Use of 3H-muscimol for GABA receptor studies

International Nuclear Information System (INIS)

Snodgrass, S.R.

1978-01-01

It is stated that gamma aminobutyric acid (GABA) is a major transmitter in the mammalian central nervous system and studies of synaptic receptors for neurotransmitters have been useful in many areas of neuropharmacology. Although GABA receptors can be studied using 3 H-GABA itself, a ligand which does not bind to GABA uptake sites would be valuable for autoradiography and for other studies of receptor function. Muscimol (3-hydroxy-5-aminomethly-isoxazole) is a naturally occurring GABA analogue found in Amanita muscaria. It seems to enter the brain after peripheral injection. Evidence is here presented of the binding of 3 H-muscimol by brain tissue. The ability of muscimol to alter evoked release of GABA by synaptosomes was also of muscimol to alter evoked release of GABA by synaptosomes was also used to verify the ability of muscimol to alter the function of GABA neurones. (author)

Novel agents acting on GABA2 receptors: potential cognitive enhancers

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Chebib, M.

2001-01-01

γ- Aminobutyric acid (GABA) is a low molecular weight ammo acid found throughout the central and peripheral nervous systems. It is a very flexible molecule and thus can attain a number of low-energy conformations which are recognised by a series of enzymes, receptors and transporter systems. This article will concentrate on the effects of GABA C as the major inhibitory neurotransmitter in the brain. GABA C receptors belong to the superfamily of ligand-gated ion channels that include nicotinic acetylcholine, GABA A , strychnine-sensitive glycine, and serotonin type 3 receptors. The compound outlined in this article provide us with novel leads for the design and development of compounds that may be selective for GABA receptors. Such compounds will help in the study of GABA C receptors both in vitro and in vivo, providing an insight into the role these receptors play in the brain

Acutely increasing δGABA(A) receptor activity impairs memory and inhibits synaptic plasticity in the hippocampus.

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Whissell, Paul D; Eng, Dave; Lecker, Irene; Martin, Loren J; Wang, Dian-Shi; Orser, Beverley A

2013-01-01

Extrasynaptic γ-aminobutyric acid type A (GABA(A)) receptors that contain the δ subunit (δGABA(A) receptors) are expressed in several brain regions including the dentate gyrus (DG) and CA1 subfields of the hippocampus. Drugs that increase δGABA(A) receptor activity have been proposed as treatments for a variety of disorders including insomnia, epilepsy and chronic pain. Also, long-term pretreatment with the δGABA(A) receptor-preferring agonist 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol (THIP) enhances discrimination memory and increases neurogenesis in the DG. Despite the potential therapeutic benefits of such treatments, the effects of acutely increasing δGABA(A) receptor activity on memory behaviors remain unknown. Here, we studied the effects of THIP (4 mg/kg, i.p.) on memory performance in wild-type (WT) and δGABA(A) receptor null mutant (Gabrd(-/-)) mice. Additionally, the effects of THIP on long-term potentiation (LTP), a molecular correlate of memory, were studied within the DG and CA1 subfields of the hippocampus using electrophysiological recordings of field potentials in hippocampal slices. The results showed that THIP impaired performance in the Morris water maze, contextual fear conditioning and object recognition tasks in WT mice but not Gabrd(-/-) mice. Furthermore, THIP inhibited LTP in hippocampal slices from WT but not Gabrd(-/-) mice, an effect that was blocked by GABA(A) receptor antagonist bicuculline. Thus, acutely increasing δGABA(A) receptor activity impairs memory behaviors and inhibits synaptic plasticity. These results have important implications for the development of therapies aimed at increasing δGABA(A) receptor activity.

GABA(A) receptor- and GABA transporter polymorphisms and risk for essential tremor

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Thier, S; Kuhlenbäumer, G; Lorenz, D

2011-01-01

Background:  Clinical features and animal models of essential tremor (ET) suggest gamma-aminobutyric acid A receptor (GABA(A) R) subunits and GABA transporters as putative candidate genes. Methods:  A total of 503 ET cases and 818 controls were investigated for an association between polymorphisms...

Connections between EM2-containing terminals and GABA/μ-opioid receptor co-expressing neurons in the rat spinal trigeminal caudal nucleus

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Li, Meng-Ying; Wu, Zhen-Yu; Lu, Ya-Cheng; Yin, Jun-Bin; Wang, Jian; Zhang, Ting; Dong, Yu-Lin; Wang, Feng

2014-01-01

Endomorphin-2 (EM2) demonstrates a potent antinociceptive effect via the μ-opioid receptor (MOR). To provide morphological evidence for the pain control effect of EM2, the synaptic connections between EM2-immunoreactive (IR) axonal terminals and γ-amino butyric acid (GABA)/MOR co-expressing neurons in lamina II of the spinal trigeminal caudal nucleus (Vc) were investigated in the rat. Dense EM2-, MOR- and GABA-IR fibers and terminals were mainly observed in lamina II of the Vc. Within lamina II, GABA- and MOR-neuronal cell bodies were also encountered. The results of immunofluorescent histochemical triple-staining showed that approximately 14.2 or 18.9% of GABA-IR or MOR-IR neurons also showed MOR- or GABA-immunopositive staining in lamina II; approximately 45.2 and 36.1% of the GABA-IR and MOR-IR neurons, respectively, expressed FOS protein in their nuclei induced by injecting formalin into the left lower lip of the mouth. Most of the GABA/MOR, GABA/FOS, and MOR/FOS double-labeled neurons made close contacts with EM2-IR fibers and terminals. Immuno-electron microscopy confirmed that the EM2-IR terminals formed synapses with GABA-IR or MOR-IR dendritic processes and neuronal cell bodies in lamina II of the Vc. These results suggest that EM2 might participate in pain transmission and modulation by binding to MOR-IR and GABAergic inhibitory interneuron in lamina II of the Vc to exert inhibitory effect on the excitatory interneuron in lamina II and projection neurons in laminae I and III. PMID:25386121

GABA-B receptor activation and conflict behavior

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Ketelaars, C.E.J.; Bollen, E.L.; Rigter, H.; Bruinvels, J.

1988-01-01

Baclofen and oxazepam enhance extinction of conflict behavior in the Geller-Seifter test while baclofen and diazepam release punished behavior in Vogel's conflict test. In order to investigate the possibility that the effect of the selective GABA-B receptor agonist baclofen is mediated indirectly via the GABA-A/benzodiazepine receptor complex, the effect of pretreatment of rats with baclofen on [ 3 H]-diazepam binding to washed and unwashed cortical and cerebellar membranes of rats has been studied. Baclofen pretreatment increase Bmax in washed cerebellar membranes when bicuculline was present in the incubation mixture. No effect was seen in cortical membranes. The present results render it unlikely that the effect of baclofen on extinction of conflict behavior and punished drinking is mediated via the GABA-A/benzodiazepine receptor complex. 50 references, 1 figure, 4 tables

Demonstration of the dynamic mass redistribution label-free technology as a useful cell-based pharmacological assay for endogenously expressed GABA_A receptors

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Klein, Anders Bue; Nittegaard-Nielsen, Mia; Christensen, Julie T.

2015-01-01

the immortalized IMR-32 neuroblastoma cell line, which expresses relatively high levels of several endogenous GABAA receptor subunits, we show that GABA produces concentration-dependent cellular responses that can be measured and quantified in real-time. With the aid of the GABAA receptor-specific agonist muscimol...

[Schizophrenia and cortical GABA neurotransmission].

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Hashimoto, Takanori; Matsubara, Takuro; Lewis, David A

2010-01-01

Individuals with schizophrenia show disturbances in a number of brain functions that regulate cognitive, affective, motor, and sensory processing. The cognitive deficits associated with dysfunction of the dorsolateral prefrontal cortex result, at least in part, from abnormalities in GABA neurotransmission, as reflected in a specific pattern of altered expression of GABA-related molecules. First, mRNA levels for the 67-kilodalton isoform of glutamic acid decarboxylase (GAD67), an enzyme principally responsible for GABA synthesis, and the GABA membrane transporter GAT1, which regulates the reuptake of synaptically released GABA, are decreased in a subset of GABA neurons. Second, affected GABA neurons include those that express the calcium-binding protein parvalbumin (PV), because PV mRNA levels are decreased in the prefrontal cortex of subjects with schizophrenia and GAD67 mRNA is undetectable in almost half of PV-containing neurons. These changes are accompanied by decreased GAT1 expression in the presynaptic terminals of PV-containing neurons and by increased postsynaptic GABA-A receptor alpha2 subunit expression at the axon initial segments of pyramidal neurons. These findings indicate decreased GABA synthesis/release by PV-containing GABA neurons and compensatory changes at synapses formed by these neurons. Third, another subset of GABA neurons that express the neuropeptide somatostatin (SST) also appear to be affected because their specific markers, SST and neuropeptide Y mRNAs, are decreased in a manner highly correlated with the decreases in GAD67 mRNA. Finally, mRNA levels for GABA-A receptor subunits for synaptic (alpha1 and gamma2) and extra-synaptic (delta) receptors are decreased, indicating alterations in both synaptic and extra-synaptic GABA neurotransmission. Together, this pattern of changes indicates that the altered GABA neurotransmission is specific to PV-containing and SST-containing GABA neuron subsets and involves both synaptic and extra

Identification of amino acids involved in histamine potentiation of GABA(A receptors

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Ulrike eThiel

2015-05-01

Full Text Available Histamine is a neurotransmitter involved in a number of physiological and neuronal functions. In mammals, such as humans and rodents, the histaminergic neurons found in the tuberomamillary nucleus (TMN project widely throughout the central nervous system (CNS. Histamine acts as positive modulator of GABA(A receptors (GABA(ARs and, in high concentrations (10 mM, as negative modulator of the strychnine-sensitive glycine receptor. However, the exact molecular mechanisms by which histamine acts on GABA(ARs are unknown. In our study, we aimed to identify amino acids potentially involved in the modulatory effect of histamine on GABA(ARs. We expressed GABA(ARs with 12 different point mutations in Xenopus laevis oocytes and characterized the effect of histamine on GABA-induced currents using the two-electrode voltage clamp technique. Our data demonstrate that the amino acid residues ß2(N265 and ß2(M286, which are important for modulation by propofol, are not involved in the action of histamine. However, we found that histamine modulation is dependent on the amino acid residues alpha1(R120, ß2(Y157, ß3(D163, ß3(V175 and ß3(Q185. We showed that the amino acid residues ß2(Y157 and ß3(Q185 mediate the positive modulatory effect of histamine on GABA-induced currents, whereas alpha1(R120 and ß2(D163 form a potential histamine interaction site in GABA(ARs.

GABA-independent GABAA Receptor Openings Maintain Tonic Currents

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Wlodarczyk, Agnieszka I.; Sylantyev, Sergiy; Herd, Murray B.; Kersanté, Flavie; Lambert, Jeremy J.; Rusakov, Dmitri A.; Linthorst, Astrid C.E.; Semyanov, Alexey; Belelli, Delia; Pavlov, Ivan; Walker, Matthew C.

2013-01-01

Activation of GABAA receptors (GABAARs) produces two forms of inhibition: ‘phasic’ inhibition generated by the rapid, transient activation of synaptic GABAARs by presynaptic GABA release, and tonic inhibition generated by the persistent activation of peri- or extrasynaptic GABAARs which can detect extracellular GABA. Such tonic GABAAR-mediated currents are particularly evident in dentate granule cells in which they play a major role in regulating cell excitability. Here we show that in rat dentate granule cells in ex-vivo hippocampal slices, tonic currents are predominantly generated by GABA-independent GABAA receptor openings. This tonic GABAAR conductance is resistant to the competitive GABAAR antagonist SR95531, which at high concentrations acts as a partial agonist, but can be blocked by an open channel blocker picrotoxin. When slices are perfused with 200 nM GABA, a concentration that is comparable to cerebrospinal fluid concentrations but is twice that measured by us in the hippocampus in vivo using zero-net-flux microdialysis, negligible GABA is detected by dentate granule cells. Spontaneously opening GABAARs, therefore, maintain dentate granule cell tonic currents in the face of low extracellular GABA concentrations. PMID:23447601

Profiling neurotransmitter receptor expression in the Ambystoma mexicanum brain.

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Reyes-Ruiz, Jorge Mauricio; Limon, Agenor; Korn, Matthew J; Nakamura, Paul A; Shirkey, Nicole J; Wong, Jamie K; Miledi, Ricardo

2013-03-22

Ability to regenerate limbs and central nervous system (CNS) is unique to few vertebrates, most notably the axolotl (Ambystoma sp.). However, despite the fact the neurotransmitter receptors are involved in axonal regeneration, little is known regarding its expression profile. In this project, RT-PCR and qPCR were performed to gain insight into the neurotransmitter receptors present in Ambystoma. Its functional ability was studied by expressing axolotl receptors in Xenopus laevis oocytes by either injection of mRNA or by direct microtransplantation of brain membranes. Oocytes injected with axolotl mRNA expressed ionotropic receptors activated by GABA, aspartate+glycine and kainate, as well as metabotropic receptors activated by acetylcholine and glutamate. Interestingly, we did not see responses following the application of serotonin. Membranes from the axolotl brain were efficiently microtransplanted into Xenopus oocytes and two types of native GABA receptors that differed in the temporal course of their responses and affinities to GABA were observed. Results of this study are necessary for further characterization of axolotl neurotransmitter receptors and may be useful for guiding experiments aimed at understanding activity-dependant limb and CNS regeneration. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Pharmacological characterization of homobaclofen on wild type and mutant GABA(B)1b receptors coexpressed with the GABA(B)2 receptor

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Jensen, Anders A.; Madsen, Bo E.; Krogsgaard-Larsen, P

2001-01-01

homogenate and in an assay of electrically induced contractions of guinea pig ileum. The results from the two tissues did, however, not correlate very well, and in order to further investigate these discrepancies, we have pharmacologically characterized these enantiomers on recombinant wild type and mutant...... rat GABA(B)1b receptors coexpressed with rat GABA(B)2 receptors. The results from this study correlate nicely with the binding data from rat brain. (R)-Homobaclofen was shown to act like (R)-baclofen albeit with 20-fold less potency, and (S)-homobaclofen was inactive on the receptor. The discrepancies...

Valerian inhibits rat hepatocarcinogenesis by activating GABA(A receptor-mediated signaling.

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Anna Kakehashi

Full Text Available Valerian is widely used as a traditional medicine to improve the quality of sleep due to interaction of several active components with the γ-aminobutyric acid (GABA A receptor (GABA(AR system. Recently, activation of GABA signaling in stem cells has been reported to suppress cell cycle progression in vivo. Furthermore, possible inhibitory effects of GABA(AR agonists on hepatocarcinogenesis have been reported. The present study was performed to investigate modulating effects of Valerian on hepatocarcinogenesis using a medium-term rat liver bioassay. Male F344 rats were treated with one of the most powerful Valerian species (Valeriana sitchensis at doses of 0, 50, 500 and 5000 ppm in their drinking water after initiation of hepatocarcinogenesis with diethylnitrosamine (DEN. Formation of glutathione S-transferase placental form positive (GST-P(+ foci was significantly inhibited by Valerian at all applied doses compared with DEN initiation control rats. Generation of 8-hydroxy-2'-deoxyguanosine in the rat liver was significantly suppressed by all doses of Valerian, likely due to suppression of Nrf2, CYP7A1 and induction of catalase expression. Cell proliferation was significantly inhibited, while apoptosis was induced in areas of GST-P(+ foci of Valerian groups associated with suppression of c-myc, Mafb, cyclin D1 and induction of p21(Waf1/Cip1, p53 and Bax mRNA expression. Interestingly, expression of the GABA(AR alpha 1 subunit was observed in GST-P(+ foci of DEN control rats, with significant elevation associated with Valerian treatment. These results indicate that Valerian exhibits inhibitory effects on rat hepatocarcinogenesis by inhibiting oxidative DNA damage, suppressing cell proliferation and inducing apoptosis in GST-P(+ foci by activating GABA(AR-mediated signaling.

Nicotinic receptors and functional regulation of GABA cell microcircuitry in bipolar disorder and schizophrenia.

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Benes, Francine M

2012-01-01

Studies of the hippocampus in postmortem brains from patients with schizophrenia and bipolar disorder have provided evidence for a defect of GABAergic interneurons. Significant decreases in the expression of GAD67, a marker for GABA cell function, have been found repeatedly in several different brain regions that include the hippocampus. In this region, nicotinic receptors are thought to play an important role in modulating the activity of GABAergic interneurons by influences of excitatory cholinergic afferents on their activity. In bipolar disorder, this influence appears to be particularly prominent in the stratum oriens of sectors CA3/2 and CA1, two sites where these cells constitute the exclusive neuronal cell type. In sector CA3/2, this layer receives a robust excitatory projection from the basolateral amygdala (BLA) and this is thought to play a central role in regulating GABA cells at this locus. Using laser microdissection, recent studies have focused selectively on these two layers and their associated GABA cells using microarray technology. The results have provided support for the idea that nicotinic cholinergic receptors play a particularly important role in regulating the activity of GABA neurons at these loci by regulating the progression of cell cycle and the repair of damaged DNA. In bipolar disorder, there is a prominent reduction in the expression of mRNAs for several different nicotinic subunit isoforms. These decreases could reflect a diminished influence of this receptor system on these GABA cells, particularly in sector CA3/2 where a preponderance of abnormalities have been observed in postmortem studies. In patients with bipolar disorder, excitatory nicotinic cholinergic fibers from the medial septum may converge with glutamatergic fibers from the BLA on GABAergic interneurons in the stratum oriens of CA3/2 and result in disturbances of their genomic and functional integrity, ones that may induce disruptions of the integration of

Context-dependent modulation of alphabetagamma and alphabetadelta GABA A receptors by penicillin: implications for phasic and tonic inhibition.

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Feng, Hua-Jun; Botzolakis, Emmanuel J; Macdonald, Robert L

2009-01-01

Penicillin, an open-channel blocker of GABA(A) receptors, was recently reported to inhibit phasic, but not tonic, currents in hippocampal neurons. To distinguish between isoform-specific and context-dependent modulation as possible explanations for this selectivity, the effects of penicillin were evaluated on recombinant GABA(A) receptors expressed in HEK293T cells. When co-applied with saturating GABA, penicillin decreased peak amplitude, induced rebound, and prolonged deactivation of currents evoked from both synaptic and extrasynaptic receptor isoforms. However, penicillin had isoform-specific effects on the extent of desensitization, reflecting its ability to differentially modulate peak (non-equilibrium) and residual (near-equilibrium) currents. This suggested that the context of activation could determine the apparent sensitivity of a given receptor isoform to penicillin. To test this hypothesis, we explored the ability of penicillin to modulate synaptic and extrasynaptic isoform currents that were activated under more physiologically relevant conditions. Interestingly, while currents evoked from synaptic isoforms under phasic conditions (transient activation by a saturating concentration of GABA) were substantially inhibited by penicillin, currents evoked from extrasynaptic isoforms under tonic conditions (prolonged application by a sub-saturating concentration of GABA) were minimally affected. We therefore concluded that the reported inability of penicillin to modulate tonic currents could not simply be attributed to insensitivity of extrasynaptic receptors, but rather, reflected an inability to modulate these receptors in their native context of activation.

A novel GABA(A) alpha 5 receptor inhibitor with therapeutic potential.

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Ling, István; Mihalik, Balázs; Etherington, Lori-An; Kapus, Gábor; Pálvölgyi, Adrienn; Gigler, Gábor; Kertész, Szabolcs; Gaál, Attila; Pallagi, Katalin; Kiricsi, Péter; Szabó, Éva; Szénási, Gábor; Papp, Lilla; Hársing, László G; Lévay, György; Spedding, Michael; Lambert, Jeremy J; Belelli, Delia; Barkóczy, József; Volk, Balázs; Simig, Gyula; Gacsályi, István; Antoni, Ferenc A

2015-10-05

Novel 2,3-benzodiazepine and related isoquinoline derivatives, substituted at position 1 with a 2-benzothiophenyl moiety, were synthesized to produce compounds that potently inhibited the action of GABA on heterologously expressed GABAA receptors containing the alpha 5 subunit (GABAA α5), with no apparent affinity for the benzodiazepine site. Substitutions of the benzothiophene moiety at position 4 led to compounds with drug-like properties that were putative inhibitors of extra-synaptic GABAA α5 receptors and had substantial blood-brain barrier permeability. Initial characterization in vivo showed that 8-methyl-5-[4-(trifluoromethyl)-1-benzothiophen-2-yl]-1,9-dihydro-2H-[1,3]oxazolo[4,5-h][2,3]benzodiazepin-2-one was devoid of sedative, pro-convulsive or motor side-effects, and enhanced the performance of rats in the object recognition test. In summary, we have discovered a first-in-class GABA-site inhibitor of extra-synaptic GABAA α5 receptors that has promising drug-like properties and warrants further development. Copyright © 2015 Elsevier B.V. All rights reserved.

Regulation of GABA and benzodiazepine receptors following neurotoxin-induced striatal and medial forebrain bundle lesions

International Nuclear Information System (INIS)

Pan, H.S.I.

1985-01-01

GABA, a major inhibitory transmitter, is used by many projection neurons of the striatum. To investigate the role of GABA in striatal function, the GABA receptor complex was studied after lesions of the striatum or the nigrostriatal neurons. Quantitative receptor autoradiography using thaw-mounted tissue slices was developed for the study of GABA and benzodiazepine (BDZ) receptors. With the technique established, binding to GABA and BDZ receptors after unilateral striatal kainate lesions was examined. Subsequently, changes in GABA and BDZ receptors were studied following the destruction of dopaminergic nigrostriatal cells by unilateral 6-hydroxydopamine lesion of the medial forebrain bundle. In summary, quantitative receptor autoradiography allowed the detection of GABA and BDZ receptor changes in multiple small areas in each lesioned brain. This technique made it feasible to carry out kinetic saturation, and competition studies using less than 1 mg of tissue. The data suggest that dopamine is functionally inhibitory on striatopallidal neurons but is functionally excitatory on striatoentopeduncular and striatonigral cells which in turn inhibit the thalamus. This quantitative autoradiographic technique can be generalized to study other transmitter receptors and can be combined with 2-deoxyglucose uptake studies

Meta-diamide insecticides acting on distinct sites of RDL GABA receptor from those for conventional noncompetitive antagonists.

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Nakao, Toshifumi; Banba, Shinich; Nomura, Michikazu; Hirase, Kangetsu

2013-04-01

The RDL GABA receptor is an attractive target of insecticides. Here we demonstrate that meta-diamides [3-benzamido-N-(4-(perfluoropropan-2-yl)phenyl)benzamides] are a distinct class of RDL GABA receptor antagonists showing high insecticidal activity against Spodoptera litura. We also suggest that the mode of action of the meta-diamides is distinct from that of conventional noncompetitive antagonists (NCAs), such as fipronil, picrotoxin, lindane, dieldrin, and α-endosulfan. Using a membrane potential assay, we examined the effects of the meta-diamide 3-benzamido-N-(2-bromo-4-(perfluoropropan-2-yl)-6-(trifluoromethyl)phenyl)-2-fluorobenzamide (meta-diamide 7) and NCAs on mutant Drosophila RDL GABA receptors expressed in Drosophila Mel-2 cells. NCAs had little or no inhibitory activity against at least one of the three mutant receptors (A2'S, A2'G, and A2'N), which were reported to confer resistance to NCAs. In contrast, meta-diamide 7 inhibited all three A2' mutant receptors, at levels comparable to its activity with the wild-type receptor. Furthermore, the A2'S·T6'V mutation almost abolished the inhibitory effects of all NCAs. However, meta-diamide 7 inhibited the A2'S・T6'S mutant receptor at the same level as its activity with the wild-type receptor. In contrast, a G336M mutation in the third transmembrane domain of the RDL GABA receptor abolished the inhibitory activities of meta-diamide 7, although the G336M mutation had little effect on the inhibitory activities of conventional NCAs. Molecular modeling studies also suggested that the binding site of meta-diamides was different from those of NCAs. Meta-diamide insecticides are expected to be prominent insecticides effective against A2' mutant RDL GABA receptors with a different mode of action. Copyright © 2013 Elsevier Ltd. All rights reserved.

Cell and receptor type-specific alterations in markers of GABA neurotransmission in the prefrontal cortex of subjects with schizophrenia.

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Lewis, David A; Hashimoto, Takanori; Morris, Harvey M

2008-10-01

Impairments in cognitive control, such as those involved in working memory, are associated with dysfunction of the dorsolateral prefrontal cortex (DLPFC) in individuals with schizophrenia. This dysfunction appears to result, at least in part, from abnormalities in GABA-mediated neurotransmission. In this paper, we review recent findings indicating that the altered DLPFC circuitry in subjects with schizophrenia reflects changes in the expression of genes that encode selective presynaptic and postsynaptic components of GABA neurotransmission. Specifically, using a combination of methods, we found that subjects with schizophrenia exhibited expression deficits in GABA-related transcripts encoding presynaptic regulators of GABA neurotransmission, neuropeptide markers of specific subpopulations of GABA neurons, and certain subunits of the GABA(A) receptor. In particular, alterations in the expression of the neuropeptide somatostatin suggested that GABA neurotransmission is impaired in the Martinotti subset of GABA neurons that target the dendrites of pyramidal cells. In contrast, none of the GABA-related transcripts assessed to date were altered in the DLPFC of monkeys chronically exposed to antipsychotic medications, suggesting that the effects observed in the human studies reflect the disease process and not its treatment. In concert with previous findings, these data suggest that working memory dysfunction in schizophrenia may be attributable to altered GABA neurotransmission in specific DLPFC microcircuits.

The changes in drug binding activity of GABA receptor and animal neural-behavior after gamma irradiation

International Nuclear Information System (INIS)

Zheng Hui; Zhen Rong; Zhao Naikun; Xue Hong; Wang Zihui

2004-01-01

Objective: The purpose of this study was to investigate the effect of irradiation on gamma-aminobutyric-acid receptor (GABA-R) as well as behavioral changes after brain 60 Co γ-irradiation. Methods: The mice were irradiated with gamma rays (20 Gy; 10 Gy and 5 Gy) . The drug binding activity of GABA receptor in brain receptor was measured by fluorescence anisotropy (FA) and equilibrium dissociation constants. The behavioral changes were observed by the locomotor activity test, elevated plus-maze test and hole-board test at 1, 10, 24 and 48 hr after irradiation. Results: 1. The drug binding activity of the GABA receptor was decreased and the equilibrium dissociation constant (K d ) was significantly increased compared with the negative control group 2 hr after irradiation, and a spike value appeared at 24 hr. It showed that the irradiation might damage or decrease the binding activity and the bio-activity of GABA receptor. 2. The animal experiment confirmed that the irradiated animal model showed neural-behavioral changes of anxiety or depression. 3. The decreased binding activity of GABA receptor and changes in behavior of irradiated animal were dependent on radiation intensity. 4. The changes of behavior was similar to the blocked GABA receptor group. It suggests the relationship of radiation and GABA receptor. Conclusion: These results suggest that GABA receptor may be involved in radiation injury. The functional changes of GABA receptor may be an induction factor of behavioral disorder. The article also discussed the effect of anxiety and results obtained from the point of view of GABA receptor system involvement in the changes observed after irradiation. (authors)

GABA(B) receptors, schizophrenia and sleep dysfunction: a review of the relationship and its potential clinical and therapeutic implications.

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Kantrowitz, Joshua; Citrome, Leslie; Javitt, Daniel

2009-08-01

Evidence for an intrinsic relationship between sleep, cognition and the symptomatic manifestations of schizophrenia is accumulating. This review presents evidence for the possible utility of GABA(B) receptor agonists for the treatment of subjective and objective sleep abnormalities related to schizophrenia. At the phenotypic level, sleep disturbance occurs in 16-30% of patients with schizophrenia and is related to reduced quality of life and poor coping skills. On the neurophysiological level, studies suggest that sleep deficits reflect a core component of schizophrenia. Specifically, slow-wave sleep deficits, which are inversely correlated with cognition scores, are seen. Moreover, sleep plays an increasingly well documented role in memory consolidation in schizophrenia. Correlations of slow-wave sleep deficits with impaired reaction time and declarative memory have also been reported. Thus, both behavioural insomnia and sleep architecture are critical therapeutic targets in patients with schizophrenia. However, long-term treatment with antipsychotics often results in residual sleep dysfunction and does not improve slow-wave sleep, and adjunctive GABA(A) receptor modulators, such as benzodiazepines and zolpidem, can impair sleep architecture and cognition in schizophrenia. GABA(B) receptor agonists have therapeutic potential in schizophrenia. These agents have minimal effect on rapid eye movement sleep while increasing slow-wave sleep. Preclinical associations with increased expression of genes related to slow-wave sleep production and circadian rhythm function have also been reported. GABA(B) receptor deficits result in a sustained hyperdopaminergic state and can be reversed by a GABA(B) receptor agonist. Genetic, postmortem and electrophysiological studies also associate GABA(B) receptors with schizophrenia. While studies thus far have not shown significant effects, prior focus on the use of GABA(B) receptor agonists has been on the positive symptoms of

GABA and its B-receptor are present at the node of Ranvier in a small population of sensory fibers, implicating a role in myelination

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Corell, Mikael; Wicher, Grzegorz; Radomska, Katarzyna J

2015-01-01

throughout development and after injury. A small population of myelinated sensory fibers displayed all of these molecules at the node of Ranvier, indicating a role in axon-glia communication. Functional studies using GABAB receptor agonists and antagonists were performed in fetal DRG primary cultures...... to study the function of this receptor during development. The results show that GABA, via its B receptor, is involved in the myelination process but not in Schwann cell proliferation. The data from adult nerves suggest additional roles in axon-glia communication after injury.......The γ-aminobutyric acid (GABA) type B receptor has been implicated in glial cell development in the peripheral nervous system (PNS), although the exact function of GABA signaling is not known. To investigate GABA and its B receptor in PNS development and degeneration, we studied the expression...

Behavioral effects of gamma-hydroxybutyrate, its precursor gamma-butyrolactone, and GABA(B) receptor agonists: time course and differential antagonism by the GABA(B) receptor antagonist 3-aminopropyl(diethoxymethyl)phosphinic acid (CGP35348).

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Koek, Wouter; Mercer, Susan L; Coop, Andrew; France, Charles P

2009-09-01

Gamma-hydroxybutyrate (GHB) is used therapeutically and recreationally. The mechanism by which GHB produces its therapeutic and recreational effects is not entirely clear, although GABA(B) receptors seem to play an important role. This role could be complex, because there are indications that different GABA(B) receptor mechanisms mediate the effects of GHB and the prototypical GABA(B) receptor agonist baclofen. To further explore possible differences in underlying GABA(B) receptor mechanisms, the present study examined the effects of GHB and baclofen on operant responding and their antagonism by the GABA(B) receptor antagonist 3-aminopropyl(diethoxymethyl)phosphinic acid (CGP35348). Pigeons were trained to peck a key for access to food during response periods that started at different times after the beginning of the session. In these pigeons, GHB, its precursor gamma-butyrolactone (GBL), and the GABA(B) receptor agonists baclofen and 3-aminopropyl(methyl)phosphinic acid hydrochloride (SKF97541) decreased the rate of responding in a dose- and time-dependent manner. CGP35348 shifted the dose-response curve of each agonist to the right, but the magnitude of the shift differed among the agonists. Schild analysis yielded a pA(2) value of CGP35348 to antagonize GHB and GBL [i.e., 3.9 (3.7-4.2)] that was different (P = 0.0011) from the pA(2) value to antagonize baclofen and SKF97541 [i.e., 4.5 (4.4-4.7)]. This finding is further evidence that the GABA(B) receptor mechanisms mediating the effects of GHB and prototypical GABA(B) receptor agonists are not identical. A better understanding of the similarities and differences between these mechanisms, and their involvement in the therapeutic effects of GHB and baclofen, could lead to more effective medications with fewer adverse effects.

Characterization of GABA/sub A/ receptor-mediated 36chloride uptake in rat brain synaptoneurosomes

International Nuclear Information System (INIS)

Luu, M.D.; Morrow, A.L.; Paul, S.M.; Schwartz, R.D.

1987-01-01

γ-Aminobutyric acid (GABA) receptor-mediated 36 chloride ( 36 Cl - ) uptake was measured in synaptoneurosomes from rat brain. GABA and GABA agonists stimulated 36 Cl - uptake in a concentration-dependent manner with the following order of potency: Muscimol>GABA>piperidine-4-sulfonic acid (P4S)>4,5,6,7-tetrahydroisoxazolo-[5,4-c]pyridin-3-ol (THIP)=3-aminopropanesulfonic acid (3APS)>>taurine. Both P4S and 3APS behaved as partial agonists, while the GABA/sub B/ agonist, baclofen, was ineffective. The response to muscimol was inhibited by bicuculline and picrotoxin in a mixed competitive/non-competitive manner. Other inhibitors of GABA receptor-opened channels or non-neuronal anion channels such as penicillin, picrate, furosemide and disulfonic acid stilbenes also inhibited the response to muscimol. A regional variation in muscimol-stimulated 36 Cl - uptake was observed; the largest responses were observed in the cerebral cortex, cerebellum and hippocampus, moderate responses were obtained in the striatum and hypothalamus and the smallest response was observed in the pons-medulla. GABA receptor-mediated 36 Cl - uptake was also dependent on the anion present in the media. The muscinol response varied in media containing the following anions: Br - >Cl - ≥NO 3 - >I - ≥SCN - >>C 3 H 5 OO - ≥ClO 4 - >F - , consistent with the relative anion permeability through GABA receptor-gated anion channels and the enhancement of convulsant binding to the GABA receptor-gated Cl - channel. 43 references, 4 figures, 3 tables

Increased GABA-A receptor binding and reduced connectivity at the motor cortex in children with hemiplegic cerebral palsy: a multimodal investigation using 18F-fluoroflumazenil PET, immunohistochemistry, and MR imaging.

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Park, Hae-Jeong; Kim, Chul Hoon; Park, Eun Sook; Park, Bumhee; Oh, So Ra; Oh, Maeng-Keun; Park, Chang Il; Lee, Jong Doo

2013-08-01

γ-aminobutyric acid (GABA)-A receptor-mediated neural transmission is important to promote practice-dependent plasticity after brain injury. This study investigated alterations in GABA-A receptor binding and functional and anatomic connectivity within the motor cortex in children with cerebral palsy (CP). We conducted (18)F-fluoroflumazenil PET on children with hemiplegic CP to investigate whether in vivo GABA-A receptor binding is altered in the ipsilateral or contralateral hemisphere of the lesion site. To evaluate changes in the GABA-A receptor subunit after prenatal brain injury, we performed GABA-A receptor immunohistochemistry using rat pups with a diffuse hypoxic ischemic insult. We also performed diffusion tensor MR imaging and resting-state functional MR imaging on the same children with hemiplegic CP to investigate alterations in anatomic and functional connectivity at the motor cortex with increased GABA-A receptor binding. In children with hemiplegic CP, the (18)F-fluoroflumazenil binding potential was increased within the ipsilateral motor cortex. GABA-A receptors with the α1 subunit were highly expressed exclusively within cortical layers III, IV, and VI of the motor cortex in rat pups. The motor cortex with increased GABA-A receptor binding in children with hemiplegic CP had reduced thalamocortical and corticocortical connectivity, which might be linked to increased GABA-A receptor distribution in cortical layers in rats. Increased expression of the GABA-A receptor α1 subunit within the ipsilateral motor cortex may be an important adaptive mechanism after prenatal brain injury in children with CP but may be associated with improper functional connectivity after birth and have adverse effects on the development of motor plasticity.

Positive selection within the Schizophrenia-associated GABA(A receptor beta(2 gene.

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Wing-Sze Lo

Full Text Available The gamma-aminobutyric acid type-A (GABA(A receptor plays a major role in inhibitory neurotransmissions. Intronic SNPs and haplotypes in GABRB2, the gene for GABA(A receptor beta(2 subunit, are associated with schizophrenia and correlated with the expression of two alternatively spliced beta(2 isoforms. In the present study, using chimpanzee as an ancestral reference, high frequencies were observed for the derived (D alleles of the four SNPs rs6556547, rs187269, rs1816071 and rs1816072 in GABRB2, suggesting the occurrence of positive selection for these derived alleles. Coalescence-based simulation showed that the population frequency spectra and the frequencies of H56, the haplotype having all four D alleles, significantly deviated from neutral-evolution expectation in various demographic models. Haplotypes containing the derived allele of rs1816072 displayed significantly less diversity compared to haplotypes containing its ancestral allele, further supporting positive selection. The variations in DD-genotype frequencies in five human populations provided a snapshot of the evolutionary history, which suggested that the positive selections of the D alleles are recent and likely ongoing. The divergence between the DD-genotype profiles of schizophrenic and control samples pointed to the schizophrenia-relevance of positive selections, with the schizophrenic samples showing weakened selections compared to the controls. These DD-genotypes were previously found to increase the expression of beta(2, especially its long isoform. Electrophysiological analysis showed that this long beta(2 isoform favored by the positive selections is more sensitive than the short isoform to the inhibition of GABA(A receptor function by energy depletion. These findings represent the first demonstration of positive selection in a schizophrenia-associated gene.

GABAA receptor B subunit expression in the superior frontal cortex of human alcoholics

International Nuclear Information System (INIS)

Buckley, S.T.; Dodd, P.R.

2001-01-01

Full text: Changes in GABA A receptor pharmacology can be ascribed to alterations in expression of specific GABA A receptor subunits. Ethanol is known to be a potent agonist of the GABA A receptor. Chronic abuse of alcohol in humans results in damage of selective brain regions such as the superior frontal cortex (SFC), leading to neuronal cell loss. Studies in our laboratory 1 and elsewhere 2 have shown differences in expression of a number of GABA A receptor subunits in chronic human alcoholism. This suggests that alterations in GABA A receptor composition may be involved in the pathogenesis of alcoholic brain damage. We analysed the expression of the β 1 ,β 2 and β 3 isoforms of the GABA A receptor by a competitive reverse transcription polymerase chain reaction (RT-PCR) technique, which utilised an internal standard (IS) for quantitation. 35 S-dATP was incorporated to enable visualisation of the PCR products. Human brain tissue was obtained at autopsy and stored in 0.32 M sucrose at -80 deg C. Total RNA was extracted from pathologically susceptible and spared regions, SFC and motor cortex respectively,of 22 control and 22 alcoholic patients. 1 μg of total RNA from each sample was co-amplified with 0.5 pg of IS and a ratio determined. A standard consisting of known amounts of β 1 cRNA titrated against 0.5 pg of IS enabled a standard curve to be generated for quantitation of each unknown sample. The samples were subjected to polyacrylamide gel electrophoresis and the dried gel exposed to a phosphorimager screen. Data analysis was performed using the ImageQuant program. Initial results indicate that there is a reduction in expression of all the β transcripts in alcoholics when compared with controls, which supports the hypothesis that the GABA A receptor is altered by alcohol abuse. Supported by NHMRC. Copyright (2001) Australian Neuroscience Society

mRNA and Protein Levels for GABA[subscript A][alpha]4, [alpha]5, [beta]1 and GABA[subscript B]R1 Receptors are Altered in Brains from Subjects with Autism

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Fatemi, S. Hossein; Reutiman, Teri J.; Folsom, Timothy D.; Rooney, Robert J.; Patel, Diven H.; Thuras, Paul D.

