-selective channels of the outward facing membrane of the stratum granulosum cells can be described as an electrodiffusion process which as such does not saturate with increasing (Na)(o). However, when added to the outer border of the membrane Na causes a decrease of P(Na) within...... was recorded. This procedure was repeated after blocking the Na channels with amiloride to obtain the current-voltage curve of transmembrane and paracellular shunt pathways. The current-voltage curve of the Na channels was computed by subtracting the shunt current from the total current.4. The instantaneous I...... several seconds. It is considered that binding of Na results in closure of Na channels....

  20. IMPROVING MODEL OF CHANNEL AIRBORN ELECTRICAL POWER SYSTEM OF ALTERNATING CURRENT

    Directory of Open Access Journals (Sweden)

    Yu. P. Artemenko

    2015-01-01

    Full Text Available This article is devoted to math modeling of channel of alternating current airborne electrical power-supply system. Mathematical modeling of generator, voltage regulator, constant speed drive is considered.

  1. Calcium-activated chloride current expression in axotomized sensory neurons: what for?

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    Mathieu eBoudes

    2012-03-01

    Full Text Available Calcium-activated chloride currents (CaCCs are activated by an increase in intracellular calcium concentration. Peripheral nerve injury induces the expression of CaCCs in a subset of adult sensory neurons in primary culture including mechano-and proprioceptors, though not nociceptors. Functional screenings of potential candidate genes established that Best1 is a molecular determinant for CaCC expression among axotomized sensory neurons, while Tmem16a accounts for inflammation-induced CaCC expression in nociceptors. In nociceptors, such CaCCs are preferentially activated under receptor-induced calcium mobilization contributing to cell excitability and pain. In axotomized mechano- and proprioceptors, CaCC activation does not promote electrical activity and prevents firing, a finding consistent with electrical silencing for growth competence of adult sensory neurons. In favor of a role in the process of neurite growth, CaCC expression is temporally correlated to neurons displaying a regenerative mode of growth. This perspective focuses on the molecular identity and role of CaCC in axotomized sensory neurons and the future directions to decipher the cellular mechanisms regulating CaCC during neurite (regrowth.

  2. Short-channel drain current model for asymmetric heavily / lightly doped DG MOSFETs

    Science.gov (United States)

    Dutta, Pradipta; Syamal, Binit; Koley, Kalyan; Dutta, Arka; Sarkar, C. K.

    2017-08-01

    The paper presents a drain current model for double gate metal oxide semiconductor field effect transistors (DG MOSFETs) based on a new velocity saturation model that accounts for short-channel velocity saturation effect independently in the front and the back gate controlled channels under asymmetric front and back gate bias and oxide thickness. To determine the front and the back-channel velocity saturation, drain-induced barrier lowering is evaluated by effective gate voltages at the front and back gates obtained from surface potential at the threshold condition after considering symmetric and asymmetric front and back oxide thickness. The model also incorporates surface roughness scattering and ionized impurity scattering to estimate drain current for heavily / lightly doped channel for short-channel asymmetric DG MOSFET and a good agreement has been achieved with TCAD simulations, with a relative error of around 3-7%.

  3. Use of digoxin, diuretics, beta blockers, angiotensin-converting enzyme inhibitors, and calcium channel blockers in older patients in an academic hospital-based geriatrics practice.

    Science.gov (United States)

    Fishkind, D; Paris, B E; Aronow, W S

    1997-07-01

    To investigate the prevalence of and indications for digoxin use and the prevalence of beta blocker and calcium channel blocker use in older patients with previous myocardial infarction or coronary artery disease (CAD), and the prevalence of use of diuretics, beta blockers, angiotensin-converting enzyme (ACE) inhibitors, and calcium channel blockers in older patients with hypertension in an academic hospital-based geriatrics practice. A retrospective analysis of charts from 528 unselected older patients, seen from June 1995 through July 1996 at an academic hospital-based geriatrics practice, was performed to investigate the prevalence of digoxin use and indications for digoxin use, the prevalence of beta blocker and calcium channel blocker use in older patients with previous myocardial infarction or coronary artery disease (CAD), and the prevalence of use of diuretics, beta blockers, angiotensin-converting enzyme (ACE) inhibitors, and calcium channel blockers in older patients with hypertension. An academic hospital-based, primary care geriatrics practice staffed by fellows in a geriatrics training program and full-time faculty geriatricians. A total of 416 women and 112 men, mean age 81 +/- 8 years (range 58 to 101), were included in the study. Ninety-two of the 528 patients (17%) were taking digoxin. Recorded indications for digoxin were atrial fibrillation with or without congestive heart failure (CHF) in 39% of patients, CHF with sinus rhythm and abnormal left ventricular ejection fraction (LVEF) in 18% of patients, a clinical assessment of CHF with sinus rhythm and no recorded measurement of LVEF in 20% of patients, paroxysmal atrial fibrillation in 14% of patients, and coronary artery disease (CAD) in 9% of patients. Of 121 patients with previous myocardial infarction, 23 (19%) were prescribed beta blockers, and 54 (45%) were taking calcium channel blockers. Of 173 patients with CAD, 41 (24%) were treated with beta blockers, and 79 (46%) were taking calcium

  4. Current noise in (111) n-channel Si-MOSFET's at T = 4.2 K

    NARCIS (Netherlands)

    Hendriks, E.A.; Zijlstra, R.J.J.; Middelhoek, J.

    1988-01-01

    We have investigated the drain current-drain voltage characteristics and the spectral noise intensity of the drain current of (111) n-channel MOSFET's at T = 4.2 K. At T = 4.2 K the drain current-drain voltage characteristics showed a hysteresis which was not observed at T =77 K and at room

  5. Inhibition of collagen synthesis by select calcium and sodium channel blockers can be mitigated by ascorbic acid and ascorbyl palmitate.

    Science.gov (United States)

    Ivanov, Vadim; Ivanova, Svetlana; Kalinovsky, Tatiana; Niedzwiecki, Aleksandra; Rath, Matthias

    2016-01-01

    Calcium, sodium and potassium channel blockers are widely prescribed medications for a variety of health problems, most frequently for cardiac arrhythmias, hypertension, angina pectoris and other disorders. However, chronic application of channel blockers is associated with numerous side effects, including worsening cardiac pathology. For example, nifedipine, a calcium-channel blocker was found to be associated with increased mortality and increased risk for myocardial infarction. In addition to the side effects mentioned above by different channel blockers, these drugs can cause arterial wall damage, thereby contributing to vascular wall structure destabilization and promoting events facilitating rupture of plaques. Collagen synthesis is regulated by ascorbic acid, which is also essential for its optimum structure as a cofactor in lysine and proline hydroxylation, a precondition for optimum crosslinking of collagen and elastin. Therefore, the main objective in this study was to evaluate effects of various types of channel blockers on intracellular accumulation and cellular functions of ascorbate, specifically in relation to formation and extracellular deposition of major collagen types relevant for vascular function. Effects of select Na- and Ca- channel blockers on collagen synthesis and deposition were evaluated in cultured human dermal fibroblasts and aortic smooth muscle cells by immunoassay. All channel blockers tested demonstrated inhibitory effects on collagen type I deposition to the ECM by fibroblasts, each to a different degree. Ascorbic acid significantly increased collagen I ECM deposition. Nifedipine (50 µM), a representative of channel blockers tested, significantly reduced ascorbic acid and ascorbyl palmitate-dependent ECM deposition of collagen type l and collagen type lV by cultured aortic smooth muscle cells. In addition, nifedipine (50 µM) significantly reduced ascorbate-dependent collagen type l and type lV synthesis by cultured aortic smooth

  6. Role of voltage-gated sodium, potassium and calcium channels in the development of cocaine-associated cardiac arrhythmias

    Science.gov (United States)

    O'Leary, Michael E; Hancox, Jules C

    2010-01-01

    Cocaine is a highly active stimulant that alters dopamine metabolism in the central nervous system resulting in a feeling of euphoria that with time can lead to addictive behaviours. Cocaine has numerous deleterious effects in humans including seizures, vasoconstriction, ischaemia, increased heart rate and blood pressure, cardiac arrhythmias and sudden death. The cardiotoxic effects of cocaine are indirectly mediated by an increase in sympathomimetic stimulation to the heart and coronary vasculature and by a direct effect on the ion channels responsible for maintaining the electrical excitability of the heart. The direct and indirect effects of cocaine work in tandem to disrupt the co-ordinated electrical activity of the heart and have been associated with life-threatening cardiac arrhythmias. This review focuses on the direct effects of cocaine on cardiac ion channels, with particular focus on sodium, potassium and calcium channels, and on the contributions of these channels to cocaine-induced arrhythmias. Companion articles in this edition of the journal examine the epidemiology of cocaine use (Wood & Dargan [1]) and the treatment of cocaine-associated arrhythmias (Hoffmann [2]). PMID:20573078