2010-01-01

We have shown altered expression of gamma-aminobutyric acid A (GABA[subscript A]) and gamma-aminobutyric acid B (GABA[subscript B]) receptors in the brains of subjects with autism. In the current study, we sought to verify our western blotting data for GABBR1 via qRT-PCR and to expand our previous work to measure mRNA and protein levels of 3…

GABA/benzodiazepine receptor complex in long-sleep and short-sleep mice

International Nuclear Information System (INIS)

Marley, R.J.

1987-01-01

LS mice are more sensitive to benzodiazepine-induced anesthesia; however, the two lines do not differ in their hypothermic response to flurazepam. SS mice are more resistant to 3-mercaptopropionic acid-induced seizures and more sensitive to the anticonvulsant effects of benzodiazepines. The various correlates of GABA and benzodiazepine actions probably are the results of different mechanisms of action and/or differential regional control. Bicuculline competition for 3 H-GABA binding sites is greater in SS cerebellar tissue and 3 H-flunitrazepam binding is greater in the mid-brain region of LS mice. GABA enhancement of 3 H-flunitrazepma binding is greater in SS mice. Ethanol also enhances 3 H-flunitrazepam binding and increases the levels of 3 H-flunitrazepam binding above those observed for GABA. Using correlational techniques on data from LS and SS mice and several inbred mouse strains, it was demonstrated that a positive relationship exists between the degree of receptor coupling within the GABA receptor complex and the degree of resistance to seizures

γ-Aminobutyric acid (GABA) signalling in plants.

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Ramesh, Sunita A; Tyerman, Stephen D; Gilliham, Matthew; Xu, Bo

2017-05-01

The role of γ-aminobutyric acid (GABA) as a signal in animals has been documented for over 60 years. In contrast, evidence that GABA is a signal in plants has only emerged in the last 15 years, and it was not until last year that a mechanism by which this could occur was identified-a plant 'GABA receptor' that inhibits anion passage through the aluminium-activated malate transporter family of proteins (ALMTs). ALMTs are multigenic, expressed in different organs and present on different membranes. We propose GABA regulation of ALMT activity could function as a signal that modulates plant growth, development, and stress response. In this review, we compare and contrast the plant 'GABA receptor' with mammalian GABA A receptors in terms of their molecular identity, predicted topology, mode of action, and signalling roles. We also explore the implications of the discovery that GABA modulates anion flux in plants, its role in signal transduction for the regulation of plant physiology, and predict the possibility that there are other GABA interaction sites in the N termini of ALMT proteins through in silico evolutionary coupling analysis; we also explore the potential interactions between GABA and other signalling molecules.

Effect of Songyu Anshen Fang on expression of hypothalamic GABA ...

African Journals Online (AJOL)

Pharmacotherapy Group, Faculty of Pharmacy, University of Benin, Benin City, 300001 Nigeria. Available online ... GABA and GABA(B) receptor proteins in insomniac rats induced by ..... induced by PCPA; ***p < 0.001 vs Saline group ; ###p.

Acute sleep deprivation preconditions the heart against ischemia/ reperfusion injury: the role of central GABA-A receptors.

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Parsa, Hoda; Imani, Alireza; Faghihi, Mahdieh; Riahi, Esmail; Badavi, Mohammad; Shakoori, Abbas; Rastegar, Tayebeh; Aghajani, Marjan; Rajani, Sulail Fatima

2017-11-01

Central γ-aminobutyric acid (GABA) neurotransmission modulates cardiovascular functions and sleep. Acute sleep deprivation (ASD) affects functions of various body organs via different mechanisms. Here, we evaluated the effect of ASD on cardiac ischemia/reperfusion injury (IRI), and studied the role of GABA-A receptor inhibition in central nucleus of amygdala (CeA) by assessing nitric oxide (NO) and oxidative stress. The CeA in sixty male Wistar rats was cannulated for saline or bicuculline (GABA-A receptor antagonist) administration. All animals underwent 30 min of coronary occlusion (ischemia), followed by 2 hr reperfusion (IR). The five experimental groups (n=12) included are as follows: IR: received saline; BIC+IR: received Bicuculline; MLP+IR: received saline, followed by the placement of animals in an aquarium with multiple large platforms; ASD+IR: underwent ASD in an aquarium with multiple small platforms; and BIC+ASD+IR: received bicuculline prior to ASD. Bicuculline administration increased the malondialdehyde levels and infarct size, and decreased the NO metabolites levels and endothelial nitric oxide synthase (eNOS) gene expression in infarcted and non-infarcted areas in comparison to IR group. ASD reduced malondialdehyde levels and infarct size and increased NO metabolites, corticosterone levels and eNOS expression in infarcted and non-infarcted areas as compared to the IR group. Levels of malondialdehyde were increased while levels of NO metabolites, corticosterone and eNOS expression in infarcted and non-infarcted areas were reduced in the BIC+ASD+IR as compared to the ASD+IR group. Blockade of GABA-A receptors in the CeA abolishes ASD-induced cardioprotection by suppressing oxidative stress and NO production.

Acute sleep deprivation preconditions the heart against ischemia/ reperfusion injury: the role of central GABA-A receptors

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Hoda Parsa

2017-11-01

Full Text Available Objective(s: Central γ-aminobutyric acid (GABA neurotransmission modulates cardiovascular functions and sleep. Acute sleep deprivation (ASD affects functions of various body organs via different mechanisms. Here, we evaluated the effect of ASD on cardiac ischemia/reperfusion injury (IRI, and studied the role of GABA-A receptor inhibition in central nucleus of amygdala (CeA by assessing nitric oxide (NO and oxidative stress. Materials and Methods: The CeA in sixty male Wistar rats was cannulated for saline or bicuculline (GABA-A receptor antagonist administration. All animals underwent 30 min of coronary occlusion (ischemia, followed by 2 hr reperfusion (IR. The five experimental groups (n=12 included are as follows: IR: received saline; BIC+IR: received Bicuculline; MLP+IR: received saline, followed by the placement of animals in an aquarium with multiple large platforms; ASD+IR: underwent ASD in an aquarium with multiple small platforms; and BIC+ASD+IR: received bicuculline prior to ASD. Results: Bicuculline administration increased the malondialdehyde levels and infarct size, and decreased the NO metabolites levels and endothelial nitric oxide synthase (eNOS gene expression in infarcted and non-infarcted areas in comparison to IR group. ASD reduced malondialdehyde levels and infarct size and increased NO metabolites, corticosterone levels and eNOS expression in infarcted and non-infarcted areas as compared to the IR group. Levels of malondialdehyde were increased while levels of NO metabolites, corticosterone and eNOS expression in infarcted and non-infarcted areas were reduced in the BIC+ASD+IR as compared to the ASD+IR group. Conclusion: Blockade of GABA-A receptors in the CeA abolishes ASD-induced cardioprotection by suppressing oxidative stress and NO production.

Functional characterization and expression of thalamic GABA(B) receptors in a rodent model of Parkinson's disease

NARCIS (Netherlands)

de Groote, C; Wullner, U; Loschmann, PA; Luiten, PGM; Klockgether, T

1999-01-01

Increased GABAergic neurotransmission of the basal ganglia output nuclei projecting to the motor thalamus is thought to contribute to the pathophysiology of Parkinson's disease. We investigated the functional role of thalamic GABA(B) receptors in a rodent model of Parkinson's disease. First, we

GABA(A) receptors mediate orexin-A induced stimulation of food intake.

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Kokare, Dadasaheb M; Patole, Angad M; Carta, Anna; Chopde, Chandrabhan T; Subhedar, Nishikant K

2006-01-01

Although the role of orexins in sleep/wake cycle and feeding behavior is well established, underlying mechanisms have not been fully understood. An attempt has been made to investigate the role of GABA(A) receptors and their benzodiazepine site on the orexin-A induced response to feeding. Different groups of rats were food deprived overnight and next day injected intracerebroventricularly (icv) with vehicle (artificial CSF; 5 microl/rat) or orexin-A (20-50 nM/rat) and the animals were given free access to food. Cumulative food intake was measured during light phase of light/dark cycle at 1-, 2-, 4- and 6-h post-injection time points. Orexin-A (30-50 nM/rat, icv) stimulated food intake at all the time points (P GABA(A) receptor agonists muscimol (25 ng/rat, icv) and diazepam (0.5 mg/kg, ip) at subeffective doses significantly potentiated the hyperphagic effect of orexin-A (30 nM/rat, icv). However, the effect was negated by the GABA(A) receptor antagonist bicuculline (1 mg/kg, ip). Interestingly, benzodiazepine receptor antagonist flumazenil (5 ng/rat, icv), augmented the orexin-A (30 nM/rat, icv) induced hyperphagia; the effect may be attributed to the intrinsic activity of the agent. The results suggest that the hyperphagic effect of orexin-A, at least in part, is mediated by enhanced GABA(A) receptor activity.

Investigation of Gamma-aminobutyric acid (GABA A receptors genes and migraine susceptibility

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Ciccodicola Alfredo

2008-12-01

Full Text Available Abstract Background Migraine is a neurological disorder characterized by recurrent attacks of severe headache, affecting around 12% of Caucasian populations. It is well known that migraine has a strong genetic component, although the number and type of genes involved is still unclear. Prior linkage studies have reported mapping of a migraine gene to chromosome Xq 24–28, a region containing a cluster of genes for GABA A receptors (GABRE, GABRA3, GABRQ, which are potential candidate genes for migraine. The GABA neurotransmitter has been implicated in migraine pathophysiology previously; however its exact role has not yet been established, although GABA receptors agonists have been the target of therapeutic developments. The aim of the present research is to investigate the role of the potential candidate genes reported on chromosome Xq 24–28 region in migraine susceptibility. In this study, we have focused on the subunit GABA A receptors type ε (GABRE and type θ (GABRQ genes and their involvement in migraine. Methods We have performed an association analysis in a large population of case-controls (275 unrelated Caucasian migraineurs versus 275 controls examining a set of 3 single nucleotide polymorphisms (SNPs in the coding region (exons 3, 5 and 9 of the GABRE gene and also the I478F coding variant of the GABRQ gene. Results Our study did not show any association between the examined SNPs in our test population (P > 0.05. Conclusion Although these particular GABA receptor genes did not show positive association, further studies are necessary to consider the role of other GABA receptor genes in migraine susceptibility.

Conserved regional patterns of GABA-related transcript expression in the neocortex of subjects with schizophrenia.

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Hashimoto, Takanori; Bazmi, H Holly; Mirnics, Karoly; Wu, Qiang; Sampson, Allan R; Lewis, David A

2008-04-01

Individuals with schizophrenia exhibit disturbances in a number of cognitive, affective, sensory, and motor functions that depend on the circuitry of different cortical areas. The cognitive deficits associated with dysfunction of the dorsolateral prefrontal cortex result, at least in part, from abnormalities in GABA neurotransmission, as reflected in a specific pattern of altered expression of GABA-related genes. Consequently, the authors sought to determine whether this pattern of altered gene expression is restricted to the dorsolateral prefrontal cortex or could also contribute to the dysfunction of other cortical areas in subjects with schizophrenia. Real-time quantitative polymerase chain reaction was used to assess the levels of eight GABA-related transcripts in four cortical areas (dorsolateral prefrontal cortex, anterior cingulate cortex, and primary motor and primary visual cortices) of subjects (N=12) with schizophrenia and matched normal comparison subjects. Expression levels of seven transcripts were lower in subjects with schizophrenia, with the magnitude of reduction for each transcript comparable across the four areas. The largest reductions were detected for mRNA encoding somatostatin and parvalbumin, followed by moderate decreases in mRNA expression for the 67-kilodalton isoform of glutamic acid decarboxylase, the GABA membrane transporter GAT-1, and the alpha 1 and delta subunits of GABA(A) receptors. In contrast, the expression of calretinin mRNA did not differ between the subject groups in any of the four areas. Because the areas examined represent the major functional domains (e.g., association, limbic, motor, and sensory) of the cerebral cortex, our findings suggest that a conserved set of molecular alterations affecting GABA neurotransmission contribute to the pathophysiology of different clinical features of schizophrenia.

Ionotropic GABA Receptors and Distal Retinal ON and OFF Responses

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E. Popova

2014-01-01

Full Text Available In the vertebrate retina, visual signals are segregated into parallel ON and OFF pathways, which provide information for light increments and decrements. The segregation is first evident at the level of the ON and OFF bipolar cells in distal retina. The activity of large populations of ON and OFF bipolar cells is reflected in the b- and d-waves of the diffuse electroretinogram (ERG. The role of gamma-aminobutyric acid (GABA, acting through ionotropic GABA receptors in shaping the ON and OFF responses in distal retina, is a matter of debate. This review summarized current knowledge about the types of the GABAergic neurons and ionotropic GABA receptors in the retina as well as the effects of GABA and specific GABAA and GABAC receptor antagonists on the activity of the ON and OFF bipolar cells in both nonmammalian and mammalian retina. Special emphasis is put on the effects on b- and d-waves of the ERG as a useful tool for assessment of the overall function of distal retinal ON and OFF channels. The role of GABAergic system in establishing the ON-OFF asymmetry concerning the time course and absolute and relative sensitivity of the ERG responses under different conditions of light adaptation in amphibian retina is also discussed.

Effect of GABA agonists and GABA-A receptor modulators on cocaine- and food-maintained responding and cocaine discrimination in rats.

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Barrett, Andrew C; Negus, S Stevens; Mello, Nancy K; Caine, S Barak

2005-11-01

Recent studies indicate that GABAergic ligands modulate abuse-related effects of cocaine. The goal of this study was to evaluate the effects of a mechanistically diverse group of GABAergic ligands on the discriminative stimulus and reinforcing effects of cocaine in rats. One group of rats was trained to discriminate 5.6 mg/kg cocaine from saline in a two-lever, food-reinforced, drug discrimination procedure. In two other groups, responding was maintained by cocaine (0-3.2 mg/kg/injection) or liquid food (0-100%) under a fixed ratio 5 schedule. Six GABA agonists were tested: the GABA-A receptor agonist muscimol, the GABA-B receptor agonist baclofen, the GABA transaminase inhibitor gamma-vinyl-GABA (GVG), and three GABA-A receptor modulators (the barbiturate pentobarbital, the high-efficacy benzodiazepine midazolam, and the low-efficacy benzodiazepine enazenil). When tested alone, none of the compounds substituted fully for the discriminative stimulus effects of cocaine. As acute pretreatments, select doses of midazolam and pentobarbital produced 2.2- to 3.6-fold rightward shifts in the cocaine dose-effect function. In contrast, muscimol, baclofen, GVG, and enazenil failed to alter the discriminative stimulus effects of cocaine. In assays of cocaine- and food-maintained responding, midazolam and pentobarbital decreased cocaine self-administration at doses 9.6- and 3.3-fold lower, respectively, than those that decreased food-maintained responding. In contrast, muscimol, baclofen, and GVG decreased cocaine self-administration at doses that also decreased food-maintained responding. Enazenil failed to alter cocaine self-administration. Together with previous studies, these data suggest that among mechanistically diverse GABA agonists, high-efficacy GABA-A modulators may be the most effective for modifying the abuse-related effects of cocaine.

Dose-dependent EEG effects of zolpidem provide evidence for GABA(A) receptor subtype selectivity in vivo.

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Visser, S A G; Wolters, F L C; van der Graaf, P H; Peletier, L A; Danhof, M

2003-03-01

Zolpidem is a nonbenzodiazepine GABA(A) receptor modulator that binds in vitro with high affinity to GABA(A) receptors expressing alpha(1) subunits but with relatively low affinity to receptors expressing alpha(2), alpha(3), and alpha(5) subunits. In the present study, it was investigated whether this subtype selectivity could be detected and quantified in vivo. Three doses (1.25, 5, and 25 mg) of zolpidem were administered to rats in an intravenous infusion over 5 min. The time course of the plasma concentrations was determined in conjunction with the change in the beta-frequency range of the EEG as pharmacodynamic endpoint. The concentration-effect relationship of the three doses showed a dose-dependent maximum effect and a dose-dependent potency. The data were analyzed for one- or two-site binding using two pharmacodynamic models based on 1) the descriptive model and 2) a novel mechanism-based pharmacokinetic/pharmacodynamic (PK/PD) model for GABA(A) receptor modulators that aims to separates drug- and system-specific properties, thereby allowing the estimation of in vivo affinity and efficacy. The application of two-site models significantly improved the fits compared with one-site models. Furthermore, in contrast to the descriptive model, the mechanism-based PK/PD model yielded dose-independent estimates for affinity (97 +/- 40 and 33,100 +/- 14,800 ng x ml(-1)). In conclusion, the mechanism-based PK/PD model is able to describe and explain the observed dose-dependent EEG effects of zolpidem and suggests the subtype selectivity of zolpidem in vivo.

Altered cortical expression of GABA-related genes in schizophrenia: illness progression vs developmental disturbance.

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Hoftman, Gil D; Volk, David W; Bazmi, H Holly; Li, Siyu; Sampson, Allan R; Lewis, David A

2015-01-01

Schizophrenia is a neurodevelopmental disorder with altered expression of GABA-related genes in the prefrontal cortex (PFC). However, whether these gene expression abnormalities reflect disturbances in postnatal developmental processes before clinical onset or arise as a consequence of clinical illness remains unclear. Expression levels for 7 GABA-related transcripts (vesicular GABA transporter [vGAT], GABA membrane transporter [GAT1], GABAA receptor subunit α1 [GABRA1] [novel in human and monkey cohorts], glutamic acid decarboxylase 67 [GAD67], parvalbumin, calretinin, and somatostatin [previously reported in human cohort, but not in monkey cohort]) were quantified in the PFC from 42 matched pairs of schizophrenia and comparison subjects and from 49 rhesus monkeys ranging in age from 1 week postnatal to adulthood. Levels of vGAT and GABRA1, but not of GAT1, messenger RNAs (mRNAs) were lower in the PFC of the schizophrenia subjects. As previously reported, levels of GAD67, parvalbumin, and somatostatin, but not of calretinin, mRNAs were also lower in these subjects. Neither illness duration nor age accounted for the levels of the transcripts with altered expression in schizophrenia. In monkey PFC, developmental changes in expression levels of many of these transcripts were in the opposite direction of the changes observed in schizophrenia. For example, mRNA levels for vGAT, GABRA1, GAD67, and parvalbumin all increased with age. Together with published reports, these findings support the interpretation that the altered expression of GABA-related transcripts in schizophrenia reflects a blunting of normal postnatal development changes, but they cannot exclude a decline during the early stages of clinical illness. © The Author 2013. Published by Oxford University Press on behalf of the Maryland Psychiatric Research Center. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Somato-synaptic variation of GABA(A) receptors in cultured murine cerebellar granule cells: investigation of the role of the alpha6 subunit.

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Mellor, J R; Wisden, W; Randall, A D

2000-07-10

Electrophysiological investigation of cultured cerebellar murine granule cells revealed differences between the GABA(A) receptors at inhibitory synapses and those on the cell body. Specifically, mIPSCs decayed more rapidly than cell body receptors deactivated, the mean single channel conductance at the synapse (32 pS) was greater than that at cell body (21 pS) and only cell body receptors were sensitive to Zn(2+) (150 microM), which depressed response amplitude by 82+/-5% and almost doubled the rate of channel deactivation. The GABA(A) receptor alpha6 subunit is selectively expressed in cerebellar granule cells. Although concentrated at synapses, it is also found on extrasynaptic membranes. Using a mouse line (Deltaalpha6lacZ) lacking this subunit, we investigated its role in the somato-synaptic differences in GABA(A) receptor function. All differences between cell body and synaptic GABA(A) receptors observed in wild-type (WT) granule cells persisted in Deltaalpha6lacZ cells, thus demonstrating that they are not specifically due to the cellular distribution of the alpha6 subunit. However, mIPSCs from WT and Deltaalpha6lacZ cells differed in both their kinetics (faster decay in WT cells) and underlying single channel conductance (32 pS WT, 25 pS Deltaalpha6lacZ). This provides good evidence for a functional contribution of the alpha6 subunit to postsynaptic GABA(A) receptors in these cells. Despite this, deactivation kinetics of mIPSCs in WT and Deltaalpha6lacZ granule cells exhibited similar benzodiazepene (BDZ) sensitivity. This suggests that the enhanced BDZ-induced ataxia seen in Deltaalpha6lacZ mice may reflect physiological activity at extrasynaptic receptors which, unlike those at synapses, display differential BDZ-sensitivity in WT and Deltaalpha6lacZ granule cells (Jones, A.M., Korpi, E.R., McKernan, R.M., Nusser, Z., Pelz, R., Makela, R., Mellor, J.R., Pollard, S., Bahn, S., Stephenson, F.A., Randall, A.D., Sieghart, W., Somogyi, P., Smith, A.J.H., Wisden

Functional characterization of the 1,5-benzodiazepine clobazam and its major active metabolite N-desmethylclobazam at human GABA(A receptors expressed in Xenopus laevis oocytes.

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Harriet Hammer

Full Text Available The 1,5-benzodiazepine clobazam is indicated for the adjunctive treatment of seizures associated with Lennox-Gastaut syndrome in patients 2 years of age or older in the United States, and for treatment of anxiety and various forms of epilepsy elsewhere. Clobazam has been reported to exhibit different in vivo adverse effects and addiction liability profile than the classic 1,4-benzodiazepines. In this study, it was investigated whether the in vitro pharmacological properties of clobazam and its major active metabolite N-desmethylclobazam could explain some of these clinical differences. The functional properties of the two 1,5-benzodiazepines were characterized at the human γ-aminobutyric acid type A receptor (GABA(AR subtypes α1β2γ(2S, α2β2γ(2S, α3β2γ(2S, α5β2γ(2S and α6β2δ expressed in Xenopus laevis oocytes by use of two-electrode voltage-clamp electrophysiology and compared to those exhibited by the 1,4-benzodiazepine clonazepam. All three compounds potentiated GABA EC20-evoked responses through the α(1,2,3,5β2γ(2S GABA(ARs in a reversible and concentration-dependent manner, with each displaying similar EC50 values at the four subtypes. Furthermore, the degrees of potentiation of the GABA EC20 currents through the four receptors mediated by saturating modulator concentrations did not differ substantially for any of the three benzodiazepines. The three compounds were substantially less potent (200-3900 fold as positive allosteric modulators at the α6β2δ GABA(AR than at the α(1,2,3,5β2γ(2S receptors. Interestingly, however, clobazam and especially N-desmethylclobazam were highly efficacious potentiators of α6β2δ receptor signaling. Although this activity component is unlikely to contribute to the in vivo effects of clobazam/N-desmethylclobazam, the 1,5-benzodiazepine could constitute an interesting lead for novel modulators targeting this low-affinity binding site in GABAARs. In conclusion, the non

Molecular basis of the alternative recruitment of GABA(A) versus glycine receptors through gephyrin

DEFF Research Database (Denmark)

Maric, Hans-Michael; Kasaragod, Vikram Babu; Hausrat, Torben Johann

2014-01-01

γ-Aminobutyric acid type A and glycine receptors (GABA(A)Rs, GlyRs) are the major inhibitory neurotransmitter receptors and contribute to many synaptic functions, dysfunctions and human diseases. GABA(A)Rs are important drug targets regulated by direct interactions with the scaffolding protein ge...

[A study on toxic effects of sodium salicylate on rat cochlear spiral ganglion neurons: dopamine receptors mediate expressions of NMDA and GABAA receptors].

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Wei, Ting-Jia; Chen, Hui-Ying; Huang, Xi; Weng, Jing-Jin; Qin, Jiang-Yuan; Su, Ji-Ping

2017-06-25

The aim of the present study was to observe whether dopamine receptor (DR) was involved in the effects of sodium salicylate (SS) on the expressions of N-methyl-D-aspartic acid (NMDA) and γ-aminobutyric acid (GABA) receptors in rat cochlear spiral ganglion neurons (SGNs). Forty-eight hours after primary culture of rat SGNs, immunofluorescence technique was applied to detect expressions of DR1 and DR2, the two subtypes of dopamine receptors. Western blot was performed to assess NMDA receptor NR1 subunit and GABA A receptor subunit α2 (GABRα2) protein expressions in the SGNs after the treatments of SS alone or in combination with DR antagonists. The results demonstrated that: (1) The DR1 and DR2 were expressed in the bodies and axons of the SGN; (2) After the treatment with SS, the surface protein expressions of GABRα2 and NR1 were decreased by 44.69% and 21.57%, respectively, while the total protein expressions showed no significant changes; (3) Neither SS + SCH23390 (DR1 antagonist) group nor SS + Eticlopride (DR2 antagonist) group showed significant differences in GABRα2 and NR1 surface protein expressions compared with the control group. These results suggest that SS regulates the surface GABA A and NMDA receptors trafficking on SGN, and the mechanism may involve DR mediation.

Quantitative autoradiography of hippocampal GABA/sub B/ and GASA/sub A/ receptor changes in Alzheimer's disease

Energy Technology Data Exchange (ETDEWEB)

Chu, D C.M.; Penney, Jr, J B; Young, A B

1987-12-04

GABA/sub B/ and GABA/sub A/ receptors were examined by quantitative (/sup 3/H) GABA autoradiography in postmortem human hippocampus from 6 histopathologically verified cases of dementia of the Alzheimer type (DAT) and 6 normal controls. Significant decrements in the B/sub max/ for both types of GABA receptors were observed in DAT hippocampus as compared to normal controls. No significant differences in K/sub d/ values were revealed. As compared to controls, DAT hippocampus exhibited fewer GABA/sub B/ receptors in stratum moleculare of the denate gyrus, stratum lacunosum-molecular and stratum pyramidale of CA/sub 1/. Significant loss of GABA/sub A/ receptors in DAT hippocampus was also observed in the CA/sub 1/ pyramidal cell region. These changes could not be correlated with differences in age nor in postmortem delay between the two groups. These findings may reflect the neuronal pathologies in CA/sub 1/ region in dentate gyrus, and in projections from the entorhinal cortex which are associated with the memory impairment of DAT. 29 refs.

Effect of Songyu Anshen Fang on expression of hypothalamic GABA ...

African Journals Online (AJOL)

Purpose: To investigate the effects of the Chinese compound, Songyu Anshen Fang (SYF) on levels of GABA and GABA(B) receptor proteins in insomniac rats induced by para-chlorophenylalanine (PCPA). Methods: All rats were randomly separated into either a control group, insomnia group, or a SYF group (at a dose of ...

GABA(A) receptors in visual and auditory cortex and neural activity changes during basic visual stimulation.

Science.gov (United States)

Qin, Pengmin; Duncan, Niall W; Wiebking, Christine; Gravel, Paul; Lyttelton, Oliver; Hayes, Dave J; Verhaeghe, Jeroen; Kostikov, Alexey; Schirrmacher, Ralf; Reader, Andrew J; Northoff, Georg

2012-01-01

Recent imaging studies have demonstrated that levels of resting γ-aminobutyric acid (GABA) in the visual cortex predict the degree of stimulus-induced activity in the same region. These studies have used the presentation of discrete visual stimulus; the change from closed eyes to open also represents a simple visual stimulus, however, and has been shown to induce changes in local brain activity and in functional connectivity between regions. We thus aimed to investigate the role of the GABA system, specifically GABA(A) receptors, in the changes in brain activity between the eyes closed (EC) and eyes open (EO) state in order to provide detail at the receptor level to complement previous studies of GABA concentrations. We conducted an fMRI study involving two different modes of the change from EC to EO: an EO and EC block design, allowing the modeling of the haemodynamic response, followed by longer periods of EC and EO to allow the measuring of functional connectivity. The same subjects also underwent [(18)F]Flumazenil PET to measure GABA(A) receptor binding potentials. It was demonstrated that the local-to-global ratio of GABA(A) receptor binding potential in the visual cortex predicted the degree of changes in neural activity from EC to EO. This same relationship was also shown in the auditory cortex. Furthermore, the local-to-global ratio of GABA(A) receptor binding potential in the visual cortex also predicted the change in functional connectivity between the visual and auditory cortex from EC to EO. These findings contribute to our understanding of the role of GABA(A) receptors in stimulus-induced neural activity in local regions and in inter-regional functional connectivity.

GABA receptor subunit distribution and FMRP-mGluR5 signaling abnormalities in the cerebellum of subjects with schizophrenia, mood disorders, and autism.

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Fatemi, S Hossein; Folsom, Timothy D

2015-09-01

Gamma-aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the brain. GABAergic receptor abnormalities have been documented in several major psychiatric disorders including schizophrenia, mood disorders, and autism. Abnormal expression of mRNA and protein for multiple GABA receptors has also been observed in multiple brain regions leading to alterations in the balance between excitatory/inhibitory signaling in the brain with potential profound consequences for normal cognition and maintenance of mood and perception. Altered expression of GABAA receptor subunits has been documented in fragile X mental retardation 1 (FMR1) knockout mice, suggesting that loss of its protein product, fragile X mental retardation protein (FMRP), impacts GABAA subunit expression. Recent postmortem studies from our laboratory have shown reduced expression of FMRP in the brains of subjects with schizophrenia, bipolar disorder, major depression, and autism. FMRP acts as a translational repressor and, under normal conditions, inhibits metabotropic glutamate receptor 5 (mGluR5)-mediated signaling. In fragile X syndrome (FXS), the absence of FMRP is hypothesized to lead to unregulated mGluR5 signaling, ultimately resulting in the behavioral and intellectual impairments associated with this disorder. Our laboratory has identified changes in mGluR5 expression in autism, schizophrenia, and mood disorders. In the current review article, we discuss our postmortem data on GABA receptors, FMRP, and mGluR5 levels and compare our results with other laboratories. Finally, we discuss the interactions between these molecules and the potential for new therapeutic interventions that target these interconnected signaling systems. Copyright © 2014 Elsevier B.V. All rights reserved.

Segregation of acetylcholine and GABA in the rat superior cervical ganglia: functional correlation.

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Diana eElinos

2016-04-01

Full Text Available Sympathetic neurons have the capability to segregate their neurotransmitters (NTs and co-transmitters to separate varicosities of single axons; furthermore, in culture, these neurons can even segregate classical transmitters. In vivo sympathetic neurons employ acetylcholine (ACh and other classical NTs such as gamma aminobutyric acid (GABA. Herein, we explore whether these neurons in vivo segregate these classical NTs in the superior cervical ganglia of the rat. We determined the topographical distribution of GABAergic varicosities, somatic GABAA receptor, as well as the regional distribution of the segregation of ACh and GABA. We evaluated possible regional differences in efficacy of ganglionic synaptic transmission, in the sensitivity of GABAA receptor to GABA and to the competitive antagonist picrotoxin (PTX. We found that sympathetic preganglionic neurons in vivo do segregate ACh and GABA. GABAergic varicosities and GABAA receptor expression showed a rostro-caudal gradient along ganglia; in contrast, segregation exhibited a caudo-rostral gradient. These uneven regional distributions in expression of GABA, GABAA receptors, and level segregation correlate with stronger synaptic transmission found in the caudal region. Accordingly, GABAA receptors of rostral region show larger sensitivity to GABA and PTX. These results suggest the presence of different types of GABAA receptors in each region that result in a different regional levels of endogenous GABA inhibition. Finally, we discuss a possible correlation of these different levels of GABA modulation and the function of the target organs innervated by rostral and caudal ganglionic neurons.

Pharmacological and biochemical properties of the benzodiazepine-GABA receptor in codfish brain in comparison with mammalian brain

International Nuclear Information System (INIS)

Deng, L.

1989-01-01

The GABA receptor of codfish brain is encoded by an ancestral gene of the mammalian GABA receptor based on phylogenetic studies. The mammalian GABA receptor consists of at least two subunits (β and α) which could be photoaffinity labeled by the GABA agonist [ 3 H]muscimol (57 kDa) and the benzodiazepine (BZ) agonist [ 3 H]flunitrazepam (52 kDa), respectively. In contrast, electrophoresis of codfish GABA receptor photoaffinity labeled by the same ligands showed a single radioactive peak on sodium dodecyl surface polyarcylamide gel, giving rise to a relative molecular weight of 56-57 kDa equivalent to the β subunit of 57 kDa in mammals. The homogeneity of purified receptor using benzodiazepine (Ro 7-1986/1) affinity chromatography was further verified by two-dimensional gel electrophoresis based on isoelectric point and molecular weight, in addition to a single band on a silver stained gel and specific activity. The receptor density and affinity constant for [ 3 H]muscimol and [ 3 H]flunitrazepam are comparable to those in bovine, rate, and human brain

Decreased agonist sensitivity of human GABA(A) receptors by an amino acid variant, isoleucine to valine, in the alpha1 subunit.

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Westh-Hansen, S E; Rasmussen, P B; Hastrup, S; Nabekura, J; Noguchi, K; Akaike, N; Witt, M R; Nielsen, M

1997-06-25

Recombinant human GABA(A) receptors were investigated in vitro by coexpression of cDNAs coding for alpha1, beta2, and gamma2 subunits in the baculovirus/Sf-9 insect cell system. We report that a single amino acid exchange (isoleucine 121 to valine 121) in the N-terminal, extracellular part of the alpha1 subunit induces a marked decrease in agonist GABA(A) receptor ligand sensitivity. The potency of muscimol and GABA to inhibit the binding of the GABA(A) receptor antagonist [3H]SR 95531 (2-(3-carboxypropyl)-3-amino-6-(4-methoxyphenyl)pyridazinium bromide) was higher in receptor complexes of alpha1(ile 121) beta2gamma2 than in those of alpha1(val 121) beta2gamma2 (IC50 values were 32-fold and 26-fold lower for muscimol and GABA, respectively). The apparent affinity of the GABA(A) receptor antagonist bicuculline methiodide to inhibit the binding of [3H]SR 95531 did not differ between the two receptor complex variants. Electrophysiological measurements of GABA induced whole-cell Cl- currents showed a ten-fold decrease in the GABA(A) receptor sensitivity of alpha1 (val 121) beta2gamma2 as compared to alpha1(ile 121) beta2gamma2 receptor complexes. Thus, a relatively small change in the primary structure of the alpha1 subunit leads to a decrease selective for GABA(A) receptor sensitivity to agonist ligands, since no changes were observed in a GABA(A) receptor antagonist affinity and benzodiazepine receptor binding.

Anion transport and GABA signaling

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Christian Andreas Huebner

2013-10-01

Full Text Available Whereas activation of GABAA receptors by GABA usually results in a hyperpolarizing influx of chloride into the neuron, the reversed chloride driving force in the immature nervous system results in a depolarizing efflux of chloride. This GABAergic depolarization is deemed to be important for the maturation of the neuronal network. The concept of a developmental GABA switch has mainly been derived from in vitro experiments and reliable in vivo evidence is still missing. As GABAA receptors are permeable for both chloride and bicarbonate, the net effect of GABA also critically depends on the distribution of bicarbonate. Whereas chloride can either mediate depolarizing or hyperpolarizing currents, bicarbonate invariably mediates a depolarizing current under physiological conditions. Intracellular bicarbonate is quickly replenished by cytosolic carbonic anhydrases. Intracellular bicarbonate levels also depend on different bicarbonate transporters expressed by neurons. The expression of these proteins is not only developmentally regulated but also differs between cell types and even subcellular regions. In this review we will summarize current knowledge about the role of some of these transporters for brain development and brain function.

Actions of insecticides on the insect GABA receptor complex

International Nuclear Information System (INIS)

Bermudez, I.; Hawkins, C.A.; Taylor, A.M.; Beadle, D.J.

1991-01-01

The actions of insecticides on the insect gamma-aminobutyric acid (GABA) receptor were investigated using [35S]t-butylbicyclophosphorothionate [( 35S]TBPS) binding and voltage-clamp techniques. Specific binding of [35S]TBPS to a membrane homogenate derived from the brain of Locusta migratoria locusts is characterised by a Kd value of 79.3 ± 2.9 nM and a Bmax value of 1770 ± 40 fmol/mg protein. [35S]TBPS binding is inhibited by mM concentrations of barbiturates and benzodiazepines. In contrast dieldrin, ivermectin, lindane, picrotoxin and TBPS are inhibitors of [35S]TBPS binding at the nanomolar range. Bicuculline, baclofen and pyrethroid insecticides have no effect on [35S]TBPS binding. These results are similar to those obtained in electrophysiological studies of the current elicited by GABA in both Locusta and Periplaneta americana central neurones. Noise analysis of the effects of lindane, TBPS, dieldrin and picrotoxin on the cockroach GABA responses reveals that these compounds decrease the variance of the GABA-induced current but have no effect on its mean open time. All these compounds, with the exception of dieldrin, significantly decrease the conductance of GABA-evoked single current

γ1-Containing GABA-A Receptors Cluster at Synapses Where they Mediate Slower Synaptic Currents than γ2-Containing GABA-A Receptors

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Christine L. Dixon

2017-06-01

Full Text Available GABA-A receptors (GABAARs are pentameric ligand-gated ion channels that are assembled mainly from α (α1–6, β (β1–3 and γ (γ1–3 subunits. Although GABAARs containing γ2L subunits mediate most of the inhibitory neurotransmission in the brain, significant expression of γ1 subunits is seen in the amygdala, pallidum and substantia nigra. However, the location and function of γ1-containing GABAARs in these regions remains unclear. In “artificial” synapses, where the subunit composition of postsynaptic receptors is specifically controlled, γ1 incorporation slows the synaptic current decay rate without affecting channel deactivation, suggesting that γ1-containing receptors are not clustered and therefore activated by diffuse neurotransmitter. However, we show that γ1-containing receptors are localized at neuronal synapses and form clusters in both synaptic and extrasynaptic regions. In addition, they exhibit rapid membrane diffusion and a higher frequency of exchange between synaptic and perisynaptic populations compared to γ2L-containing GABAARs. A point mutation in the large intracellular domain and a pharmacological analysis reveal that when a single non-conserved γ2L residue is mutated to its γ1 counterpart (T349L, the synaptic current decay is slowed from γ2L- to γ1-like without changing the clustering or diffusion properties of the receptors. In addition, previous fast perfusion and single channel kinetic experiments revealed no difference in the intrinsic closing rates of γ2L- and γ1-containing receptors when expressed in HEK293 cells. These observations together with Monte Carlo simulations of synaptic function confirm that decreased clustering does not control γ1-containing GABAAR kinetics. Rather, they suggest that γ1- and γ2L-containing receptors exhibit differential synaptic current decay rates due to differential gating dynamics when localized at the synapse.

GABA(B), not GABA(A) receptors play a role in cortical postictal refractoriness

Czech Academy of Sciences Publication Activity Database

Mareš, Pavel; Kubová, Hana

2015-01-01

Roč. 88, Jan 2015 (2015), s. 99-102 ISSN 0028-3908 R&D Projects: GA MŠk(CZ) LH11015; GA ČR(CZ) GAP302/10/0971; GA ČR(CZ) GBP304/12/G069 Institutional support: RVO:67985823 Keywords : cortical seizures * postictal refractoriness * GABA receptors * pharmacology Subject RIV: FH - Neurology Impact factor: 4.936, year: 2015

Actions of Agonists, Fipronil and Ivermectin on the Predominant In Vivo Splice and Edit Variant (RDLbd, I/V) of the Drosophila GABA Receptor Expressed in Xenopus laevis Oocytes

Science.gov (United States)

Suwanmanee, Siros; Buckingham, Steven David; Biggin, Philip; Sattelle, David

2014-01-01

Ionotropic GABA receptors are the targets for several classes of insecticides. One of the most widely-studied insect GABA receptors is RDL (resistance to dieldrin), originally isolated from Drosophila melanogaster. RDL undergoes alternative splicing and RNA editing, which influence the potency of GABA. Most work has focussed on minority isoforms. Here, we report the first characterisation of the predominant native splice variant and RNA edit, combining functional characterisation with molecular modelling of the agonist-binding region. The relative order of agonist potency is GABA> muscimol> TACA> β-alanine. The I/V edit does not alter the potency of GABA compared to RDLbd. Docking calculations suggest that these agonists bind and activate RDLbdI/V through a similar binding mode. TACA and β-alanine are predicted to bind with lower affinity than GABA, potentially explaining their lower potency, whereas the lower potency of muscimol and isoguvacine cannot be explained structurally from the docking calculations. The A301S (resistance to dieldrin) mutation reduced the potency of antagonists picrotoxin, fipronil and pyrafluprole but the I/V edit had no measurable effect. Ivermectin suppressed responses to GABA of RDLbdI/V, RDLbd and RDLbdI/VA301S. The dieldrin resistant variant also showed reduced sensitivity to Ivermectin. This study of a highly abundant insect GABA receptor isoform will help the design of new insecticides. PMID:24823815

Dual Modulators of GABA-A and Alpha 7 Nicotinic Receptors for Treating Autism

Science.gov (United States)

2015-10-01

AWARD NUMBER: W81XWH-13-1-0144 TITLE: Dual Modulators of GABA-A and Alpha 7 Nicotinic Receptors for Treating Autism PRINCIPAL INVESTIGATOR...SUBTITLE 5a. CONTRACT NUMBER Dual Modulators of GABA-A and Alpha 7 Nicotinic Receptors for Treating Autism 5b. GRANT NUMBER W81XWH-13-1-0144 5c...ABSTRACT Autism spectrum disorder (ASD) is a polygenic signaling disorder that may result, in part, from an imbalance in excitatory and inhibitory

Salmon lice (Lepeophtheirus salmonis) showing varying emamectin benzoate susceptibilities differ in neuronal acetylcholine receptor and GABA-gated chloride channel mRNA expression.

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Carmichael, Stephen N; Bron, James E; Taggart, John B; Ireland, Jacqueline H; Bekaert, Michaël; Burgess, Stewart Tg; Skuce, Philip J; Nisbet, Alasdair J; Gharbi, Karim; Sturm, Armin

2013-06-18

Caligid copepods, also called sea lice, are fish ectoparasites, some species of which cause significant problems in the mariculture of salmon, where the annual cost of infection is in excess of €300 million globally. At present, caligid control on farms is mainly achieved using medicinal treatments. However, the continued use of a restricted number of medicine actives potentially favours the development of drug resistance. Here, we report transcriptional changes in a laboratory strain of the caligid Lepeophtheirus salmonis (Krøyer, 1837) that is moderately (~7-fold) resistant to the avermectin compound emamectin benzoate (EMB), a component of the anti-salmon louse agent SLICE® (Merck Animal Health). Suppression subtractive hybridisation (SSH) was used to enrich transcripts differentially expressed between EMB-resistant (PT) and drug-susceptible (S) laboratory strains of L. salmonis. SSH libraries were subjected to 454 sequencing. Further L. salmonis transcript sequences were available as expressed sequence tags (EST) from GenBank. Contiguous sequences were generated from both SSH and EST sequences and annotated. Transcriptional responses in PT and S salmon lice were investigated using custom 15 K oligonucleotide microarrays designed using the above sequence resources. In the absence of EMB exposure, 359 targets differed in transcript abundance between the two strains, these genes being enriched for functions such as calcium ion binding, chitin metabolism and muscle structure. γ-aminobutyric acid (GABA)-gated chloride channel (GABA-Cl) and neuronal acetylcholine receptor (nAChR) subunits showed significantly lower transcript levels in PT lice compared to S lice. Using RT-qPCR, the decrease in mRNA levels was estimated at ~1.4-fold for GABA-Cl and ~2.8-fold for nAChR. Salmon lice from the PT strain showed few transcriptional responses following acute exposure (1 or 3 h) to 200 μg L-1 of EMB, a drug concentration tolerated by PT lice, but toxic for S lice

Role of GABA(B) receptors in learning and memory and neurological disorders.

Science.gov (United States)

Heaney, Chelcie F; Kinney, Jefferson W

2016-04-01

Although it is evident from the literature that altered GABAB receptor function does affect behavior, these results often do not correspond well. These differences could be due to the task protocol, animal strain, ligand concentration, or timing of administration utilized. Because several clinical populations exhibit learning and memory deficits in addition to altered markers of GABA and the GABAB receptor, it is important to determine whether altered GABAB receptor function is capable of contributing to the deficits. The aim of this review is to examine the effect of altered GABAB receptor function on synaptic plasticity as demonstrated by in vitro data, as well as the effects on performance in learning and memory tasks. Finally, data regarding altered GABA and GABAB receptor markers within clinical populations will be reviewed. Together, the data agree that proper functioning of GABAB receptors is crucial for numerous learning and memory tasks and that targeting this system via pharmaceuticals may benefit several clinical populations. Copyright © 2016 Elsevier Ltd. All rights reserved.

Co-release of glutamate and GABA from single vesicles in GABAergic neurons exogenously expressing VGLUT3

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Johannes eZimmermann

2015-09-01

Full Text Available The identity of the vesicle neurotransmitter transporter expressed by a neuron largely corresponds with the primary neurotransmitter that cell releases. However, the vesicular glutamate transporter subtype 3 (VGLUT3 is mainly expressed in non-glutamatergic neurons, including cholinergic, serotonergic, or GABAergic neurons. Though a functional role for glutamate release from these non-glutamatergic neurons has been demonstrated, the interplay between VGLUT3 and the neuron’s characteristic neurotransmitter transporter, particularly in the case of GABAergic neurons, at the synaptic and vesicular level is less clear. In this study, we explore how exogenous expression of VGLUT3 in striatal GABAergic neurons affects the packaging and release of glutamate and GABA in synaptic vesicles. We found that VGLUT3 expression in isolated, autaptic GABAergic neurons leads to action potential evoked release of glutamate. Under these conditions, glutamate and GABA could be packaged together in single vesicles release either spontaneously or asynchronously. However, the presence of glutamate in GABAergic vesicles did not affect uptake of GABA itself, suggesting a lack of synergy in vesicle filling for these transmitters. Finally, we found postsynaptic detection of glutamate released from GABAergic terminals difficult when bona fide glutamatergic synapses were present, suggesting that co-released glutamate cannot induce postsynaptic glutamate receptor clustering.

Positive allosteric modulation of GABA-A receptors reduces capsaicin-induced primary and secondary hypersensitivity in rats

DEFF Research Database (Denmark)

Hansen, Rikke Rie; Erichsen, Helle K; Brown, David T

2012-01-01

GABA-A receptor positive allosteric modulators (PAMs) mediate robust analgesia in animal models of pathological pain, in part via enhancing injury-induced loss of GABA-A-α2 and -α3 receptor function within the spinal cord. As yet, a lack of clinically suitable tool compounds has prevented this co...

A Review of the Updated Pharmacophore for the Alpha 5 GABA(A Benzodiazepine Receptor Model

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Terry Clayton

2015-01-01

Full Text Available An updated model of the GABA(A benzodiazepine receptor pharmacophore of the α5-BzR/GABA(A subtype has been constructed prompted by the synthesis of subtype selective ligands in light of the recent developments in both ligand synthesis, behavioral studies, and molecular modeling studies of the binding site itself. A number of BzR/GABA(A α5 subtype selective compounds were synthesized, notably α5-subtype selective inverse agonist PWZ-029 (1 which is active in enhancing cognition in both rodents and primates. In addition, a chiral positive allosteric modulator (PAM, SH-053-2′F-R-CH3 (2, has been shown to reverse the deleterious effects in the MAM-model of schizophrenia as well as alleviate constriction in airway smooth muscle. Presented here is an updated model of the pharmacophore for α5β2γ2 Bz/GABA(A receptors, including a rendering of PWZ-029 docked within the α5-binding pocket showing specific interactions of the molecule with the receptor. Differences in the included volume as compared to α1β2γ2, α2β2γ2, and α3β2γ2 will be illustrated for clarity. These new models enhance the ability to understand structural characteristics of ligands which act as agonists, antagonists, or inverse agonists at the Bz BS of GABA(A receptors.

Reduction of GABA/sub B/ receptor binding induced by climbing fiber degeneration in the rat cerebellum

International Nuclear Information System (INIS)

Kato, K.; Fukuda, H.

1985-01-01

When the rat cerebellar climbing fibers degenerated, as induced by lesioning the inferior olive with 3-acetylpyridine (3-AP), GABA/sub B/ receptor binding determined with 3 H-(+/-)baclofen was reduced in the cerebellum but not in the cerebral cortex of rats. Computer analysis of saturation data revealed two components of the binding sites, and indicated that decrease of the binding in the cerebellum was due to reduction in receptor density, mainly of the high-affinity sites, the B/sub max/ of which was reduced to one-third that in the control animals. In vitro treatment with 3-AP, of the membranes prepared from either the cerebellum or the cerebral cortex, induced no alteration in the binding sites, thereby indicating that the alteration of GABA/sub B/ sites induced by in vivo treatment with 3-AP is not due to a direct action of 3-AP on the receptor. GABA/sub A/ and benzodiazepine receptor binding labelled with 3 H-muscimol and 3 H-diazepam, respectively, in both of brain regions was not affected by destruction of the inferior olive. These results provide evidence that some of the GABA/sub B/ sites but neither GABA/sub A/ nor benzodiazepine receptors in the cerebellum are located at the climbing fiber terminals. 28 references, 4 figures, 2 tables

Gamma-aminobutyric acid (GABA)-B receptor 1 in cerebellar cortex of essential tremor.

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Luo, C; Rajput, A H; Robinson, C A; Rajput, A

2012-06-01

Some reports suggest cerebellar dysfunction as the basis of essential tremor (ET). Several drugs with the action of gamma-aminobutyric acid (GABA) are known to improve ET. Autopsy studies were performed on brains from nine former patients followed at the Movement Disorders Clinic Saskatchewan, Canada, and compared with five normal control brains. We aimed to measure the concentration of GABA B receptor 1 (GBR1) in the brains of patients who had had ET and to compare them to the GABA concentration in brains of controls. Western blot was used to determine the expression of GBR1 in cerebellar cortex tissue. We found that compared to the controls, the ET brains had three different patterns of GBR1 protein concentration--two with high, four comparable, and three with marginally low levels. There was no association between the age of onset, severity or duration of tremor, the response to alcohol or other drugs and GBR1 level. Thus, we conclude that our study does not support that GBR1 is involved in ET. Further studies are needed to verify these results. Copyright © 2011 Elsevier Ltd. All rights reserved.

Triton X-100 inhibits agonist-induced currents and suppresses benzodiazepine modulation of GABA(A) receptors in Xenopus oocytes

DEFF Research Database (Denmark)

Søgaard, Rikke; Ebert, Bjarke; Klaerke, Dan

2009-01-01

Changes in lipid bilayer elastic properties have been proposed to underlie the modulation of voltage-gated Na(+) and L-type Ca(2+) channels and GABA(A) receptors by amphiphiles. The amphiphile Triton X-100 increases the elasticity of lipid bilayers at micromolar concentrations, assessed from its...... by flunitrazepam at alpha(1)beta(3)gamma(2S) receptors. All effects were independent of the presence of a gamma(2S) subunit in the GABA(A) receptor complex. The present study suggests that Triton X-100 may stabilize open and desensitized states of the GABA(A) receptor through changes in lipid bilayer elasticity....

Fast detection of extrasynaptic GABA with a whole-cell sniffer.

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Christensen, Rasmus K; Petersen, Anders V; Schmitt, Nicole; Perrier, Jean-François

2014-01-01

Gamma-amino-butyric acid (GABA) is the main inhibitory transmitter of the brain. It operates by binding to specific receptors located both inside and outside synapses. The extrasynaptic receptors are activated by spillover from GABAergic synapses and by ambient GABA in the extracellular space. Ambient GABA is essential for adjusting the excitability of neurons. However, due to the lack of suitable methods, little is known about its dynamics. Here we describe a new technique that allows detection of GABA transients and measurement of the steady state GABA concentration with high spatial and temporal resolution. We used a human embryonic kidney (HEK) cell line that stably expresses GABAA receptors composed of α1, β2, and γ2 subunits. We recorded from such a HEK cell with the whole-cell patch-clamp technique. The presence of GABA near the HEK cell generated a measurable electric current whose magnitude increased with concentration. A fraction of the current did not inactivate during prolonged exposition to GABA. This technique, which we refer to as a "sniffer" allows the measurement of ambient GABA concentration inside nervous tissue with a resolution of few tens of nanomolars. In addition, the sniffer detects variations in the extrasynaptic GABA concentration with millisecond time resolution. Pilot experiments demonstrate that the sniffer is able to report spillover of GABA induced by synaptic activation in real time. This is the first report on a GABA sensor that combines the ability to detect fast transients and to measure steady concentrations.

PKC/CREB pathway mediates the expressions of GABAA receptor subunits in cultured hippocampal neurons after low-Mg2+ solution treatment.

Science.gov (United States)

Wu, Guofeng; Yu, Jinpeng; Wang, Likun; Ren, Siying; Zhang, Yixia

2018-02-01

To investigate the potential effects of the PKC/CREB pathway on the expressions of GABA A receptor subunits α1, γ2, and δ in cultured hippocampal neurons using a model of epilepsy that employed conditions of low magnesium (Mg 2+ ). A total of 108 embryonic rats at the age of 18 embryonic days (E18)prepared from adult female SD rats were used as experimental subjects. Primary rat hippocampal cultures were prepared from the embryonic 18 days rats. The cultured hippocampal neurons were then treated with artificial cerebrospinal fluid containing low Mg 2+ solutions to generate a low Mg 2+ model of epilepsy. The low Mg 2+ stimulation lasted for 3 h and then returned to in maintenance medium for 20 h. The changes of the GABA A receptor subunit α1, γ2, δ were observed by blocking or activating the function of the CREB. The quantification of the GABA A receptor subunit α1, γ2, δ and the CREB were determined by a qRT-PCR and a Western blot method. After the neurons were exposed to a low-Mg 2+ solution for 3 h, GABA A receptor mRNA expression markedly increased compared to the control, and then gradually decreased. In contrast, CREB mRNA levels exhibited a dramatic down-regulation 3 h after terminating low-Mg 2+ treatment, and then peaked at 9 h. Western blot analyses verified that staurosporine suppressed CREB phosphorylation (p-CREB). The mRNA expression of GABA A receptor subunit α1 increased only in the presence of staurosporine, whereas the expressions of subunits γ2 and δ significantly increased in the presence of either KG-501 or staurosporine. Furthermore, phorbol 12-myristate 13-acetate (PMA) decreased the expressions of GABA A subunits α1, γ2, and δ when administered alone. However, the administration of either KG-501 or staurosporine reversed the inhibitory effects of PMA. The PKC/CREB pathway may negatively regulate the expressions of GABA A receptor subunits α1, γ2, and δ in cultured hippocampal neurons in low Mg 2+ model of

Aluminum-Activated Malate Transporters Can Facilitate GABA Transport.

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Ramesh, Sunita A; Kamran, Muhammad; Sullivan, Wendy; Chirkova, Larissa; Okamoto, Mamoru; Degryse, Fien; McLaughlin, Michael; Gilliham, Matthew; Tyerman, Stephen D

2018-05-01

Plant aluminum-activated malate transporters (ALMTs) are currently classified as anion channels; they are also known to be regulated by diverse signals, leading to a range of physiological responses. Gamma-aminobutyric acid (GABA) regulation of anion flux through ALMT proteins requires a specific amino acid motif in ALMTs that shares similarity with a GABA binding site in mammalian GABA A receptors. Here, we explore why TaALMT1 activation leads to a negative correlation between malate efflux and endogenous GABA concentrations ([GABA] i ) in both wheat ( Triticum aestivum ) root tips and in heterologous expression systems. We show that TaALMT1 activation reduces [GABA] i because TaALMT1 facilitates GABA efflux but GABA does not complex Al 3+ TaALMT1 also leads to GABA transport into cells, demonstrated by a yeast complementation assay and via 14 C-GABA uptake into TaALMT1 -expressing Xenopus laevis oocytes; this was found to be a general feature of all ALMTs we examined. Mutation of the GABA motif (TaALMT1 F213C ) prevented both GABA influx and efflux, and resulted in no correlation between malate efflux and [GABA] i We conclude that ALMTs are likely to act as both GABA and anion transporters in planta. GABA and malate appear to interact with ALMTs in a complex manner to regulate each other's transport, suggestive of a role for ALMTs in communicating metabolic status. © 2018 American Society of Plant Biologists. All rights reserved.

Gaba /SUB a/ vs gaba /SUB b/ modulation of septal-hippocampal interconnections

International Nuclear Information System (INIS)

Blaker, W.D.; Cheney, D.L.; Costa, E.

1986-01-01

The authors perform studies to correlate pharmacologically induced decreases in the hippocampal TR /SUB ACh/ with changes in extinction of a foodreinforced lever press response. The authors differentiate the behavioral effects elicited by GABAergic vs. non-GABAergic inhibition of hippocampal cholinergic activity as well as show that GABA /SUB A/ receptor activation in the septum produces a behavioral-biochemical profile different from that elicited by GABA /SUB B/ receptor activation. To characterize GABA receptors tritium-GABA binding was performed in rats injected bilaterally with 1 ug kainic acid into the ventral and dorsal hippocampi. Representative cumulative recorder tracings showing the effect of varius intraseptal doses of the GABA /SUB A/ agonist muscimol on extinction after CRF training are show for one experiment. The most marked differences between muscimol and saline treated rats were seen in the extinction response patterns

Rat intra-hippocampal NMDA infusion induces cell-specific damage and changes in expression of NMDA and GABA(A) receptor subunits

Czech Academy of Sciences Publication Activity Database

Rambousek, Lukáš; Kletečková, Lenka; Kubesová, A.; Jirák, D.; Valeš, Karel; Fritschy, J.M.

2016-01-01

Roč. 105, Jun (2016), s. 594-606 ISSN 0028-3908 R&D Projects: GA ČR(CZ) GBP304/12/G069; GA ČR(CZ) GA14-20613S; GA ČR(CZ) GAP303/12/1464 Institutional support: RVO:67985823 Keywords : excitotoxicity * NMDA receptor * GABA A receptor * hippocampus * neuroinflammation * neurodegeneration * interneurons * spatial learning * carousel maze Subject RIV: FH - Neurology Impact factor: 5.012, year: 2016

Investigation of autism and GABA receptor subunit genes in multiple ethnic groups

OpenAIRE

Collins, Ann L.; Ma, Deqiong; Whitehead, Patrice L.; Martin, Eden R.; Wright, Harry H.; Abramson, Ruth K.; Hussman, John P.; Haines, Jonathan L.; Cuccaro, Michael L.; Gilbert, John R.; Pericak-Vance, Margaret A.

2006-01-01

Autism is a neurodevelopmental disorder of complex genetics, characterized by impairment in social interaction and communication, as well as repetitive behavior. Multiple lines of evidence, including alterations in levels of GABA and GABA receptors in autistic patients, indicate that the GABAergic system, which is responsible for synaptic inhibition in the adult brain, may be involved in autism. Previous studies in our lab indicated association of noncoding single nucleotide polymorphisms (SN...

Neonatal blockade of GABA-A receptors alters behavioral and physiological phenotypes in adult mice.

Science.gov (United States)

Salari, Ali-Akbar; Amani, Mohammad

2017-04-01

Gamma-aminobutyric acid (GABA) plays an inhibitory role in the mature brain, and has a complex and bidirectional effect in different parts of the immature brain which affects proliferation, migration and differentiation of neurons during development. There is also increasing evidence suggesting that activation or blockade of the GABA-A receptors during early life can induce brain and behavioral abnormalities in adulthood. We investigated whether neonatal blockade of the GABA-A receptors by bicuculline can alter anxiety- and depression-like behaviors, body weight, food intake, corticosterone and testosterone levels in adult mice (postnatal days 80-95). To this end, neonatal mice were treated with either DMSO or bicuculline (70, 150 and 300μg/kg) during postnatal days 7, 9 and 11. When grown to adulthood, mice were exposed to behavioral tests to measure anxiety- (elevated plus-maze and light-dark box) and depression-like behaviors (tail suspension test and forced swim test). Stress-induced serum corticosterone and testosterone levels, body weight and food intake were also evaluated. Neonatal bicuculline exposure at dose of 300μg/kg decreased anxiety-like behavior, stress-induced corticosterone levels and increased testosterone levels, body weight and food intake, without significantly influencing depression-like behavior in adult male mice. However, no significant changes in these parameters were observed in adult females. These findings suggest that neonatal blockade of GABA-A receptors affects anxiety-like behavior, physiological and hormonal parameters in a sex-dependent manner in mice. Taken together, these data corroborate the concept that GABA-A receptors during early life have an important role in programming neurobehavioral phenotypes in adulthood. Copyright © 2017 ISDN. Published by Elsevier Ltd. All rights reserved.

Fast detection of extrasynaptic GABA with a whole-cell sniffer

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Rasmus Kordt Christensen

2014-05-01

Full Text Available Gamma-amino-butyric acid (GABA is the main inhibitory transmitter of the brain. It operates by binding to specific receptors located both inside and outside synapses. The extrasynaptic receptors are activated by spillover from GABAergic synapses and by ambient GABA in the extracellular space. Ambient GABA is essential for adjusting the excitability of neurons. However, due to the lack of suitable methods, little is known about its dynamics. Here we describe a new technique that allows detection of GABA transients and measurement of the steady state GABA concentration with high spatial and temporal resolution. We used a Human Embryonic Kidney (HEK cell line that stably expresses GABAA receptors composed of α1, β2, and γ2 subunits. We recorded from such a HEK cell with the whole-cell patch-clamp technique. The presence of GABA near the HEK cell generated a measurable electric current whose magnitude increased with concentration. A fraction of the current did not inactivate during prolonged exposition to GABA. This technique, which we refer to as a sniffer allows the measurement of ambient GABA concentration inside nervous tissue with a resolution of few tens of nanomolars. In addition, the sniffer detects variations in the extrasynaptic GABA concentration with millisecond time resolution. Pilot experiments demonstrate that the sniffer is able to report spillover of GABA induced by synaptic activation in real time. This is the first report on a GABA sensor that combines the ability to detect fast transients and to measure steady concentrations.

Embryonic GABA(B receptor blockade alters cell migration, adult hypothalamic structure, and anxiety- and depression-like behaviors sex specifically in mice.

Directory of Open Access Journals (Sweden)

Matthew S Stratton

Full Text Available Neurons of the paraventricular nucleus of the hypothalamus (PVN regulate the hypothalamic- pituitary-adrenal (HPA axis and the autonomic nervous system. Females lacking functional GABA(B receptors because of a genetic disruption of the R1 subunit have altered cellular characteristics in and around the PVN at birth. The genetic disruption precluded appropriate assessments of physiology or behavior in adulthood. The current study was conducted to test the long term impact of a temporally restricting pharmacological blockade of the GABA(B receptor to a 7-day critical period (E11-E17 during embryonic development. Experiments tested the role of GABA(B receptor signaling in fetal development of the PVN and later adult capacities for adult stress related behaviors and physiology. In organotypic slices containing fetal PVN, there was a female specific, 52% increase in cell movement speeds with GABA(B receptor antagonist treatment that was consistent with a sex-dependent lateral displacement of cells in vivo following 7 days of fetal exposure to GABA(B receptor antagonist. Anxiety-like and depression-like behaviors, open-field activity, and HPA mediated responses to restraint stress were measured in adult offspring of mothers treated with GABA(B receptor antagonist. Embryonic exposure to GABA(B receptor antagonist resulted in reduced HPA axis activation following restraint stress and reduced depression-like behaviors. There was also increased anxiety-like behavior selectively in females and hyperactivity in males. A sex dependent response to disruptions of GABA(B receptor signaling was identified for PVN formation and key aspects of physiology and behavior. These changes correspond to sex specific prevalence in similar human disorders, namely anxiety disorders and hyperactivity.

Pharmacological analysis of the activation and receptor properties of the tonic GABA(CR current in retinal bipolar cell terminals.

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Stefanie M Jones

Full Text Available GABAergic inhibition in the central nervous system (CNS can occur via rapid, transient postsynaptic currents and via a tonic increase in membrane conductance, mediated by synaptic and extrasynaptic GABA(A receptors (GABA(ARs respectively. Retinal bipolar cells (BCs exhibit a tonic current mediated by GABA(CRs in their axon terminal, in addition to synaptic GABA(AR and GABA(CR currents, which strongly regulate BC output. The tonic GABA(CR current in BC terminals (BCTs is not dependent on vesicular GABA release, but properties such as the alternative source of GABA and the identity of the GABA(CRs remain unknown. Following a recent report that tonic GABA release from cerebellar glial cells is mediated by Bestrophin 1 anion channels, we have investigated their role in non-vesicular GABA release in the retina. Using patch-clamp recordings from BCTs in goldfish retinal slices, we find that the tonic GABA(CR current is not reduced by the anion channel inhibitors NPPB or flufenamic acid but is reduced by DIDS, which decreases the tonic current without directly affecting GABA(CRs. All three drugs also exhibit non-specific effects including inhibition of GABA transporters. GABA(CR ρ subunits can form homomeric and heteromeric receptors that differ in their properties, but BC GABA(CRs are thought to be ρ1-ρ2 heteromers. To investigate whether GABA(CRs mediating tonic and synaptic currents may differ in their subunit composition, as is the case for GABA(ARs, we have examined the effects of two antagonists that show partial ρ subunit selectivity: picrotoxin and cyclothiazide. Tonic and synaptic GABA(CR currents were differentially affected by both drugs, suggesting that a population of homomeric ρ1 receptors contributes to the tonic current. These results extend our understanding of the multiple forms of GABAergic inhibition that exist in the CNS and contribute to visual signal processing in the retina.

The GABA A-Receptor γ2 (GABRG2 Gene in obsessive-compulsive disorder O gene do receptor GABA A- γ2 (GABRG2 no transtorno obsessivo-compulsivo

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Margaret A. Richter

2009-12-01

Full Text Available OBJECTIVE: The γ-aminobutyric acid type A (GABA A system may be implicated in obsessive-compulsive disorder, based on its major role in modulation of anxiety and its function as the principal inhibitory neurotransmitter system in the cortex. In addition, glutamatergic/GABAergic mechanisms appear to play a role in the pathophysiology of obsessive-compulsive disorder, making the GABA A receptor-γ2 (GABργ2 gene a good candidate for susceptibility in this disorder. METHOD: 118 probands meeting DSM-IV criteria for primary obsessive-compulsive disorder and their available parents were recruited for participation in this study and informed consent was obtained. An NciI restriction site polymorphism in the second intron was genotyped and data was analyzed using the Transmission Disequilibrium Test. RESULTS: In total, 61 of the participating families were informative (i.e., with at least one heterozygous parent. No biases were observed in the transmission of either of the two alleles (χ2 = 0.016, 1 d.f., p = 0.898 to the affected probands in the total sample. CONCLUSION/DISCUSSION: While these results do not provide support for a major role for the GABA A receptor-γ2 in obsessive-compulsive disorder, further investigations of this gene in larger samples are warranted.OBJETIVO: O sistema gabaérgico tipo A (GABA A pode estar implicado no transtorno obsessivo-compulsivo devido ao seu grande papel na modulação da ansiedade e da sua função como o principal neurotransmissor inibidor no córtex. Além disso, mecanismos glutamatérgicos/gabaérgicos parecem desempenhar um papel na fisiopatologia do transtorno obsessivo-compulsivo, tornando o gene do receptor GABA A-γ2 (GABRG2 um bom gene candidato para a suscetibilidade genética a este transtorno. MÉTODO: 118 probandos que preencheram os critérios do DSM-IV para transtorno obsessivo-compulsivo primário e seus pais (quando disponíveis foram recrutados para a participação neste estudo

GABA(B) receptor phosphorylation regulates KCTD12-induced K+ current desensitization

Czech Academy of Sciences Publication Activity Database

Adelfinger, L.; Tureček, Rostislav; Ivankova, K.; Jensen, A. A.; Moss, S. J.; Gassmann, M.; Bettler, B.

2014-01-01

Roč. 91, č. 3 (2014), s. 369-379 ISSN 0006-2952 Institutional support: RVO:68378041 Keywords : GABA-B * G-protein coupled receptor * GPCR Subject RIV: FH - Neurology Impact factor: 5.009, year: 2014

GABA dramatically improves glucose tolerance in streptozotocin-induced diabetic rats fed with high-fat diet.

Science.gov (United States)

Sohrabipour, Shahla; Sharifi, Mohammad Reza; Talebi, Ardeshir; Sharifi, Mohammadreza; Soltani, Nepton

2018-05-05

Skeletal muscle, hepatic insulin resistance, and beta cell dysfunction are the characteristic pathophysiological features of type 2 diabetes mellitus. GABA has an important role in pancreatic islet cells. The present study attempted to clarify the possible mechanism of GABA to improve glucose tolerance in a model of type 2 diabetes mellitus in rats. Fifty Wistar rats were divided into five groups: NDC that was fed the normal diet, CD which received a high-fat diet with streptozotocin, CD-GABA animals that received GABA via intraperitoneal injection, plus CD-Ins1 and CD-Ins2 groups which were treated with low and high doses of insulin, respectively. Body weight and blood glucose were measured weekly. Intraperitoneal glucose tolerance test (IPGTT), insulin tolerance test (ITT), urine volume, amount of water drinking, and food intake assessments were performed monthly. The hyperinsulinemic euglycemic clamp was done for assessing insulin resistance. Plasma insulin and glucagon were measured. Abdominal fat was measured. Glucagon receptor, Glucose 6 phosphatase, Phosphoenolpyruvate carboxykinase genes expression were evaluated in liver and Glucose transporter 4 (GLUT4) genes expression and protein translocation were evaluated in the muscle. GABA or insulin therapy improved blood glucose, insulin level, IPGTT, ITT, gluconeogenesis pathway, Glucagon receptor, body weight and body fat in diabetic rats. GLUT4 gene and protein expression increased. GABA whose beneficial effect was comparable to that of insulin, also increased glucose infusion rate during an euglycemic clamp. GABA could improve insulin resistance via rising GLUT4 and also decreasing the gluconeogenesis pathway and Glucagon receptor gene expression. Copyright © 2018. Published by Elsevier B.V.

The benzodiazepine/GABA receptor complex during severe ethanol intoxication and withdrawal in the rat

International Nuclear Information System (INIS)

Hemmingsen, R.; Braestrup, C.; Nielsen, M.; Barry, D.I.

1982-01-01

The benzodiazepine/GABA (gammaaminobutyric acid) receptor complex was investigated during severe ethanol intoxication and withdrawal in the rat. The intragastric intubation technique was used to establish physical ethanol dependence in the animals. Cerebral cortex from male Wistar rats was studied 1) after 31/2 days of severe ethanol intoxication, 2) during the ethanol withdrawal reaction and 3) in a control group. The effect of GABA-ergic activation by muscimol and THIP (4,5,6,7-tetrahydroisoxazole(5,4-c)pyridin-3-01) on 3 H-diazepam binding was unchanged during ethanol intoxication and withdrawal, as was the affinity constant (Ksub(D)) and the maximal number of binding sites (Bsub(max)) for 3 H-flunitrazepam. In conclusion, the benzodiazepine/GABA receptor complex is unlikely to play any causual part in physical ethanol dependence. (author)

Experiment K-6-18. Study of muscarinic and gaba (benzodiazepine) receptors in the sensory-motor cortex, hippcampus and spinal code

Science.gov (United States)

Daunton, N.; Damelio, F.; Krasnov, I.

1990-01-01

Frontal lobe samples of rat brains flown aboard Cosmos 1887 were processed for the study of muscarinic (cholinergic) and GABA (benzodiazepine) receptors and for immunocytochemical localization of the neurotransmitter gamma-aminobutyric acid (GABA) and glial fibrillary acidic protein (GFAP). Although radioactive labeling of both muscarinic cholinergic and GABA (benzodiazepine) receptors proved to be successful with the techniques employed, distinct receptor localization of individual laminae of the frontal neocortex was not possible since the sampling of the area was different in the various groups of animals. In spite of efforts made for proper orientation and regional identification of laminae, it was found that a densitometric (quantitation of autoradiograms) analysis of the tissue did not contribute to the final interpretation of the effects of weightlessness on these receptors. As to the immunocytochemical studies the use of both markers, GFAP and GABA antiserum, confirmed the suitability of the techniques for use in frozen material. However, similar problems to those encountered in the receptor studies prevented an adequate interpretation of the effects of micro-G exposure on the localization and distribution of GABA and GFAP. This study did, however, confirm the feasibility of investigating neurotransmitters and their receptors in future space flight experiments.

Effects of central histamine receptors blockade on GABA(A) agonist-induced food intake in broiler cockerels.

Science.gov (United States)

Morteza, Zendehdel; Vahhab, Babapour; Hossein, Jonaidi

2008-02-01

In this study, the effect of intracerebroventricular (i.c.v) injection of H1, H2 and H3 antagonists on feed intake induced by GABA(A) agonist was evaluated. In Experiment 1, the animals received chloropheniramine, a H1 antagonist and then muscimol, a GABA(A) agonist. In Experiment 2, chickens received famotidine, a H2 receptor antagonist, prior to injection of muscimol. Finally in Experiment 3, the birds were injected with thioperamide, a H3 receptor antagonist and muscimol. Cumulative food intake was measured 15, 30, 45, 60, 90, 120, 150 and 180 min after injections. The results of this study indicated that effects of muscimol on food intake inhibited by pretreatment with chloropheneramine maleate (p GABA(A) receptor interaction on food intake in broiler cockerels.

p-Coumaric acid activates the GABA-A receptor in vitro and is orally anxiolytic in vivo.

Science.gov (United States)

Scheepens, Arjan; Bisson, Jean-Francois; Skinner, Margot

2014-02-01

The increasing prevalence and social burden of subclinical anxiety in the western world represents a significant psychosocial and financial cost. Consumers are favouring a more natural and nonpharmacological approach for alleviating the effects of everyday stress and anxiety. The gamma-aminobutyric acid (GABA) receptor is the primary mediator of central inhibitory neurotransmission, and GABA-receptor agonists are well known to convey anxiolytic effects. Using an in vitro screening approach to identify naturally occurring phytochemical GABA agonists, we discovered the plant secondary metabolite p-coumaric acid to have significant GABAergic activity, an effect that could be blocked by co-administration of the specific GABA-receptor antagonist, picrotoxin. Oral administration of p-coumaric acid to rodents induced a significant anxiolytic effect in vivo as measured using the elevated plus paradigm, in line with the effects of oral diazepam. Given that p-coumaric acid is reasonably well absorbed following oral consumption in man and is relatively nontoxic, it may be suitable for the formulation of a safe and effective anxiolytic functional food. Copyright © 2013 John Wiley & Sons, Ltd.

A Unified Model of the GABA(A) Receptor Comprising Agonist and Benzodiazepine Binding Sites

DEFF Research Database (Denmark)

Kongsbak, Kristine Grønning; Bergmann, Rikke; Sørensen, Pernille Louise

2013-01-01

We present a full-length a1b2c2 GABA receptor model optimized for agonists and benzodiazepine (BZD) allosteric modulators. We propose binding hypotheses for the agonists GABA, muscimol and THIP and for the allosteric modulator diazepam (DZP). The receptor model is primarily based on the glutamate......-gated chloride channel (GluCl) from C. elegans and includes additional structural information from the prokaryotic ligand-gated ion channel ELIC in a few regions. Available mutational data of the binding sites are well explained by the model and the proposed ligand binding poses. We suggest a GABA binding mode...... of the agonists in the orthosteric site. The carbonyl group of DZP is predicted to interact with two threonines a1T206 and c2T142, similar to the acidic moiety of GABA. The chlorine atom of DZP is placed near the important a1H101 and the N-methyl group near a1Y159, a1T206, and a1Y209. We present a binding mode...

Gamma-hydroxybutyric acid (GHB) and the mesoaccumbens reward circuit: evidence for GABA(B) receptor-mediated effects.

Science.gov (United States)

Pistis, M; Muntoni, A L; Pillolla, G; Perra, S; Cignarella, G; Melis, M; Gessa, G L

2005-01-01

Gamma-hydroxybutyric acid (GHB) is a short-chain fatty acid naturally occurring in the mammalian brain, which recently emerged as a major recreational drug of abuse. GHB has multiple neuronal mechanisms including activation of both the GABA(B) receptor, and a distinct GHB-specific receptor. This complex GHB-GABA(B) receptor interaction is probably responsible for the multifaceted pharmacological, behavioral and toxicological profile of GHB. Drugs of abuse exert remarkably similar effects upon reward-related circuits, in particular the mesolimbic dopaminergic system and the nucleus accumbens (NAc). We used single unit recordings in vivo from urethane-anesthetized rats to characterize the effects of GHB on evoked firing in NAc "shell" neurons and on spontaneous activity of antidromically identified dopamine (DA) cells located in the ventral tegmental area. GHB was studied in comparison with the GABA(B) receptor agonist baclofen and antagonist (2S)(+)-5,5-dimethyl-2-morpholineacetic acid (SCH50911). Additionally, we utilized a GHB analog, gamma-(p-methoxybenzil)-gamma-hydroxybutyric acid (NCS-435), devoid of GABA(B) binding properties, but with high affinity for specific GHB binding sites. In common with other drugs of abuse, GHB depressed firing in NAc neurons evoked by the stimulation of the basolateral amygdala. On DA neurons, GHB exerted heterogeneous effects, which were correlated to the baseline firing rate of the cells but led to a moderate stimulation of the DA system. All GHB actions were mediated by GABA(B) receptors, since they were blocked by SCH50911 and were not mimicked by NCS-435. Our study indicates that the electrophysiological profile of GHB is close to typical drugs of abuse: both inhibition of NAc neurons and moderate to strong stimulation of DA transmission are distinctive features of diverse classes of abused drugs. Moreover, it is concluded that addictive and rewarding properties of GHB do not necessarily involve a putative high affinity GHB

The Memory-Impairing Effects of Septal GABA Receptor Activation Involve GABAergic Septo-Hippocampal Projection Neurons

Science.gov (United States)

Krebs-Kraft, Desiree L.; Wheeler, Marina G.; Parent, Marise B.