  7. Calcium-activated chloride channel ANO1 promotes breast cancer progression by activating EGFR and CAMK signaling.

    Science.gov (United States)

    Britschgi, Adrian; Bill, Anke; Brinkhaus, Heike; Rothwell, Christopher; Clay, Ieuan; Duss, Stephan; Rebhan, Michael; Raman, Pichai; Guy, Chantale T; Wetzel, Kristie; George, Elizabeth; Popa, M Oana; Lilley, Sarah; Choudhury, Hedaythul; Gosling, Martin; Wang, Louis; Fitzgerald, Stephanie; Borawski, Jason; Baffoe, Jonathan; Labow, Mark; Gaither, L Alex; Bentires-Alj, Mohamed

    2013-03-12

    The calcium-activated chloride channel anoctamin 1 (ANO1) is located within the 11q13 amplicon, one of the most frequently amplified chromosomal regions in human cancer, but its functional role in tumorigenesis has remained unclear. The 11q13 region is amplified in ∼15% of breast cancers. Whether ANO1 is amplified in breast tumors, the extent to which gene amplification contributes to ANO1 overexpression, and whether overexpression of ANO1 is important for tumor maintenance have remained unknown. We have found that ANO1 is amplified and highly expressed in breast cancer cell lines and primary tumors. Amplification of ANO1 correlated with disease grade and poor prognosis. Knockdown of ANO1 in ANO1-amplified breast cancer cell lines and other cancers bearing 11q13 amplification inhibited proliferation, induced apoptosis, and reduced tumor growth in established cancer xenografts. Moreover, ANO1 chloride channel activity was important for cell viability. Mechanistically, ANO1 knockdown or pharmacological inhibition of its chloride-channel activity reduced EGF receptor (EGFR) and calmodulin-dependent protein kinase II (CAMKII) signaling, which subsequently attenuated AKT, v-src sarcoma viral oncogene homolog (SRC), and extracellular signal-regulated kinase (ERK) activation in vitro and in vivo. Our results highlight the involvement of the ANO1 chloride channel in tumor progression and provide insights into oncogenic signaling in human cancers with 11q13 amplification, thereby establishing ANO1 as a promising target for therapy in these highly prevalent tumor types.

  8. T-type calcium channels promote predictive homeostasis of input-output relations in thalamocortical neurons of lateral geniculate nucleus

    Directory of Open Access Journals (Sweden)

    Su Z. Hong

    2014-08-01

    Full Text Available A general theory views the function of all neurons as prediction, and one component of this theory is that of predictive homeostasis or prediction error. It is well established that sensory systems adapt so that neuronal output maintains sensitivity to sensory input, in accord with information theory. Predictive homeostasis applies the same principle at the cellular level, where the challenge is to maintain membrane excitability at the optimal homeostatic level so that spike generation is maximally sensitive to small gradations in synaptic drive. Negative feedback is a hallmark of homeostatic mechanisms, as exemplified by depolarization-activated potassium channels. However, T-type calcium channels exhibit positive feedback that appears at odds with the theory. In thalamocortical neurons of lateral geniculate nucleus (LGN, T-type channels are capable of causing bursts of spikes with an all-or-none character in response to excitation from a hyperpolarized potential. This burst mode would partially uncouple visual input from spike output and reduce the information spikes convey about gradations in visual input. However, past observations of T-type-driven bursts may have resulted from unnaturally high membrane excitability. By mimicking natural patterns of synaptic conductance that occur during vision, we found that T-type channels in rat brain slices did not cause bursts, but rather enabled retinogeniculate excitation to cause spikes despite sustained hyperpolarization, thereby restoring the homeostatic input-output relation observed at depolarized potentials. Our results suggest that T-type channels help to maintain a single optimal mode of transmission rather than creating a second mode. In addition, our results provide evidence for the general theory, which seeks to predict the properties of a neuron’s ion channels and synapses given knowledge of natural patterns of synaptic input.

  9. Efficacy of methylene blue in an experimental model of calcium channel blocker-induced shock.

    Science.gov (United States)

    Jang, David H; Donovan, Sean; Nelson, Lewis S; Bania, Theodore C; Hoffman, Robert S; Chu, Jason

    2015-04-01

    Calcium channel blocker poisonings account for a substantial number of reported deaths from cardiovascular drugs. Although supportive care is the mainstay of treatment, experimental therapies such as high-dose insulin-euglycemia and lipid emulsion have been studied in animal models and used in humans. In the most severe cases, even aggressive care is inadequate and deaths occur. In both experimental models and clinical cases of vasodilatory shock, methylene blue improves hemodynamic measures. It acts as a nitric oxide scavenger and inhibits guanylate cyclase that is responsible for the production of cyclic guanosine monophosphate (cGMP). Excessive cGMP production is associated with refractory vasodilatory shock in sepsis and anaphylaxis. The aim of this study is to determine the efficacy of methylene blue in an animal model of amlodipine-induced shock. Sprague-Dawley rats were anesthetized, ventilated, and instrumented for continuous blood pressure and pulse rate monitoring. The dose of amlodipine that produced death within 60 minutes was 17 mg/kg per hour (LD50). Rats were divided into 2 groups: amlodipine followed by methylene blue or amlodipine followed by normal saline solution, with 15 rats in each group. Rats received methylene blue at 2 mg/kg during 5 minutes or an equivalent amount of normal saline solution in 3 intervals from the start of the protocol: minutes 5, 30, and 60. The animals were observed for a total of 2 hours after the start of the protocol. Mortality risk and survival time were analyzed with Fisher's exact test and Kaplan-Meier survival analysis with the log rank test. Overall, 1 of 15 rats (7%) in the saline solution-treated group survived to 120 minutes compared with 5 of 15 (33%) in the methylene blue-treated group (difference -26%; 95% confidence interval [CI] -54% to 0.3%). The median survival time for the normal saline solution group was 42 minutes (95% CI 28.1 to 55.9 minutes); for the methylene blue group, 109 minutes (95% CI 93.9 to

  10. Compartmentalized beta subunit distribution determines characteristics and ethanol sensitivity of somatic, dendritic, and terminal large-conductance calcium-activated potassium channels in the rat central nervous system.

    Science.gov (United States)

    Wynne, P M; Puig, S I; Martin, G E; Treistman, S N

    2009-06-01

    Neurons are highly differentiated and polarized cells, whose various functions depend upon the compartmentalization of ion channels. The rat hypothalamic-neurohypophysial system (HNS), in which cell bodies and dendrites reside in the hypothalamus, physically separated from their nerve terminals in the neurohypophysis, provides a particularly powerful preparation in which to study the distribution and regional properties of ion channel proteins. Using electrophysiological and immunohistochemical techniques, we characterized the large-conductance calcium-activated potassium (BK) channel in each of the three primary compartments (soma, dendrite, and terminal) of HNS neurons. We found that dendritic BK channels, in common with somatic channels but in contrast to nerve terminal channels, are insensitive to iberiotoxin. Furthermore, analysis of dendritic BK channel gating kinetics indicates that they, like somatic channels, have fast activation kinetics, in contrast to the slow gating of terminal channels. Dendritic and somatic channels are also more sensitive to calcium and have a greater conductance than terminal channels. Finally, although terminal BK channels are highly potentiated by ethanol, somatic and dendritic channels are insensitive to the drug. The biophysical and pharmacological properties of somatic and dendritic versus nerve terminal channels are consistent with the characteristics of exogenously expressed alphabeta1 versus alphabeta4 channels, respectively. Therefore, one possible explanation for our findings is a selective distribution of auxiliary beta1 subunits to the somatic and dendritic compartments and beta4 to the terminal compartment. This hypothesis is supported immunohistochemically by the appearance of distinct punctate beta1 or beta4 channel clusters in the membrane of somatic and dendritic or nerve terminal compartments, respectively.

  11. The Peptide PnPP-19, a Spider Toxin Derivative, Activates μ-Opioid Receptors and Modulates Calcium Channels

    Directory of Open Access Journals (Sweden)

    Ana C. N. Freitas

    2018-01-01

    Full Text Available The synthetic peptide PnPP-19 comprehends 19 amino acid residues and it represents part of the primary structure of the toxin δ-CNTX-Pn1c (PnTx2-6, isolated from the venom of the spider Phoneutria nigriventer. Behavioural tests suggest that PnPP-19 induces antinociception by activation of CB1, μ and δ opioid receptors. Since the peripheral and central antinociception induced by PnPP-19 involves opioid activation, the aim of this work was to identify whether this synthetic peptide could directly activate opioid receptors and investigate the subtype selectivity for μ-, δ- and/or κ-opioid receptors. Furthermore, we also studied the modulation of calcium influx driven by PnPP-19 in dorsal root ganglion neurons, and analyzed whether this modulation was opioid-mediated. PnPP-19 selectively activates μ-opioid receptors inducing indirectly inhibition of calcium channels and hereby impairing calcium influx in dorsal root ganglion (DRG neurons. Interestingly, notwithstanding the activation of opioid receptors, PnPP-19 does not induce β-arrestin2 recruitment. PnPP-19 is the first spider toxin derivative that, among opioid receptors, selectively activates μ-opioid receptors. The lack of β-arrestin2 recruitment highlights its potential for the design of new improved opioid agonists.