2007-01-01

Septal infusions of the [gamma]-aminobutyric acid (GABA)[subscript A] agonist muscimol impair memory, and the effect likely involves the hippocampus. GABA[subscript A] receptors are present on the perikarya of cholinergic and GABAergic septo-hippocampal (SH) projections. The current experiments determined whether GABAergic SH projections are…

Acid stimulation (sour taste elicits GABA and serotonin release from mouse taste cells.

Directory of Open Access Journals (Sweden)

Yijen A Huang

Full Text Available Several transmitter candidates including serotonin (5-HT, ATP, and norepinephrine (NE have been identified in taste buds. Recently, γ-aminobutyric acid (GABA as well as the associated synthetic enzymes and receptors have also been identified in taste cells. GABA reduces taste-evoked ATP secretion from Receptor cells and is considered to be an inhibitory transmitter in taste buds. However, to date, the identity of GABAergic taste cells and the specific stimulus for GABA release are not well understood. In the present study, we used genetically-engineered Chinese hamster ovary (CHO cells stably co-expressing GABA(B receptors and Gαqo5 proteins to measure GABA release from isolated taste buds. We recorded robust responses from GABA biosensors when they were positioned against taste buds isolated from mouse circumvallate papillae and the buds were depolarized with KCl or a stimulated with an acid (sour taste. In contrast, a mixture of sweet and bitter taste stimuli did not trigger GABA release. KCl- or acid-evoked GABA secretion from taste buds was Ca(2+-dependent; removing Ca(2+ from the bathing medium eliminated GABA secretion. Finally, we isolated individual taste cells to identify the origin of GABA secretion. GABA was released only from Presynaptic (Type III cells and not from Receptor (Type II cells. Previously, we reported that 5-HT released from Presynaptic cells inhibits taste-evoked ATP secretion. Combined with the recent findings that GABA depresses taste-evoked ATP secretion, the present results indicate that GABA and 5-HT are inhibitory transmitters in mouse taste buds and both likely play an important role in modulating taste responses.

Delta Subunit-Containing Gamma-Aminobutyric Acid A Receptor Disinhibits Lateral Amygdala and Facilitates Fear Expression in Mice.

Science.gov (United States)

Liu, Zhi-Peng; He, Qing-Hai; Pan, Han-Qing; Xu, Xiao-Bin; Chen, Wen-Bing; He, Ye; Zhou, Jin; Zhang, Wen-Hua; Zhang, Jun-Yu; Ying, Xiao-Ping; Han, Ren-Wen; Li, Bao-Ming; Gao, Tian-Ming; Pan, Bing-Xing

2017-06-15

Maintaining gamma-aminobutyric acidergic (GABAergic) inhibition in the amygdala within a physiological range is critical for the appropriate expression of emotions such as fear and anxiety. The synaptic GABA type A receptor (GABA A R) is generally known to mediate the primary component of amygdala inhibition and prevent inappropriate expression of fear. However, little is known about the contribution of the extrasynaptic GABA A R to amygdala inhibition and fear. By using mice expressing green fluorescent protein in interneurons (INs) and lacking the δ subunit-containing GABA A R (GABA A (δ)R), which is exclusively situated in the extrasynaptic membrane, we systematically investigated the role of GABA A (δ)R in regulating inhibition in the lateral amygdala (LA) and fear learning using the combined approaches of immunohistochemistry, electrophysiology, and behavior. In sharp contrast to the established role of synaptic GABA A R in mediating LA inhibition, we found that either pharmacological or physiological recruitment of GABA A (δ)R resulted in the weakening of GABAergic transmission onto projection neurons in LA while leaving the glutamatergic transmission unaltered, suggesting disinhibition by GABA A (δ)R. The disinhibition arose from IN-specific expression of GABA A (δ)R with its activation decreasing the input resistance of local INs and suppressing their activation. Genetic deletion of GABA A (δ)R attenuated its role in suppressing LA INs and disinhibiting LA. Importantly, the GABA A (δ)R facilitated long-term potentiation in sensory afferents to LA and permitted the expression of learned fear. Our findings suggest that GABA A (δ)R serves as a brake rather than a mediator of GABAergic inhibition in LA. The disinhibition by GABA A (δ)R may help to prevent excessive suppression of amygdala activity and thus ensure the expression of emotion. Copyright © 2016 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.

Loss of ethanol conditioned taste aversion and motor stimulation in knockin mice with ethanol-insensitive α2-containing GABA(A) receptors.

Science.gov (United States)

Blednov, Y A; Borghese, C M; McCracken, M L; Benavidez, J M; Geil, C R; Osterndorff-Kahanek, E; Werner, D F; Iyer, S; Swihart, A; Harrison, N L; Homanics, G E; Harris, R A

2011-01-01

GABA type A receptors (GABA(A)-Rs) are potential targets of ethanol. However, there are multiple subtypes of this receptor, and, thus far, individual subunits have not been definitively linked with specific ethanol behavioral actions. Interestingly, though, a chromosomal cluster of four GABA(A)-R subunit genes, including α2 (Gabra2), was associated with human alcoholism (Am J Hum Genet 74:705-714, 2004; Pharmacol Biochem Behav 90:95-104, 2008; J Psychiatr Res 42:184-191, 2008). The goal of our study was to determine the role of receptors containing this subunit in alcohol action. We designed an α2 subunit with serine 270 to histidine and leucine 277 to alanine mutations that was insensitive to potentiation by ethanol yet retained normal GABA sensitivity in a recombinant expression system. Knockin mice containing this mutant subunit were tested in a range of ethanol behavioral tests. These mutant mice did not develop the typical conditioned taste aversion in response to ethanol and showed complete loss of the motor stimulant effects of ethanol. Conversely, they also demonstrated changes in ethanol intake and preference in multiple tests. The knockin mice showed increased ethanol-induced hypnosis but no difference in anxiolytic effects or recovery from acute ethanol-induced motor incoordination. Overall, these studies demonstrate that the effects of ethanol at GABAergic synapses containing the α2 subunit are important for specific behavioral effects of ethanol that may be relevant to the genetic linkage of this subunit with human alcoholism.

Hyperalgesic effect induced by barbiturates, midazolam and ethanol: pharmacological evidence for GABA-A receptor involvement

Directory of Open Access Journals (Sweden)

M.A.K.F. Tatsuo

1997-02-01

Full Text Available The involvement of GABA-A receptors in the control of nociception was studied using the tail-flick test in rats. Non-hypnotic doses of the barbiturates phenobarbital (5-50 mg/kg, pentobarbital (17-33 mg/kg, and thiopental (7.5-30 mg/kg, of the benzodiazepine midazolam (10 mg/kg or of ethanol (0.4-1.6 g/kg administered by the systemic route reduced the latency for the tail-flick response, thus inducing a 'hyperalgesic' state in the animals. In contrast, non-convulsant doses of the GABA-A antagonist picrotoxin (0.12-1.0 mg/kg administered systemically induced an increase in the latency for the tail-flick response, therefore characterizing an 'antinociceptive' state. Previous picrotoxin (0.12 mg/kg treatment abolished the hyperalgesic state induced by effective doses of the barbiturates, midazolam or ethanol. Since phenobarbital, midazolam and ethanol reproduced the described hyperalgesic effect of GABA-A-specific agonists (muscimol, THIP, which is specifically antagonized by the GABA-A antagonist picrotoxin, our results suggest that GABA-A receptors are tonically involved in the modulation of nociception in the rat central nervous system

The insecticide fipronil and its metabolite fipronil sulphone inhibit the rat alpha1beta2gamma2L GABA(A) receptor.

Science.gov (United States)

Li, P; Akk, G

2008-11-01

Fipronil is the active ingredient in a number of widely used insecticides. Human exposure to fipronil leads to symptoms (headache, nausea and seizures) typically associated with the antagonism of GABA(A) receptors in the brain. In this study, we have examined the modulation of the common brain GABA(A) receptor subtype by fipronil and its major metabolite, fipronil sulphone. Whole-cell and single-channel recordings were made from HEK 293 cells transiently expressing rat alpha1beta2gamma2L GABA(A) receptors. The major effect of fipronil was to increase the rate of current decay in macroscopic recordings. In single-channel recordings, the presence of fipronil resulted in shorter cluster durations without affecting the intracluster open and closed time distributions or the single-channel conductance. The alpha1V256S mutation, previously shown alleviate channel inhibition by inhibitory steroids and several insecticides, had a relatively small effect on channel block by fipronil. The mode of action of fipronil sulphone was similar to that of its parent compound but the metabolite was less potent at inhibiting the alpha1beta2gamma2L receptor. We conclude that exposure to fipronil induces accumulation of receptors in a novel, long-lived blocked state. This process proceeds in parallel with and independently of, channel desensitization. The lower potency of fipronil sulphone indicates that the conversion serves as a detoxifying process in mammalian brain.

Early continuous white noise exposure alters l-alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor subunit glutamate receptor 2 and gamma-aminobutyric acid type a receptor subunit beta3 protein expression in rat auditory cortex.

Science.gov (United States)

Xu, Jinghong; Yu, Liping; Zhang, Jiping; Cai, Rui; Sun, Xinde

2010-02-15

Auditory experience during the postnatal critical period is essential for the normal maturation of auditory function. Previous studies have shown that rearing infant rat pups under conditions of continuous moderate-level noise delayed the emergence of adult-like topographic representational order and the refinement of response selectivity in the primary auditory cortex (A1) beyond normal developmental benchmarks and indefinitely blocked the closure of a brief, critical-period window. To gain insight into the molecular mechanisms of these physiological changes after noise rearing, we studied expression of the AMPA receptor subunit GluR2 and GABA(A) receptor subunit beta3 in the auditory cortex after noise rearing. Our results show that continuous moderate-level noise rearing during the early stages of development decreases the expression levels of GluR2 and GABA(A)beta3. Furthermore, noise rearing also induced a significant decrease in the level of GABA(A) receptors relative to AMPA receptors. However, in adult rats, noise rearing did not have significant effects on GluR2 and GABA(A)beta3 expression or the ratio between the two units. These changes could have a role in the cellular mechanisms involved in the delayed maturation of auditory receptive field structure and topographic organization of A1 after noise rearing. Copyright 2009 Wiley-Liss, Inc.

Antagonism of GABA-B but not GABA-A receptors in the VTA prevents stress- and intra-VTA CRF-induced reinstatement of extinguished cocaine seeking in rats.

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Blacktop, Jordan M; Vranjkovic, Oliver; Mayer, Matthieu; Van Hoof, Matthew; Baker, David A; Mantsch, John R

2016-03-01

Stress-induced reinstatement of cocaine seeking requires corticotropin releasing factor (CRF) actions in the ventral tegmental area (VTA). However the mechanisms through which CRF regulates VTA function to promote cocaine use are not fully understood. Here we examined the role of GABAergic neurotransmission in the VTA mediated by GABA-A or GABA-B receptors in the reinstatement of extinguished cocaine seeking by a stressor, uncontrollable intermittent footshock, or bilateral intra-VTA administration of CRF. Rats underwent repeated daily cocaine self-administration (1.0 mg/kg/ing; 14 × 6 h/day) and extinction and were tested for reinstatement in response to footshock (0.5 mA, 0.5" duration, average every 40 s; range 10-70 s) or intra-VTA CRF delivery (500 ng/side) following intra-VTA pretreatment with the GABA-A antagonist, bicuculline, the GABA-B antagonist, 2-hydroxysaclofen or vehicle. Intra-VTA bicuculline (1, 10 or 20 ng/side) failed to block footshock- or CRF-induced cocaine seeking at either dose tested. By contrast, 2-hydroxysaclofen (0.2 or 2 μg/side) prevented reinstatement by both footshock and intra-VTA CRF at a concentration that failed to attenuate food-reinforced lever pressing (45 mg sucrose-sweetened pellets; FR4 schedule) in a separate group of rats. These data suggest that GABA-B receptor-dependent CRF actions in the VTA mediate stress-induced cocaine seeking and that GABA-B receptor antagonists may have utility for the management of stress-induced relapse in cocaine addicts. Copyright © 2015 Elsevier Ltd. All rights reserved.

Systematic Analysis of γ-Aminobutyric Acid (GABA) Metabolism and Function in the Social Amoeba Dictyostelium discoideum*

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Wu, Yuantai; Janetopoulos, Chris

2013-01-01

While GABA has been suggested to regulate spore encapsulation in the social amoeba Dictyostelium discoideum, the metabolic profile and other potential functions of GABA during development remain unclear. In this study, we investigated the homeostasis of GABA metabolism by disrupting genes related to GABA metabolism and signaling. Extracellular levels of GABA are tightly regulated during early development, and GABA is generated by the glutamate decarboxylase, GadB, during growth and in early development. However, overexpression of the prespore-specific homologue, GadA, in the presence of GadB reduces production of extracellular GABA. Perturbation of extracellular GABA levels delays the process of aggregation. Cytosolic GABA is degraded by the GABA transaminase, GabT, in the mitochondria. Disruption of a putative vesicular GABA transporter (vGAT) homologue DdvGAT reduces secreted GABA. We identified the GABAB receptor-like family member GrlB as the major GABA receptor during early development, and either disruption or overexpression of GrlB delays aggregation. This delay is likely the result of an abolished pre-starvation response and late expression of several “early” developmental genes. Distinct genes are employed for GABA generation during sporulation. During sporulation, GadA alone is required for generating GABA and DdvGAT is likely responsible for GABA secretion. GrlE but not GrlB is the GABA receptor during late development. PMID:23548898

Pharmacological approaches to the study of CHOLINO- and GABA-receptor states in nerve cells after irradiation with low intensity

International Nuclear Information System (INIS)

Anan'eva, T.V.; Dvoretskij, A.I.

2000-01-01

The peculiarities of functioning specific cholino- and GABA-receptors (ChR and GABA-R) by modeling the effect of synaptic neuromediators, correspondingly acetocholine (ACh) and gamma-aminobutyric acid (GABA), in low concentrations on the K + active transport in the rats cerebral cortex after single-time or chronical total irradiation with the dose of 0.25 Gy are studied. As a result of the study of both the acetocholine (10 -10 and 10 -6 mole/l) and gamma-aminobutyric avid (10 -9 and 10 -5 mole/l) effects on the K + active transport in the rats cerebral cortex slices in presence of any selective antagonists of the choline- and GABA-receptors, it is shown, that after the whole body irradiation with 25 c Gy (1.75 m Gy/min) the metabotropic muscarinic ChR and GABA B - receptors were involved into the processes of neurotransmitter modulation, whereas under ionotropic nicotinic choline- and GAB A - receptors. The observed changes are supposed to be of adaptive character. The post irradiation structural and functional disturbances may be considered as one of the causes of essential distortions in the processes of interneuronal metabolic communication in the central nerve system [ru

Effects of GABA(B) receptor agents on cocaine priming, discrete contextual cue and food induced relapses.

Science.gov (United States)

Filip, Małgorzata; Frankowska, Małgorzata

2007-10-01

In the present study we investigated the effects of the GABA(B) receptor antagonist (2S)-(+)-5,5-dimethyl-2-morpholineacetic acid (SCH 50911), the agonists baclofen and 3-aminopropyl(methyl)phosphinic acid (SKF 97541), and the allosteric positive modulator 3,5-bis(1,1-dimethylethyl)-4-hydroxy-beta,beta-dimethylbenzenepropanol (CGP 7930) on cocaine seeking behavior. The effects of the above drugs on the reinstatement of responding induced by natural reinforcer (food) were also studied. Male Wistar rats were trained to self-administer either cocaine (0.5 mg/kg/infusion) or food (sweet milk) and responding on the reinforcer-paired lever was extinguished. Reinstatement of responding was induced by a noncontingent presentation of the self-administered reinforcer (10 mg/kg cocaine, i.p.), a discrete contextual cue, or a contingent presentation of food. SCH 50911 (3-10 mg/kg) dose-dependently attenuated responding on the previously cocaine-paired lever during both reinstatement conditions, with slightly greater efficacy at reducing conditioned cue reinstatement. At the same time, it failed to alter reinstatement of food-seeking behavior. Baclofen (1.25-5 mg/kg) and SKF 97541 (0.03-0.3 mg/kg) attenuated cocaine- or food-seeking behavior; the effect of the drug appeared more effective for cocaine-seeking than food-seeking. CGP 7930 (10-30 mg/kg) reduced cocaine seeking without affecting food-induced reinstatement on reward seeking. Our results indicate that tonic activation of GABA(B) receptors is required for cocaine seeking behavior in rats. Moreover, the GABA(B) receptor antagonist SCH 50911 was effective in reducing relapse to cocaine at doses that failed to alter reinstatement of food-seeking behavior (present study), basal locomotor activity, cocaine and food self-administration (Filip et al., submitted for publication), suggesting its selective effects on motivated drug-seeking behavior. The potent inhibitory responses on cocaine seeking behavior were also seen

GABA_A receptor function is regulated by lipid bilayer elasticity

DEFF Research Database (Denmark)

Søgaard, Rikke; Werge, Thomas; Berthelsen, Camilla

2006-01-01

( s) underlying these effects are poorly understood. DHA and Triton X-100, at concentrations that affect GABAA receptor function, increase the elasticity of lipid bilayers measured as decreased bilayer stiffness using gramicidin channels as molecular force transducers. We have previously shown...... reduced the peak amplitude of the GABA-induced currents and increased the rate of receptor desensitization. The effects of the amphiphiles did not correlate with the expected changes in monolayer spontaneous curvature. We conclude that GABAA receptor function is regulated by lipid bilayer elasticity....... PUFAs may generally regulate membrane protein function by affecting the elasticity of the host lipid bilayer....

Hap1 and GABA: thinking about food intake.

Science.gov (United States)

Woods, Stephen C; Seeley, Randy J

2006-06-01

GABA stimulation of hypothalamic GABAA receptors increases food intake and body weight. Huntingtin-associated protein-1 (Hap1), is highly expressed in the hypothalamus and increases activity at GABAA receptors; mice lacking Hap1 are hypophagic. A recent paper (Sheng et al.,2006) further explores the role of Hap1 in the control of food intake.

Glutamate Receptors GluR1 and GluR4 in the Hamster Superior Colliculus: Distribution and Co-localization with Calcium-Binding Proteins and GABA

International Nuclear Information System (INIS)

Choi, Jae-Sik; Lee, Jea-Young; Jeon, Chang-Jin

2009-01-01

We investigated the distributions of AMPA glutamate receptor subtypes GluR1 and GluR4 in the hamster superior colliculus (SC) with antibody immunocytochemistry and the effect of enucleation on these distributions. We compared these labelings to those of GluR2/3 in our previous report (Park et al., 2004, Neurosci Res., 49:139–155) and calcium-binding proteins calbindin D28K, calretinin, parvalbumin, and GABA. Anti-GluR1-immunoreactive (IR) cells were scattered throughout the SC. By contrast, anti-GluR4-IR cells formed distinct clusters within the lower lateral stratum griseum intermediale (SGI) and lateral stratum album intermediale (SAI). The GluR1- and GluR4-IR neurons varied in size and morphology. The average diameter of the GluR1-IR cells was 13.00 µm, while the GluR4-IR cells was 20.00 µm. The large majority of IR neurons were round or oval cells, but they also included stellate, vertical fusiform and horizontal cells. Monocular enucleation appeared to have no effect on the GluR1 and GluR4 immunoreactivity. Some GluR1-IR cells expressed calbindin D28K (9.50%), calretinin (6.59%), parvalbumin (2.53%), and GABA (20.54%). By contrast, no GluR4-IR cells expressed calcium-binding proteins or GABA. Although the function of the AMPA receptor subunits in SC is not yet clear, the distinct segregation of the GluR subunits, its differential colocalization with calcium-binding proteins and GABA, and differential responses to enucleation suggest the functional diversity of the receptor subunits in visuo-motor integration in the SC

Viral Vector Mediated Over-Expression of Estrogen Receptor–α in Striatum Enhances the Estradiol-induced Motor Activity in Female Rats and Estradiol Modulated GABA Release

Science.gov (United States)

Schultz, Kristin N.; von Esenwein, Silke A.; Hu, Ming; Bennett, Amy L.; Kennedy, Robert T.; Musatov, Sergei; Toran-Allerand, C. Dominique; Kaplitt, Michael G.; Young, Larry J.; Becker, Jill B.

2009-01-01

Classical estrogen receptor signaling mechanisms involve estradiol binding to intracellular nuclear receptors (estrogen receptor-α (ERα) and estrogen receptor-β (ERβ)) to promote changes in protein expression. Estradiol can also exert effects within seconds to minutes, however, a timescale incongruent with genomic signaling. In the brain, estradiol rapidly potentiates stimulated dopamine release in the striatum of female rats and enhances spontaneous rotational behavior. Furthermore, estradiol rapidly attenuates the K+- evoked increase of GABA in dialysate. We hypothesize that these rapid effects of estradiol in the striatum are mediated by ERα located on the membrane of medium spiny GABAergic neurons. This experiment examined whether over-expression of ERα in the striatum would enhance the effect of estradiol on rotational behavior and the K+- evoked increase in GABA in dialysate. Ovariectomized female rats were tested for rotational behavior or underwent microdialysis experiments after unilateral intrastriatal injections of a recombinant adeno-associated virus (AAV) containing the human ERα cDNA (AAV.ERα) into the striatum; controls received either the same vector into areas outside the striatum or an AAV containing the human alkaline phosphatase gene into the striatum (AAV.ALP). Animals that received AAV.ERα in the striatum exhibited significantly greater estradiol-induced contralateral rotations compared to controls and exhibited behavioral sensitization of contralateral rotations induced by a low dose of amphetamine. ERα over-expression also enhanced the inhibitory effect of estradiol on K+- evoked GABA release suggesting that disinhibition of dopamine release from terminals in the striatum resulted in the enhanced rotational behavior. PMID:19211896

Synchronization by food access modifies the daily variations in expression and activity of liver GABA transaminase.

Science.gov (United States)

De Ita-Pérez, Dalia; Méndez, Isabel; Vázquez-Martínez, Olivia; Villalobos-Leal, Mónica; Díaz-Muñoz, Mauricio

2014-01-01

Daytime restricted feeding (DRF) is an experimental protocol that influences the circadian timing system and underlies the expression of a biological clock known as the food entrained oscillator (FEO). Liver is the organ that reacts most rapidly to food restriction by adjusting the functional relationship between the molecular circadian clock and the metabolic networks. γ-Aminobutyric acid (GABA) is a signaling molecule in the liver, and able to modulate the cell cycle and apoptosis. This study was aimed at characterizing the expression and activity of the mostly mitochondrial enzyme GABA transaminase (GABA-T) during DRF/FEO expression. We found that DRF promotes a sustained increase of GABA-T in the liver homogenate and mitochondrial fraction throughout the entire day-night cycle. The higher amount of GABA-T promoted by DRF was not associated to changes in GABA-T mRNA or GABA-T activity. The GABA-T activity in the mitochondrial fraction even tended to decrease during the light period. We concluded that DRF influences the daily variations of GABA-T mRNA levels, stability, and catalytic activity of GABA-T. These data suggest that the liver GABAergic system responds to a metabolic challenge such as DRF and the concomitant appearance of the FEO.

Synchronization by Food Access Modifies the Daily Variations in Expression and Activity of Liver GABA Transaminase

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Dalia De Ita-Pérez

2014-01-01

Full Text Available Daytime restricted feeding (DRF is an experimental protocol that influences the circadian timing system and underlies the expression of a biological clock known as the food entrained oscillator (FEO. Liver is the organ that reacts most rapidly to food restriction by adjusting the functional relationship between the molecular circadian clock and the metabolic networks. γ-Aminobutyric acid (GABA is a signaling molecule in the liver, and able to modulate the cell cycle and apoptosis. This study was aimed at characterizing the expression and activity of the mostly mitochondrial enzyme GABA transaminase (GABA-T during DRF/FEO expression. We found that DRF promotes a sustained increase of GABA-T in the liver homogenate and mitochondrial fraction throughout the entire day-night cycle. The higher amount of GABA-T promoted by DRF was not associated to changes in GABA-T mRNA or GABA-T activity. The GABA-T activity in the mitochondrial fraction even tended to decrease during the light period. We concluded that DRF influences the daily variations of GABA-T mRNA levels, stability, and catalytic activity of GABA-T. These data suggest that the liver GABAergic system responds to a metabolic challenge such as DRF and the concomitant appearance of the FEO.

Verification of γ-Amino-Butyric Acid (GABA) Signaling System Components in Periodontal Ligament Cells In Vivo and In Vitro.

Science.gov (United States)

Konermann, Anna; Kantarci, Alpdogan; Wilbert, Steven; Van Dyke, Thomas; Jäger, Andreas

2016-11-01

CNS key neurotransmitter γ-amino-butyric acid (GABA) and its signaling components are likewise detectable in non-neuronal tissues displaying inter alia immunomodulatory functions. This study aimed at identifying potential glutamate decarboxylase (GAD)65 and GABA receptor expression in periodontal ligament (PDL) cells in vivo and in vitro, with particular regard to inflammation and mechanical loading. Gene expression was analyzed in human PDL cells at rest or in response to IL-1ß (5 ng/ml) or TNFα (5 ng/ml) challenge via qRT-PCR. Western blot determined constitutive receptor expression, and confocal laser scanning fluorescence microscopy visualized expression changes induced by inflammation. ELISA quantified GAD65 release. Immunocytochemistry was performed for GABA component detection in vitro on mechanically loaded PDL cells, and in vivo on rat upper jaw biopsies with mechanically induced root resorptions. Statistical significance was set at p GABA B1 , GABA B2 , GABA A1 , and GABA A3 were ubiquitously expressed both on gene and protein level. GABA A2 and GAD65 were undetectable in resting cells, but induced by inflammation. GABA B1 exhibited the highest basal gene expression (6.97 % ± 0.16). IL-1ß markedly increased GABA B2 on a transcriptional (57.28-fold ± 12.40) and protein level seen via fluorescence microscopy. TNFα-stimulated PDL cells released GAD65 (3.68 pg/ml ± 0.17 after 24 h, 5.77 pg/ml ± 0.65 after 48 h). Immunocytochemistry revealed GAD65 expression in mechanically loaded PDL cells. In vivo, GABA components were varyingly expressed in an inflammatory periodontal environment. PDL cells differentially express GABA signaling components and secrete GAD65. Inflammation and mechanical loading regulate these neurotransmitter molecules, which are also detectable in vivo and are potentially involved in periodontal pathophysiology.

Ionotropic Glutamate Receptor GluR1 in the Visual Cortex of Hamster: Distribution and Co-Localization with Calcium-Binding Proteins and GABA

International Nuclear Information System (INIS)

Ye, Eun-Ah; Kim, Tae-Jin; Choi, Jae-Sik; Jin, Mi-Joo; Jeon, Young-Ki; Kim, Moon-Sook; Jeon, Chang-Jin

2006-01-01

The subunit composition of the AMPA receptor is critical to its function. AMPA receptors that display very low calcium permeability include the GluR2 subunit, while AMPA receptors that contain other subunits, such as GluR1, display high calcium permeability. We have studied the distribution and morphology of neurons containing GluR1 in the hamster visual cortex with antibody immunocytochemistry. We compared this labeling to that for calbindin D28K, parvalbumin, and GABA. Anti-GluR1-immunoreactive (IR) neurons were located in all layers. The highest density of GluR1-IR neurons was found in layers II/III. The labeled neurons were non-pyramidal neurons, but were varied in morphology. The majority of the labeled neurons were round or oval cells. However, stellate, vertical fusiform, pyriform, and horizontal neurons were also labeled with the anti-GluR1 antibody. Two-color immunofluorescence revealed that many of the GluR1-IR neurons in the hamster visual cortex were double-labeled with either calbindin D28K (31.50%), or parvalbumin (22.91%), or GABA (63.89%). These results indicate that neurons in the hamster visual cortex express GluR1 differently according to different layers and selective cell types, and that many of the GluR1-IR neurons are limited to neurons that express calbindin D28K, parvalbumin, or GABA. The present study elucidates the neurochemical structure of GluR1, a useful clue in understanding the differential vulnerability of GluR1-containing neurons with regard to calcium-dependent excitotoxic mechanisms

Early continuous white noise exposure alters auditory spatial sensitivity and expression of GAD65 and GABAA receptor subunits in rat auditory cortex.

Science.gov (United States)

Xu, Jinghong; Yu, Liping; Cai, Rui; Zhang, Jiping; Sun, Xinde

2010-04-01

Sensory experiences have important roles in the functional development of the mammalian auditory cortex. Here, we show how early continuous noise rearing influences spatial sensitivity in the rat primary auditory cortex (A1) and its underlying mechanisms. By rearing infant rat pups under conditions of continuous, moderate level white noise, we found that noise rearing markedly attenuated the spatial sensitivity of A1 neurons. Compared with rats reared under normal conditions, spike counts of A1 neurons were more poorly modulated by changes in stimulus location, and their preferred locations were distributed over a larger area. We further show that early continuous noise rearing induced significant decreases in glutamic acid decarboxylase 65 and gamma-aminobutyric acid (GABA)(A) receptor alpha1 subunit expression, and an increase in GABA(A) receptor alpha3 expression, which indicates a returned to the juvenile form of GABA(A) receptor, with no effect on the expression of N-methyl-D-aspartate receptors. These observations indicate that noise rearing has powerful adverse effects on the maturation of cortical GABAergic inhibition, which might be responsible for the reduced spatial sensitivity.

GABA(A)-benzodiazepine receptor complex sensitivity in 5-HT(1A) receptor knockout mice on a 129/Sv background.

NARCIS (Netherlands)

Pattij, T.; Groenink, L.; Oosting, R.S.; Gugten, J. van der; Maes, R.A.A.; Olivier, B.

2002-01-01

Previous studies in 5-HT(1A) receptor knockout (1AKO) mice on a mixed Swiss Websterx129/Sv (SWx129/Sv) and a pure 129/Sv genetic background suggest a differential gamma-aminobutyric acid (GABA(A))-benzodiazepine receptor complex sensitivity in both strains, independent from the anxious phenotype. To

CB1 cannabinoid receptor expression in the striatum: Association with corticostriatal circuits and developmental regulation

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Vincent eVan Waes

2012-03-01

Full Text Available Corticostriatal circuits mediate various aspects of goal-directed behavior and are critically important for basal ganglia-related disorders. Activity in these circuits is regulated by the endocannabinoid system via stimulation of CB1 cannabinoid receptors. CB1 receptors are highly expressed in projection neurons and select interneurons of the striatum, but expression levels vary considerably between different striatal regions (functional domains. We investigated CB1 receptor expression within specific corticostriatal circuits by mapping CB1 mRNA levels in striatal sectors defined by their cortical inputs in rats. We also assessed changes in CB1 expression in the striatum during development. Our results show that CB1 expression is highest in juveniles (P25 and then progressively decreases towards adolescent (P40 and adult (P70 levels. At every age, CB1 receptors are predominantly expressed in sensorimotor striatal sectors, with considerably lower expression in associative and limbic sectors. Moreover, for most corticostriatal circuits there is an inverse relationship between cortical and striatal expression levels. Thus, striatal sectors with high CB1 expression (sensorimotor sectors tend to receive inputs from cortical areas with low expression, while striatal sectors with low expression (associative/limbic sectors receive inputs from cortical regions with higher expression (medial prefrontal cortex. In so far as CB1 mRNA levels reflect receptor function, our findings suggest differential CB1 signaling between different developmental stages and between sensorimotor and associative/limbic circuits. The regional distribution of CB1 receptor expression in the striatum further suggests that, in sensorimotor sectors, CB1 receptors mostly regulate GABA inputs from local axon collaterals of projection neurons, whereas in associative/limbic sectors, CB1 regulation of GABA inputs from interneurons and glutamate inputs may be more important.

Histamine H3 receptor activation selectively inhibits dopamine D1 receptor-dependent [3H]GABA release from depolarization-stimulated slices of rat substantia nigra pars reticulata

International Nuclear Information System (INIS)

Aceves, J.; Young, J.M.; Arias-Montano, J.A.; Floran, B.; Garcia, M.

1997-01-01

The release of [ 3 H]GABA from slices of rat substantia nigra pars reticulata induced by increasing extracellular K + from 6 to 15 mM in the presence of 10 μM sulpiride was inhibited by 73±3% by 1 μM SCH 23390, consistent with a large component of release dependent upon D 1 receptor activation. The histamine H 3 receptor-selective agonist immepip (1 μM) and the non-selective agonist histamine (100 μM) inhibited [ 3 H]GABA release by 78±2 and 80±2%, respectively. The inhibition by both agonists was reversed by the H 3 receptor antagonist thioperamide (1 μM). However, in the presence of 1 μM SCH 23390 depolarization-induced release of [ 3 H]GABA was not significantly decreased by 1 μM immepip. In rats depleted of dopamine by pretreatment with reserpine, immepip no longer inhibited control release of [ 3 H]GABA, but in the presence of 1 μM SKF 38393, which produced a 7±1-fold stimulation of release, immepip reduced the release to a level not statistically different from that in the presence of immepip alone. Immepip (1 μM) also inhibited the depolarization-induced release of [ 3 H]dopamine from substantia nigra pars reticulata slices, by 38±3%.The evidence is consistent with the proposition that activation of histamine H 3 receptors leads to the selective inhibition of the component of depolarization-induced [ 3 H]GABA release in substantia nigra pars reticulata slices which is dependent upon D 1 receptor activation. This appears to be largely an action at the terminals of the striatonigral GABA projection neurons, which may be enhanced by a partial inhibition of dendritic [ 3 H]dopamine release. (Copyright (c) 1997 Elsevier Science B.V., Amsterdam. All rights reserved.)

Molecular determinants of desensitization and assembly of the chimeric GABA(A) receptor subunits (alpha1/gamma2) and (gamma2/alpha1) in combinations with beta2 and gamma2

DEFF Research Database (Denmark)

Elster, L; Kristiansen, U; Pickering, D S

2001-01-01

Two gamma-aminobutyric acid(A) (GABA(A)) receptor chimeras were designed in order to elucidate the structural requirements for GABA(A) receptor desensitization and assembly. The (alpha1/gamma2) and (gamma2/alpha1) chimeric subunits representing the extracellular N-terminal domain of alpha1 or gamma......, as opposed to the staining of the (gamma2/alpha1)-containing receptors, which was only slightly higher than background. To explain this, the (alpha1/gamma2) and (gamma2/alpha1) chimeras may act like alpha1 and gamma2 subunits, respectively, indicating that the extracellular N-terminal segment is important...... for assembly. However, the (alpha1/gamma2) chimeric subunit had characteristics different from the alpha1 subunit, since the (alpha1/gamma2) chimera gave rise to no desensitization after GABA stimulation in whole-cell patch-clamp recordings, which was independent of whether the chimera was expressed...

Evaluation of GABA Receptors of Ventral Tegmental Area in Cardiovascular Responses in Rat

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Minoo Rasoulpanah

2015-07-01

Full Text Available Background: The ventral tegmental area (VTA is well known for its role in cardiovascular control. It is demonstrated that about 20-30% of the VTA neurons are GABAergic though their role in cardiovascular control is not yet understood. This study is carried out to find the effects of GABA A and GABA B receptors on cardiovascular response of the VTA. Methods: Experiments were performed on urethane anesthetized male Wistar rats. Drugs were microinjected unilaterally into the VTA. The average changes in mean arterial pressure (MAP and heart rate (HR were compared between the case and the control groups using t test and with the pre-injection values using paired t test. Results: Microinjection of muscimol, a GABAA agonist (500, 1500 and 2500 pmol/100nl into the VTA had no significant effect on MAP and HR compared with the saline group and pre-injection values. Injection of bicuculline methiodide (BMI, 100 and 200 pmol/100 nl, a GABAA antagonist, caused a significant increase in the MAP (11.1±1.95mmHg, P<0.5 and a decrease in HR (-32.07±10.2, P<0.01. Microinjection of baclofen a GABAB receptor agonist (500 or 1000 pmole/100 nl and phaclofen a GABAB receptor antagonist (500 or 1000 pmole/100 nl had no significant effects on MAP and HR. Conclusion: For the first time it was demonstrated that GABA system of the VTA inhibits the cardiovascular system through the activation of GABAA but not the GABAB receptors.

The effect of heart-and kidney-Benefiting Chinese Herbal Medicine on the function of cholinergic M-and Gamma amino-butyric acid (GABA) receptor in brain tissues of analogue dementia rats

International Nuclear Information System (INIS)

Mo Qizhong; Gong Bin; Fang Jun

1993-01-01

3 H-QNB and 3 H-GABA were used as radioactive ligand for M-and GABA receptors respectively. M-and GABA receptors were assayed by radioligand binding assay (RBA) in cerebral cortex, hippocampus and cerebellum of analogue dementia rats. It was found that R t of M receptor was decreased in cerebral cortex and hippocampus and R t of GABA receptor was decreased in cerebellum of analogue dementia rats. The dissociation constant (K D ) of M-receptor was decreased significantly in cerebral cortex and K D value of (GABA) receptor was decreased in cerebellum of analogue dementia rats. The decreased R t of M-and GABA receptor in brain tissue of analogue dementia rats was raised by Heart- and Kidney-Benefiting Chinese Herbs as well as hydergin

Basolateral amygdala GABA-A receptors mediate stress-induced memory retrieval impairment in rats.

Science.gov (United States)

Sardari, Maryam; Rezayof, Ameneh; Khodagholi, Fariba; Zarrindast, Mohammad-Reza

2014-04-01

The present study was designed to investigate the involvement of GABA-A receptors of the basolateral amygdala (BLA) in the impairing effect of acute stress on memory retrieval. The BLAs of adult male Wistar rats were bilaterally cannulated and memory retrieval was measured in a step-through type passive avoidance apparatus. Acute stress was evoked by placing the animals on an elevated platform for 10, 20 and 30 min. The results indicated that exposure to 20 and 30 min stress, but not 10 min, before memory retrieval testing (pre-test exposure to stress) decreased the step-through latency, indicating stress-induced memory retrieval impairment. Intra-BLA microinjection of a GABA-A receptor agonist, muscimol (0.005-0.02 μg/rat), 5 min before exposure to an ineffective stress (10 min exposure to stress) induced memory retrieval impairment. It is important to note that pre-test intra-BLA microinjection of the same doses of muscimol had no effect on memory retrieval in the rats unexposed to 10 min stress. The blockade of GABA-A receptors of the BLA by injecting an antagonist, bicuculline (0.4-0.5 μg/rat), 5 min before 20 min exposure to stress, prevented stress-induced memory retrieval. Pre-test intra-BLA microinjection of the same doses of bicuculline (0.4-0.5 μg/rat) in rats unexposed to 20 min stress had no effect on memory retrieval. In addition, pre-treatment with bicuculline (0.1-0.4 μg/rat, intra-BLA) reversed muscimol (0.02 μg/rat, intra-BLA)-induced potentiation on the effect of stress in passive avoidance learning. It can be concluded that pre-test exposure to stress can induce memory retrieval impairment and the BLA GABA-A receptors may be involved in stress-induced memory retrieval impairment.