  12. Failure of intravenous lipid emulsion in treatment of cardiotoxicity caused by mixed overdose including dihydropyridine calcium channel blockers

    Directory of Open Access Journals (Sweden)

    Jović-Stošić Jasmina

    2016-01-01

    Full Text Available Introduction. Calcium channel blockers and beta-blockers are among the most frequently ingested cardiovascular drugs in self-poisoning causing significant mortality. Intravenous lipid emulsion (ILE is reported as a potentially novel antidote for treatment of acute poisoning caused by some of these drugs. Case report. We presented two cases of poisoning with these drugs. The case 1, a 24-year-old woman ingested amplodipine, metformin and gliclazide for self-poisoning. She presented with tachycardia and hypotension. Laboratory analyses revealed hyperglycaemia and metabolic acidosis. Despite the treatment which included fluid resuscitation, vasopressors, intravenous calcium, glucagon and ILE, circulatory shock occurred. The patient died 10 hours after admission due to cardiac arrest refractory to cardiopulmonary resuscitation. The case 2, a 41-year old man, was found in a coma with empty packages of nifedipine, metoprolol and diazepam tablets. On admission vital signs included Glasgow Coma Scale (GCS of 3, weak palpable pulses, undetectable blood pressure, and irregular breathing with oxygen saturation of 60%. An electrocardiography showed AV block (Mobitz II with ventricular rate of 44/min with progression to third degree of AV block. In attempt to increase heart rate and blood pressure the following agents were administered: atropine boluses, normal saline with dopamine, glucagon, calcium chloride and ILE. Temporary transvenous pacemaker was placed, electrical capture was recorded, but without improvement in haemodynamics. Three hours after admission cardiac arrest happened and cardiopulmonary resuscitation was unsuccessful. Conclusion. Intravenous lipid emulsion may be ineffective in acute poisonings with amlodipine, nifedipine or metoprolol.

  13. Prognostic relevance of a T-type calcium channels gene signature in solid tumours: A correlation ready for clinical validation.

    Science.gov (United States)

    Fornaro, Lorenzo; Vivaldi, Caterina; Lin, Dong; Xue, Hui; Falcone, Alfredo; Wang, Yuzhuo; Crea, Francesco; Bootman, Martin D

    2017-01-01

    T-type calcium channels (TTCCs) mediate calcium influx across the cell membrane. TTCCs regulate numerous physiological processes including cardiac pacemaking and neuronal activity. In addition, they have been implicated in the proliferation, migration and differentiation of tumour tissues. Although the signalling events downstream of TTCC-mediated calcium influx are not fully elucidated, it is clear that variations in the expression of TTCCs promote tumour formation and hinder response to treatment. We examined the expression of TTCC genes (all three subtypes; CACNA-1G, CACNA-1H and CACNA-1I) and their prognostic value in three major solid tumours (i.e. gastric, lung and ovarian cancers) via a publicly accessible database. In gastric cancer, expression of all the CACNA genes was associated with overall survival (OS) among stage I-IV patients (all p<0.05). By combining the three potential biomarkers, a TTCC signature was developed, which retained a significant association with OS both in stage IV and stage I-III patients. In lung and ovarian cancer, association with OS was also significant when all tumour stages were considered, but was partly lost or inconclusive after splitting cases into localized and metastatic subsets. Alterations in CACNA gene expression are linked to tumour prognosis. Gastric cancer represents the most promising setting for further evaluation.

  14. The role of the GABA(B) receptor and calcium channels in a Drosophila model of Parkinson's Disease.

    Science.gov (United States)

    Hillman, Ralph; Sinani, Jonida; Pendleton, Robert

    2012-05-16

    Transgenic Drosophila melanogaster carrying the human gene for alpha synuclein is an animal model for the study of Parkinson's Disease. Climbing activity in these flies is reduced as a result of the effect of this protein on the locomotor activity of the transgenic fly. L-DOPA and gamma amino butyric acid (GABA) reverse the loss of this activity when placed in the food fed to these flies. While muscimol, a GABA(A) receptor agonist has no effect in this system, baclofen and the allosteric agonists CG 7930 and GS 39783 which affect the GABA(B) receptor reverse this activity. This latter effect is eliminated when these compounds are fed in conjunction with the GABA(B) receptor antagonist 2-hydroxysaclofen. In addition, fendiline which is a Ca(++) receptor blocker also reverses the loss of climbing ability. Because there is a calcium channel close to the GABA(B) receptor on the cell surface, these data are indicative of a relationship between the roles of the GABA(B) receptor, the calcium channel and the effect of alpha-synuclein on the motor activity of the transgenic fly. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

  15. PhTx3-4, a Spider Toxin Calcium Channel Blocker, Reduces NMDA-Induced Injury of the Retina

    Directory of Open Access Journals (Sweden)

    Nancy Scardua Binda

    2016-03-01

    Full Text Available The in vivo neuroprotective effect of PhTx3-4, a spider toxin N-P/Q calcium channel blocker, was studied in a rat model of NMDA-induced injury of the retina. NMDA (N-Methyl-d-Aspartate-induced retinal injury in rats reduced the b-wave amplitude by 62% ± 3.6%, indicating the severity of the insult. PhTx3-4 treatment increased the amplitude of the b-wave, which was almost equivalent to the control retinas that were not submitted to injury. The PhTx3-4 functional protection of the retinas recorded on the ERG also was observed in the neuroprotection of retinal cells. NMDA-induced injury reduced live cells in the retina layers and the highest reduction, 84%, was in the ganglion cell layer. Notably, PhTx3-4 treatment caused a remarkable reduction of dead cells in the retina layers, and the highest neuroprotective effect was in the ganglion cells layer. NMDA-induced cytotoxicity of the retina increased the release of glutamate, reactive oxygen species (ROS production and oxidative stress. PhTx3-4 treatment reduced glutamate release, ROS production and oxidative stress measured by malondialdehyde. Thus, we presented for the first time evidence of in vivo neuroprotection from NMDA-induced retinal injury by PhTx3-4 (-ctenitoxin-Pn3a, a spider toxin that blocks N-P/Q calcium channels.

  16. Neurobehavioral protection by the neuronal calcium channel blocker ziconotide in a model of traumatic diffuse brain injury in rats.

    Science.gov (United States)

    Berman, R F; Verweij, B H; Muizelaar, J P

    2000-11-01

    Abnormal accumulation of intracellular calcium following traumatic brain injury (TBI) is thought to contribute to a cascade of cellular events that lead to neuropathological conditions. Therefore, the possibility that specific calcium channel antagonists might exert neuroprotective effects in TBI has been of interest. The focus of this study was to examine whether Ziconotide produces such neuroprotective effects. The authors report that the acceleration-deceleration model of TBI developed by Marmarou, et al., induces a long-lasting deficit of neuromotor and behavioral function. The voltage-sensitive calcium channel blocker Ziconotide (also known as SNX-111 and CI-1009) exerts neuroprotective effects in this model of diffuse brain injury (DBI) in rats. The dose and time of injection of Ziconotide chosen for the present study was based on the authors' previous biochemical studies of mitochondria. Rats were trained in a series of motor and memory tasks, following which they were subjected to DBI using the Marmarou, et al., model. At 3, 5, and 24 hours, all rats were injected with 2 mg/kg Ziconotide for a total cumulative dose of 6 mg/kg Ziconotide. Control brain-injured animals were injected with an equal volume of saline vehicle at each of these time points. The rats were tested for motor and cognitive performance at 1, 3, 7,14, 21, 28, 35, and 42 days postinjury. Saline-treated rats displayed severe motor and cognitive deficits after DBI. Compared with saline-treated control animals, rats treated with Ziconotide displayed better motor performance during inclined plane, beam balance, and beam walk tests; improved memory while in the radial arm maze; and improved learning while in the Morris water maze. These results demonstrated that the acceleration-deceleration model, which had been developed by Marmarou, et al., induces severe motor and cognitive deficits. We also demonstrated that Ziconotide exhibits substantial neuroprotective activity in this model of TBI

  17. Optical modulation of neurotransmission using calcium photocurrents through the ion channel LiGluR

    Directory of Open Access Journals (Sweden)

    Mercè eIzquierdo-Serra

    2013-03-01

    Full Text Available A wide range of light-activated molecules (photoswitches and phototriggers have been used to the study of computational properties of an isolated neuron by acting pre and postsynaptically. However, new tools are being pursued to elicit a presynaptic calcium influx that triggers the release of neurotransmitters, most of them based in calcium-permeable Channelrhodopsin-2 mutants. Here we describe a method to control exocytosis of synaptic vesicles through the use of a light-gated glutamate receptor (LiGluR, which has recently been demonstrated that supports secretion by means of calcium influx in chromaffin cells. Expression of LiGluR in hippocampal neurons enables reversible control of neurotransmission with light, and allows modulating the firing rate of the postsynaptic neuron with the wavelength of illumination. This method may be useful for the determination of the complex transfer function of individual synapses.