Activation of GABA(A) receptors in the accessory olfactory bulb does not prevent the formation of an olfactory memory in mice.

Science.gov (United States)

Otsuka, T; Hashida, M; Oka, T; Kaba, H

2001-07-01

When female mice are mated, they form a memory to the pheromonal signal of their male partner. The neural mechanisms underlying this memory involve changes at the reciprocal dendrodendritic synapses between glutamatergic mitral cells and gamma-aminobutyric acid (GABA)-ergic granule cells in the accessory olfactory bulb (AOB). Blockade of GABA(A) receptors in the AOB leads to the formation of an olfactory memory. In an attempt to disrupt memory formation at mating, we used local infusions of the GABA(A) receptor agonist muscimol into the AOB during the critical period for memory formation. Muscimol across a wide range of doses (1-1000 pmol) did not prevent memory formation. The resistance of this memory to GABA(A) receptor activation may reflect the complexity of synaptic microcircuits in the AOB.

Effect of genetic and pharmacological blockade of GABA receptors on the 5-HT2C receptor function during stress.

OpenAIRE

Martin Cédric B P; Gassmann Martin; Chevarin Caroline; Hamon Michel; Rudolph Uwe; Bettler Bernhard; Lanfumey Laurence; Mongeau Raymond

2014-01-01

5-HT2C receptors play a role in psychoaffective disorders and often contribute to the antidepressant and anxiolytic effects of psychotropic drugs. During stress, activation of these receptors exerts a negative feedback on serotonin (5-HT) release, probably by increasing the activity of GABAergic interneurons. However, to date, the GABA receptor types that mediate the 5-HT2C receptor-induced feedback inhibition are still unknown. To address this question, we assessed the inhibition of 5-HT tur...

GABA and Topiramate Inhibit the Formation of Human Macrophage-Derived Foam Cells by Modulating Cholesterol-Metabolism-Associated Molecules

Directory of Open Access Journals (Sweden)

Ying Yang

2014-04-01

Full Text Available Aims: γ-aminobutyric acid (GABA, the principal inhibitory neurotransmitter, acts on GABA receptors to play an important role in the modulation of macrophage functions. The present study examined the effects of GABA and a GABA receptor agonist on modulating cholesterol-metabolism-associated molecules in human monocyte-derived macrophages (HMDMs. Methods: ORO stain, HPLC, qRT-PCR, Western blot and EMSA were carried out using HMDMs exposed to ox-LDL with or without GABAergic agents as the experimental model. Results: GABA and topiramate reduced the percentage of cholesterol ester in lipid-laden HMDMs by down-regulating SR-A, CD36 and LOX-1 expression and up-regulating ABCA1, ABCG1 and SR-BI expression in lipid-laden HMDMs. The production of TNF-a was decreased in GABA-and topiramate-treated lipid-laden HMDMs, and levels of interleukin (IL-6 did not change. The activation of two signaling pathways, p38MAPK and NF-γB, was repressed by GABA and topiramate in lipid-laden HMDMs. Conclusion: GABA and topiramate inhibit the formation of human macrophage-derived foam cells and may be a possibility for macrophage targeted therapy of atherosclerotic lesions.

The brain GABA-benzodiazepine receptor alpha-5 subtype in autism spectrum disorder: a pilot [(11)C]Ro15-4513 positron emission tomography study.

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Mendez, Maria Andreina; Horder, Jamie; Myers, Jim; Coghlan, Suzanne; Stokes, Paul; Erritzoe, David; Howes, Oliver; Lingford-Hughes, Anne; Murphy, Declan; Nutt, David

2013-05-01

GABA (gamma-amino-butyric-acid) is the primary inhibitory neurotransmitter in the human brain. It has been proposed that the symptoms of autism spectrum disorders (ASDs) are the result of deficient GABA neurotransmission, possibly including reduced expression of GABAA receptors. However, this hypothesis has not been directly tested in living adults with ASD. In this preliminary investigation, we used Positron Emission Tomography (PET) with the benzodiazepine receptor PET ligand [(11)C]Ro15-4513 to measure α1 and α5 subtypes of the GABAA receptor levels in the brain of three adult males with well-characterized high-functioning ASD compared with three healthy matched volunteers. We found significantly lower [(11)C]Ro15-4513 binding throughout the brain of participants with ASD (p < 0.0001) compared with controls. Planned region of interest analyses also revealed significant reductions in two limbic brain regions, namely the amygdala and nucleus accumbens bilaterally. Further analysis suggested that these results were driven by lower levels of the GABAA α5 subtype. These results provide initial evidence of a GABAA α5 deficit in ASD and support further investigations of the GABA system in this disorder. This article is part of the Special Issue entitled 'Neurodevelopmental Disorders'. Copyright © 2012 Elsevier Ltd. All rights reserved.

Altered organization of GABAA receptor mRNA expression in the depressed suicide brain

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Michael O Poulter

2010-03-01

Full Text Available Inter-relationships ordinarily exist between mRNA expression of GABA-A subunits in the frontopolar cortex (FPC of individuals that had died suddenly from causes other than suicide. However, these correlations were largely absent in persons that had died by suicide. In the present investigation, these findings were extended by examining GABA-A receptor expression patterns (of controls and depressed individuals that died by suicide in the orbital frontal cortex (OFC, hippocampus, amygdala. locus coeruleus (LC,and paraventricular nucleus (PVN, all of which have been implicated in either depression, anxiety or stress responsivity. Results Using QPCR analysis, we found that in controls the inter-relations between GABA-A subunits varied across brain regions, being high in the hippocampus and amygdala, intermediate in the LC, and low in the OFC and PVN. The GABA-A subunit inter-relations were markedly different in persons that died by suicide, being reduced in hippocampus and amygdala, stable in the LC, but more coordinated in the OFC and to some extent in the PVN. Conclusions It seems that altered brain region-specific inhibitory signaling, stemming from altered GABA-A subunit coordination, are associated with depression/suicide. Although, it is unknown whether GABA-A subunit re-organization was specifically tied to depression, suicide, or the accompanying distress, these data show that the co-ordinate expression of this transcriptome does vary depending on brain region and is plastic.

Contribution of ventral tegmental GABA receptors to cocaine self-administration in rats.

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Backes, E N; Hemby, S E

2008-03-01

Recent evidence has suggested that compounds affecting GABAergic transmission may provide useful pharmacological tools for the treatment of cocaine addiction. Using a rat model of self-administration, the present study examined the effects of GABA agonists and antagonists injected directly into the ventral tegmental area (VTA) on cocaine intake in rats trained to self-administer cocaine (0, 125, 250 and 500 microg/infusion) under an FR5 schedule of reinforcement. Separate groups of rats received bilateral intra-VTA injections of the GABA-A antagonist picrotoxin (34 ng/side, n = 7; 68 ng/side, n = 8), GABA-A agonist muscimol (14 ng/side, n = 8), GABA-B agonist baclofen (56 ng/side, n = 7; 100 ng/side, n = 6), picrotoxin (68 ng/side) co-injected with the GABA-B antagonist 2-hydroxysaclofen (100 ng/side, n = 7; 2 microg/side, n = 8) or artificial cerebrospinal fluid (aCSF, n = 6) to assess the effects of the various compounds on the cocaine self-administration dose-response curve. Both picrotoxin and baclofen reduced responding maintained by cocaine, whereas muscimol had no effect on responding. In contrast, neither picrotoxin (n = 6) nor baclofen (n = 8) affected responding maintained by food. Interestingly, 2-hydroxysaclofen effectively blocked the suppression of responding produced by picrotoxin, suggesting that both picrotoxin and baclofen exert their effects via activation of GABA-B receptors. Additionally, these effects appear to be specific to cocaine reinforcement, supporting current investigation of baclofen as a treatment for cocaine addiction.

GABA(A receptor-mediated acceleration of aging-associated memory decline in APP/PS1 mice and its pharmacological treatment by picrotoxin.

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Yuji Yoshiike

Full Text Available Advanced age and mutations in the genes encoding amyloid precursor protein (APP and presenilin (PS1 are two serious risk factors for Alzheimer's disease (AD. Finding common pathogenic changes originating from these risks may lead to a new therapeutic strategy. We observed a decline in memory performance and reduction in hippocampal long-term potentiation (LTP in both mature adult (9-15 months transgenic APP/PS1 mice and old (19-25 months non-transgenic (nonTg mice. By contrast, in the presence of bicuculline, a GABA(A receptor antagonist, LTP in adult APP/PS1 mice and old nonTg mice was larger than that in adult nonTg mice. The increased LTP levels in bicuculline-treated slices suggested that GABA(A receptor-mediated inhibition in adult APP/PS1 and old nonTg mice was upregulated. Assuming that enhanced inhibition of LTP mediates memory decline in APP/PS1 mice, we rescued memory deficits in adult APP/PS1 mice by treating them with another GABA(A receptor antagonist, picrotoxin (PTX, at a non-epileptic dose for 10 days. Among the saline vehicle-treated groups, substantially higher levels of synaptic proteins such as GABA(A receptor alpha1 subunit, PSD95, and NR2B were observed in APP/PS1 mice than in nonTg control mice. This difference was insignificant among PTX-treated groups, suggesting that memory decline in APP/PS1 mice may result from changes in synaptic protein levels through homeostatic mechanisms. Several independent studies reported previously in aged rodents both an increased level of GABA(A receptor alpha1 subunit and improvement of cognitive functions by long term GABA(A receptor antagonist treatment. Therefore, reduced LTP linked to enhanced GABA(A receptor-mediated inhibition may be triggered by aging and may be accelerated by familial AD-linked gene products like Abeta and mutant PS1, leading to cognitive decline that is pharmacologically treatable at least at this stage of disease progression in mice.

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

In the adult neurogenic subventricular zone (SVZ), the behavior of astrocyte-like cells and some of their functions depend on changes in intracellular Ca(2+) levels and tonic GABA(A) receptor activation. However, it is unknown whether, and if so how, GABA(A) receptor activity regulates...... intracellular Ca(2+) dynamics in SVZ astrocytes. To monitor Ca(2+) activity selectively in astrocyte-like cells, we used two lines of transgenic mice expressing either GFP fused to a Gq-coupled receptor or DsRed under the human glial fibrillary acidic protein (hGFAP) promoter. GABA(A) receptor activation...... 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...

The effect of heart-and kidney-Benefiting Chinese Herbal Medicine on the function of cholinergic M-and Gamma amino-butyric acid (GABA) receptor in brain tissues of analogue dementia rats

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Qizhong, Mo; Bin, Gong; Jun, Fang [Shanghai College of TCM, Shanghai (China); and others

1993-05-01

[sup 3]H-QNB and [sup 3]H-GABA were used as radioactive ligand for M-and GABA receptors respectively. M-and GABA receptors were assayed by radioligand binding assay (RBA) in cerebral cortex, hippocampus and cerebellum of analogue dementia rats. It was found that R[sub t] of M receptor was decreased in cerebral cortex and hippocampus and R[sub t] of GABA receptor was decreased in cerebellum of analogue dementia rats. The dissociation constant (K[sub D]) of M-receptor was decreased significantly in cerebral cortex and K[sub D] value of (GABA) receptor was decreased in cerebellum of analogue dementia rats. The decreased R[sub t] of M-and GABA receptor in brain tissue of analogue dementia rats was raised by Heart- and Kidney-Benefiting Chinese Herbs as well as hydergin.

Modulation of acetylcholine release from rat striatal slices by the GABA/benzodiazepine receptor complex

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Supavilai, P.; Karobath, M.

1985-02-04

GABA, THIP and muscimol enhance spontaneous and inhibit electrically induced release of tritium labelled compounds from rat striatal slices which have been pre-labelled with /sup 3/H-choline. Baclofen is inactive in this model. Muscimol can inhibit electrically induced release of tritiated material by approximately 75% with half maximal effects at 2 ..mu..M. The response to muscimol can be blocked by the GABA antagonists bicuculline methobromide, picrotoxin, anisatin, R 5135 and CPTBO (cyclopentylbicyclophosphate). Drugs which act on the benzodiazepine receptor (BR) require the presence of muscimol to be effective and they modulate the effects of muscimol in a bidirectional manner. Thus BR agonists enhance and inverse BR agonists attenuate the inhibitory effects of muscimol on electrically induced release. Ro15-1788, a BR antagonist, does not modulate the inhibitory effects of muscimol but antagonizes the actions of clonazepam, a BR agonist, and of DMCM, an inverse BR agonist. These results demonstrate that a GABA/benzodiazepine receptor complex can modulate acetylcholine release from rat striatal slices in vitro. 24 references, 3 figures, 5 table.

Block of GABA(A) receptor ion channel by penicillin: electrophysiological and modeling insights toward the mechanism.

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Rossokhin, Alexey V; Sharonova, Irina N; Bukanova, Julia V; Kolbaev, Sergey N; Skrebitsky, Vladimir G

2014-11-01

GABA(A) receptors (GABA(A)R) mainly mediate fast inhibitory neurotransmission in the central nervous system. Different classes of modulators target GABA(A)R properties. Penicillin G (PNG) belongs to the class of noncompetitive antagonists blocking the open GABA(A)R and is a prototype of β-lactam antibiotics. In this study, we combined electrophysiological and modeling approaches to investigate the peculiarities of PNG blockade of GABA-activated currents recorded from isolated rat Purkinje cells and to predict the PNG binding site. Whole-cell patch-сlamp recording and fast application system was used in the electrophysiological experiments. PNG block developed after channel activation and increased with membrane depolarization suggesting that the ligand binds within the open channel pore. PNG blocked stationary component of GABA-activated currents in a concentration-dependent manner with IC50 value of 1.12mM at -70mV. The termination of GABA and PNG co-application was followed by a transient tail current. Protection of the tail current from bicuculline block and dependence of its kinetic parameters on agonist affinity suggest that PNG acts as a sequential open channel blocker that prevents agonist dissociation while the channel remains blocked. We built the GABA(A)R models based on nAChR and GLIC structures and performed an unbiased systematic search of the PNG binding site. Monte-Carlo energy minimization was used to find the lowest energy binding modes. We have shown that PNG binds close to the intracellular vestibule. In both models the maximum contribution to the energy of ligand-receptor interactions revealed residues located on the level of 2', 6' and 9' rings formed by a bundle of M2 transmembrane segments, indicating that these residues most likely participate in PNG binding. The predicted structural models support the described mechanism of PNG block. Copyright © 2014 Elsevier Inc. All rights reserved.

Successful combination immunotherapy of anti-gamma aminobutyric acid (GABA)A receptor antibody-positive encephalitis with extensive multifocal brain lesions.

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Fukami, Yuki; Okada, Hiroaki; Yoshida, Mari; Yamaguchi, Keiji

2017-08-31

A 78-year old woman who presented with akinetic mutism was admitted to our hospital. Brain MRI showed multifocal increased T 2 /FLAIR signal with extensive cortical-subcortical involvement. We suspected autoimmune encephalitis and the patient received methylprednisolone pulse. Her conscious level gradually recovered, but later relapsed again and presented with refractory status epilepticus. We treated her with intravenous immunoglobulin, plasma exchange and pulsed cyclophosphamide, with satisfactory response. A brain biopsy showed perivascular lymphocytic infiltrates and reactive gliosis. Anti-gamma aminobutyric acid (GABA) A receptor antibodies test came back to be positive after her recovery, and the diagnosis of anti-GABA A receptor antibody-positive encephalitis was made. This is a very rare case where brain biopsies were performed in a patient with anti-GABA A receptor antibody-positive encephalitis.

Effects of gamma-aminobutyric acid (GABA) on synaptogenesis and synaptic function

DEFF Research Database (Denmark)

Belhage, B; Hansen, G H; Elster, L

1998-01-01

The correct establishment and function of synapses depend on a variety of factors, such as guidance of pre- and postsynaptic neurons as well as receptor development and localization. gamma-Aminobutyric acid (GABA) has a pronounced effect on these events and elicits differentiation of neurons......; that is, GABA acts as a trophic signal. Accordingly, activating preexisting GABA receptors, a trophic GABA signal enhances the growth rate of neuronal processes, facilitates synapse formation, and promotes synthesis of specific proteins. Transcription and de novo synthesis are initiated by the GABA signal......, but the intracellular link between GABA receptor activation and DNA transcription is largely unknown. GABA also controls the induction and development of functionally and pharmacologically different GABAA receptor subtypes. The induced receptors are likely to be inserted only into the synaptic membrane domain. However...

GABAergic Neurons in the Rat Medial Septal Complex Express Relaxin-3 Receptor (RXFP3 mRNA

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Hector Albert-Gascó

2018-01-01

Full Text Available The medial septum (MS complex modulates hippocampal function and related behaviors. Septohippocampal projections promote and control different forms of hippocampal synchronization. Specifically, GABAergic and cholinergic projections targeting the hippocampal formation from the MS provide bursting discharges to promote theta rhythm, or tonic activity to promote gamma oscillations. In turn, the MS is targeted by ascending projections from the hypothalamus and brainstem. One of these projections arises from the nucleus incertus in the pontine tegmentum, which contains GABA neurons that co-express the neuropeptide relaxin-3 (Rln3. Both stimulation of the nucleus incertus and septal infusion of Rln3 receptor agonist peptides promotes hippocampal theta rhythm. The Gi/o-protein-coupled receptor, relaxin-family peptide receptor 3 (RXFP3, is the cognate receptor for Rln3 and identification of the transmitter phenotype of neurons expressing RXFP3 in the septohippocampal system can provide further insights into the role of Rln3 transmission in the promotion of septohippocampal theta rhythm. Therefore, we used RNAscope multiplex in situ hybridization to characterize the septal neurons expressing Rxfp3 mRNA in the rat. Our results demonstrate that Rxfp3 mRNA is abundantly expressed in vesicular GABA transporter (vGAT mRNA- and parvalbumin (PV mRNA-positive GABA neurons in MS, whereas ChAT mRNA-positive acetylcholine neurons lack Rxfp3 mRNA. Approximately 75% of Rxfp3 mRNA-positive neurons expressed vGAT mRNA (and 22% were PV mRNA-positive, while the remaining 25% expressed Rxfp3 mRNA only, consistent with a potential glutamatergic phenotype. Similar proportions were observed in the posterior septum. The occurrence of RXFP3 in PV-positive GABAergic neurons gives support to a role for the Rln3-RXFP3 system in septohippocampal theta rhythm.

Alteration of glutamate/GABA balance during acute alcohol intoxication in rats: effect of Xingnaojing injection.

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Wei, Jingjing; Yao, Limei; Yang, Lei; Zhao, Wei; Shi, Si; Cai, Qingyan; Chen, Dingsheng; Li, Weirong; Wang, Qi

2015-05-26

Xingnaojing Injection (XNJI) is a modern Chinese formula came from famous Chinese medicine An Gong Niu Huang Pill. XNJI has been used for treatment of cerebral diseases and stroke in China, and is approved by the State Food and Drug Administration of China for the treatment of acute alcohol intoxication (AAI). XNJI belongs to the ethnopharmacological family of medicines. In this study, we investigated the mechanisms of the XNJI effect on AAI. To investigate the effects of XNJI on glutamate, gamma-aminobutyric acid (GABA) and related receptor in lateral hypothalamic area (LHA) of AAI rat. Adult male Sprague-Dawley rats were implanted with microdialysis probes in LHA. Rats were randomly divided into control, model, 1.36mg/kg XNJI, 0.68mg/kg XNJI and 0.34mg/kg XNJI groups. During microdialysis, baseline samples were collected from 1h to 2.5h; thereafter, the rats were given an intraperitoneal injection of 52% ethanol, 5.2g/kg, or saline for control group. Twenty minutes later, three doses of XNJI was given by unilateral injection respectively, while saline for control and model groups, and samples were collected for the next 4h. The extracellular glutamate and GABA levels were measured in the LHA by a high performance liquid chromatography coupled with fluorescence detector (HPLC-FLU). The expression levels of related receptors N-methyl-d-aspartate receptor (NR) subunit NR2A, NR2B and GABAA were analyzed by reverse transcription polymerase chain reaction (RT-PCR). Ethanol (5.2g/kg) significantly decreased the extracellular levels of glutamate and increased extracellular GABA in LHA. On the other hand ethanol significantly decreased NR2A and NR2B mRNAs expression, and increase GABAA mRNA expression. XNJI could increase the extracellular level of glutamate and decrease that of GABA; moreover, induced an increase in NR2A and NR2B mRNA expression, and a decrease in GABAA mRNA expression in LHA. The current changes in glutamate, GABA and mRNA expressions of related

Nerve Regenerative Effects of GABA-B Ligands in a Model of Neuropathic Pain

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Valerio Magnaghi

2014-01-01

Full Text Available Neuropathic pain arises as a direct consequence of a lesion or disease affecting the peripheral somatosensory system. It may be associated with allodynia and increased pain sensitivity. Few studies correlated neuropathic pain with nerve morphology and myelin proteins expression. Our aim was to test if neuropathic pain is related to nerve degeneration, speculating whether the modulation of peripheral GABA-B receptors may promote nerve regeneration and decrease neuropathic pain. We used the partial sciatic ligation- (PSL- induced neuropathic model. The biochemical, morphological, and behavioural outcomes of sciatic nerve were analysed following GABA-B ligands treatments. Simultaneous 7-days coadministration of baclofen (10 mg/kg and CGP56433 (3 mg/kg alters tactile hypersensitivity. Concomitantly, specific changes of peripheral nerve morphology, nerve structure, and myelin proteins (P0 and PMP22 expression were observed. Nerve macrophage recruitment decreased and step coordination was improved. The PSL-induced changes in nociception correlate with altered nerve morphology and myelin protein expression. Peripheral synergic effects, via GABA-B receptor activation, promote nerve regeneration and likely ameliorate neuropathic pain.

GABA and glycine as neurotransmitters: a brief history.

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Bowery, N G; Smart, T G

2006-01-01

gamma-Aminobutyric acid (GABA) emerged as a potentially important brain chemical just over 50 years ago, but its significance as a neurotransmitter was not fully realized until over 16 years later. We now know that at least 40% of inhibitory synaptic processing in the mammalian brain uses GABA. Establishing its role as a transmitter was a lengthy process and it seems hard to believe with our current knowledge that there was ever any dispute about its role in the mammalian brain. The detailed information that we now have about the receptors for GABA together with the wealth of agents which facilitate or reduce GABA receptor mechanisms make the prospects for further research very exciting. The emergence of glycine as a transmitter seems relatively painless by comparison to GABA. Perhaps this is appropriate for the simplest of transmitter structures! Its discovery within the spinal cord and brainstem approximately 40 years ago was followed only 2 years later by the proposal that it be conferred with 'neurotransmitter' status. It was another 16 years before the receptor was biochemically isolated. Now it is readily accepted as a vital spinal and supraspinal inhibitory transmitter and we know many details regarding its molecular structure and trafficking around neurones. The pharmacology of these receptors has lagged behind that of GABA. There is not the rich variety of allosteric modulators that we have come to readily associate with GABA receptors and which has provided us with a virtual treasure trove of important drugs used in anxiety, insomnia, epilepsy, anaesthesia, and spasticity, all stemming from the actions of the simple neutral amino acid GABA. Nevertheless, the realization that glycine receptors are involved in motor reflexes and nociceptive pathways together with the more recent advent of drugs that exhibit some subtype selectivity make the goal of designing selective therapeutic ligands for the glycine receptor that much closer.

3β-Methyl-Neurosteroid Analogs are Preferential Positive Allosteric Modulators and Direct Activators of Extrasynaptic δGABA-A Receptors in the Hippocampus Dentate Gyrus Subfield.

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Chuang, Shu-Hui; Reddy, Doodipala Samba

2018-03-30

Neurosteroids are powerful modulators of GABA-A receptors. Ganaxolone (3α-hydroxy-3β-methyl-5α-pregnan-20-one, GX) and synthetic analogs of the neurosteroid allopregnanolone (AP) are designed to treat epilepsy and related conditions. However, their precise mechanism of action in native neurons remains unclear. Here, we sought to determine the mode of action of GX and its analogs at GABA-A receptors in native hippocampal neurons by analyzing extrasynaptic receptor-mediated tonic currents and synaptic receptor-mediated phasic currents. Concentration-response profiles of GX were determined in two cell types: δ-containing dentate gyrus granule cells (DGGCs) and γ2-containing CA1 pyramidal cells (CA1PCs). GX produced significantly greater potentiation of the GABA-A receptor-activated chloride currents in DGGCs (500%) than CA1PCs (200%). In the absence of GABA, GX evoked 2-fold greater inward currents in DGGCs than CA1PCs, which were 2-fold greater than AP within DGGCs. In hippocampus slices, GX potentiated and directly activated tonic currents in DGGCs. These responses were significantly diminished in DGGCs from δ-subunit knockout (δKO) mice, confirming GX's selectivity for δGABA-A receptors. Like AP, GX potentiation of tonic currents was prevented by protein kinase C inhibition. Furthermore, GX's protection against hippocampus kindled seizures was significantly diminished in δKO mice. GX analogs exhibited greater potency and efficacy than GX on δGABA-A receptor-mediated tonic inhibition. In summary, these results provide strong evidence that GX and its analogs are preferential allosteric modulators and direct activators of extrasynaptic δGABA-A receptors regulating network inhibition and seizures in the dentate gyrus. Therefore, these findings provide a mechanistic rationale for the clinical use of synthetic neurosteroids in epilepsy and seizure disorders. The American Society for Pharmacology and Experimental Therapeutics.

GABAA receptor subunit expression changes in the human Alzheimer's disease hippocampus, subiculum, entorhinal cortex and superior temporal gyrus.

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Kwakowsky, Andrea; Calvo-Flores Guzmán, Beatriz; Pandya, Madhavi; Turner, Clinton; Waldvogel, Henry J; Faull, Richard L

2018-02-27

Gamma-aminobutyric acid (GABA) is the primary inhibitory neurotransmitter in the central nervous system. GABA type A receptors (GABA A Rs) are severely affected in Alzheimer's disease (AD). However, the distribution and subunit composition of GABA A Rs in the AD brain are not well understood. This is the first comprehensive study to show brain region- and cell layer-specific alterations in the expression of the GABA A R subunits α1-3, α5, β1-3 and γ2 in the human AD hippocampus, entorhinal cortex and superior temporal gyrus (STG). In late-stage AD tissue samples using immunohistochemistry we found significant alteration of all investigated GABA A Rs subunits except for α3 and β1 that were well preserved. The most prominent changes include an increase in GABA A R α1 expression associated with AD in all layers of the CA3 region, in the stratum (str.) granulare and hilus of the dentate gyrus (DG). We found a significant increase in GABA A R α2 expression in the str. oriens of the CA1-3, str. radiatum of the CA2,3 and decrease in the str. pyramidale of the CA1 region in AD cases. In AD there was a significant increase in GABA A R α5 subunit expression in str. pyramidale, str. oriens of the CA1 region and decrease in the STG. We also found a significant decrease in the GABA A R β3 subunit immunoreactivity in the str. oriens of the CA2, str. granulare and str. moleculare of the DG. In conclusion, these findings indicate that the expression of the GABA A R subunits shows brain region- and layer-specific alterations in AD, and these changes could significantly influence and alter GABA A R function in the disease. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

GABA-A Receptor Modulation and Anticonvulsant, Anxiolytic, and Antidepressant Activities of Constituents from Artemisia indica Linn

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Imran Khan

2016-01-01

Full Text Available Artemisia indica, also known as “Mugwort,” has been widely used in traditional medicines. However, few studies have investigated the effects of nonvolatile components of Artemisia indica on central nervous system’s function. Fractionation of Artemisia indica led to the isolation of carnosol, ursolic acid, and oleanolic acid which were evaluated for their effects on GABA-A receptors in electrophysiological studies in Xenopus oocytes and were subsequently investigated in mouse models of acute toxicity, convulsions (pentylenetetrazole induced seizures, depression (tail suspension and forced swim tests, and anxiety (elevated plus maze and light/dark box paradigms. Carnosol, ursolic acid, and oleanolic acid were found to be positive modulators of α1β2γ2L GABA-A receptors and the modulation was antagonized by flumazenil. Carnosol, ursolic acid, and oleanolic acid were found to be devoid of any signs of acute toxicity (50–200 mg/kg but elicited anticonvulsant, antidepressant, and anxiolytic activities. Thus carnosol, ursolic acid, and oleanolic acid demonstrated CNS activity in mouse models of anticonvulsant, antidepressant, and anxiolysis. The anxiolytic activity of all three compounds was ameliorated by flumazenil suggesting a mode of action via the benzodiazepine binding site of GABA-A receptors.

5-HT1A receptor blockade reverses GABA(A) receptor alpha(3) subunit-mediated anxiolytic effects on stress-induced hyperthermia

NARCIS (Netherlands)

Vinkers, Christiaan H.; van Oorschot, Ruud; Korte, S. Mechiel; Olivier, Berend; Groenink, Lucianne

Stress-related disorders are associated with dysfunction of both serotonergic and GABAergic pathways, and clinically effective anxiolytics act via both neurotransmitter systems. As there is evidence that the GABA(A) and the serotonin receptor system interact, a serotonergic component in the

The role of GABA-A and mitochondrial diazepam-binding inhibitor receptors on the effects of neurosteroids on food intake in mice.

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Reddy, D S; Kulkarni, S K

1998-06-01

The present studies were undertaken to investigate the neuroactive steroidal modulation of feeding behavior and possible involvement of gamma-aminobutyric acid type-A (GABA-A) and mitochondrial diazepam binding inhibitor (DBI) receptors (MDR) in food-deprived male mice. Allopregnanolone (0.5-2 mg/kg), a neurosteroid, progesterone (1-10 mg/kg), a neurosteroid precursor, and 4'-chlordiazepam (0.25-1 mg/kg), a specific high affinity MDR agonist, produced a dose-dependent hyperphagic effects. In contrast, neurosteroids pregnenolone sulfate (PS) (1-10 mg/kg) and dehydroepiandrosterone sulfate (DHEAS) (1-10 mg/kg) produced a hypophagic effect, in a dose-dependent manner. The allopregnanolone-, progesterone- and 4'-chlordiazepam-induced hyperphagic effect was blocked by picrotoxin (1 mg/kg), a GABA-A chloride channel antagonist, but not by flumazenil (2 mg/kg), a benzodiazepine (BZD) antagonist. The 4'-chlordiazepam-induced hyperphagic effect was prevented by pretreatment with PK11195 (2 mg/kg), a selective partial MDR antagonist. The hypophagic effect of DHEAS (10 mg/kg) was reversed by dizocilpine (10 microg/kg), an NMDA receptor antagonist, but resistant to muscimol (0.1 mg/kg), a selective GABA-A receptor agonist. In contrast, the PS (10 mg/kg)-induced hypophagic response was resistant to dizocilpine, but sensitive to muscimol (0.1 mg/kg). Both the sulfated neurosteroids PS and DHEAS also reversed the hyperphagic effect of allopregnanolone. In addition, the BZD agonist triazolam (0.05-0.25 mg/kg) also produced a flumazenil- and picrotoxin-sensitive hyperphagic effects, thereby suggesting the changes in feeding behavior by neurosteroids represent GABA-A receptor mediated hyperphagic action. Although the possible antistress or anxiolytic actions of neurosteroids may confound the hyperphagia, behavioral effects observed were specific to food because the mice were adopted to the test environment and diet, and of a possible variation between various neurosteroids in the

Viral vector-mediated overexpression of estrogen receptor-alpha in striatum enhances the estradiol-induced motor activity in female rats and estradiol-modulated GABA release.

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Schultz, Kristin N; von Esenwein, Silke A; Hu, Ming; Bennett, Amy L; Kennedy, Robert T; Musatov, Sergei; Toran-Allerand, C Dominique; Kaplitt, Michael G; Young, Larry J; Becker, Jill B

2009-02-11

Classical estrogen receptor-signaling mechanisms involve estradiol binding to intracellular nuclear receptors [estrogen receptor-alpha (ERalpha) and estrogen receptor-beta (ERbeta)] to promote changes in protein expression. Estradiol can also exert effects within seconds to minutes, however, a timescale incongruent with genomic signaling. In the brain, estradiol rapidly potentiates stimulated dopamine release in the striatum of female rats and enhances spontaneous rotational behavior. Furthermore, estradiol rapidly attenuates the K(+)-evoked increase of GABA in dialysate. We hypothesize that these rapid effects of estradiol in the striatum are mediated by ERalpha located on the membrane of medium spiny GABAergic neurons. This experiment examined whether overexpression of ERalpha in the striatum would enhance the effect of estradiol on rotational behavior and the K(+)-evoked increase in GABA in dialysate. Ovariectomized female rats were tested for rotational behavior or underwent microdialysis experiments after unilateral intrastriatal injections of a recombinant adeno-associated virus (AAV) containing the human ERalpha cDNA (AAV.ERalpha) into the striatum; controls received either the same vector into areas outside the striatum or an AAV containing the human alkaline phosphatase gene into the striatum (AAV.ALP). Animals that received AAV.ERalpha in the striatum exhibited significantly greater estradiol-induced contralateral rotations compared with controls and exhibited behavioral sensitization of contralateral rotations induced by a low-dose of amphetamine. ERalpha overexpression also enhanced the inhibitory effect of estradiol on K(+)-evoked GABA release suggesting that disinhibition of dopamine release from terminals in the striatum resulted in the enhanced rotational behavior.

Music therapy inhibits morphine-seeking behavior via GABA receptor and attenuates anxiety-like behavior induced by extinction from chronic morphine use.

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Kim, Ki Jin; Lee, Sang Nam; Lee, Bong Hyo

2018-05-01

Morphine is a representative pain killer. However, repeated use tends to induce addiction. Music therapy has been gaining interest as a useful type of therapy for neuropsychiatric diseases. The present study examined whether Korean traditional music (KT) could suppress morphine-seeking behavior and anxiety-like behavior induced by extinction from chronic morphine use and additionally investigated a possible neuronal mechanism. Male Sprague-Dawley rats were trained to intravenously self-administer morphine hydrochloride (1.0 mg/kg) using a fixed ratio 1 schedule in daily 2 h session during 3 weeks. After training, rats who established baseline (variation less than 20% of the mean of infusion for 3 consecutive days) underwent extinction. Music was played twice a day during extinction. In the second experiment, the selective antagonists of GABA A and GABA B receptors were treated before the last playing to investigate the neuronal mechanism focusing on the GABA receptor pathway. Another experiment of elevated plus maze was performed to investigate whether music therapy has an anxiolytic effect at the extinction phase. KT but not other music (Indian road or rock music) reduced morphine-seeking behavior induced by a priming challenge with morphine. And, this effect was blocked by the GABA receptor antagonists. In addition, KT showed anxiolytic effects against withdrawal from morphine. Results of this study suggest that KT suppresses morphine-seeking behavior via GABA receptor pathway. In addition, KT showed to have anxiolytic effects, suggesting it has bi-directional effects on morphine. Copyright © 2018 Elsevier B.V. All rights reserved.

Allosteric ligands and their binding sites define γ-aminobutyric acid (GABA) type A receptor subtypes.

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Olsen, Richard W

2015-01-01

GABAA receptors (GABA(A)Rs) mediate rapid inhibitory transmission in the brain. GABA(A)Rs are ligand-gated chloride ion channel proteins and exist in about a dozen or more heteropentameric subtypes exhibiting variable age and brain regional localization and thus participation in differing brain functions and diseases. GABA(A)Rs are also subject to modulation by several chemotypes of allosteric ligands that help define structure and function, including subtype definition. The channel blocker picrotoxin identified a noncompetitive channel blocker site in GABA(A)Rs. This ligand site is located in the transmembrane channel pore, whereas the GABA agonist site is in the extracellular domain at subunit interfaces, a site useful for low energy coupled conformational changes of the functional channel domain. Two classes of pharmacologically important allosteric modulatory ligand binding sites reside in the extracellular domain at modified agonist sites at other subunit interfaces: the benzodiazepine site and the high-affinity, relevant to intoxication, ethanol site. The benzodiazepine site is specific for certain GABA(A)R subtypes, mainly synaptic, while the ethanol site is found at a modified benzodiazepine site on different, extrasynaptic, subtypes. In the transmembrane domain are allosteric modulatory ligand sites for diverse chemotypes of general anesthetics: the volatile and intravenous agents, barbiturates, etomidate, propofol, long-chain alcohols, and neurosteroids. The last are endogenous positive allosteric modulators. X-ray crystal structures of prokaryotic and invertebrate pentameric ligand-gated ion channels, and the mammalian GABA(A)R protein, allow homology modeling of GABA(A)R subtypes with the various ligand sites located to suggest the structure and function of these proteins and their pharmacological modulation. © 2015 Elsevier Inc. All rights reserved.

Kampo medicine: Evaluation of the pharmacological activity of 121 herbal drugs on GABA(A and 5 HT3A receptors

Directory of Open Access Journals (Sweden)

Katrin M Hoffmann

2016-07-01

Full Text Available Kampo medicine is a form of Japanese phytotherapy originating from traditional Chinese medicine (TCM. During the last several decades, much attention has been paid to the pharmacological effects of these medical plants and its constituents. However, in many cases, a systematic screening of Kampo remedies to determine pharmacologically relevant targets is still lacking. In this study, we performed a broad screening of Kampo remedies to look for pharmacologically relevant 5 HT3A and GABA(A receptor ligands. Several of the Kampo remedies are currently used for symptoms such as nausea, emesis, gastrointestinal motility disorders, anxiety, restlessness or insomnia. Therefore, we analyzed the pharmacological effects of 121 herbal drugs from Kampo medicine as ethanol tinctures on heterologously expressed 5 HT3A and GABA(A receptors, due to the involvement of these receptors in such pathophysiological processes. The tinctures of Lindera aggregata (radix and Leonurus japonicus (herba were the most effective inhibitory compounds on the 5 HT3A receptor. Further investigation of known ingredients in these compounds led to the identification of leonurine from Leonurus as a new natural 5 HT3A receptor antagonist. We also identified several potentiating herbs (e.g., Magnolia officinalis (cortex, Syzygium aromaticum (flos and Panax ginseng (radix for the GABAA receptor, which are all traditionally used for their sedative or anxiolytic effects. A variety of tinctures with antagonistic effects, for instance Salvia miltiorrhiza (radix were also detected. Therefore, this study reveals new insights into the pharmacological action of a broad spectrum of herbal drugs from Kampo, allowing a better understanding of their physiological effects and clinical applications.

Alterations in food intake elicited by GABA and opioid agonists and antagonists administered into the ventral tegmental area region of rats.