  18. Role of calcium activated potassium channels in atrial fibrillation pathophysiology and therapy

    DEFF Research Database (Denmark)

    Diness, Jonas G.; Bentzen, Bo H.; S. Sørensen, Ulrik

    2015-01-01

    Small-conductance Ca2+-activated potassium (SK) channels are relative newcomers within the field of cardiac electrophysiology. In recent years, an increased focus has been given to these channels since they might constitute a relatively atrial selective target. The present review will give...

  19. The Epithelial Calcium Channel TRPV5 Is Regulated Differentially by Klotho and Sialidase.

    NARCIS (Netherlands)

    Leunissen, E.H.P.; Nair, A.V.; Büll, C.; Lefeber, D.J.; Delft, F.L. van; Bindels, R.J.M.; Hoenderop, J.G.J.

    2013-01-01

    The transient receptor potential vanilloid type 5 (TRPV5) Ca(2+) channel facilitates transcellular Ca(2+) transport in the distal convoluted tubule (DCT) of the kidney. The channel is glycosylated with a complex type N-glycan and it has been postulated that hydrolysis of the terminal sialic acid(s)

  20. Calcium-activated potassium channels - a therapeutic target for modulating nitric oxide in cardiovascular disease?

    DEFF Research Database (Denmark)

    Dalsgaard, Thomas; Kroigaard, Christel; Simonsen, Ulf

    2010-01-01

    IMPORTANCE OF THE FIELD: Cardiovascular risk factors are often associated with endothelial dysfunction, which is also prognostic for occurrence of cardiovascular events. Endothelial dysfunction is reflected by blunted vasodilatation and reduced nitric oxide (NO) bioavailability. Endothelium......-dependent vasodilatation is mediated by NO, prostacyclin, and an endothelium-derived hyperpolarising factor (EDHF), and involves small (SK) and intermediate (IK) conductance Ca(2+)-activated K(+) channels. Therefore, SK and IK channels may be drug targets for the treatment of endothelial dysfunction in cardiovascular...... disease. AREAS COVERED IN THIS REVIEW: SK and IK channels are involved in EDHF-type vasodilatation, but recent studies suggest that these channels are also involved in the regulation of NO bioavailability. Here we review how SK and IK channels may regulate NO bioavailability. WHAT THE READER WILL GAIN...

  1. T-type calcium channels, but not Cav3.2, in the peripheral sensory afferents are involved in acute itch in mice.

    Science.gov (United States)

    Lin, Si-Fang; Wang, Bing; Zhang, Feng-Ming; Fei, Yuan-Hui; Gu, Jia-Hui; Li, Jie; Bi, Ling-Bo; Liu, Xing-Jun

    2017-06-10

    T-type calcium channels are prominently expressed in primary nociceptive fibers and well characterized in pain processes. Although itch and pain share many similarities including primary sensory fibers, the function of T-type calcium channels on acute itch has not been explored. We investigated whether T-type calcium channels expressed within primary sensory fibers of mouse skin, especially Cav3.2 subtype, involve in chloroquine-, endothelin-1- and histamine-evoked acute itch using pharmacological, neuronal imaging and behavioral analyses. We found that pre-locally blocking three subtypes of T-type calcium channels in the peripheral afferents of skins, yielded an inhibition in acute itch or pain behaviors, while selectively blocking the Cav3.2 channel in the skin peripheral afferents only inhibited acute pain but not acute itch. These results suggest that T-type Cav3.1 or Cav3.3, but not Cav3.2 channel, have an important role in acute itch processing, and their distinctive roles in modulating acute itch are worthy of further investigation. Copyright © 2017 Elsevier Inc. All rights reserved.

  2. Evaluation Effects of Verapamil as a Calcium Channel Blocker on Acquisition, Consolidation and Retrieval of Memory in Mice

    Directory of Open Access Journals (Sweden)

    Nooshin Masoudian

    2015-04-01

    Full Text Available Many factors are involved in learning and memory processes including brain nuclei, neurotransmitter systems, and the activity of ion channels. Studies showed inconsistent effects of calcium channel blockers on learning process, especially memory consolidation; however, little is known about their effect on memory acquisition and retrieval. Accordingly, the present study aimed to determine the effects of verapamil calcium channel antagonist as a representative of the phenylalkylamine group on different stages of memory and learning processes including acquisition, consolidation and retrieval in mice. In this experimental study, 150 male albino mice with a mean weight of 30 g were used. The mice were trained in a passive avoidance-learning task (1 mA shock for 2 seconds for evaluation of memory acquisition and consolidation and 3 seconds for evaluation of memory retrieval. The effect of verapamil (1, 2.5, 5, 10, and 20 mg/kg on memory consolidation and the most effective dose of consolidation phase on memory acquisition and retrieval was assessed. For the evaluation of memory consolidation, the animals received the drug intraperitoneally immediately after training, while for evaluation of memory acquisition and retrieval, the drug was injected one hour before training. Memory retrieval test was performed 48 hours after training (the length of time it took the animal to enter the dark part of the device. The results showed that verapamil injection exerted no effect on memory acquisition and consolidation; nevertheless, it was capable to disrupt memory retrieval in 10 and 20 mg doses. These results indicate that as a phenylalkylamine calcium channel antagonist, high doses of verapamil can impair memory. Normal 0 false false false EN-US X-NONE AR-SA /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso

  3. A rendezvous with the queen of ion channels: Three decades of ion channel research by David T Yue and his Calcium Signals Laboratory.

    Science.gov (United States)

    Dick, Ivy E; Limpitikul, Worawan B; Niu, Jacqueline; Banerjee, Rahul; Issa, John B; Ben-Johny, Manu; Adams, Paul J; Kang, Po Wei; Lee, Shin Rong; Sang, Lingjie; Yang, Wanjun; Babich, Jennifer; Zhang, Manning; Bazazzi, Hojjat; Yue, Nancy C; Tomaselli, Gordon F

    2016-01-01

    David T. Yue was a renowned biophysicist who dedicated his life to the study of Ca(2+) signaling in cells. In the wake of his passing, we are left not only with a feeling of great loss, but with a tremendous and impactful body of work contributed by a remarkable man. David's research spanned the spectrum from atomic structure to organ systems, with a quantitative rigor aimed at understanding the fundamental mechanisms underlying biological function. Along the way he developed new tools and approaches, enabling not only his own research but that of his contemporaries and those who will come after him. While we cannot hope to replicate the eloquence and style we are accustomed to in David's writing, we nonetheless undertake a review of David's chosen field of study with a focus on many of his contributions to the calcium channel field.

  4. Stretch induced endothelin-1 secretion by adult rat astrocytes involves calcium influx via stretch-activated ion channels (SACs)

    Energy Technology Data Exchange (ETDEWEB)

    Ostrow, Lyle W., E-mail: lostrow1@jhmi.edu [Department of Neurology, Johns Hopkins School of Medicine, Baltimore, MD 21205 (United States); Suchyna, Thomas M.; Sachs, Frederick [Department of Physiology and Biophysical Sciences, State University of New York at Buffalo, Buffalo, NY 14214 (United States)

    2011-06-24

    Highlights: {yields} Endothelin-1 expression by adult rat astrocytes correlates with cell proliferation. {yields} Stretch-induced ET-1 is inhibited by GsMtx-4, a specific inhibitor of Ca{sup 2+} permeant SACs. {yields} The less specific SAC inhibitor streptomycin also inhibits ET-1 secretion. {yields} Stretch-induced ET-1 production depends on a calcium influx. {yields} SAC pharmacology may provide a new class of therapeutic agents for CNS pathology. -- Abstract: The expression of endothelins (ETs) and ET-receptors is often upregulated in brain pathology. ET-1, a potent vasoconstrictor, also inhibits the expression of astrocyte glutamate transporters and is mitogenic for astrocytes, glioma cells, neurons, and brain capillary endothelia. We have previously shown that mechanical stress stimulates ET-1 production by adult rat astrocytes. We now show in adult astrocytes that ET-1 production is driven by calcium influx through stretch-activated ion channels (SACs) and the ET-1 production correlates with cell proliferation. Mechanical stimulation using biaxial stretch (<20%) of a rubber substrate increased ET-1 secretion, and 4 {mu}M GsMTx-4 (a specific inhibitor of SACs) inhibited secretion by 30%. GsMTx-4 did not alter basal ET-1 levels in the absence of stretch. Decreasing the calcium influx by lowering extracellular calcium also inhibited stretch-induced ET-1 secretion without effecting ET-1 secretion in unstretched controls. Furthermore, inhibiting SACs with the less specific inhibitor streptomycin also inhibited stretch-induced ET-1 secretion. The data can be explained with a simple model in which ET-1 secretion depends on an internal Ca{sup 2+} threshold. This coupling of mechanical stress to the astrocyte endothelin system through SACs has treatment implications, since all pathology deforms the surrounding parenchyma.

  5. Is Shock Index a Valid Predictor of Mortality in Emergency Department Patients With Hypertension, Diabetes, High Age, or Receipt of β- or Calcium Channel Blockers?

    DEFF Research Database (Denmark)

    Kristensen, Anders K B; Holler, Jon G; Hallas, Jesper

    2016-01-01

    differences within subgroups. The adjusted analyses showed similar ORs. CONCLUSION: Shock index is independently associated with 30-day mortality in a broad population of ED patients. Old age, hypertension, and β- or calcium channel blockers weaken this association. However, a shock index greater than......STUDY OBJECTIVE: Shock index is a widely reported tool to identify patients at risk for circulatory collapse. We hypothesize that old age, diabetes, hypertension, and β- or calcium channel blockers weaken the association between shock index and mortality. METHODS: This was a cohort study of all...... first-time emergency department (ED) visits between 1995 and 2011 (n=111,019). We examined whether age 65 years or older, diabetes, hypertension, and use of β- or calcium channel blockers modified the association between shock index and 30-day mortality. RESULTS: The 30-day mortality was 3.0%. For all...

  6. Distribution of high-voltage-activated calcium channels in cultured gamma-aminobutyric acidergic neurons from mouse cerebral cortex.

    Science.gov (United States)

    Timmermann, Daniel B; Westenbroek, Ruth E; Schousboe, Arne; Catterall, William A

    2002-01-01

    The localization of voltage-gated calcium channel (VGCC) alpha(1) subunits in cultured GABAergic mouse cortical neurons was examined by immunocytochemical methods. Ca(v)1.2 and Ca(v)1.3 subunits of L-type VGCCs were found in cell bodies and dendrites of GABA-immunopositive neurons. Likewise, the Ca(v)2.3 subunit of R-type VGCCs was expressed in a somatodendritic pattern. Ca(v)2.2 subunits of N-type channels were found exclusively in small varicosities that were identified as presynaptic nerve terminals based on their expression of synaptic marker proteins. Two splice variants of the Ca(v)2.1 subunit of P/Q-type VGCCs showed widely differing expression patterns. The rbA isoform displayed a purely somatodendritic staining pattern, whereas the BI isoform was confined to axon-like fibers and nerve terminals. The nerve terminals of these cultured GABAergic neurons express Ca(v)2.2 either alone or in combination with Ca(v)2.1 (BI isoform) but never express Ca(v)2.1 alone. The functional association between VGCCs and the neurotransmitter release machinery was probed using the FM1-43 dye-labeling technique. N-type VGCCs were found to be tightly coupled to exocytosis in these cultured cortical neurons, and P-type VGCCs were also important in a fraction of the cells. The predominant role of N-type VGCCs in neurotransmitter release and the specific localization of the BI isoform of Ca(v)2.1 in the nerve terminals of these neurons distinguish them from previously studied central neurons. The complementary localization patterns observed for two different isoforms of the Ca(v)2.1 subunits provide direct evidence for alternative splicing as a means of generating functional diversity among neuronal calcium channels. Copyright 2002 Wiley-Liss, Inc.

  7. Nitric Oxide Protects L-Type Calcium Channel of Cardiomyocyte during Long-Term Isoproterenol Stimulation in Tail-Suspended Rats.

    Science.gov (United States)

    Yue, Zhi-Jie; Xu, Peng-Tao; Jiao, Bo; Chang, Hui; Song, Zhen; Xie, Man-Jiang; Yu, Zhi-Bin

    2015-01-01

    The aim of this study was to investigate the effects of nitric oxide (NO) and reactive oxygen species (ROS) on L-type calcium channel (LTCC) gating properties of cardiomyocytes during long-term isoproterenol (ISO) stimulation. Expression and activity of nNOS as well as S-nitrosylation of LTCC α1C subunit significantly decreased in the myocardium of SUS rats. Long-term ISO stimulation increased ROS in cardiomyocytes of SUS rats. ISO-enhanced calcium current (I Ca,L) in the SUS group was less than that in the CON group. The maximal I Ca,L decreased to about 80% or 60% of initial value at the 50th minute of ISO treatment in CON or SUS group, respectively. Specific inhibitor NAAN of nNOS reduced maximal I Ca,L to 50% of initial value in the CON group; in contrast, NO donor SNAP maintained maximal I Ca,L in SUS group to similar extent of CON group after 50 min of ISO treatment. Long-term ISO stimulation also changed steady-state activation (P < 0.01), inactivation (P < 0.01), and recovery (P < 0.05) characteristics of LTCC in SUS group. In conclusion, NO-induced S-nitrosylation of LTCC α1C subunit may competitively prevent oxidation from ROS at the same sites. Furthermore, LTCC can be protected by NO during long-term ISO stimulation.

  8. Nitric Oxide Protects L-Type Calcium Channel of Cardiomyocyte during Long-Term Isoproterenol Stimulation in Tail-Suspended Rats

    Directory of Open Access Journals (Sweden)

    Zhi-Jie Yue

    2015-01-01

    Full Text Available The aim of this study was to investigate the effects of nitric oxide (NO and reactive oxygen species (ROS on L-type calcium channel (LTCC gating properties of cardiomyocytes during long-term isoproterenol (ISO stimulation. Expression and activity of nNOS as well as S-nitrosylation of LTCC α1C subunit significantly decreased in the myocardium of SUS rats. Long-term ISO stimulation increased ROS in cardiomyocytes of SUS rats. ISO-enhanced calcium current (ICa,L in the SUS group was less than that in the CON group. The maximal ICa,L decreased to about 80% or 60% of initial value at the 50th minute of ISO treatment in CON or SUS group, respectively. Specific inhibitor NAAN of nNOS reduced maximal ICa,L to 50% of initial value in the CON group; in contrast, NO donor SNAP maintained maximal ICa,L in SUS group to similar extent of CON group after 50 min of ISO treatment. Long-term ISO stimulation also changed steady-state activation (P<0.01, inactivation (P<0.01, and recovery (P<0.05 characteristics of LTCC in SUS group. In conclusion, NO-induced S-nitrosylation of LTCC α1C subunit may competitively prevent oxidation from ROS at the same sites. Furthermore, LTCC can be protected by NO during long-term ISO stimulation.

  9. Current and Future Theranostic Applications of the Lipid-Calcium-Phosphate Nanoparticle Platform.

    Science.gov (United States)

    Satterlee, Andrew B; Huang, Leaf

    2016-01-01

    Over the last four years, the Lipid-Calcium-Phosphate (LCP) nanoparticle platform has shown success in a wide range of treatment strategies, recently including theranostics. The high specific drug loading of radiometals into LCP, coupled with its ability to efficiently encapsulate many types of cytotoxic agents, allows a broad range of theranostic applications, many of which are yet unexplored. In addition to providing an overview of current medical imaging modalities, this review highlights the current theranostic applications for LCP using SPECT and PET, and discusses potential future uses of the platform by comparing it with both systemically and locally delivered clinical radiotherapy options as well as introducing its applications as an MRI contrast agent. Strengths and weaknesses of LCP and of nanoparticles in general are discussed, as well as caveats regarding the use of fluorescence to determine the accumulation or biodistribution of a probe.

  10. Vertebrate rod photoreceptors express both BK and IK calcium-activated potassium channels, but only BK channels are involved in receptor potential regulation.

    Science.gov (United States)

    Pelucchi, Bruna; Grimaldi, Annalisa; Moriondo, Andrea

    2008-01-01

    In salamander rods, Ca(2+)-activated K(+) current (I(KCa)) provides an effective "clamp" of the dark membrane potential to its normal resting level. By a combination of electrophysiological, pharmacological, and immunohistochemical approaches, we show that salamander rods functionally express large-conductance Ca(2+)- and voltage-dependent potassium (BK) channel and intermediate-conductance Ca(2+)-dependent potassium (IK) channel, but not small-conductance Ca(2+)-dependent potassium channel (SK) subtypes. Application of 100 nM iberiotoxin and 100 nM clotrimazole reduced net I(KCa) to 36% and 63%, respectively, whereas the current was unaffected by application of 1 microM apamin. Consistently, anti- SK1, -SK2, and -SK3 antibodies were unable to stain rod photoreceptors, whereas both anti-BK and -SK4/ IK1 antibodies heavily stained the ellipsoid region of the inner segments of the rods. Moreover, by using current-clamp experiments, it was clearly seen that the strong clamping effect of the total I(KCa) was lost when IbTx, but not CLTZ, was applied to the bath. This behavior strongly suggests that of BK and IK channels, only the former are responsible for the clamping effect on the photoreceptor membrane potential.