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Echo, Joyce A; Lamonte, Nicole; Ackerman, Tsippa F; Bodnar, Richard J

2002-05-01

Food intake is significantly increased following administration of mu-selective opioid agonists into the ventral tegmental area (VTA) region acting through multiple local opioid receptor subtypes. Since GABA receptor agonists in the VTA region are capable of eliciting feeding, the present study investigated whether feeding elicited by the mu-selective opioid agonist [D-Ala(2), NMe(4), Gly-ol(5)]-enkephalin (DAMGO) in the VTA region was altered by pretreatment into the same site with equimolar doses of either GABA(A) (bicuculline) or GABA(B) (saclofen) antagonists, and further, whether pretreatment with either general opioid or selective GABA receptor antagonists decreased feeding elicited by GABA(A) (muscimol) or GABA(B) (baclofen) agonists in the VTA region. DAMGO-induced feeding in the VTA region was dose-dependently decreased following pretreatment with either GABA(A) or GABA(B) antagonists in the absence of significant alterations in food intake by the antagonists per se. However, the presence of short-lived seizures following bicuculline in the VTA region suggests that this ingestive effect was caused by nonspecific actions. In contrast, GABA(B) receptors are involved in the full expression of mu-opioid agonist-induced feeding in this region since saclofen failed to elicit either seizure activity or a conditioned taste aversion. Pretreatment with naltrexone in the VTA region reduced intake elicited by baclofen, but not muscimol. Finally, baclofen-induced feeding was significantly reduced by saclofen, but not bicuculline, pretreatment in the VTA region. Therefore, possible coregulation between GABA(B) and opioid receptors in the VTA region, as suggested by immunocytochemical evidence, is supported by these behavioral effects upon ingestion.

GABAA receptor-expressing neurons promote consumption in Drosophila melanogaster.

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Cheung, Samantha K; Scott, Kristin

2017-01-01

Feeding decisions are highly plastic and bidirectionally regulated by neurons that either promote or inhibit feeding. In Drosophila melanogaster, recent studies have identified four GABAergic interneurons that act as critical brakes to prevent incessant feeding. These GABAergic neurons may inhibit target neurons that drive consumption. Here, we tested this hypothesis by examining GABA receptors and neurons that promote consumption. We find that Resistance to dieldrin (RDL), a GABAA type receptor, is required for proper control of ingestion. Knockdown of Rdl in a subset of neurons causes overconsumption of tastants. Acute activation of these neurons is sufficient to drive consumption of appetitive substances and non-appetitive substances and acute silencing of these neurons decreases consumption. Taken together, these studies identify GABAA receptor-expressing neurons that promote Drosophila ingestive behavior and provide insight into feeding regulation.

Recruitment of GABA(A) receptors and fearfulness in chicks: modulation by systemic insulin and/or epinephrine.

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Cid, Mariana Paula; Toledo, Carolina Maribel; Salvatierra, Nancy Alicia

2013-02-01

One-day-old chicks were individually assessed on their latency to peck pebbles, and categorized as low latency (LL) or high latency (HL) according to fear. Interactions between acute stress and systemic insulin and epinephrine on GABA(A) receptor density in the forebrain were studied. At 10 days of life, LL and HL chicks were intraperitoneally injected with insulin, epinephrine or saline, and immediately after stressed by partial water immersion for 15 min and killed by decapitation. Forebrains were dissected and the GABA(A) receptor density was measured ex vivo by the (3)[H]-flunitrazepam binding assay in synaptosomes. In non-stressed chicks, insulin (non-hypoglycemic dose) at 2.50 IU/kg of body weight incremented the Bmax by 40.53% in the HL chicks compared to saline group whereas no significant differences were observed between individuals in the LL subpopulation. Additionally, insulin increased the Bmax (23.48%) in the HL group with respect to the LL ones, indicating that the insulin responses were different according to the anxiety of each category. Epinephrine administration (0.25 and 0.50mg/kg) incremented the Bmax in non-stressed chicks, in the LL group by about 37% and 33%, respectively, compared to ones injected with saline. In the stressed chicks, 0.25mg/kg bw epinephrine increased the Bmax significantly in the HL group by about 24% compared to saline, suggesting that the effect of epinephrine was only observed in the HL group under acute stress conditions. Similarly, the same epinephrine doses co-administered with insulin increased the receptor density in both subpopulations and also showed that the highest dose of epinephrine did not further increase the maximum density of GABA(A)R in HL chicks. These results suggest that systemic epinephrine, perhaps by evoking central norepinephrine release, modulated the increase in the forebrain GABA(A) receptor recruitment induced by both insulin and stress in different ways depending on the subpopulation

Anticonvulsant action of GABA(B) receptor positive modulator CGP7930 in immature rats

Czech Academy of Sciences Publication Activity Database

Mareš, Pavel

2012-01-01

Roč. 100, 1-2 (2012), s. 49-54 ISSN 0920-1211 R&D Projects: GA MŠk(CZ) LC554; GA ČR(CZ) GAP304/10/1274 Institutional research plan: CEZ:AV0Z50110509 Keywords : GABA(B) receptors * cerebral cortex * epileptic afterdischarges * immature rats Subject RIV: FH - Neurology Impact factor: 2.241, year: 2012

Flavylium salts as in vitro precursors of potent ligands to brain GABA-A receptors

DEFF Research Database (Denmark)

Kueny-Stotz, Marie; Chassaing, Stefan; Brouillard, Raymond

2008-01-01

The synthesis of a series of derivatized flavylium cations was undertaken and the affinity to the benzodiazepine binding site of the GABA-A receptor evaluated. The observed high affinity for some derivatives (sub-muM range) was explained by an in vitro transformation of the flavylium cations into...

Glutamate and GABA in appetite regulation

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Teresa Cardoso Delgado

2013-08-01

Full Text Available Appetite is regulated by a coordinated interplay between gut, adipose tissue and brain. A primary site for the regulation of appetite is the hypothalamus where interaction between orexigenic neurons, expressing Neuropeptide Y/Agouti-related protein, and anorexigenic neurons, expressing Pro-opiomelanocortin cocaine/Amphetamine-related transcript, controls energy homeostasis. Within the hypothalamus, several peripheral signals have been shown to modulate the activity of these neurons, including the orexigenic peptide ghrelin and the anorexigenic hormones insulin and leptin. In addition to the accumulated knowledge on neuropeptide signaling, presence and function of amino acid neurotransmitters in key hypothalamic neurons brought a new light into appetite regulation. Therefore, the principal aim of this review will be to describe the current knowledge of the role of amino acid neurotransmitters in the mechanism of neuronal activation during appetite regulation and the associated neuronal-astrocytic metabolic coupling mechanisms.Glutamate and GABA dominate synaptic transmission in the hypothalamus and administration of their receptors agonists into hypothalamic nuclei stimulates feeding. By using 13C High-Resolution Magic Angle Spinning Nuclear Magnetic Resonance spectroscopy based analysis, the Cerdán group has shown that increased neuronal firing in mice hypothalamus, as triggered by appetite during the feeding-fasting paradigm, may stimulate the use of lactate as neuronal fuel leading to increased astrocytic glucose consumption and glycolysis. Moreover, fasted mice showed increased hypothalamic [2-13C]GABA content, which may be explained by the existence of GABAergic neurons in key appetite regulation hypothalamic nuclei. Interestingly, increased [2-13C]GABA concentration in the hypothalamus of fasted animals appears to result mainly from reduction in GABA metabolizing pathways, rather than increased GABA synthesis by augmented activity of the

Probing GABA Receptor Function in Schizophrenia with Iomazenil

OpenAIRE

Ahn, Kyungheup; Gil, Roberto; Seibyl, John; Sewell, Richard Andrew; D'Souza, Deepak Cyril

2010-01-01

Several lines of evidence from post-mortem, brain imaging, and genetic studies in schizophrenia patients suggest that Gamma-amino butyric acid (GABA) deficits may contribute to the pathophysiology of schizophrenia. Pharmacological induction of a transient GABA-deficit state has been shown to enhance vulnerability of healthy subjects to the psychotomimetic effects of various drugs. Exacerbating or creating a GABA deficit was hypothesized to induce or unmask psychosis in schizophrenia patients,...

Functional loss of GABA transaminase (GABA-T) expressed early leaf senescence under various stress conditions in Arabidopsis thaliana

OpenAIRE

Jalil, Syed Uzma; Ahmad, Iqbal; Ansari, Mohammad Israil

2017-01-01

GABA-transaminase (GABA-T) involved in carbon and nitrogen metabolism during the plant development process via GABA shunt and GABA-T mutant, which is defective in GABA catabolism, is ideal model to examine the role of GABA-T in plant development and leaf senescence of plant. We have characterized GABA transaminase knock out mutant pop2-1 that is transition and pop2-3 which is T-DNA insertion mutant of Arabidopsis thaliana during various stress conditions.The GABA-T knockout mutant plants disp...

Astrocytic GABA Transporters

DEFF Research Database (Denmark)

Schousboe, Arne; Wellendorph, Petrine; Frølund, Bente

2017-01-01

, and several of these compounds have been shown to exhibit pronounced anticonvulsant activity in a variety of animal seizure models. As proof of concept of the validity of this drug development approach, one GABA-transport inhibitor, tiagabine, has been developed as a clinically active antiepileptic drug......Inactivation of GABA-mediated neurotransmission is achieved by high-affinity transporters located at both GABAergic neurons and the surrounding astrocytes. Early studies of the pharmacological properties of neuronal and glial GABA transporters suggested that different types of transporters might...... be expressed in the two cell types, and such a scenario was confirmed by the cloning of four distinctly different GABA transporters from a number of different species. These GABA-transport entities have been extensively characterized using a large number of GABA analogues of restricted conformation...

GABAB Receptor Constituents Revealed by Tandem Affinity Purification from Transgenic Mice

DEFF Research Database (Denmark)

Bartoi, Tudor; Rigbolt, Kristoffer T G; Du, Dan

2010-01-01

lines that allow a straightforward biochemical isolation of GABA(B) receptors. The transgenic mice express GABA(B1) isoforms that contain sequences for a two-step affinity purification, in addition to their endogenous subunit repertoire. Comparative analyses of purified samples from the transgenic mice...... and wild-type control animals revealed two novel components of the GABA(B1) complex. One of the identified proteins, potassium channel tetramerization domain-containing protein 12, associates with heterodimeric GABA(B) receptors via the GABA(B2) subunit. In transfected hippocampal neurons, potassium...

The interaction between hippocampal GABA-B and cannabinoid receptors upon spatial change and object novelty discrimination memory function.

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Nasehi, Mohammad; Alaghmandan-Motlagh, Niyousha; Ebrahimi-Ghiri, Mohaddeseh; Nami, Mohammad; Zarrindast, Mohammad-Reza

2017-10-01

Previous studies have postulated functional links between GABA and cannabinoid systems in the hippocampus. The aim of the present study was to investigate any possible interaction between these systems in spatial change and object novelty discrimination memory consolidation in the dorsal hippocampus (CA1 region) of NMRI mice. Assessment of the spatial change and object novelty discrimination memory function was carried out in a non-associative task. The experiment comprised mice exposure to an open field containing five objects followed by the examination of their reactivity to object displacement (spatial change) and object substitution (object novelty) after three sessions of habituation. Our results showed that the post-training intraperitoneal administration of the higher dose of ACPA (0.02 mg/kg) impaired both spatial change and novelty discrimination memory functions. Meanwhile, the higher dose of GABA-B receptor agonist, baclofen, impaired the spatial change memory by itself. Moreover, the post-training intra-CA1 microinjection of a subthreshold dose of baclofen increased the ACPA effect on spatial change and novelty discrimination memory at a lower and higher dose, respectively. On the other hand, the lower and higher but not mid-level doses of GABA-B receptor antagonist, phaclofen, could reverse memory deficits induced by ACPA. However, phaclofen at its mid-level dose impaired the novelty discrimination memory and whereas the higher dose impaired the spatial change memory. Based on our findings, GABA-B receptors in the CA1 region appear to modulate the ACPA-induced cannabinoid CB1 signaling upon spatial change and novelty discrimination memory functions.

Interaction of GABAA receptors with purinergic P2X2 receptors

International Nuclear Information System (INIS)

Shrivastava, A.

2010-01-01

GABA A Rs in the spinal cord are evolving as an important target for drug development against pain. Purinergic P2X 2 Rs are also expressed in spinal cord neurons and are known to cross-talk with GABA A Rs. Here we investigated a possible 'dynamic' interaction between GABA A Rs and P2X 2 Rs using co-immunoprecipitation and FRET studies in HEK cells along with co-localization and single particle tracking studies in spinal cord neurons. Our results suggest that a significant proportion of P2X 2 Rs forms a transient complex with GABA A Rs inside the cell, thus stabilizing these receptors and using them for co-trafficking to the cell surface. P2X 2 Rs and GABA A Rs are then co-inserted into the cell membrane and are primarily located extra-synaptically. Furthermore, agonist induced activation of P2X 2 Rs results in disassembly of the receptor complex and destabilization of GABA A Rs whereas P2X 2 Rs are stabilized and form larger clusters. Antagonist-induced blocking of P2XRs results in co-stabilization of this receptor complex at the cell surface. These results suggest a novel mechanism where association of P2XRs with other receptors could be used for specific targeting to the neuronal membrane, thus providing an extrasynaptic receptor reserve that could regulate the excitability of neurons. We further conclude that blocking the excitatory activity of excessively released ATP under diseased state by P2XR antagonists could simultaneously enhance synaptic inhibition mediated by GABA A Rs.(author) (author) [de

GABA(A) receptor antagonism in the ventrocaudal periaqueductal gray increases anxiety in the anxiety-resistant postpartum rat.

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Miller, Stephanie M; Piasecki, Christopher C; Peabody, Mitchell F; Lonstein, Joseph S

2010-06-01

Postpartum mammals show suppressed anxiety, which is necessary for their ability to appropriately care for offspring. It is parsimonious to suggest that the neurobiological basis of this reduced anxiety is similar to that of non-parturient animals, involving GABA(A) receptor activity in sites including the midbrain periaqueductal gray (PAG). In Experiment 1, postpartum and diestrous virgin female rats received an intraperitoneal injection of the GABA(A) receptor antagonist (+)-bicuculline (0, 2 and 4 mg/kg) and anxiety-related behavior was assessed with an elevated plus maze. The 4 mg/kg dose of (+)-bicuculline significantly increased anxiety-related behavior, particularly in the postpartum females. Experiment 2 revealed that bicuculline's action was within the central nervous system, because anxiety in neither dams nor virgins was significantly affected by intraperitoneal injection of bicuculline methiodide (0, 2 and 6 mg/kg), which does not readily cross the blood-brain-barrier. In Experiment 3, bicuculline methiodide (2.5 ng/side) was directly infused into the ventrocaudal PAG (cPAGv) and significantly increased dams' anxiety compared to saline-infused controls. These studies expand our knowledge of how GABA(A) receptor modulators affect anxiety behaviors in postpartum rats to the widely-used elevated plus maze, and indicate that the postpartum suppression of anxiety is in part a consequence of elevated GABAergic neurotransmission in the cPAGv. Copyright 2010 Elsevier Inc. All rights reserved.

Honokiol promotes non-rapid eye movement sleep via the benzodiazepine site of the GABA(A) receptor in mice.

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Qu, Wei-Min; Yue, Xiao-Fang; Sun, Yu; Fan, Kun; Chen, Chang-Rui; Hou, Yi-Ping; Urade, Yoshihiro; Huang, Zhi-Li

2012-10-01

Decoctions of the Chinese herb houpu contain honokiol and are used to treat a variety of mental disorders, including depression. Depression commonly presents alongside sleep disorders and sleep disturbances, which appear to be a major risk factor for depression. Here, we have evaluated the somnogenic effect of honokiol and the mechanisms involved. Honokiol was administered i.p. at 20:00 h in mice. Flumazenil, an antagonist at the benzodiazepine site of the GABA(A) receptor, was administered i.p. 15 min before honokiol. The effects of honokiol were measured by EEG and electromyogram (EMG), c-Fos expression and in vitro electrophysiology. Honokiol (10 and 20 mg·kg⁻¹) significantly shortened the sleep latency to non-rapid eye movement (non-REM, NREM) sleep and increased the amount of NREM sleep. Honokiol increased the number of state transitions from wakefulness to NREM sleep and, subsequently, from NREM sleep to wakefulness. However, honokiol had no effect on either the amount of REM sleep or EEG power density of both NREM and REM sleep. Honokiol increased c-Fos expression in ventrolateral preoptic area (VLPO) neurons, as examined by immunostaining, and excited sleep-promoting neurons in the VLPO by whole-cell patch clamping in the brain slice. Pretreatment with flumazenil abolished the somnogenic effects and activation of the VLPO neurons by honokiol. Honokiol promoted NREM sleep by modulating the benzodiazepine site of the GABA(A) receptor, suggesting potential applications in the treatment of insomnia, especially for patients who experience difficulty in falling and staying asleep. © 2012 The Authors. British Journal of Pharmacology © 2012 The British Pharmacological Society.

Saturable binding of 35S-t-butylbicyclophosphorothionate to the sites linked to the GABA receptor and the interaction with gabaergic agents

International Nuclear Information System (INIS)

Wong, D.T.; Threlkeld, P.G.; Bymaster, F.P.; Squires, R.F.

1984-01-01

35 -S-t-Butylbicyclophosphorothionate ( 35 S-TBPS) binds in a concentration-saturable manner to specific sites on membranes from rat cerebral cortex. Using a filtration assay at 25 0 C, in 250 mM NaCl, specific binding of 35 S-TBPS constitutes about 84 to 94 percent of total binding, depending on radioligand concentrations. 35 S-TBPS binding is optimal in the presence of NaCl or NaBr and substantially less in the presence of NaI or NaF. It is sensitive to the treatment with 0.05 percent Triton X-100 but not to repeated freezing and thawing, procedures which increase 3 H-GABA binding. Pharmacological studies show that 35 S-TBPS binding is strongly inhibited by GABA-A receptor agonists (e.g., GABA and muscimol) and by the noncompetitive antagonist, picrotoxin, but not the competitive antagonist, bicuculline. Compounds which enhance binding of radioactive GABA and benzodiazepines, such as the pyrazolopyridines, cartazolate and trazolate, and a diaryl-triazine, LY81067, are also potent inhibitors of 35 S-TBPS binding, with LY81067 being the most effective. The effects of GABA, picrotoxin and LY81067 on the saturable binding of 35 S-TBPS in cortical membranes are compared. The present bindings are consistent with the interpretation that 35 S-TBPS binds, at or near the picrotoxin-sensitive anion recognition sites of the GABA/benzodiazepine/picrotoxin receptor complex

Effects of gamma-aminobutyric acid (GABA) on synaptogenesis and synaptic function

DEFF Research Database (Denmark)

Belhage, B; Hansen, Gert Helge; Elster, L

1998-01-01

, but the intracellular link between GABA receptor activation and DNA transcription is largely unknown. GABA also controls the induction and development of functionally and pharmacologically different GABAA receptor subtypes. The induced receptors are likely to be inserted only into the synaptic membrane domain. However...

Long-Range Regulatory Polymorphisms Affecting a GABA Receptor Constitute a Quantitative Trait Locus (QTL) for Social Behavior in Caenorhabditis elegans

Science.gov (United States)

Bendesky, Andres; Pitts, Jason; Rockman, Matthew V.; Chen, William C.; Tan, Man-Wah; Kruglyak, Leonid; Bargmann, Cornelia I.

2012-01-01

Aggregation is a social behavior that varies between and within species, providing a model to study the genetic basis of behavioral diversity. In the nematode Caenorhabditis elegans, aggregation is regulated by environmental context and by two neuromodulatory pathways, one dependent on the neuropeptide receptor NPR-1 and one dependent on the TGF-β family protein DAF-7. To gain further insight into the genetic regulation of aggregation, we characterize natural variation underlying behavioral differences between two wild-type C. elegans strains, N2 and CB4856. Using quantitative genetic techniques, including a survey of chromosome substitution strains and QTL analysis of recombinant inbred lines, we identify three new QTLs affecting aggregation in addition to the two known N2 mutations in npr-1 and glb-5. Fine-mapping with near-isogenic lines localized one QTL, accounting for 5%–8% of the behavioral variance between N2 and CB4856, 3′ to the transcript of the GABA neurotransmitter receptor gene exp-1. Quantitative complementation tests demonstrated that this QTL affects exp-1, identifying exp-1 and GABA signaling as new regulators of aggregation. exp-1 interacts genetically with the daf-7 TGF-β pathway, which integrates food availability and population density, and exp-1 mutations affect the level of daf-7 expression. Our results add to growing evidence that genetic variation affecting neurotransmitter receptor genes is a source of natural behavioral variation. PMID:23284308

Long-range regulatory polymorphisms affecting a GABA receptor constitute a quantitative trait locus (QTL for social behavior in Caenorhabditis elegans.

Directory of Open Access Journals (Sweden)

Andres Bendesky

Full Text Available Aggregation is a social behavior that varies between and within species, providing a model to study the genetic basis of behavioral diversity. In the nematode Caenorhabditis elegans, aggregation is regulated by environmental context and by two neuromodulatory pathways, one dependent on the neuropeptide receptor NPR-1 and one dependent on the TGF-β family protein DAF-7. To gain further insight into the genetic regulation of aggregation, we characterize natural variation underlying behavioral differences between two wild-type C. elegans strains, N2 and CB4856. Using quantitative genetic techniques, including a survey of chromosome substitution strains and QTL analysis of recombinant inbred lines, we identify three new QTLs affecting aggregation in addition to the two known N2 mutations in npr-1 and glb-5. Fine-mapping with near-isogenic lines localized one QTL, accounting for 5%-8% of the behavioral variance between N2 and CB4856, 3' to the transcript of the GABA neurotransmitter receptor gene exp-1. Quantitative complementation tests demonstrated that this QTL affects exp-1, identifying exp-1 and GABA signaling as new regulators of aggregation. exp-1 interacts genetically with the daf-7 TGF-β pathway, which integrates food availability and population density, and exp-1 mutations affect the level of daf-7 expression. Our results add to growing evidence that genetic variation affecting neurotransmitter receptor genes is a source of natural behavioral variation.

Hippocampal infusions of glucose reverse memory deficits produced by co-infusions of a GABA receptor agonist.

Science.gov (United States)

Krebs-Kraft, Desiree L; Parent, Marise B

2008-02-01

Although septal infusions of glucose typically have positive effects on memory, we have shown repeatedly that this treatment exacerbates memory deficits produced by co-infusions of gamma-aminobutyric acid (GABA) receptor agonists. The present experiments tested whether this negative interaction between glucose and GABA in the medial septum would be observed in the hippocampus, a brain region where glucose typically has positive effects on memory. Specifically, we determined whether hippocampal infusions of glucose would reverse or exacerbate memory deficits produced by hippocampal co-infusions of the GABA receptor agonist muscimol. Fifteen minutes prior to either assessing spontaneous alternation (SA) or continuous multiple trial inhibitory avoidance (CMIA) training, male Sprague-Dawley-derived rats were given bilateral hippocampal infusions of vehicle (phosphate-buffered saline [PBS], 1 microl/2 min), glucose (33 or 50 nmol), muscimol (0.3 or 0.4 microg, SA or 3 microg, CMIA) or muscimol and glucose combined in one solution. The results indicated that hippocampal infusions of muscimol alone decreased SA scores and CMIA retention latencies. More importantly, hippocampal infusions of glucose, at doses that had no effect when infused alone, attenuated (33 nmol) or reversed (50 nmol) the muscimol-induced memory deficits. Thus, although co-infusions of glucose with muscimol into the medial septum impair memory, the present findings show that an opposite effect is observed in the hippocampus. Collectively, these findings suggest that the memory-impairing interaction between glucose and GABA in the medial septum is not a general property of the brain, but rather is brain region-dependent.

Novel GABA receptor pesticide targets.

Science.gov (United States)

Casida, John E; Durkin, Kathleen A

2015-06-01

The γ-aminobutyric acid (GABA) receptor has four distinct but overlapping and coupled targets of pesticide action importantly associated with little or no cross-resistance. The target sites are differentiated by binding assays with specific radioligands, resistant strains, site-directed mutagenesis and molecular modeling. Three of the targets are for non-competitive antagonists (NCAs) or channel blockers of widely varied chemotypes. The target of the first generation (20th century) NCAs differs between the larger or elongated compounds (NCA-IA) including many important insecticides of the past (cyclodienes and polychlorocycloalkanes) or present (fiproles) and the smaller or compact compounds (NCA-IB) highly toxic to mammals and known as cage convulsants, rodenticides or chemical threat agents. The target of greatest current interest is designated NCA-II for the second generation (21st century) of NCAs consisting for now of isoxazolines and meta-diamides. This new and uniquely different NCA-II site apparently differs enough between insects and mammals to confer selective toxicity. The fourth target is the avermectin site (AVE) for allosteric modulators of the chloride channel. NCA pesticides vary in molecular surface area and solvent accessible volume relative to avermectin with NCA-IBs at 20-22%, NCA-IAs at 40-45% and NCA-IIs at 57-60%. The same type of relationship relative to ligand-docked length is 27-43% for NCA-IBs, 63-71% for NCA-IAs and 85-105% for NCA-IIs. The four targets are compared by molecular modeling for the Drosophila melanogaster GABA-R. The principal sites of interaction are proposed to be: pore V1' and A2' for NCA-IB compounds; pore A2', L6' and T9' for NCA-IA compounds; pore T9' to S15' in proximity to M1/M3 subunit interface (or alternatively an interstitial site) for NCA-II compounds; and M1/M3, M2 interfaces for AVE. Understanding the relationships of these four binding sites is important in resistance management and in the discovery and use

Expression of GABA signaling molecules KCC2, NKCC1, and GAD1 in cortical development and schizophrenia.

Science.gov (United States)

Hyde, Thomas M; Lipska, Barbara K; Ali, Towhid; Mathew, Shiny V; Law, Amanda J; Metitiri, Ochuko E; Straub, Richard E; Ye, Tianzhang; Colantuoni, Carlo; Herman, Mary M; Bigelow, Llewellyn B; Weinberger, Daniel R; Kleinman, Joel E

2011-07-27

GABA signaling molecules are critical for both human brain development and the pathophysiology of schizophrenia. We examined the expression of transcripts derived from three genes related to GABA signaling [GAD1 (GAD67 and GAD25), SLC12A2 (NKCC1), and SLC12A5 (KCC2)] in the prefrontal cortex (PFC) and hippocampal formation of a large cohort of nonpsychiatric control human brains (n = 240) across the lifespan (from fetal week 14 to 80 years) and in patients with schizophrenia (n = 30-31), using quantitative RT-PCR. We also examined whether a schizophrenia risk-associated promoter SNP in GAD1 (rs3749034) is related to expression of these transcripts. Our studies revealed that development and maturation of both the PFC and hippocampal formation are characterized by progressive switches in expression from GAD25 to GAD67 and from NKCC1 to KCC2. Previous studies have demonstrated that the former leads to GABA synthesis, and the latter leads to switching from excitatory to inhibitory neurotransmission. In the hippocampal formation, GAD25/GAD67 and NKCC1/KCC2 ratios are increased in patients with schizophrenia, reflecting a potentially immature GABA physiology. Remarkably, GAD25/GAD67 and NKCC1/KCC2 expression ratios are associated with rs3749034 genotype, with risk alleles again predicting a relatively less mature pattern. These findings suggest that abnormalities in GABA signaling critical to brain development contribute to genetic risk for schizophrenia.

General, kappa, delta and mu opioid receptor antagonists mediate feeding elicited by the GABA-B agonist baclofen in the ventral tegmental area and nucleus accumbens shell in rats: reciprocal and regional interactions.

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Miner, Patricia; Shimonova, Lyudmila; Khaimov, Arthur; Borukhova, Yaffa; Ilyayeva, Ester; Ranaldi, Robert; Bodnar, Richard J

2012-03-14

Food intake is significantly increased following administration of agonists of GABA and opioid receptors into the nucleus accumbens shell (NACs) and ventral tegmental area (VTA). GABA-A or GABA-B receptor antagonist pretreatment within the VTA or NACs differentially affects mu-opioid agonist-induced feeding elicited from the same site. Correspondingly, general or selective opioid receptor antagonist pretreatment within the VTA or NACs differentially affects GABA agonist-induced feeding elicited from the same site. Regional interactions have been evaluated in feeding studies by administering antagonists in one site prior to agonist administration in a second site. Thus, opioid antagonist-opioid agonist and GABA antagonist-GABA agonist feeding interactions have been identified between the VTA and NACs. However, pretreatment with GABA-A or GABA-B receptor antagonists in the VTA failed to affect mu opioid agonist-induced feeding elicited from the NACs, and correspondingly, these antagonists administered in the NACs failed to affect mu opioid-induced feeding elicited from the VTA. To evaluate whether regional and reciprocal VTA and NACs feeding interactions occur for opioid receptor modulation of GABA agonist-mediated feeding, the present study examined whether feeding elicited by the GABA-B agonist, baclofen microinjected into the NACs was dose-dependently blocked by pretreatment with general (naltrexone: NTX), mu (beta-funaltrexamine: BFNA), kappa (nor-binaltorphamine: NBNI) or delta (naltrindole: NTI) opioid antagonists in the VTA, and correspondingly, whether VTA baclofen-induced feeding was dose-dependently blocked by NACs pretreatment with NTX, BFNA, NBNI or NTI in rats. Bilateral pairs of cannulae aimed at the VTA and NACs were stereotaxically implanted in rats, and their food intakes were assessed following vehicle and baclofen (200 ng) in each site. Baclofen produced similar magnitudes of increased food intake following VTA and NACs treatment. Baclofen

Downregulation of GABA[Subscript A] Receptor Protein Subunits a6, ß2, d, e, ?2, ?, and ?2 in Superior Frontal Cortex of Subjects with Autism

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Fatemi, S. Hossein; Reutiman, Teri J.; Folsom, Timothy D.; Rustan, Oyvind G.; Rooney, Robert J.; Thuras, Paul D.

2014-01-01

We measured protein and mRNA levels for nine gamma-aminobutyric acid A (GABA[subscript A]) receptor subunits in three brain regions (cerebellum, superior frontal cortex, and parietal cortex) in subjects with autism versus matched controls. We observed changes in mRNA for a number of GABA[subscript A] and GABA[subscript B] subunits and overall…

Effects of acute administration of the GABA(B) receptor agonist baclofen on behavioral flexibility in rats.

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Beas, B Sofia; Setlow, Barry; Bizon, Jennifer L

2016-07-01

The ability to adjust response strategies when faced with changes in the environment is critical for normal adaptive behavior. Such behavioral flexibility is compromised by experimental disruption of cortical GABAergic signaling, as well as in conditions such as schizophrenia and normal aging that are characterized by cortical hyperexcitability. The current studies were designed to determine whether stimulation of GABAergic signaling using the GABA(B) receptor agonist baclofen can facilitate behavioral flexibility. Male Fischer 344 rats were trained in a set-shifting task in which they learned to discriminate between two response levers to obtain a food reward. Correct levers were signaled in accordance with two distinct response rules (rule 1: correct lever signaled by a cue light; rule 2: correct lever signaled by its left/right position). The order of rule presentation varied, but they were always presented sequentially, with the trials and errors to reach criterion performance on the second (set shift) rule providing the measure of behavioral flexibility. Experiments determined the effects of the GABA(B) receptor agonist baclofen (intraperitoneal, 0, 1.0, 2.5, and 4.0 mg/kg) administered acutely before the shift to the second rule. Baclofen enhanced set-shifting performance. Control experiments demonstrated that this enhancement was not simply due to improved discrimination learning, nor was it due to impaired recall of the initial discrimination rule. The results demonstrate that baclofen can facilitate behavioral flexibility, suggesting that GABA(B) receptor agonists may have utility for treating behavioral dysfunction in neuropsychiatric disorders.

Functional loss of GABA transaminase (GABA-T expressed early leaf senescence under various stress conditions in Arabidopsis thaliana

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Syed Uzma Jalil

2017-06-01

Full Text Available GABA-transaminase (GABA-T involved in carbon and nitrogen metabolism during the plant development process via GABA shunt and GABA-T mutant, which is defective in GABA catabolism, is ideal model to examine the role of GABA-T in plant development and leaf senescence of plant. We have characterized GABA transaminase knock out mutant pop2-1 that is transition and pop2-3 which is T-DNA insertion mutant of Arabidopsis thaliana during various stress conditions.The GABA-T knockout mutant plants displayed precocious leaf senescence, which was accompanied by the assays of physiological parameters of leaf senescence during various stress conditions. Furthermore, our physiological evidence indicates that pop2-1 and pop2-3 mutations rapidly decreased the efficiency of leaf photosynthesis, chlorophyll content, GABA content, GABA-T, and glutamate decarboxylase (GAD activity and on the other hand increases membrane ion leakage, malondialdehyde (MDA level in stress induced leaves. However, cell viability assay by trypan blue and insitu Hydrogen peroxidation assay by 3,3-diaminobenzidine (DAB in stress induced leaves also display that pop2-1 and pop2-3 mutant leaves show oversensitivity in response to different stress conditions as compared to wild type. These results strongly indicate that the loss-of-function of GABA transaminase gene induces early leaf senescence in Arabidopsis thaliana during various stress conditions.

Olfactory bulb short axon cell release of GABA and dopamine produces a temporally biphasic inhibition-excitation response in external tufted cells.

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Liu, Shaolin; Plachez, Celine; Shao, Zuoyi; Puche, Adam; Shipley, Michael T

2013-02-13

Evidence for coexpression of two or more classic neurotransmitters in neurons has increased, but less is known about cotransmission. Ventral tegmental area (VTA) neurons corelease dopamine (DA), the excitatory transmitter glutamate, and the inhibitory transmitter GABA onto target cells in the striatum. Olfactory bulb (OB) short axon cells (SACs) form interglomerular connections and coexpress markers for DA and GABA. Using an optogenetic approach, we provide evidence that mouse OB SACs release both GABA and DA onto external tufted cells (ETCs) in other glomeruli. Optical activation of channelrhodopsin specifically expressed in DAergic SACs produced a GABA(A) receptor-mediated monosynaptic inhibitory response, followed by DA-D(1)-like receptor-mediated excitatory response in ETCs. The GABA(A) receptor-mediated hyperpolarization activates I(h) current in ETCs; synaptically released DA increases I(h), which enhances postinhibitory rebound spiking. Thus, the opposing actions of synaptically released GABA and DA are functionally integrated by I(h) to generate an inhibition-to-excitation "switch" in ETCs. Consistent with the established role of I(h) in ETC burst firing, we show that endogenous DA release increases ETC spontaneous bursting frequency. ETCs transmit sensory signals to mitral/tufted output neurons and drive intraglomerular inhibition to shape glomerulus output to downstream olfactory networks. GABA and DA cotransmission from SACs to ETCs may play a key role in regulating output coding across the glomerular array.

Epigenetic regulation of dorsal raphe GABA(B1a) associated with isolation-induced abnormal responses to social stimulation in mice.

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Araki, Ryota; Hiraki, Yosuke; Nishida, Shoji; Kuramoto, Nobuyuki; Matsumoto, Kinzo; Yabe, Takeshi

2016-02-01

In isolation-reared mice, social encounter stimulation induces locomotor hyperactivity and activation of the dorsal raphe nucleus (DRN), suggesting that dysregulation of dorsal raphe function may be involved in abnormal behaviors. In this study, we examined the involvement of dorsal raphe GABAergic dysregulation in the abnormal behaviors of isolation-reared mice. We also studied an epigenetic mechanism underlying abnormalities of the dorsal raphe GABAergic system. Both mRNA and protein levels of GABA(B1a), a GABA(B) receptor subunit, were increased in the DRN of isolation-reared mice, compared with these levels in group-reared mice. In contrast, mRNA levels for other GABAergic system-related genes (GABA(A) receptor α1, β2 and γ2 subunits, GABA(B) receptor 1b and 2 subunits, and glutamate decarboxylase 67 and 65) were unchanged. Intra-DRN microinjection of 0.06 nmol baclofen (a GABA(B) receptor agonist) exacerbated encounter-induced hyperactivity and aggressive behavior, while microinjection of 0.3 nmol phaclofen (a GABA(B) receptor antagonist) attenuated encounter-induced hyperactivity and aggressive behavior in isolation-reared mice. Furthermore, microinjection of 0.06 nmol baclofen elicited encounter-induced hyperactivity in group-reared mice. Neither baclofen nor phaclofen affected immobility time in the forced swim test and hyperactivity in a novel environment of isolation reared mice. Bisulfite sequence analyses revealed that the DNA methylation level of the CpG island around the transcription start site (TSS) of GABA(B1a) was decreased in the DRN of isolation-reared mice. Chromatin immunoprecipitation analysis showed that histone H3 was hyperacetylated around the TSS of GABA(B1a) in the DRN of isolation-reared mice. These findings indicate that an increase in dorsal raphe GABA(B1a) expression via epigenetic regulation is associated with abnormal responses to social stimulation such as encounter-induced hyperactivity and aggressive behavior in isolation

Dopamine D1-D2 receptor heteromer in dual phenotype GABA/glutamate-coexpressing striatal medium spiny neurons: regulation of BDNF, GAD67 and VGLUT1/2.

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Melissa L Perreault

Full Text Available In basal ganglia a significant subset of GABAergic medium spiny neurons (MSNs coexpress D1 and D2 receptors (D1R and D2R along with the neuropeptides dynorphin (DYN and enkephalin (ENK. These coexpressing neurons have been recently shown to have a region-specific distribution throughout the mesolimbic and basal ganglia circuits. While the functional relevance of these MSNs remains relatively unexplored, they have been shown to exhibit the unique property of expressing the dopamine D1-D2 receptor heteromer, a novel receptor complex with distinct pharmacology and cell signaling properties. Here we showed that MSNs coexpressing the D1R and D2R also exhibited a dual GABA/glutamate phenotype. Activation of the D1R-D2R heteromer in these neurons resulted in the simultaneous, but differential regulation of proteins involved in GABA and glutamate production or vesicular uptake in the nucleus accumbens (NAc, ventral tegmental area (VTA, caudate putamen and substantia nigra (SN. Additionally, activation of the D1R-D2R heteromer in NAc shell, but not NAc core, differentially altered protein expression in VTA and SN, regions rich in dopamine cell bodies. The identification of a MSN with dual inhibitory and excitatory intrinsic functions provides new insights into the neuroanatomy of the basal ganglia and demonstrates a novel source of glutamate in this circuit. Furthermore, the demonstration of a dopamine receptor complex with the potential to differentially regulate the expression of proteins directly involved in GABAergic inhibitory or glutamatergic excitatory activation in VTA and SN may potentially provide new insights into the regulation of dopamine neuron activity. This could have broad implications in understanding how dysregulation of neurotransmission within basal ganglia contributes to dopamine neuronal dysfunction.

Effect of GABA, a Bacterial Metabolite, on Pseudomonas fluorescens Surface Properties and Cytotoxicity

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Marc G. J. Feuilloley

2013-06-01

Full Text Available Different bacterial species and, particularly Pseudomonas fluorescens, can produce gamma-aminobutyric acid (GABA and express GABA-binding proteins. In this study, we investigated the effect of GABA on the virulence and biofilm formation activity of different strains of P. fluorescens. Exposure of a psychotropic strain of P. fluorescens (MF37 to GABA (10−5 M increased its necrotic-like activity on eukaryotic (glial cells, but reduced its apoptotic effect. Conversely, muscimol and bicuculline, the selective agonist and antagonist of eukaryote GABAA receptors, respectively, were ineffective. P. fluorescens MF37 did not produce biosurfactants, and its caseinase, esterase, amylase, hemolytic activity or pyoverdine productions were unchanged. In contrast, the effect of GABA was associated to rearrangements of the lipopolysaccharide (LPS structure, particularly in the lipid A region. The surface hydrophobicity of MF37 was marginally modified, and GABA reduced its biofilm formation activity on PVC, but not on glass, although the initial adhesion was increased. Five other P. fluorescens strains were studied, and only one, MFP05, a strain isolated from human skin, showed structural differences of biofilm maturation after exposure to GABA. These results reveal that GABA can regulate the LPS structure and cytotoxicity of P. fluorescens, but that this property is specific to some strains.

Gene Expression in Accumbens GABA Neurons from Inbred Rats with Different Drug-Taking Behavior

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Sharp, B.M.; Chen, H.; Gong, S.; Wu, X.; Liu, Z.; Hiler, K.; Taylor, W.L.; Matta, S.G.

2011-01-01

Inbred Lewis and Fisher 344 rat strains differ greatly in drug self-administration; Lewis rats operantly self-administer drugs of abuse including nicotine, whereas Fisher self-administer poorly. As shown herein, operant food self-administration is similar. Based on their pivotal role in drug reward, we hypothesized that differences in basal gene expression in GABAergic neurons projecting from nucleus accumbens (NAcc) to ventral pallidum (VP) play a role in vulnerability to drug taking behavior. The transcriptomes of NAcc shell-VP GABAergic neurons from these two strains were analyzed in adolescents, using a multidisciplinary approach that combined stereotaxic ionotophoretic brain microinjections, laser-capture microdissection (LCM) and microarray measurement of transcripts. LCM enriched the gene transcripts detected in GABA neurons compared to the residual NAcc tissue: a ratio of neuron/residual > 1 and false discovery rate (FDR) 3 yielded 3,514. Strain-dependent differences in gene expression within GABA neurons were identified; 322 vs. 60 transcripts showed 1.5-fold vs. 2-fold differences in expression (FDR<5%). Classification by gene ontology showed these 322 transcripts were widely distributed, without categorical enrichment. This is most consistent with a global change in GABA neuron function. Literature-mining by Chilibot found 38 genes related to synaptic plasticity, signaling and gene transcription, all of which determine drug-abuse; 33 genes have no known association with addiction or nicotine. In Lewis rats, upregulation of Mint-1, Cask, CamkIIδ, Ncam1, Vsnl1, Hpcal1 and Car8 indicates these transcripts likely contribute to altered signaling and synaptic function in NAcc GABA projection neurons to VP. PMID:21745336

GABA-mediated synchronization in the human neocortex: elevations in extracellular potassium and presynaptic mechanisms.

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Louvel, J; Papatheodoropoulos, C; Siniscalchi, A; Kurcewicz, I; Pumain, R; Devaux, B; Turak, B; Esposito, V; Villemeure, J G; Avoli, M

2001-01-01

Field potential and extracellular [K(+)] ([K(+)](o)) recordings were made in the human neocortex in an in vitro slice preparation to study the synchronous activity that occurs in the presence of 4-aminopyridine (50 microM) and ionotropic excitatory amino acid receptor antagonists. Under these experimental conditions, negative or negative-positive field potentials accompanied by rises in [K(+)](o) (up to 4.1 mM from a baseline of 3.25 mM) occurred spontaneously at intervals of 3-27 s. Both field potentials and [K(+)](o) elevations were largest at approximately 1000 microm from the pia. Similar events were induced by neocortical electrical stimuli. Application of medium containing low [Ca(2+)]/high [Mg(2+)] (n=3 slices), antagonism of the GABA(A) receptor (n=7) or mu-opioid receptor activation (n=4) abolished these events. Hence, they represented network, GABA-mediated potentials mainly reflecting the activation of type A receptors following GABA release from interneurons. The GABA(B) receptor agonist baclofen (10-100 microM, n=11) reduced and abolished the GABA-mediated potentials (ID(50)=18 microM). Baclofen effects were antagonized by the GABA(B) receptor antagonist CGP 35348 (0.1-1 mM, n=6; ID(50)=0.19 mM). CGP 38345 application to control medium increased the amplitude of the GABA-mediated potentials and the concomitant [K(+)](o) rises without modifying their rate of occurrence. The GABA-mediated potentials were not influenced by the broad-spectrum metabotropic glutamate agonist (+/-)-1-aminocyclopentane-trans-1,3-dicarboxylic acid (100 microM, n=10), but decreased in rate with the group I receptor agonist (S)-3,5-dihydroxyphenylglycine (10-100 microM, n=9). Our data indicate that human neocortical networks challenged with 4-aminopyridine generate glutamatergic-independent, GABA-mediated potentials that are modulated by mu-opioid and GABA(B) receptors presumably located on interneuron terminals. These events are associated with [K(+)](o) elevations that may

Reduced binding potential of GABA-A/benzodiazepine receptors in individuals at ultra-high risk for psychosis: an [18F]-fluoroflumazenil positron emission tomography study.

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Kang, Jee In; Park, Hae-Jeong; Kim, Se Joo; Kim, Kyung Ran; Lee, Su Young; Lee, Eun; An, Suk Kyoon; Kwon, Jun Soo; Lee, Jong Doo

2014-05-01

Altered transmission of gamma-aminobutyric acid (GABA), a major inhibitory neurotransmitter, may contribute to the development of schizophrenia. The purpose of the present study was to investigate the presence of GABA-A/benzodiazepine (BZ) receptor binding abnormalities in individuals at ultra-high risk (UHR) for psychosis in comparison with normal controls using [(18)F]-fluoroflumazenil (FFMZ) positron emission tomography (PET). In particular, we set regions of interest in the striatum (caudate, putamen, and nucleus accumbens) and medial temporal area (hippocampus and parahippocampal gyrus). Eleven BZ-naive people at UHR and 15 normal controls underwent PET scanning using [(18)F]-FFMZ to measure GABA-A/BZ receptor binding potential. The regional group differences between UHR individuals and normal controls were analyzed using Statistical Parametric Mapping 8 software. Participants were evaluated using the structured interview for prodromal syndromes and neurocognitive function tasks. People at UHR demonstrated significantly reduced binding potential of GABA-A/BZ receptors in the right caudate. Altered GABAergic transmission and/or the imbalance of inhibitory and excitatory systems in the striatum may be present at the putative prodromal stage and play a pivotal role in the pathophysiology of psychosis.

Tracking cell surface GABAB receptors using an alpha-bungarotoxin tag.

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Wilkins, Megan E; Li, Xinyan; Smart, Trevor G

2008-12-12

GABA(B) receptors mediate slow synaptic inhibition in the central nervous system and are important for synaptic plasticity as well as being implicated in disease. Located at pre- and postsynaptic sites, GABA(B) receptors will influence cell excitability, but their effectiveness in doing so will be dependent, in part, on their trafficking to, and stability on, the cell surface membrane. To examine the dynamic behavior of GABA(B) receptors in GIRK cells and neurons, we have devised a method that is based on tagging the receptor with the binding site components for the neurotoxin, alpha-bungarotoxin. By using the alpha-bungarotoxin binding site-tagged GABA(B) R1a subunit (R1a(BBS)), co-expressed with the R2 subunit, we can track receptor mobility using the small reporter, alpha-bungarotoxin-conjugated rhodamine. In this way, the rates of internalization and membrane insertion for these receptors could be measured with fixed and live cells. The results indicate that GABA(B) receptors rapidly turnover in the cell membrane, with the rate of internalization affected by the state of receptor activation. The bungarotoxin-based method of receptor-tagging seems ideally suited to follow the dynamic regulation of other G-protein-coupled receptors.

Zolpidem, a selective GABA(A) receptor alpha1 subunit agonist, induces comparable Fos expression in oxytocinergic neurons of the hypothalamic paraventricular and accessory but not supraoptic nuclei in the rat

DEFF Research Database (Denmark)

Kiss, Alexander; Søderman, Andreas; Bundzikova, Jana

2006-01-01

Functional activation of oxytocinergic (OXY) cells in the hypothalamic paraventricular (PVN), supraoptic (SON), and accessory (ACC) nuclei was investigated in response to acute treatment with Zolpidem (a GABA(A) receptor agonist with selectivity for alpha(1) subunits) utilizing dual Fos/OXY immun...

Lipid raft localization of GABA A receptor and Na+, K+-ATPase in discrete microdomain clusters in rat cerebellar granule cells

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Dalskov, Stine-Mathilde; Immerdal, Lissi; Niels-Christiansen, Lise-Lotte W

2005-01-01

The microdomain localization of the GABA(A) receptor in rat cerebellar granule cells was studied by subcellular fractionation and fluorescence- and immunogold electron microscopy. The receptor resided in lipid rafts, prepared at 37 degrees C by extraction with the nonionic detergent Brij 98......, but the raft fraction, defined by the marker ganglioside GM(1) in the floating fractions following density gradient centrifugation, was heterogeneous in density and protein composition. Thus, another major raft-associated membrane protein, the Na(+), K(+)-ATPase, was found in discrete rafts of lower density......, reflecting clustering of the two proteins in separate membrane microdomains. Both proteins were observed in patchy "hot spots" at the cell surface as well as in isolated lipid rafts. Their insolubility in Brij 98 was only marginally affected by methyl-beta-cyclodextrin. In contrast, both the GABA(A) receptor...

SKF97541, GABA-B receptor agonist, exhibits both anti- and procovulsant effets in immature rats

Czech Academy of Sciences Publication Activity Database

Mareš, Pavel; Tabashidze, Nana

2007-01-01

Roč. 48, s6 (2007), s. 18-18 ISSN 0013-9580. [Annual Meeting of the American Epilepsy Society. 31.112007-3.12.2007, Philadelphia] R&D Projects: GA ČR(CZ) GA304/05/2582 Institutional research plan: CEZ:AV0Z50110509 Keywords : cpo1 * GABA-B receptor * anti- and proconvulsant effects Subject RIV: FH - Neurology

KCTD Hetero-oligomers Confer Unique Kinetic Properties on Hippocampal GABA(B) Receptor-Induced K+ Currents

Czech Academy of Sciences Publication Activity Database

Fritzius, T.; Tureček, Rostislav; Seddik, R.; Kobayashi, H.; Tiao, J.; Rem, P.D.; Metz, M.; Králíková, Michaela; Bouvier, M.; Gassmann, M.; Bettler, B.

2017-01-01

Roč. 37, č. 5 (2017), s. 1162-1175 ISSN 0270-6474 R&D Projects: GA ČR(CZ) GA14-28334S Institutional support: RVO:68378041 Keywords : G-protein coupled receptor * GABA-B * GPCR Subject RIV: FH - Neurology OBOR OECD: Biology (theoretical, mathematical, thermal, cryobiology, biological rhythm), Evolutionary biology Impact factor: 5.988, year: 2016

GABA(A) receptor modulation during adolescence alters adult ethanol intake and preference in rats.

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Hulin, Mary W; Amato, Russell J; Winsauer, Peter J

2012-02-01

To address the hypothesis that GABA(A) receptor modulation during adolescence may alter the abuse liability of ethanol during adulthood, the effects of adolescent administration of both a positive and negative GABA(A) receptor modulator on adult alcohol intake and preference were assessed. Three groups of adolescent male rats received 12 injections of lorazepam (3.2 mg/kg), dehydroepiandrosterone (DHEA, 56 mg/kg), or vehicle on alternate days starting on postnatal day (PD) 35. After this time, the doses were increased to 5.6 and 100 mg/kg, respectively, for 3 more injections on alternate days. Subjects had access to 25 to 30 g of food daily, during the period of the first 6 injections, and 18 to 20 g thereafter. Food intake of each group was measured 60 minutes after food presentation, which occurred immediately after drug administration on injection days or at the same time of day on noninjection days. When subjects reached adulthood (PD 88), ethanol preference was determined on 2 separate occasions, an initial 3-day period and a 12-day period, in which increasing concentrations of ethanol were presented. During each preference test, intake of water, saccharin, and an ethanol/saccharin solution was measured after each 23-hour access period. During adolescence, lorazepam increased 60-minute food intake, and this effect was enhanced under the more restrictive feeding schedule. DHEA had the opposite effect on injection days, decreasing food intake compared with noninjection days. In adulthood, the lorazepam-treated group preferred the 2 lowest concentrations of ethanol/saccharin more than saccharin alone compared with vehicle-treated subjects, which showed no preference for any concentration of ethanol/saccharin over saccharin. DHEA-treated subjects showed no preference among the 3 solutions. These data demonstrate that GABA(A) receptor modulation during adolescence can alter intake and preference for ethanol in adulthood and highlights the importance of drug history

Galanin-Expressing GABA Neurons in the Lateral Hypothalamus Modulate Food Reward and Noncompulsive Locomotion.

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Qualls-Creekmore, Emily; Yu, Sangho; Francois, Marie; Hoang, John; Huesing, Clara; Bruce-Keller, Annadora; Burk, David; Berthoud, Hans-Rudolf; Morrison, Christopher D; Münzberg, Heike

2017-06-21

GABA neurons is heterogeneous and largely undefined. Here we introduce LHA Gal neurons as a subset of LHA GABA neurons that lack direct innervation of the ventral tegmental area (VTA). LHA Gal neurons are sufficient to drive motivated feeding and locomotor activity similar to LHA GABA neurons, but without inducing compulsive-like behaviors, which we propose to require direct VTA innervation. Our study integrates galanin-expressing LHA neurons into our current understanding of the neuronal circuits and molecular mechanisms of the LHA that contribute to motivated feeding behaviors. Copyright © 2017 the authors 0270-6474/17/376053-13$15.00/0.

Ipsilateral feeding-specific circuits between the nucleus accumbens shell and the lateral hypothalamus: regulation by glutamate and GABA receptor subtypes.

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Urstadt, Kevin R; Kally, Peter; Zaidi, Sana F; Stanley, B Glenn

2013-04-01

The nucleus accumbens shell (AcbSh) and the lateral hypothalamus (LH) are both involved in the control of food intake. Activation of GABA(A) receptors or blockade of AMPA and kainate receptors within the AcbSh induces feeding, as does blockade of GABA(A) receptors or activation of NMDA receptors in the LH. Further, evidence suggests that feeding induced via the AcbSh can be suppressed by LH inhibition. However, it is unclear if this suppression is specific to feeding. Adult male Sprague-Dawley rats with 3 intracranial guide cannulas, one unilaterally into the AcbSh and two bilaterally into the LH, were used to explore this issue. DNQX (1.25 μg) or muscimol (100 ng) infused into the AcbSh unilaterally elicited feeding, and this elicited intake was suppressed by bilateral LH injection of d-AP5 (2 μg) or muscimol (25 ng). The effectiveness of d-AP5 or muscimol infusion into either the LH site ipsilateral or contralateral to the AcbSh injection was compared. Ipsilateral LH injection of d-AP5 or muscimol was significantly more effective than contralateral injection in suppressing food intake initiated by AcbSh injection of DNQX or muscimol. These results add to the prior evidence that inhibition of the LH through pharmacological modulation of NMDA or GABA(A) receptors specifically suppresses feeding initiated by AcbSh inhibition, and that these two regions communicate via an ipsilateral circuit to specifically regulate feeding. Copyright © 2012 Elsevier Ltd. All rights reserved.

Glutamate modulation of GABA transport in retinal horizontal cells of the skate

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Kreitzer, Matthew A; Andersen, Kristen A; Malchow, Robert Paul

2003-01-01

Transport of the amino acid GABA into neurons and glia plays a key role in regulating the effects of GABA in the vertebrate retina. We have examined the modulation of GABA-elicited transport currents of retinal horizontal cells by glutamate, the likely neurotransmitter of vertebrate photoreceptors. Enzymatically isolated external horizontal cells of skate were examined using whole-cell voltage-clamp techniques. GABA (1 mm) elicited an inward current that was completely suppressed by the GABA transport inhibitors tiagabine (10 μm) and SKF89976-A (100 μm), but was unaffected by 100 μm picrotoxin. Prior application of 100 μm glutamate significantly reduced the GABA-elicited current. Glutamate depressed the GABA dose-response curve without shifting the curve laterally or altering the voltage dependence of the current. The ionotropic glutamate receptor agonists kainate and AMPA also reduced the GABA-elicited current, and the effects of glutamate and kainate were abolished by the ionotropic glutamate receptor antagonist 6-cyano-7-nitroquinoxaline. NMDA neither elicited a current nor modified the GABA-induced current, and metabotropic glutamate analogues were also without effect. Inhibition of the GABA-elicited current by glutamate and kainate was reduced when extracellular calcium was removed and when recording pipettes contained high concentrations of the calcium chelator BAPTA. Caffeine (5 mm) and thapsigargin (2 nm), agents known to alter intracellular calcium levels, also reduced the GABA-elicited current, but increases in calcium induced by depolarization alone did not. Our data suggest that glutamate regulates GABA transport in retinal horizontal cells through a calcium-dependent process, and imply a close physical relationship between calcium-permeable glutamate receptors and GABA transporters in these cells. PMID:12562999

Sodium-independent, bicuculline-sensitive [3H]GABA binding to isolated rat hepatocytes

International Nuclear Information System (INIS)

Minuk, G.Y.; Bear, C.E.; Sarjeant, E.J.

1987-01-01

To determine whether hepatocytes possess specific receptor sites for gamma-aminobutyric acid (GABA), a potent amino acid neurotransmitter, [ 3 H]GABA, was added to sodium-free suspensions of Percoll-purified hepatocytes derived from collagenase-perfused rat livers under various experimental conditions and in the presence or absence of specific GABA receptor agonists (muscimol) and antagonists (bicuculline). The effects of GABA, muscimol, and bicuculline on hepatocyte resting membrane potentials were also determined. Specific binding of [ 3 H]GABA to hepatocytes was a consistent finding. GABA-hepatocyte interactions were reversible and temperature dependent. Muscimol and bicuculline inhibited binding in a dose-dependent manner (IC50, 30 nM and 50 microM, respectively), whereas strychnine (1.0-100 microM), a nonspecific central nervous system stimulant, had no appreciable effect. Both GABA and muscimol (100 microM) caused significant hyperpolarization of hepatocyte resting membrane potential (delta PD 5.4 +/- 3.1 and 22.2 +/- 16.2 mV, respectively, means +/- SD, P less than 0.0005). Bicuculline (100 microM) inhibited the effect of muscimol (P less than 0.05). The results of this study suggest that specific GABA receptor sites exist on the surface of isolated rat hepatocytes. The presence of such sites raises the possibility that, in addition to adrenergic and cholinergic innervation, hepatic function may be influenced by GABA-ergic neurotransmitter mechanisms

Drug-induced GABA transporter currents enhance GABA release to induce opioid withdrawal behaviors.

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Bagley, Elena E; Hacker, Jennifer; Chefer, Vladimir I; Mallet, Christophe; McNally, Gavan P; Chieng, Billy C H; Perroud, Julie; Shippenberg, Toni S; Christie, MacDonald J

2011-10-30

Neurotransmitter transporters can affect neuronal excitability indirectly via modulation of neurotransmitter concentrations or directly via transporter currents. A physiological or pathophysiological role for transporter currents has not been described. We found that GABA transporter 1 (GAT-1) cation currents directly increased GABAergic neuronal excitability and synaptic GABA release in the periaqueductal gray (PAG) during opioid withdrawal in rodents. In contrast, GAT-1 did not indirectly alter GABA receptor responses via modulation of extracellular GABA concentrations. Notably, we found that GAT-1-induced increases in GABAergic activity contributed to many PAG-mediated signs of opioid withdrawal. Together, these data support the hypothesis that GAT-1 activity directly produces opioid withdrawal signs through direct hyperexcitation of GABAergic PAG neurons and nerve terminals, which presumably enhances GABAergic inhibition of PAG output neurons. These data provide, to the best of our knowledge, the first evidence that dysregulation of a neurotransmitter transporter current is important for the maladaptive plasticity that underlies opiate withdrawal.

The residence time of GABA(A)Rs at inhibitory synapses is determined by direct binding of the receptor α1 subunit to gephyrin

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Mukherjee, Jayanta; Kretschmannova, Karla; Gouzer, Geraldine

2011-01-01

The majority of fast synaptic inhibition in the brain is mediated by benzodiazepine-sensitive α1-subunit-containing GABA type A receptors (GABA(A)Rs); however, our knowledge of the mechanisms neurons use to regulate their synaptic accumulation is rudimentary. Using immunoprecipitation, we....... Mutating residues 360-375 decreases both the accumulation of α1-containing GABA(A)Rs at gephyrin-positive inhibitory synapses in hippocampal neurons and the amplitude of mIPSCs. We also demonstrate that the affinity of gephyrin for the α1 subunit is modulated by Thr375, a putative phosphorylation site....... Mutation of Thr375 to a phosphomimetic, negatively charged amino acid decreases both the affinity of the α1 subunit for gephyrin, and therefore receptor accumulation at synapses, and the amplitude of mIPSCs. Finally, single-particle tracking reveals that gephyrin reduces the diffusion of α1-subunit...

Selective GABA transporter inhibitors tiagabine and EF1502 exhibit mechanistic differences in their ability to modulate the ataxia and anticonvulsant action of the extrasynaptic GABA(A) receptor agonist gaboxadol

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Madsen, Karsten Kirkegaard; Ebert, Bjarke; Clausen, Rasmus Prætorius

2011-01-01

seizures. Even though less is known about the therapeutic potential of other GABA transport inhibitors, previous investigations have demonstrated that N-[4,4-bis(3-methyl-2-thienyl)-3-butenyl]-3-hydroxy-4-(methylamino)-4,5,6,7-tetrahydrobenzo[d]isoxazol-3-ol (EF1502), which, like tiagabine, is inactive...... of gaboxadol (4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol), which, at the doses used in this study (i.e., 1-5 mg/kg) selectively activates extrasynaptic a4-containing GABA(A) receptors, was determined alone and in combination with either tiagabine or EF1502 using Frings audiogenic seizure-susceptible and CF...

A versatile optical tool for studying synaptic GABAA receptor trafficking.

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Lorenz-Guertin, Joshua M; Wilcox, Madeleine R; Zhang, Ming; Larsen, Mads B; Pilli, Jyotsna; Schmidt, Brigitte F; Bruchez, Marcel P; Johnson, Jon W; Waggoner, Alan S; Watkins, Simon C; Jacob, Tija C

2017-11-15

Live-cell imaging methods can provide critical real-time receptor trafficking measurements. Here, we describe an optical tool to study synaptic γ-aminobutyric acid (GABA) type A receptor (GABA A R) dynamics through adaptable fluorescent-tracking capabilities. A fluorogen-activating peptide (FAP) was genetically inserted into a GABA A R γ2 subunit tagged with pH-sensitive green fluorescent protein (γ2 pH FAP). The FAP selectively binds and activates Malachite Green (MG) dyes that are otherwise non-fluorescent in solution. γ2 pH FAP GABA A Rs are expressed at the cell surface in transfected cortical neurons, form synaptic clusters and do not perturb neuronal development. Electrophysiological studies show γ2 pH FAP GABA A Rs respond to GABA and exhibit positive modulation upon stimulation with the benzodiazepine diazepam. Imaging studies using γ2 pH FAP-transfected neurons and MG dyes show time-dependent receptor accumulation into intracellular vesicles, revealing constitutive endosomal and lysosomal trafficking. Simultaneous analysis of synaptic, surface and lysosomal receptors using the γ2 pH FAP-MG dye approach reveals enhanced GABA A R turnover following a bicucculine-induced seizure paradigm, a finding not detected by standard surface receptor measurements. To our knowledge, this is the first application of the FAP-MG dye system in neurons, demonstrating the versatility to study nearly all phases of GABA A R trafficking. © 2017. Published by The Company of Biologists Ltd.

Prefrontal cortical GABA transmission modulates discrimination and latent inhibition of conditioned fear: relevance for schizophrenia.

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Piantadosi, Patrick T; Floresco, Stan B

2014-09-01

Inhibitory gamma-aminobutyric acid (GABA) transmission within the prefrontal cortex (PFC) regulates numerous functions, and perturbations in GABAergic transmission within this region have been proposed to contribute to some of the cognitive and behavioral abnormalities associated with disorders such as schizophrenia. These abnormalities include deficits in emotional regulation and aberrant attributions of affective salience. Yet, how PFC GABA regulates these types of emotional processes are unclear. To address this issue, we investigated the contribution of PFC GABA transmission to different aspects of Pavlovian emotional learning in rats using translational discriminative fear conditioning and latent inhibition (LI) assays. Reducing prelimbic PFC GABAA transmission via infusions of the antagonist bicuculline before the acquisition or expression of fear conditioning eliminated the ability to discriminate between an aversive conditioned stimulus (CS+) paired with footshock vs a neutral CS-, resembling similar deficits observed in schizophrenic patients. In a separate experiment, blockade of PFC GABAA receptors before CS preexposure (PE) and conditioning did not affect subsequent expression of LI, but did enhance fear in rats that were not preexposed to the CS. In contrast, PFC GABA-blockade before a fear expression test disrupted the recall of learned irrelevance and abolished LI. These data suggest that normal PFC GABA transmission is critical for regulating and mitigating multiple aspects of aversive learning, including discrimination between fear vs safety signals and recall of information about the irrelevance of stimuli. Furthermore, they suggest that similar deficits in emotional regulation observed in schizophrenia may be driven in part by deficient PFC GABA activity.

GABA not only a neurotransmitter: osmotic regulation by GABAAR signalling

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Tiziana eCesetti

2012-01-01

Full Text Available In neurons the anionic channel γ-aminobutyric (GABA A receptor (GABAAR plays a central role in mediating both the neurotrophic and neurotransmitter role of GABA. Activation of this receptor by GABA also affects the function of non-neuronal cells in the central nervous system (CNS, as GABAARs are expressed in mature macroglia and in almost all progenitor types, including neural stem cells. The relevance of GABA signalling in non-neuronal cells has been comparatively less investigated than in neurons. However, it is becoming increasingly evident that these cells are direct targets of GABA regulation. In non-neuronal cells GABAAR activation leads to influx or efflux of chloride (Cl- depending on the electrochemical gradient. Ion transport is indissolubly associated to water fluxes across the plasma membrane and plays a key role in brain physiology. Therefore, GABAAR could affect osmotic tension in the brain by modulating ion gradients. In addition, since water movements also occur through specialized water channels and transporters, GABAAR signalling could affect the movement of water also by regulating the function of the channels and transporters involved, thereby affecting not only the direction of the water fluxes but also their dynamics. This regulation has consequences at the cellular level as it modulates cell volume and activates multiple intracellular signalling mechanisms important for cell proliferation, maturation and survival. It may also have consequences at the systemic level. For example, it may indirectly control neuronal excitability, by regulating the extracellular space and interstitial concentration of Cl-, and contribute to brain water homeostasis. Therefore, GABAergic osmotic regulation should be taken into account during the treatment of pathologies requiring the administration of GABAAR modulators and for the development of therapies for diseases causing water unbalance in the brain.

Different in vitro and in vivo profiles of substituted 3-aminopropylphosphinate and 3-aminopropyl(methyl)phosphinate GABA(B) receptor agonists as inhibitors of transient lower oesophageal sphincter relaxation.

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Lehmann, A; Antonsson, M; Aurell-Holmberg, A; Blackshaw, L A; Brändén, L; Elebring, T; Jensen, J; Kärrberg, L; Mattsson, J P; Nilsson, K; Oja, S S; Saransaari, P; von Unge, S

2012-03-01

Gastro-oesophageal reflux is predominantly caused by transient lower oesophageal sphincter relaxation (TLOSR) and GABA(B) receptor stimulation inhibits TLOSR. Lesogaberan produces fewer CNS side effects than baclofen, which has been attributed to its affinity for the GABA transporter (GAT), the action of which limits stimulation of central GABA(B) receptors. To understand the structure-activity relationship for analogues of lesogaberan (3-aminopropylphosphinic acids), and corresponding 3-aminopropyl(methyl)phosphinic acids, we have compared representatives of these classes in different in vitro and in vivo models. The compounds were characterized in terms of GABA(B) agonism in vitro. Binding to GATs and cellular uptake was done using rat brain membranes and slices respectively. TLOSR was measured in dogs, and CNS side effects were evaluated as hypothermia in mice and rats. 3-Aminopropylphosphinic acids inhibited TLOSR with a superior therapeutic index compared to 3-aminopropyl(methyl)phosphinic acids. This difference was most likely due to differential GAT-mediated uptake into brain cells of the former but not latter. In agreement, 3-aminopropyl(methyl)phosphinic acids were much more potent in producing hypothermia in rats even when administered i.c.v. An enhanced therapeutic window for 3-aminopropylphosphinic acids compared with 3-aminopropyl(methyl)phosphinic acids with respect to inhibition of TLOSR was observed and is probably mechanistically linked to neural cell uptake of the former but not latter group of compounds. These findings offer a platform for discovery of new GABA(B) receptor agonists for the treatment of reflux disease and other conditions where selective peripheral GABA(B) receptor agonism may afford therapeutic effects. © 2011 The Authors. British Journal of Pharmacology © 2011 The British Pharmacological Society.

GABA, a natural immunomodulator of T lymphocytes

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Bjurstöm, Helen; Wang, Junyang; Ericsson, Ida

2008-01-01

gamma-aminobutyric acid (GABA) is the main neuroinhibitory transmitter in the brain. Here we show that GABA in the extracellular space may affect the fate of pathogenic T lymphocytes entering the brain. We examined in encephalitogenic T cells if they expressed functional GABA channels that could...

GABAA receptor: Positive and negative allosteric modulators.

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Olsen, Richard W

2018-01-31

gamma-Aminobutyric acid (GABA)-mediated inhibitory neurotransmission and the gene products involved were discovered during the mid-twentieth century. Historically, myriad existing nervous system drugs act as positive and negative allosteric modulators of these proteins, making GABA a major component of modern neuropharmacology, and suggesting that many potential drugs will be found that share these targets. Although some of these drugs act on proteins involved in synthesis, degradation, and membrane transport of GABA, the GABA receptors Type A (GABA A R) and Type B (GABA B R) are the targets of the great majority of GABAergic drugs. This discovery is due in no small part to Professor Norman Bowery. Whereas the topic of GABA B R is appropriately emphasized in this special issue, Norman Bowery also made many insights into GABA A R pharmacology, the topic of this article. GABA A R are members of the ligand-gated ion channel receptor superfamily, a chloride channel family of a dozen or more heteropentameric subtypes containing 19 possible different subunits. These subtypes show different brain regional and subcellular localization, age-dependent expression, and potential for plastic changes with experience including drug exposure. Not only are GABA A R the targets of agonist depressants and antagonist convulsants, but most GABA A R drugs act at other (allosteric) binding sites on the GABA A R proteins. Some anxiolytic and sedative drugs, like benzodiazepine and related drugs, act on GABA A R subtype-dependent extracellular domain sites. General anesthetics including alcohols and neurosteroids act at GABA A R subunit-interface trans-membrane sites. Ethanol at high anesthetic doses acts on GABA A R subtype-dependent trans-membrane domain sites. Ethanol at low intoxicating doses acts at GABA A R subtype-dependent extracellular domain sites. Thus GABA A R subtypes possess pharmacologically specific receptor binding sites for a large group of different chemical classes of

Neuroendocrine response to GABA-B receptor agonism in alcohol-dependent individuals: Results from a combined outpatient and human laboratory experiment.

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Farokhnia, Mehdi; Sheskier, Mikela B; Lee, Mary R; Le, April N; Singley, Erick; Bouhlal, Sofia; Ton, Timmy; Zhao, Zhen; Leggio, Lorenzo

2018-04-14

Gamma-aminobutyric acid (GABA), the main inhibitory neurotransmitter in the nervous system, plays an important role in biobehavioral processes that regulate alcohol seeking, food intake, and stress response. The metabotropic GABA-B receptor has been investigated as a potential therapeutic target for alcohol use disorder, by using orthosteric agonists (e.g., baclofen) and positive allosteric modulators. Whether and how pharmacological manipulation of the GABA-B receptor, in combination with alcohol intake, may affect feeding- and stress-related neuroendocrine pathways remains unknown. In the present randomized, double-blind, placebo-controlled study, thirty-four alcohol-dependent individuals received baclofen (30 mg/day) or placebo in a naturalistic outpatient setting for one week, and then performed a controlled laboratory experiment which included alcohol cue-reactivity, fixed-dose priming, and self-administration procedures. Blood samples were collected, and the following neuroendocrine markers were measured: ghrelin, leptin, amylin, glucagon-like peptide-1 (GLP-1), insulin, prolactin, thyroid-stimulating hormone, growth hormone, cortisol, and adrenocorticotropic hormone (ACTH). During the outpatient phase, baclofen significantly increased blood concentrations of acyl-ghrelin (p = 0.01), leptin (p = 0.01), amylin (p = 0.004), and GLP-1 (p = 0.02). Significant drug × time-point interaction effects for amylin (p = 0.001) and insulin (p = 0.03), and trend-level interaction effects for GLP-1 (p = 0.06) and ACTH (p = 0.10) were found during the laboratory experiment. Baclofen, compared to placebo, had no effect on alcohol drinking in this study (p's ≥ 0.05). Together with previous studies, these findings shed light on the role of the GABAergic system and GABA-B receptors in the shared neurobiology of alcohol-, feeding-, and stress-related behaviors. Copyright © 2018. Published by Elsevier Ltd.

Ventral tegmental area GABA neurons and opiate motivation

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Vargas-Perez, Hector; Mabey, Jennifer K.; Shin, Samuel I.; Steffensen, Scott C.; van der Kooy, Derek

2013-01-01

Rational Past research has demonstrated that when an animal changes from a previously drug-naive to an opiate-dependent and withdrawn state, morphine’s motivational effects are switched from a tegmental pedunculopontine nucleus (TPP)-dependent to a dopamine-dependent pathway. Interestingly, a corresponding change is observed in ventral tegmental area (VTA) GABAA receptors, which change from mediating hyperpolarization of VTA GABA neurons to mediating depolarization. Objectives The present study investigated whether pharmacological manipulation of VTA GABAA receptor activity could directly influence the mechanisms underlying opiate motivation. Results Using an unbiased place conditioning procedure, we demonstrated that in Wistar rats, intra-VTA administration of furosemide, a Cl− cotransporter inhibitor, was able to promote a switch in the mechanisms underlying morphine’s motivational properties, one which is normally observed only after chronic opiate exposure. This behavioral switch was prevented by intra-VTA administration of acetazolamide, an inhibitor of the bicarbonate ion-producing carbonic anhydrase enzyme. Electrophysiological recordings of mouse VTA showed that furosemide reduced the sensitivity of VTA GABA neurons to inhibition by the GABAA receptor agonist muscimol, instead increasing the firing rate of a significant subset of these GABA neurons. Conclusion Our results suggest that the carbonic anhydrase enzyme may constitute part of a common VTA GABA neuron-based biological pathway responsible for controlling the mechanisms underlying opiate motivation, supporting the hypothesis that VTA GABAA receptor hyperpolarization or depolarization is responsible for selecting TPP- or dopamine-dependent motivational outputs, respectively. PMID:23392354

GABA interaction with lipids in organic medium

International Nuclear Information System (INIS)

Beltramo, D.; Kivatinitz, S.; Lassaga, E.; Arce, A.

1987-01-01

The interaction of 3 H-GABA and 14 C-glutamate with lipids in an aqueous organic partition system was studied. With this partition system 3 H-GABA and 14 C-glutamate were able to interact with sphingomyelin, sulfatide, phosphatidylcholine, phosphatidylserine, phosphatidylethanolamine and phosphatidic acid but not with cholesterol or ceramide. In an homogeneous aqueous medium the authors could not demonstrate any interaction between 3 H-GABA-lipids. The apparent dissociation constants (K/sub d/) for 3 H-GABA-lipids or 14 C-glutamate-lipids interactions inorganic medium were in the millimolar range and maximal charge between 3 and 7 moles of GABA or glutamate by mole of lipid. Amino acids such as glutamic acid, β-alanine and glycine displaced 3 H-GABA with the same potency as GABA itself; thus these results show that the interaction lacks pharmacological specificity. To detect this interaction lipid concentrations higher than 2 μM were required and in the partition system 3 H-GABA and lipid phosphorus were both concentrated at the interface. Therefore, lipids tested with a biphasic partition system do not fulfill the classical criteria for a neurotransmitter receptor at least not for GABA and glutamate. 15 references, 1 figure, 3 tables

Further characterization of benzodiazepine receptor differences in long-sleep and short-sleep mice

International Nuclear Information System (INIS)

Marley, R.J.; Stinchcomb, A.; Wehner, J.M.

1988-01-01

Molecular and conformational characteristics of benzodiazepine (BZ) receptors in cortex and cerebellum from long-sleep and mice were investigated using heat inactivation and beta-carboline competition techniques. To investigate differences in the allosteric coupling between GABA and BZ receptors, the protection of BZ receptors from heat inactivation, by GABA, was also evaluated. The two genotypes do not differ in the affinity or number of BZ receptors in the cortex or cerebellum. They do, however, appear to differ in the molecular structure and/or regulation of the conformational state of the receptor in the cortex, as indicated by a greater sensitivity of LS mice to both heat inactivation and beta-carboline competition of 3 H-flunitrazepam (FNZ) binding in this region. Evidence for differences in the nature of coupling between GABA and BZ receptors is provided by the finding in that in both regions, GABA protected BZ receptors from inactivation to a greater degree in LS mice. The relationship between these differences and the multiplicity of expression of BZ receptors is discussed

In vivo imaging of GABA{sub A} receptors using sequential whole-volume iodine-123 iomazenil single-photon emission tomography

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Busatto, G.F. [Dept. of Psychological Medicine, Inst. of Psychiatry, London (United Kingdom); Pilowsky, L.S. [Dept. of Psychological Medicine, Inst. of Psychiatry, London (United Kingdom); Costa, D.C. [Inst. of Nuclear Medicine, University Coll. and Middlesex School of Medicine, London (United Kingdom); Ell, P.J. [Inst. of Nuclear Medicine, University Coll. and Middlesex School of Medicine, London (United Kingdom); Lingford-Hughes, A. [Dept. of Psychological Medicine, Inst. of Psychiatry, London (United Kingdom); Kerwin, R.W. [Dept. of Psychological Medicine, Inst. of Psychiatry, London (United Kingdom)

1995-01-01

Using a brain-dedicated triple-headed single-photon emission tomography (SPET) system, a sequential whole-volume imaging protocol has been devised to evaluate the regional distribution of iodine-123 iomazenil binding to GABA{sub A} receptors in the entire brain. The protocol was piloted in eight normal volunteers (seven males and one female; mean age, 24.8{+-}3.9 years). The patterns obtained were largely compatible with the known distribution of GABA{sub A} receptors in the brain as reported in autoradiographic studies, with cerebral cortical regions, particularly the occipital and frontal cortices, displaying the highest {sup 123}I-iomazenil uptake. Measures of time to peak uptake and tracer washout rates presented with the same pattern of regional variation, with later times to peak and slower washout rates in cortical regions compared to other brain areas. Semiquantitative analysis of the data using white matter/ventricle regions as reference demonstrated a plateau of specific {sup 123}I-iomazenil binding in neocortical and cerebellar regions from 60-75 min onwards. These data demonstrate the feasibility of sequential, dynamic whole-volume {sup 123}I-iomazenil SPET imaging. The protocol may be particularly useful in the investigation of neuropsychiatric conditions which are likely to involve more than one focus of GABA abnormalities, such as anxiety disorders and schizophrenia. (orig.)