  11. Clusters of calcium release channels harness the Ising phase transition to confine their elementary intracellular signals.

    Science.gov (United States)

    Maltsev, Anna V; Maltsev, Victor A; Stern, Michael D

    2017-07-18

    Intracellular Ca signals represent a universal mechanism of cell function. Messages carried by Ca are local, rapid, and powerful enough to be delivered over the thermal noise. A higher signal-to-noise ratio is achieved by a cooperative action of Ca release channels such as IP3 receptors or ryanodine receptors arranged in clusters (release units) containing a few to several hundred release channels. The channels synchronize their openings via Ca-induced Ca release, generating high-amplitude local Ca signals known as puffs in neurons and sparks in muscle cells. Despite the positive feedback nature of the activation, Ca signals are strictly confined in time and space by an unexplained termination mechanism. Here we show that the collective transition of release channels from an open to a closed state is identical to the phase transition associated with the reversal of magnetic field in an Ising ferromagnet. Our simple quantitative criterion closely predicts the Ca store depletion level required for spark termination for each cluster size. We further formulate exact requirements that a cluster of release channels should satisfy in any cell type for our mapping to the Ising model and the associated formula to remain valid. Thus, we describe deterministically the behavior of a system on a coarser scale (release unit) that is random on a finer scale (release channels), bridging the gap between scales. Our results provide exact mapping of a nanoscale biological signaling model to an interacting particle system in statistical physics, making the extensive mathematical apparatus available to quantitative biology.

  12. A 128-channel picoammeter system and its application on charged particle beam current distribution measurements.

    Science.gov (United States)

    Yu, Deyang; Liu, Junliang; Xue, Yingli; Zhang, Mingwu; Cai, Xiaohong; Hu, Jianjun; Dong, Jinmei; Li, Xin

    2015-11-01

    A 128-channel picoammeter system is constructed based on instrumentation amplifiers. Taking advantage of a high electric potential and narrow bandwidth in DC energetic charged beam measurements, a current resolution better than 5 fA can be achieved. Two sets of 128-channel strip electrodes are implemented on printed circuit boards and are employed for ion and electron beam current distribution measurements. Tests with 60 keV O(3+) ions and 2 keV electrons show that it can provide exact boundaries when a positive charged particle beam current distribution is measured.

  13. Developmental regulation of expression of the alpha 1 and alpha 2 subunits mRNAs of the voltage-dependent calcium channel in a differentiating myogenic cell line.

    Science.gov (United States)

    Varadi, G; Orlowski, J; Schwartz, A

    1989-07-03

    The voltage-dependent calcium channel (VDCC) in skeletal muscle probably plays a key role in transducing membrane charge movement to the calcium release channel. We report here that the expression of VDCC alpha 1 and alpha 2 mRNAs is developmentally regulated in differentiating C2C12 myogenic cells. The alpha 1 mRNA is not detectable in the myoblast form of C2C12 cells while its expression is induced 20-fold in differentiated myotubes. In contrast, the alpha 2 mRNA is weakly expressed in myoblasts but is also induced upon myogenic differentiation.

  14. A Blocker of N- and T-type Voltage-Gated Calcium Channels Attenuates Ethanol-Induced Intoxication, Place Preference, Self-Administration, and Reinstatement

    OpenAIRE

    Newton, Philip M.; Zeng, Lily; Wang, Victoria; Connolly, Jacklyn; Wallace, Melisa Joellan; Kim, Chanki; Shin, Hee-sup; Belardetti, Francesco; Snutch, Terrance P; Messing, Robert O.

    2008-01-01

    There is a clear need for new therapeutics to treat alcoholism. Here, we test our hypothesis that selective inhibitors of neuronal calcium channels will reduce ethanol consumption and intoxication, based on our previous studies using knock-out mice and cell culture systems. We demonstrate that pretreatment with the novel mixed N-type and T-type calcium channel antagonist 1-(6,6-bis(4-fluorophenyl)hexyl)-4-(3,4,5-trimethoxybenzyl)piperazine (NP078585) reduced ethanol intoxication. NP078585 als...

  15. Toward Reservoir-on-a-Chip: Fabricating Reservoir Micromodels by in Situ Growing Calcium Carbonate Nanocrystals in Microfluidic Channels.

    Science.gov (United States)

    Wang, Wei; Chang, Sehoon; Gizzatov, Ayrat

    2017-08-30

    We introduce a novel and simple method to fabricate calcium carbonate (CaCO3) micromodels by in situ growing a thin layer of CaCO3 nanocrystals with a thickness of 1-2 μm in microfluidic channels. This approach enables us to fabricate synthetic CaCO3 reservoir micromodels having surfaces fully covered with calcite, while the dimensions and geometries of the micromodels are controllable on the basis of the original microfluidic channels. We have tuned the wettability of the CaCO3-coated microchannels at simulated oil reservoir conditions without introducing any chemical additives to the system; thus the resulting oil-wet surface makes the micromodel more faithfully resemble a natural carbonate reservoir rock. With the advantage of its excellent optical transparency, the micromodel allows us to directly visualize the complex multiphase flows and geochemical fluid-calcite interactions by spectroscopic and microscopic imaging techniques. The CaCO3-coated microfluidic channels provide new capabilities as a micromodel system to mimic real carbonate reservoir properties, which would allow us to perform a water-oil displacement experiment in small-volume samples for the rapid screening of candidate fluids for enhanced oil recovery (EOR). The immiscible fluid displacement process within carbonate micromodels has been demonstrated showing the water-oil-carbonate interactions at pore-scale in real time by fluorescence microscopic imaging.

  16. Anti-tumor Necrosis Factor Alpha (Infliximab) Attenuates Apoptosis, Oxidative Stress, and Calcium Ion Entry Through Modulation of Cation Channels in Neutrophils of Patients with Ankylosing Spondylitis.

    Science.gov (United States)

    Ugan, Yunus; Nazıroğlu, Mustafa; Şahin, Mehmet; Aykur, Mehmet

    2016-08-01

    Ankylosing Spondylitis (AS) is known to be associated with increased neutrophil activation and oxidative stress, however, the mechanism of neutrophil activation is still unclear. We have hypothesized that the antioxidant and anti-tumor necrosis factor properties of infliximab may affect intracellular Ca(2+) concentration in the neutrophils of AS patients. The objective of this study was to investigate the effects of infliximab on calcium signaling, oxidative stress, and apoptosis in neutrophils of AS patients. Neutrophils collected from ten patients with AS and ten healthy controls were used in the study. In a cell viability test, the ideal non-toxic dose and incubation time of infliximab were found as 100 μM and 1 h, respectively. In some experiments, the neutrophils were incubated with the voltage-gated calcium channel (VGCC) blockers verapamil + diltiazem (V + D) and the TRPM2 channel blocker 2-aminoethyl diphenylborinate (2-APB). Intracellular Ca(2+) concentration, lipid peroxidation, apoptosis, caspase 3, and caspase 9 values were high in neutrophils of AS patients and were reduced with infliximab treatment. Reduced glutathione level and glutathione peroxidase activity were low in the patients and increased with infliximab treatment. The intracellular Ca(2+) concentrations were low in 2-APB and V + D groups. In conclusion, the current study suggests that infliximab is useful against apoptotic cell death and oxidative stress in neutrophils of patients with AS, which seem to be dependent on increased levels of intracellular Ca(2+) through activation of TRPM2 and VGCC.

  17. Calcium-release-channel genotypes in several pig populations-associations with halothane and CK reactions.

    Science.gov (United States)

    Knorr, C; Schwille, M; Moser, G; Müller, E; Bartenschlager, H; Geldermann, H

    1994-01-12

    DNA of 2985 pigs from different sources were tested for variants of the calcium-release-channel (CRC) gene. Frequencies of the C allele, associated with stress resistance, were 0.0 for Belgian Landrace, 0.01 for Pietrain, 0.54 for German Landrace, 0.86 for German-Landrace sowline, 0.91 for Schwäbisch-Hällisches swine, 0.95 for European Wildboar, and 0.99 for Large White. All 50 Meishan individuals tested were C/C. In the two German Landrace populations more individuals with heterozygous genotypes were observed than had been expected. These results may indicate balanced allele frequencies caused by overdominance-type selection associated with meat quantity. 6.0 % of the halothane-positive pigs were C/C or C/T, and 3.6 % of the halothane-negative animals were T/T. As some of the pig groups were crossbreeds from extremely divergent sources (e.g. European Wildboar, Meishan, Pietrain), special gene effects may have influenced the phenotypic reaction to halothane. The average CK values vary between pigs of different CRC genotypes, e.g., the CK(80) values 2.64 ± 0.023, 2.83 ± 0.027, and 3.19 ± 0.036 were measured for individuals of C/C, C/T and T/T, respectively. For the German Landrace, culling according to a threshold of CK(80) ≥ 2.70 would eliminate 29.1 % of C/C, 63.0 % of C/T, and 90.4 % of T/T individuals. Whether CK-based selection may be used for further selection in populations with a fixed CRC C allele is discussed. ZUSAMMENFASSUNG: Genotypen des Kalziumfreisetzungskanals in verschiedenen Schweinepopulationen-Zusammenhänge mit Halothan- und CK-Reaktionen Auf die Genvariante des Calciumfreisetzungskanales (CRC), die als Ursache für das Maligne Hyperthermic Syndrom beim Schwein angesehen wird, wurden 2985 Schweine verschiedener Herkünfte untersucht. Dabei ergaben sich folgende Allelfrequenzen für das C-Allel, welches in Zusammenhang mit der Streßresistenz steht: 0,0 bei der Belgischen Landrasse, 0,01 bei der Rasse Pietrain, 0,54 bei der Deutschen

  18. Isolation of somatic Na+ currents by selective inactivation of axonal channels with a voltage prepulse.

    Science.gov (United States)

    Milescu, Lorin S; Bean, Bruce P; Smith, Jeffrey C

    2010-06-02

    We present a simple and effective method for isolating the somatic Na(+) current recorded under voltage clamp from neurons in brain slices. The principle is to convert the axon from an active compartment capable of generating uncontrolled axonal spikes into a passive structure by selectively inactivating axonal Na(+) channels. Typically, whole-cell currents from intact neurons under somatic voltage clamp contain a mixture of Na(+) current and axial current caused by escaped axonal spikes. We found that a brief prepulse to voltages near spike threshold evokes the axonal spike, which inactivates axonal but not somatic channels. A subsequent voltage step then evokes only somatic Na(+) current from electrotonically proximal sodium channels under good voltage-clamp control. Simulations using a neuron compartmental model support the idea that the prepulse effectively inactivates currents from the axon and isolates well controlled somatic currents. Na(+) currents recorded from cortical pyramidal neurons in slices, using the prepulse, were found to have voltage dependence nearly identical to that of currents recorded from acutely dissociated pyramidal neurons. In addition, studies in dissociated neurons show that the prepulse has no visible effect on the voltage dependence and kinetics of Na(+) currents elicited by the subsequent voltage step, only decreasing the amplitude of the currents by 10-20%. The technique was effective in several neuronal types in brain slices from male and female neonatal rats and mice, including raphé neurons, cortical pyramidal neurons, inferior olivary neurons, and hypoglossal motoneurons.

  19. Calcium channel regulator Mid1 links TORC2-mediated changes in mitochondrial respiration to autophagy

    OpenAIRE

    Vlahakis, Ariadne; Lopez Muniozguren, Nerea; Powers, Ted

    2016-01-01

    Autophagy is a catabolic process that recycles cytoplasmic contents and is crucial for cell survival during stress. The target of rapamycin (TOR) kinase regulates autophagy as part of two distinct protein complexes, TORC1 and TORC2. TORC1 negatively regulates autophagy according to nitrogen availability. In contrast, TORC2 functions as a positive regulator of autophagy during amino acid starvation, via its target kinase Ypk1, by repressing the activity of the calcium-dependent phosphatase cal...

  20. Calcium and Vitamin D Supplementation on Bone Health: Current Evidence and Recommendations

    OpenAIRE

    Chen, Li-Ru; Wen, Yu-Tang; Kuo, Chih-Lin; Chen, Kuo-Hu

    2014-01-01

    Population aging and osteoporosis are global public health challenges. Osteoporosis markedly increases the risk of fractures, and further morbidity and mortality. Calcium is a major constituent of the bone and vitamin D helps maintain calcium homeostasis. Calcium and vitamin D supplements have long been recognized as the cornerstones for prevention and management of osteoporosis and fractures. Although the associations between calcium and vitamin D supplementation and bone mineral density, fr...

  1. Calcium signaling of in situ chondrocytes in articular cartilage under compressive loading: Roles of calcium sources and cell membrane ion channels.

    Science.gov (United States)

    Lv, Mengxi; Zhou, Yilu; Chen, Xingyu; Han, Lin; Wang, Liyun; Lu, X Lucas

    2017-10-05

    Mechanical loading on articular cartilage can induce many physical and chemical stimuli on chondrocytes residing in the extracellular matrix (ECM). Intracellular calcium ([Ca2+ ]i ) signaling is among the earliest responses of chondrocytes to physical stimuli, but the [Ca2+ ]i signaling of in situ chondrocytes in loaded cartilage is not fully understood due to the technical challenges in [Ca2+ ]i imaging of chondrocytes in a deforming ECM. This study developed a novel bi-directional microscopy loading device that enables the record of transient [Ca2+ ]i responses of in situ chondrocytes in loaded cartilage. It was found that compressive loading significantly promoted [Ca2+ ]i signaling in chondrocytes with faster [Ca2+ ]i oscillations in comparison to the non-loaded cartilage. Seven [Ca2+ ]i signaling pathways were further investigated by treating the cartilage with antagonists prior to and/or during the loading. Removal of extracellular Ca2+ ions completely abolished the [Ca2+ ]i responses of in situ chondrocytes, suggesting the indispensable role of extracellular Ca2+ sources in initiating the [Ca2+ ]i signaling in chondrocytes. Depletion of intracellular Ca2+ stores, inhibition of PLC-IP3 pathway, and block of purinergic receptors on plasma membrane led to significant reduction in the responsive rate of cells. Three types of ion channels that are regulated by different physical signals, TRPV4 (osmotic and mechanical stress), T-type VGCCs (electrical potential), and mechanical sensitive ion channels (mechanical loading) all demonstrated critical roles in controlling the [Ca2+ ]i responses of in situ chondrocyte in the loaded cartilage. This study provided new knowledge about the [Ca2+ ]i signaling and mechanobiology of chondrocytes in its natural residing environment. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

  2. Calcium dysregulation via L-type voltage-dependent calcium channels and ryanodine receptors underlies memory deficits and synaptic dysfunction during chronic neuroinflammation.

    Science.gov (United States)

    Hopp, Sarah C; D'Angelo, Heather M; Royer, Sarah E; Kaercher, Roxanne M; Crockett, Alexis M; Adzovic, Linda; Wenk, Gary L

    2015-03-25

    Chronic neuroinflammation and calcium (Ca(+2)) dysregulation are both components of Alzheimer's disease. Prolonged neuroinflammation produces elevation of pro-inflammatory cytokines and reactive oxygen species which can alter neuronal Ca(+2) homeostasis via L-type voltage-dependent Ca(+2) channels (L-VDCCs) and ryanodine receptors (RyRs). Chronic neuroinflammation also leads to deficits in spatial memory, which may be related to Ca(+2) dysregulation. The studies herein use an in vivo model of chronic neuroinflammation: rats were infused intraventricularly with a continuous small dose of lipopolysaccharide (LPS) or artificial cerebrospinal fluid (aCSF) for 28 days. The rats were treated with the L-VDCC antagonist nimodipine or the RyR antagonist dantrolene. LPS-infused rats had significant memory deficits in the Morris water maze, and this deficit was ameliorated by treatment with nimodipine. Synaptosomes from LPS-infused rats had increased Ca(+2) uptake, which was reduced by a blockade of L-VDCCs either in vivo or ex vivo. Taken together, these data indicate that Ca(+2) dysregulation during chronic neuroinflammation is partially dependent on increases in L-VDCC function. However, blockade of the RyRs also slightly improved spatial memory of the LPS-infused rats, demonstrating that other Ca(+2) channels are dysregulated during chronic neuroinflammation. Ca(+2)-dependent immediate early gene expression was reduced in LPS-infused rats treated with dantrolene or nimodipine, indicating normalized synaptic function that may underlie improvements in spatial memory. Pro-inflammatory markers are also reduced in LPS-infused rats treated with either drug. Overall, these data suggest that Ca(+2) dysregulation via L-VDCCs and RyRs play a crucial role in memory deficits resulting from chronic neuroinflammation.

  3. The Role of Parvalbumin, Sarcoplasmatic Reticulum Calcium Pump Rate, Rates of Cross-Bridge Dynamics, and Ryanodine Receptor Calcium Current on Peripheral Muscle Fatigue: A Simulation Study

    Science.gov (United States)

    Neumann, Verena

    2016-01-01

    A biophysical model of the excitation-contraction pathway, which has previously been validated for slow-twitch and fast-twitch skeletal muscles, is employed to investigate key biophysical processes leading to peripheral muscle fatigue. Special emphasis hereby is on investigating how the model's original parameter sets can be interpolated such that realistic behaviour with respect to contraction time and fatigue progression can be obtained for a continuous distribution of the model's parameters across the muscle units, as found for the functional properties of muscles. The parameters are divided into 5 groups describing (i) the sarcoplasmatic reticulum calcium pump rate, (ii) the cross-bridge dynamics rates, (iii) the ryanodine receptor calcium current, (iv) the rates of binding of magnesium and calcium ions to parvalbumin and corresponding dissociations, and (v) the remaining processes. The simulations reveal that the first two parameter groups are sensitive to contraction time but not fatigue, the third parameter group affects both considered properties, and the fourth parameter group is only sensitive to fatigue progression. Hence, within the scope of the underlying model, further experimental studies should investigate parvalbumin dynamics and the ryanodine receptor calcium current to enhance the understanding of peripheral muscle fatigue. PMID:27980606

  4. How to resolve microsecond current fluctuations in single ion channels: The power of beta distributions

    Science.gov (United States)

    Schroeder, Indra

    2015-01-01

    Abstract A main ingredient for the understanding of structure/function correlates of ion channels is the quantitative description of single-channel gating and conductance. However, a wealth of information provided from fast current fluctuations beyond the temporal resolution of the recording system is often ignored, even though it is close to the time window accessible to molecular dynamics simulations. This kind of current fluctuations provide a special technical challenge, because individual opening/closing or blocking/unblocking events cannot be resolved, and the resulting averaging over undetected events decreases the single-channel current. Here, I briefly summarize the history of fast-current fluctuation analysis and focus on the so-called “beta distributions.” This tool exploits characteristics of current fluctuation-induced excess noise on the current amplitude histograms to reconstruct the true single-channel current and kinetic parameters. A guideline for the analysis and recent applications demonstrate that a construction of theoretical beta distributions by Markov Model simulations offers maximum flexibility as compared to analytical solutions. PMID:26368656

  5. Sodium-calcium exchanger and multiple sodium channel isoforms in intra-epidermal nerve terminals

    Directory of Open Access Journals (Sweden)

    Gasser Andreas

    2010-11-01

    Full Text Available Abstract Background Nociception requires transduction and impulse electrogenesis in nerve fibers which innervate the body surface, including the skin. However, the molecular substrates for transduction and action potential initiation in nociceptors are incompletely understood. In this study, we examined the expression and distribution of Na+/Ca2+ exchanger (NCX and voltage-gated sodium channel isoforms in intra-epidermal free nerve terminals. Results Small diameter DRG neurons exhibited robust NCX2, but not NCX1 or NCX3 immunolabeling, and virtually all PGP 9.5-positive intra-epidermal free nerve terminals displayed NCX2 immunoreactivity. Sodium channel NaV1.1 was not detectable in free nerve endings. In contrast, the majority of nerve terminals displayed detectable levels of expression of NaV1.6, NaV1.7, NaV1.8 and NaV1.9. Sodium channel immunoreactivity in the free nerve endings extended from the dermal boundary to the terminal tip. A similar pattern of NCX and sodium channel immunolabeling was observed in DRG neurons in vitro. Conclusions NCX2, as well as NaV1.6, NaV1.7, NaV1.8 and NaV1.9, are present in most intra-epidermal free nerve endings. The presence of NCX2, together with multiple sodium channel isoforms, in free nerve endings may have important functional implications.

  6. Myosin Va and Endoplasmic Reticulum Calcium Channel Complex Regulates Membrane Export during Axon Guidance

    Directory of Open Access Journals (Sweden)

    Fumitaka Wada

    2016-05-01

    Full Text Available During axon guidance, growth cones navigate toward attractive cues by inserting new membrane on the cue side. This process depends on Ca2+ release from endoplasmic reticulum (ER Ca2+ channels, but the Ca2+ sensor and effector governing this asymmetric vesicle export remain unknown. We identified a protein complex that controls asymmetric ER Ca2+-dependent membrane vesicle export. The Ca2+-dependent motor protein myosin Va (MyoVa tethers membrane vesicles to the ER via a common binding site on the two major ER Ca2+ channels, inositol 1,4,5-trisphosphate and ryanodine receptors. In response to attractive cues, micromolar Ca2+ from ER channels triggers MyoVa-channel dissociation and the movement of freed vesicles to the cue side, enabling growth cone turning. MyoVa-Ca2+ channel interactions are required for proper long-range axon growth in developing spinal cord in vivo. These findings reveal a peri-ER membrane export pathway for Ca2+-dependent attraction in axon guidance.

  7. Sodium-calcium exchanger and multiple sodium channel isoforms in intra-epidermal nerve terminals.

    Science.gov (United States)

    Persson, Anna-Karin; Black, Joel A; Gasser, Andreas; Cheng, Xiaoyang; Fischer, Tanya Z; Waxman, Stephen G

    2010-11-30

    Nociception requires transduction and impulse electrogenesis in nerve fibers which innervate the body surface, including the skin. However, the molecular substrates for transduction and action potential initiation in nociceptors are incompletely understood. In this study, we examined the expression and distribution of Na+/Ca2+ exchanger (NCX) and voltage-gated sodium channel isoforms in intra-epidermal free nerve terminals. Small diameter DRG neurons exhibited robust NCX2, but not NCX1 or NCX3 immunolabeling, and virtually all PGP 9.5-positive intra-epidermal free nerve terminals displayed NCX2 immunoreactivity. Sodium channel NaV1.1 was not detectable in free nerve endings. In contrast, the majority of nerve terminals displayed detectable levels of expression of NaV1.6, NaV1.7, NaV1.8 and NaV1.9. Sodium channel immunoreactivity in the free nerve endings extended from the dermal boundary to the terminal tip. A similar pattern of NCX and sodium channel immunolabeling was observed in DRG neurons in vitro. NCX2, as well as NaV1.6, NaV1.7, NaV1.8 and NaV1.9, are present in most intra-epidermal free nerve endings. The presence of NCX2, together with multiple sodium channel isoforms, in free nerve endings may have important functional implications.

  8. Autosomal dominant hypercalciuria in a mouse model due to a mutation of the epithelial calcium channel, TRPV5.

    Directory of Open Access Journals (Sweden)

    Nellie Y Loh

    Full Text Available Hypercalciuria is a major cause of nephrolithiasis, and is a common and complex disorder involving genetic and environmental factors. Identification of genetic factors for monogenic forms of hypercalciuria is hampered by the limited availability of large families, and to facilitate such studies, we screened for hypercalciuria in mice from an N-ethyl-N-nitrosourea mutagenesis programme. We identified a mouse with autosomal dominant hypercalciuria (HCALC1. Linkage studies mapped the Hcalc1 locus to a 11.94 Mb region on chromosome 6 containing the transient receptor potential cation channel, subfamily V, members 5 (Trpv5 and 6 (Trpv6 genes. DNA sequence analysis of coding regions, intron-exon boundaries and promoters of Trpv5 and Trpv6 identified a novel T to C transition in codon 682 of TRPV5, mutating a conserved serine to a proline (S682P. Compared to wild-type littermates, heterozygous (Trpv5(682P/+ and homozygous (Trpv5(682P/682P mutant mice had hypercalciuria, polyuria, hyperphosphaturia and a more acidic urine, and ∼10% of males developed tubulointerstitial nephritis. Trpv5(682P/682P mice also had normal plasma parathyroid hormone but increased 1,25-dihydroxyvitamin D(3 concentrations without increased bone resorption, consistent with a renal defect for the hypercalciuria. Expression of the S682P mutation in human embryonic kidney cells revealed that TRPV5-S682P-expressing cells had a lower baseline intracellular calcium concentration than wild-type TRPV5-expressing cells, suggesting an altered calcium permeability. Immunohistological studies revealed a selective decrease in TRPV5-expression from the renal distal convoluted tubules of Trpv5(682P/+ and Trpv5(682P/682P mice consistent with a trafficking defect. In addition, Trpv5(682P/682P mice had a reduction in renal expression of the intracellular calcium-binding protein, calbindin-D(28K, consistent with a specific defect in TRPV5-mediated renal calcium reabsorption. Thus, our findings

  9. Lack of delta waves and sleep disturbances during non-rapid eye movement sleep in mice lacking α1G-subunit of T-type calcium channels

    OpenAIRE

    Lee, Jungryun; Kim, Daesoo; Shin, Hee-Sup

    2004-01-01

    T-type calcium channels have been implicated as a pacemaker for brain rhythms during sleep but their contribution to behavioral states of sleep has been relatively uncertain. Here, we found that mice lacking α1G T-type Ca2+ channels showed a loss of the thalamic delta (1–4 Hz) waves and a reduction of sleep spindles (7–14 Hz), whereas slow (16 sec compared with the wild-type, whereas no difference was seen in BAs of

  10. [Biological activity of Ungernia victoris extract in the Escherichia coli CaCl2-transformation system in the presence of calcium channel modulators].

    Science.gov (United States)

    Miriuta, A Iu; Pererva, T P

    2008-01-01

    Furosemid and verapamil appear to have an effect on the yield of E. coli plasmid transformants according to their properties as calc