GABA in Paraventricular Nucleus Regulates Adipose Afferent Reflex in Rats.

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Lei Ding

Full Text Available Chemical stimulation of white adipose tissue (WAT induces adipose afferent reflex (AAR, and thereby causes a general sympathetic activation. Paraventricular nucleus (PVN is important in control of sympathetic outflow. This study was designed to investigate the role of γ-aminobutyric acid (GABA in PVN in regulating the AAR.Experiments were carried out in anesthetized rats. Renal sympathetic nerve activity (RSNA and mean arterial pressure (MAP were continuously recorded. AAR was evaluated by the RSNA and MAP responses to electrical stimulation of the right epididymal WAT (eWAT afferent nerve. Electrical stimulation of eWAT afferent nerve increase RSNA. Bilateral microinjection of the GABAA receptor agonist isoguvacine or the GABAB receptor agonist baclofen attenuated the AAR. The effect of isoguvacine on the AAR was greater than that of baclofen. The GABAA receptor antagonist gabazine enhanced the AAR, while the GABAB receptor antagonist CGP-35348 had no significant effect on the AAR. Bilateral PVN microinjection of vigabatrin, a selective GABA-transaminase inhibitor, to increase endogenous GABA levels in the PVN abolished the AAR. The inhibitory effect of vigabatrin on the AAR was attenuated by the pretreatment with gabazine or CGP-35348. Pretreatment with combined gabazine and CGP-35348 abolished the effects of vigabatrin.Activation of GABAA or GABAB receptors in the PVN inhibits the AAR. Blockade of GABAA receptors in the PVN enhances the AAR. Endogenous GABA in the PVN plays an important role in regulating the AAR.

Affinities and densities of high-affinity [3H]muscimol (GABA-A) binding sites and of central benzodiazepine receptors are unchanged in autopsied brain tissue from cirrhotic patients with hepatic encephalopathy

International Nuclear Information System (INIS)

Butterworth, R.F.; Lavoie, J.; Giguere, J.F.; Pomier-Layrargues, G.

1988-01-01

The integrity of GABA-A receptors and of central benzodiazepine receptors was evaluated in membrane preparations from prefrontal cortex and caudate nuclei obtained at autopsy from nine cirrhotic patients who died in hepatic coma and an equal number of age-matched control subjects. Histopathological studies revealed Alzheimer Type II astrocytosis in all cases in the cirrhotic group; controls were free from neurological, psychiatric or hepatic diseases. Binding to GABA-A receptors was studied using [ 3 H]muscimol as radioligand. The integrity of central benzodiazepine receptors was evaluated using [ 3 H]flunitrazepam and [ 3 H]Ro15-1788. Data from saturation binding assays was analyzed by Scatchard plot. No modifications of either affinities (Kd) or densities (Bmax) of [ 3 H]muscimol of central benzodiazepine binding sites were observed. These findings do not support recent suggestions that alterations of either high-affinity GABA or benzodiazepine receptors play a significant role in the pathogenesis of hepatic encephalopathy

Regulation of (/sup 3/H)GABA release from strips of guinea pig urinary bladder

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Shirakawa, J.; Taniyama, K.; Iwai, S.; Tanaka, C.

1988-12-01

The presence of receptors that regulate the release of gamma-aminobutyric acid (GABA) was studied in strips of the guinea pig urinary bladder. GABA (10(-8)-10(-5) M) and muscimol (10(-8)-10(-5) M), but not baclofen (10(-5) M), reduced the Ca2+-dependent, tetrodotoxin-resistant release of (/sup 3/H)GABA evoked by high K+ from the urinary bladder strips preloaded with (/sup 3/H)GABA. The inhibitory effect of muscimol was antagonized by bicuculline and potentiated by diazepam, clonazepam, and pentobarbital sodium. The potentiating effect of clonazepam was antagonized by Ro 15-1788. Acetylcholine (ACh) inhibited the high K+-evoked release of (/sup 3/H)GABA. The inhibitory effect of ACh was antagonized by atropine sulfate and pirenzepine but not by hexamethonium. Norepinephrine (NE) inhibited the evoked release of (/sup 3/H)GABA. The inhibitory effect of NE was mimicked by clonidine, but not by phenylephrine, and was antagonized by yohimbine but not by prazosin. These results provide evidence that the release of GABA from strips of guinea pig urinary bladder is regulated via the bicuculline-sensitive GABAA receptor, M1-muscarinic, and alpha 2-adrenergic receptors.

Somato-dendritic localization and signaling by leptin receptors in hypothalamic POMC and AgRP neurons.

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Sangdeuk Ha

Full Text Available Leptin acts via neuronal leptin receptors to control energy balance. Hypothalamic pro-opiomelanocortin (POMC and agouti-related peptide (AgRP/Neuropeptide Y (NPY/GABA neurons produce anorexigenic and orexigenic neuropeptides and neurotransmitters, and express the long signaling form of the leptin receptor (LepRb. Despite progress in the understanding of LepRb signaling and function, the sub-cellular localization of LepRb in target neurons has not been determined, primarily due to lack of sensitive anti-LepRb antibodies. Here we applied light microscopy (LM, confocal-laser scanning microscopy (CLSM, and electron microscopy (EM to investigate LepRb localization and signaling in mice expressing a HA-tagged LepRb selectively in POMC or AgRP/NPY/GABA neurons. We report that LepRb receptors exhibit a somato-dendritic expression pattern. We further show that LepRb activates STAT3 phosphorylation in neuronal fibers within several hypothalamic and hindbrain nuclei of wild-type mice and rats, and specifically in dendrites of arcuate POMC and AgRP/NPY/GABA neurons of Leprb (+/+ mice and in Leprb (db/db mice expressing HA-LepRb in a neuron specific manner. We did not find evidence of LepRb localization or STAT3-signaling in axon-fibers or nerve-terminals of POMC and AgRP/NPY/GABA neurons. Three-dimensional serial EM-reconstruction of dendritic segments from POMC and AgRP/NPY/GABA neurons indicates a high density of shaft synapses. In addition, we found that the leptin activates STAT3 signaling in proximity to synapses on POMC and AgRP/NPY/GABA dendritic shafts. Taken together, these data suggest that the signaling-form of the leptin receptor exhibits a somato-dendritic expression pattern in POMC and AgRP/NPY/GABA neurons. Dendritic LepRb signaling may therefore play an important role in leptin's central effects on energy balance, possibly through modulation of synaptic activity via post-synaptic mechanisms.

Suppression of Human Liver Cancer Cell Migration and Invasion via the GABAA Receptor

International Nuclear Information System (INIS)

Chen, Zhi-ao; Bao, Mei-yan; Xu, Yong-fen; Zha, Ruo-peng; Shi, Hai-bing; Chen, Tao-yang; He, Xiang-huo

2012-01-01

To investigate the roles of the γ-aminobutyric acid (GABA) in the metastasis of hepatocellular carcinoma (HCC) and to explore the potential of a novel therapeutic approach for the treatment of HCC. The expression levels of GABA receptor subunit genes in various HCC cell lines and patients‘ tissues were detected by quantitative real-time polymerase chain reaction and Western blot analysis. Transwell cell migration and invasion assays were carried out for functional analysis. The effects of GABA on liver cancer cell cytoskeletal were determined by immunofluorescence staining. And the effects of GABA on HCC metastasis in nude mice were evaluated using an in vivo orthotopic model of liver cancer. The mRNA level of GABA receptor subunits varied between the primary hepatocellular carcinoma tissue and the adjacent non-tumor liver tissue. GABA inhibited human liver cancer cell migration and invasion via the ionotropic GABA A receptor as a result of the induction of liver cancer cell cytoskeletal reorganization. Pretreatment with GABA also significantly reduced intrahepatic liver metastasis and primary tumor formation in vivo. These findings introduce a potential and novel therapeutic approach for the treatment of cancer patients based on the modulation of the GABAergic system

The role of GABA in NMDA-dependent long term depression (LTD) of rat medial vestibular nuclei.

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Grassi, S; Della Torre, G; Capocchi, G; Zampolini, M; Pettorossi, V E

1995-11-20

The role of GABA in NMDA-dependent long term depression (LTD) in the medial vestibular nuclei (MVN) was studied on rat brainstem slices. High frequency stimulation (HFS) of the primary vestibular afferents induces a long lasting reduction of the polysynaptic (N2) component of the field potentials recorded in the dorsal portion of the MVN. The induction but not the maintenance of this depression was abolished by AP5, a specific blocking agent for glutamate NMDA receptors. The involvement of GABA in mediating the depression was checked by applying the GABAA and GABAB receptor antagonists, bicuculline and saclofen, before and after HFS. Under bicuculline and saclofen perfusion, HFS provoked a slight potentiation of the N2 wave, while the N2 depression clearly emerged after drug wash-out. This indicates that GABA is not involved in inducing the long term effect, but it is necessary for its expression. Similarly, the LTD reversed and a slight potentiation appeared when both drugs were administered after its induction. Most of these effects were due to the bicuculline, suggesting that GABAA receptors contribute to LTD more than GABAB do. According to our results, it is unlikely that the long lasting vestibular depression is the result of a homosynaptic LTD. On the contrary, our findings suggest that the depression is due to an enhancement of the GABA inhibitory effect, caused by an HFS dependent increase in gabaergic interneuron activity, which resets vestibular neuron excitability at a lower level.

Cocaine Dysregulates Opioid Gating of GABA Neurotransmission in the Ventral Pallidum

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Scofield, Michael D.; Rice, Kenner C.; Cheng, Kejun; Roques, Bernard P.

2014-01-01

The ventral pallidum (VP) is a target of dense nucleus accumbens projections. Many of these projections coexpress GABA and the neuropeptide enkephalin, a δ and μ opioid receptor (MOR) ligand. Of these two, the MOR in the VP is known to be involved in reward-related behaviors, such as hedonic responses to palatable food, alcohol intake, and reinstatement of cocaine seeking. Stimulating MORs in the VP decreases extracellular GABA, indicating that the effects of MORs in the VP on cocaine seeking are via modulating GABA neurotransmission. Here, we use whole-cell patch-clamp on a rat model of withdrawal from cocaine self-administration to test the hypothesis that MORs presynaptically regulate GABA transmission in the VP and that cocaine withdrawal changes the interaction between MORs and GABA. We found that in cocaine-extinguished rats pharmacological activation of MORs no longer presynaptically inhibited GABA release, whereas blocking the MORs disinhibited GABA release. Moreover, MOR-dependent long-term depression of GABA neurotransmission in the VP was lost in cocaine-extinguished rats. Last, GABA neurotransmission was found to be tonically suppressed in cocaine-extinguished rats. These substantial synaptic changes indicated that cocaine was increasing tone on MOR receptors. Accordingly, increasing endogenous tone by blocking the enzymatic degradation of enkephalin inhibited GABA neurotransmission in yoked saline rats but not in cocaine-extinguished rats. In conclusion, our results indicate that following withdrawal from cocaine self-administration enkephalin levels in the VP are elevated and the opioid modulation of GABA neurotransmission is impaired. This may contribute to the difficulties withdrawn addicts experience when trying to resist relapse. PMID:24431463

Action of bicyclic isoxazole GABA analogues on GABA transporters and its relation to anticonvulsant activity

DEFF Research Database (Denmark)

Bolvig, T; Larsson, O M; Pickering, D S

1999-01-01

The inhibitory action of bicyclic isoxazole gamma-aminobutyric acid (GABA) analogues and their 4,4-diphenyl-3-butenyl (DPB) substituted derivatives has been investigated in cortical neurones and astrocytes as well as in human embryonic kidney (HEK 293) cells transiently expressing either mouse GA...... anticonvulsant activity, lack of proconvulsant activity and the ability of THPO to increase extracellular GABA concentration, indicate that these bicyclic isoxazole GABA analogues and their DPB derivatives may be useful lead structures in future search for new antiepileptic drugs....

Studying cerebellar circuits by remote control of selected neuronal types with GABA-A receptors

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William Wisden

2009-12-01

Full Text Available Although GABA-A receptor-mediated inhibition of cerebellar Purkinje cells by molecular layer interneurons (MLIs has been studied intensely on the cellular level, it has remained unclear how this inhibition regulates cerebellum-dependent behaviour. We have implemented two complementary approaches to investigate the function of the MLI-Purkinje cell synapse on the behavioral level. In the first approach we permanently disrupted inhibitory fast synaptic transmission at the synapse by genetically removing the postsynaptic GABA-A receptors from Purkinje cells (PC-Δγ2 mice. We found that chronic disruption of the MLI-Purkinje cell synapse strongly impaired cerebellar learning of the vestibular occular reflex (VOR, presumably by disrupting the temporal patterns of Purkinje cell activity. However, in PC-Δγ2 mice the baseline VOR reflex was only mildly affected; indeed PC-Δγ2 mice showed no ataxia or gait abnormalities suggesting that MLI control of Purkinje cell activity is either not involved in ongoing motor tasks or that the system has found a way to compensate for its loss. To investigate the latter possibility we have developed an alternative genetic technique; we made the MLI-Purkinje cell synapse selectively sensitive to rapid manipulation with the GABAA receptor modulator zolpidem (PC-γ2-swap mice. Minutes after intraperitoneal zolpidem injection, these PC-γ2-swap mice developed severe motor abnormalities, revealing a substantial contribution of the MLI-Purkinje cell synapse to real time motor control. The cell-type selective permanent knockout of synaptic GABAergic input, and the fast reversible modulation of GABAergic input at the same synapse illustrate how pursuing both strategies gives a fuller view.

GABA and benzodiazepine receptors in the gerbil brain after transient ischemia: demonstration by quantitative receptor autoradiography

International Nuclear Information System (INIS)

Onodera, H.; Sato, G.; Kogure, K.

1987-01-01

Quantitative receptor autoradiography was used to measure the binding of gamma-aminobutyric acid (GABA) and benzodiazepine receptors after ischemia by means of transient occlusion of bilateral common carotid arteries in the gerbil. [ 3 H]Muscimol was used to label the GABAA receptors and [ 3 H]flunitrazepam to label central type benzodiazepine receptors. In the superolateral convexities of the frontal cortices, [ 3 H]muscimol binding was increased in 60% of the animals killed 3 days after ischemia, and decreased in 67% of the animals killed 27 days after ischemia. Twenty-seven days after ischemia, [ 3 H]flunitrazepam binding in the substantia nigra pars reticulata increased to 252% of the control, though the increase in [ 3 H]muscimol binding was not significant. In the dorsolateral region of the caudate putamen, marked neuronal necrosis and depletion of both [ 3 H]muscimol and [ 3 H]flunitrazepam binding sites were observed 27 days after ischemia, the ventromedial region being left intact. In spite of the depletion of pyramidal cells in the CA1 region of the hippocampus, both [ 3 H]muscimol and [ 3 H]flunitrazepam binding sites were preserved 27 days after ischemia. Since our previous study revealed that adenosine A1 binding sites were depleted in the CA1 subfield of the hippocampus after ischemia correlating with neuronal damage, GABAA and benzodiazepine receptors may not be distributed predominantly on the pyramidal cells in the CA1 region

Efficient Production of γ-GABA Using Recombinant E. coli Expressing Glutamate Decarboxylase (GAD) Derived from Eukaryote Saccharomyces cerevisiae.

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Xiong, Qiang; Xu, Zheng; Xu, Lu; Yao, Zhong; Li, Sha; Xu, Hong

2017-12-01

γ-Aminobutyric acid (γ-GABA) is a non-proteinogenic amino acid, which acts as a major regulator in the central nervous system. Glutamate decarboxylase (namely GAD, EC 4.1.1.15) is known to be an ideal enzyme for γ-GABA production using L-glutamic acid as substrate. In this study, we cloned and expressed GAD gene from eukaryote Saccharomyces cerevisiae (ScGAD) in E. coli BL21(DE3). This enzyme was further purified and its optimal reaction temperature and pH were 37 °C and pH 4.2, respectively. The cofactor of ScGAD was verified to be either pyridoxal 5'-phosphate (PLP) or pyridoxal hydrochloride. The optimal concentration of either cofactor was 50 mg/L. The optimal medium for E. coli-ScGAD cultivation and expression were 10 g/L lactose, 5 g/L glycerol, 20 g/L yeast extract, and 10 g/L sodium chloride, resulting in an activity of 55 U/mL medium, three times higher than that of using Luria-Bertani (LB) medium. The maximal concentration of γ-GABA was 245 g/L whereas L-glutamic acid was near completely converted. These findings provided us a good example for bio-production of γ-GABA using recombinant E. coli expressing a GAD enzyme derived from eukaryote.

Three-Step Test System for the Identification of Novel GABAA Receptor Modulating Food Plants.

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Sahin, Sümeyye; Eulenburg, Volker; Kreis, Wolfgang; Villmann, Carmen; Pischetsrieder, Monika

2016-12-01

Potentiation of γ-amino butyric acid (GABA)-induced GABA A receptor (GABA A R) activation is a common pathway to achieve sedative, sleep-enhancing, anxiolytic, and antidepressant effects. Presently, a three-component test system was established for the identification of novel GABA A R modulating food plants. In the first step, potentiation of GABA-induced response of the GABA A R was analysed by two-electrode voltage clamp (TEVC) for activity on human α1β2-GABA A R expressed in Xenopus laevis oocytes. Positively tested food plants were then subjected to quantification of GABA content by high-performance liquid chromatography with fluorescence detection (HPLC-FLD) to exclude test foods, which evoke a TEVC-response by endogenous GABA. In the third step, specificity of GABA A -modulating activity was assessed by TEVC analysis of Xenopus laevis oocytes expressing the homologous glycine receptor (GlyR). The three-component test was then applied to screen 10 aqueous extracts of food plants for their GABA A R activity. Thus, hop cones (Humulus lupulus) and Sideritis sipylea were identified as the most potent specific GABA A R modulators eliciting significant potentiation of the current by 182 ± 27 and 172 ± 19 %, respectively, at the lowest concentration of 0.5 μg/mL. The extracts can now be further evaluated by in vivo studies and by structural evaluation of the active components.

Association between the GABA(A) receptor alpha5 subunit gene locus (GABRA5) and bipolar affective disorder.

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Papadimitriou, G N; Dikeos, D G; Karadima, G; Avramopoulos, D; Daskalopoulou, E G; Vassilopoulos, D; Stefanis, C N

1998-02-07

Genetic factors seem to play an important role in the pathogenesis of affective disorder. The candidate gene strategies are being used, among others, to identify the genes conferring vulnerability to the disease. The genes coding for the receptors of gamma-aminobutyric acid (GABA) have been proposed as candidates for affective disorder, since the GABA neurotransmitter system has been implicated in the pathogenesis of the illness. We examined the possible genetic association between the GABA(A) receptor alpha5 subunit gene locus (GABRA5) on chromosome 15 and affective disorder, in 48 bipolar patients (BP), 40 unipolar patients (UP), and 50 healthy individuals, age- and sex-matched to the patients. All patients and controls were unrelated Greeks. Diagnoses were made after direct interviews according to the DSM-IV and ICD-10 criteria. For the genotyping, a dinucleotide (CA) repeat marker was used. The polymerase chain reaction (PCR) products found were nine alleles with lengths between 272 and 290 base pairs (bp). The distribution of allelic frequencies of the GABRA5 locus differed significantly between BP patients and controls with the 282-bp allele found to be associated with BP affective disorder, while no such difference was observed between the groups of UP patients and controls nor between the two patient groups. The presence or absence of the 282-bp allele in the genotype of BP patients was not shown to influence the age of onset and the overall clinical severity, but was found to be associated with a preponderance of manic over depressive episodes in the course of the illness.

Estradiol and luteinizing hormone regulate recognition memory following subchronic phencyclidine: Evidence for hippocampal GABA action.

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Riordan, Alexander J; Schaler, Ari W; Fried, Jenny; Paine, Tracie A; Thornton, Janice E

2018-05-01

The cognitive symptoms of schizophrenia are poorly understood and difficult to treat. Estrogens may mitigate these symptoms via unknown mechanisms. To examine these mechanisms, we tested whether increasing estradiol (E) or decreasing luteinizing hormone (LH) could mitigate short-term episodic memory loss in a phencyclidine (PCP) model of schizophrenia. We then assessed whether changes in cortical or hippocampal GABA may underlie these effects. Female rats were ovariectomized and injected subchronically with PCP. To modulate E and LH, animals received estradiol capsules or Antide injections. Short-term episodic memory was assessed using the novel object recognition task (NORT). Brain expression of GAD67 was analyzed via western blot, and parvalbumin-containing cells were counted using immunohistochemistry. Some rats received hippocampal infusions of a GABA A agonist, GABA A antagonist, or GAD inhibitor before behavioral testing. We found that PCP reduced hippocampal GAD67 and abolished recognition memory. Antide restored hippocampal GAD67 and rescued recognition memory in PCP-treated animals. Estradiol prevented PCP's amnesic effect in NORT but failed to restore hippocampal GAD67. PCP did not cause significant differences in number of parvalbumin-expressing cells or cortical expression of GAD67. Hippocampal infusions of a GABA A agonist restored recognition memory in PCP-treated rats. Blocking hippocampal GAD or GABA A receptors in ovx animals reproduced recognition memory loss similar to PCP and inhibited estradiol's protection of recognition memory in PCP-treated animals. In summary, decreasing LH or increasing E can lessen short-term episodic memory loss, as measured by novel object recognition, in a PCP model of schizophrenia. Alterations in hippocampal GABA may contribute to both PCP's effects on recognition memory and the hormones' ability to prevent or reverse them. Copyright © 2018 Elsevier Ltd. All rights reserved.

Editing modifies the GABA(A) receptor subunit alpha3

DEFF Research Database (Denmark)

Ohlson, Johan; Pedersen, Jakob Skou; Haussler, David

2007-01-01

Adenosine to inosine (A-to-I) pre-mRNA editing by the ADAR enzyme family has the potential to increase the variety of the proteome. This editing by adenosine deamination is essential in mammals for a functional brain. To detect novel substrates for A-to-I editing we have used an experimental method...... to find selectively edited sites and combined it with bioinformatic techniques that find stem-loop structures suitable for editing. We present here the first verified editing candidate detected by this screening procedure. We show that Gabra-3, which codes for the alpha3 subunit of the GABA(A) receptor......, is a substrate for editing by both ADAR1 and ADAR2. Editing of the Gabra-3 mRNA recodes an isoleucine to a methionine. The extent of editing is low at birth but increases with age, reaching close to 100% in the adult brain. We therefore propose that editing of the Gabra-3 mRNA is important for normal brain...

Negative modulation of the GABAA ρ1 receptor function by l-cysteine.

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Beltrán González, Andrea N; Vicentini, Florencia; Calvo, Daniel J

2018-01-01

l-Cysteine is an endogenous sulfur-containing amino acid with multiple and varied roles in the central nervous system, including neuroprotection and the maintenance of the redox balance. However, it was also suggested as an excitotoxic agent implicated in the pathogenesis of neurological disorders such as Parkinson's and Alzheimer's disease. l-Cysteine can modulate the activity of ionic channels, including voltage-gated calcium channels and glutamatergic NMDA receptors, whereas its effects on GABAergic neurotransmission had not been studied before. In the present work, we analyzed the effects of l-cysteine on responses mediated by homomeric GABA A ρ1 receptors, which are known for mediating tonic γ-aminobutyric acid (GABA) responses in retinal neurons. GABA A ρ1 receptors were expressed in Xenopus laevis oocytes and GABA-evoked chloride currents recorded by two-electrode voltage-clamp in the presence or absence of l-cysteine. l-Cysteine antagonized GABA A ρ1 receptor-mediated responses; inhibition was dose-dependent, reversible, voltage independent, and susceptible to GABA concentration. Concentration-response curves for GABA were shifted to the right in the presence of l-cysteine without a substantial change in the maximal response. l-Cysteine inhibition was insensitive to chemical protection of the sulfhydryl groups of the ρ1 subunits by the irreversible alkylating agent N-ethyl maleimide. Our results suggest that redox modulation is not involved during l-cysteine actions and that l-cysteine might be acting as a competitive antagonist of the GABA A ρ1 receptors. © 2017 International Society for Neurochemistry.

GABA abnormalities in schizophrenia: a methodological review of in vivo studies.

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Taylor, Stephan F; Tso, Ivy F

2015-09-01

Abnormalities of GABAergic interneurons are some of the most consistent findings from post-mortem studies of schizophrenia. However, linking these molecular deficits with in vivo observations in patients - a critical goal in order to evaluate interventions that would target GABAergic deficits - presents a challenge. Explanatory models have been developed based on animal work and the emerging experimental literature in schizophrenia patients. This literature includes: neuroimaging ligands to GABA receptors, magnetic resonance spectroscopy (MRS) of GABA concentration, transcranial magnetic stimulation of cortical inhibitory circuits and pharmacologic probes of GABA receptors to dynamically challenge the GABA system, usually in combination with neuroimaging studies. Pharmacologic challenges have elicited behavioral changes, and preliminary studies of therapeutic GABAergic interventions have been conducted. This article critically reviews the evidence for GABAergic dysfunction from each of these areas. These methods remain indirect measures of GABAergic function, and a broad array of dysfunction is linked with the putative GABAergic measures, including positive symptoms, cognition, emotion, motor processing and sensory processing, covering diverse brain areas. Measures of receptor binding have not shown replicable group differences in binding, and MRS assays of GABA concentration have yielded equivocal evidence of large-scale alteration in GABA concentration. Overall, the experimental base remains sparse, and much remains to be learned about the role of GABAergic interneurons in healthy brains. Challenges with pharmacologic and functional probes show promise, and may yet enable a better characterization of GABAergic deficits in schizophrenia. Copyright © 2014 Elsevier B.V. All rights reserved.

GABA-BZD Receptor Modulating Mechanism of Panax quinquefolius against 72-h Sleep Deprivation Induced Anxiety like Behavior: Possible Roles of Oxidative Stress, Mitochondrial Dysfunction and Neuroinflammation

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Chanana, Priyanka; Kumar, Anil

2016-01-01

Rationale: Panax quinquefolius (American Ginseng) is known for its therapeutic potential against various neurological disorders, but its plausible mechanism of action still remains undeciphered. GABA (Gamma Amino Butyric Acid) plays an important role in sleep wake cycle homeostasis. Thus, there exists rationale in exploring the GABA-ergic potential of Panax quinquefolius as neuroprotective strategy in sleep deprivation induced secondary neurological problems. Objective: The present study was designed to explore the possible GABA-ergic mechanism in the neuro-protective effect of Panax quinquefolius against 72-h sleep deprivation induced anxiety like behavior, oxidative stress, mitochondrial dysfunction, HPA-axis activation and neuroinflammation. Materials and Methods: Male laca mice were sleep deprived for 72-h by using Grid suspended over water method. Panax quinquefolius (American Ginseng 50, 100, and 200 mg/kg) was administered alone and in combination with GABA modulators (GABA Cl− channel inhibitor, GABA-benzodiazepine receptor inhibitor and GABAA agonist) for 8 days, starting 5 days prior to 72-h sleep deprivation period. Various behavioral (locomotor activity, mirror chamber test), biochemical (lipid peroxidation, reduced glutathione, catalase, nitrite levels), mitochondrial complexes, neuroinflammation marker (Tumor Necrosis Factor, TNF-alpha), serum corticosterone, and histopathological sections of brains were assessed. Results: Seventy two hours sleep deprivation significantly impaired locomotor activity, caused anxiety-like behavior, conditions of oxidative stress, alterations in mitochondrial enzyme complex activities, raised serum corticosterone levels, brain TNFα levels and led to neuroinflammation like signs in discrete brain areas as compared to naive group. Panax quinquefolius (100 and 200 mg/kg) treatment restored the behavioral, biochemical, mitochondrial, molecular and histopathological alterations. Pre-treatment of GABA Cl− channel

[ERK activation effects on GABA secretion inhibition induced by SDF-1 in hippocampal neurons of rats].

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Zhang, Zi-juan; Guo, Mei-xia; Xing, Ying

2015-09-01

To investigate the effect of extracellular regulating kinase (ERK) signaling pathway on the secretion of gamma-aminobutyric acid (GABA) in cultured rat hippocampal neurons induced by stromal cell derived factor-1 (SDF-1). The hippocampal neurons of newborn SD rats were cultured and identified in vitro; the phosphorylation level of ERK1/2 was examined by Western blot; ELISA was used to detect the effect of PD98059, a ERK1/2 specific blocker on GABA secretion of cultured hippocampal neurons and Western blot were adopted to measure the protein expression levels of glutamate decarboxylase (GAD65/67) and gamma aminobutyric acid transporter (GAT); after blocking ERK1/2 signaling pathway with PD98059; RT-PCR was used to detect the mRNA expression levels of GAT-1 and GAD65 after treated with PD98059. The levels of ERKl/2 phosphorylation were increased significantly by SDF1 acting on hippocampal neurons, and CX-CR4 receptor blocker AMD3100, could inhibit SDF-1 induced ERK1/2 activation; SDF-1 could inhibit the secretion of GABA in cultured hippocampal neurons, and ERK1/2 specific inhibitor PD98059, could partly reverse the inhibition of GABA secretion by SDF-1. The effects of SDF-1 on cultured hippocampal neurons was to decrease the mRNA genesis of glutamic acid decarboxylase GAD65 and GABA transporter GAT-1, besides, ERK inhibitor PD98059 could effectively flip the effect of SDF-1. The results of Western blot showed that SDF-1 could inhibit the protein expression of GAT-1 and GAD65/67 in hippocampal neurons and the inhibition of GAT-1 and GAD65/67 protein expression could be partially restored by ERK1/2 blocker. SDF-1 acts on the CXCR4 of hippocampal neurons in vitro, and inhibits the expression of GAD by activating the ERK1/2 signaling pathway, and this may represent one possible pathway of GABA secretion inhibition.

Opioid modulation of GABA release in the rat inferior colliculus

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Forge Andrew

2004-09-01

Full Text Available Abstract Background The inferior colliculus, which receives almost all ascending and descending auditory signals, plays a crucial role in the processing of auditory information. While the majority of the recorded activities in the inferior colliculus are attributed to GABAergic and glutamatergic signalling, other neurotransmitter systems are expressed in this brain area including opiate peptides and their receptors which may play a modulatory role in neuronal communication. Results Using a perfusion protocol we demonstrate that morphine can inhibit KCl-induced release of [3H]GABA from rat inferior colliculus slices. DAMGO ([D-Ala(2, N-Me-Phe(4, Gly(5-ol]-enkephalin but not DADLE ([D-Ala2, D-Leu5]-enkephalin or U69593 has the same effect as morphine indicating that μ rather than δ or κ opioid receptors mediate this action. [3H]GABA release was diminished by 16%, and this was not altered by the protein kinase C inhibitor bisindolylmaleimide I. Immunostaining of inferior colliculus cryosections shows extensive staining for glutamic acid decarboxylase, more limited staining for μ opiate receptors and relatively few neurons co-stained for both proteins. Conclusion The results suggest that μ-opioid receptor ligands can modify neurotransmitter release in a sub population of GABAergic neurons of the inferior colliculus. This could have important physiological implications in the processing of hearing information and/or other functions attributed to the inferior colliculus such as audiogenic seizures and aversive behaviour.

Opioid modulation of GABA release in the rat inferior colliculus

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Tongjaroenbungam, Walaiporn; Jongkamonwiwat, Nopporn; Cunningham, Joanna; Phansuwan-Pujito, Pansiri; Dodson, Hilary C; Forge, Andrew; Govitrapong, Piyarat; Casalotti, Stefano O

2004-01-01

Background The inferior colliculus, which receives almost all ascending and descending auditory signals, plays a crucial role in the processing of auditory information. While the majority of the recorded activities in the inferior colliculus are attributed to GABAergic and glutamatergic signalling, other neurotransmitter systems are expressed in this brain area including opiate peptides and their receptors which may play a modulatory role in neuronal communication. Results Using a perfusion protocol we demonstrate that morphine can inhibit KCl-induced release of [3H]GABA from rat inferior colliculus slices. DAMGO ([D-Ala(2), N-Me-Phe(4), Gly(5)-ol]-enkephalin) but not DADLE ([D-Ala2, D-Leu5]-enkephalin or U69593 has the same effect as morphine indicating that μ rather than δ or κ opioid receptors mediate this action. [3H]GABA release was diminished by 16%, and this was not altered by the protein kinase C inhibitor bisindolylmaleimide I. Immunostaining of inferior colliculus cryosections shows extensive staining for glutamic acid decarboxylase, more limited staining for μ opiate receptors and relatively few neurons co-stained for both proteins. Conclusion The results suggest that μ-opioid receptor ligands can modify neurotransmitter release in a sub population of GABAergic neurons of the inferior colliculus. This could have important physiological implications in the processing of hearing information and/or other functions attributed to the inferior colliculus such as audiogenic seizures and aversive behaviour. PMID:15353008

GABA transporter-1 deficiency confers schizophrenia-like behavioral phenotypes.

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Zhe Yu

Full Text Available The mechanism underlying the pathogenesis of schizophrenia remains poorly understood. The hyper-dopamine and hypo-NMDA receptor hypotheses have been the most enduring ideas. Recently, emerging evidence implicates alterations of the major inhibitory system, GABAergic neurotransmission in the schizophrenic patients. However, the pathophysiological role of GABAergic system in schizophrenia still remains dubious. In this study, we took advantage of GABA transporter 1 (GAT1 knockout (KO mouse, a unique animal model with elevated ambient GABA, to study the schizophrenia-related behavioral abnormalities. We found that GAT1 KO mice displayed multiple behavioral abnormalities related to schizophrenic positive, negative and cognitive symptoms. Moreover, GAT1 deficiency did not change the striatal dopamine levels, but significantly enhanced the tonic GABA currents in prefrontal cortex. The GABA(A receptor antagonist picrotoxin could effectively ameliorate several behavioral defects of GAT1 KO mice. These results identified a novel function of GAT1, and indicated that the elevated ambient GABA contributed critically to the pathogenesis of schizophrenia. Furthermore, several commonly used antipsychotic drugs were effective in treating the locomotor hyperactivity in GAT1 KO mice, suggesting the utility of GAT1 KO mice as an alternative animal model for studying schizophrenia pathogenesis and developing new antipsychotic drugs.

Altered expression of genes involved in GABAergic transmission and neuromodulation of granule cell activity in the cerebellum of schizophrenia patients.

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Bullock, W Michael; Cardon, Karen; Bustillo, Juan; Roberts, Rosalinda C; Perrone-Bizzozero, Nora I

2008-12-01

Deficits in gamma-aminobutyric acid (GABA) signaling have been described in the prefrontal cortex, limbic system, and cerebellum in individuals with schizophrenia. The purpose of the present study was to further investigate cerebellar gene expression alterations as they relate to decreases in GABAergic transmission by examining the expression of GABAergic markers, N-methyl-d-aspartic-acid (NMDA) receptor subunits, and cerebellum neuromodulators in individuals with schizophrenia. Subjects were postmortem men with a diagnosis of schizophrenia (N=13) and a postmortem interval-matched non-psychiatric male comparison group (N=13). The authors utilized real-time-quantitative polymerase chain reaction (PCR) to measure mRNA levels of the following GABAergic markers: glutamic acid decarboxylase (GAD) 65 and 67; GABA plasma membrane transporter-1 (GAT-1); GABA type A (GABA(A)) receptor subunits alpha(6), beta(3), and delta; and parvalbumin. In addition, real-time-quantitative PCR was utilized to assess mRNA levels of the NMDA receptor (NR) subunits NR1, NR2-A, NR2-B, NR2-C, and NR2-D as well as the cerebellar neuromodulators glutamate receptor (GluR)-6, kainate-preferring glutamate receptor subunit-2 (KA2), metabotropic glutamate receptor (mGluR)-2 and mGluR3, and neuronal nitric oxide synthase. Measurements for mRNA levels were determined using lateral cerebellar hemisphere tissue from both schizophrenia and comparison subjects. Schizophrenia subjects showed significant decreases in mRNA levels of GAD(67), GAD(65), GAT-1, mGluR2, and neuronal nitric oxide synthase. Increases in GABA(A)-alpha(6 )and GABA(A)-delta as well as GluR6 and KA2 were also observed. Medication effects on the expression of the same genes were examined in rats treated with either haloperidol (Sprague-Dawley rats [N=16]) or clozapine (Long-Evans rats [N=20]). Both haloperidol and clozapine increased the levels of GAD(67) in the cerebellum and altered the expression of other cerebellar mRNAs. These

Effects of disrupting medial prefrontal cortex GABA transmission on decision-making in a rodent gambling task.

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Paine, T A; O'Hara, A; Plaut, B; Lowes, D C

2015-05-01

Decision-making is a complex cognitive process that is mediated, in part, by subregions of the medial prefrontal cortex (PFC). Decision-making is impaired in a number of psychiatric conditions including schizophrenia. Notably, people with schizophrenia exhibit reductions in GABA function in the same PFC areas that are implicated in decision-making. For example, expression of the GABA-synthesizing enzyme GAD67 is reduced in the dorsolateral PFC of people with schizophrenia. The goal of this experiment was to determine whether disrupting cortical GABA transmission impairs decision-making using a rodent gambling task (rGT). Rats were trained on the rGT until they reached stable performance and then were implanted with guide cannulae aimed at the medial PFC. Following recovery, the effects of intra-PFC infusions of the GABAA receptor antagonist bicuculline methiodide (BMI) or the GABA synthesis inhibitor L-allylglycine (LAG) on performance on the rGT were assessed. Intracortical infusions of BMI (25 ng/μl/side), but not LAG (10 μg/μl/side), altered decision-making. Following BMI infusions, rats made fewer advantageous choices. Follow-up experiments suggested that the change in decision-making was due to a change in the sensitivity to the punishments, rather than a change in the sensitivity to reward magnitudes, associated with each outcome. LAG infusions increased premature responding, a measure of response inhibition, but did not affect decision-making. Blocking GABAA receptors, but not inhibiting cortical GABA synthesis, within the medial PFC affects decision-making in the rGT. These data provide proof-of-concept evidence that disruptions in GABA transmission can contribute to the decision-making deficits in schizophrenia.

Baclofen blocks the acquisition and expression of mitragynine-induced conditioned place preference in rats.

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Yusoff, Nurul H M; Mansor, Sharif M; Müller, Christian P; Hassan, Zurina

2018-06-01

Mitragynine is the major alkaloid found in the leaves of M. speciosa Korth (Rubiaceae), a plant that is native to Southeast Asia. This compound has been used, either traditionally or recreationally, due to its psychostimulant and opioid-like effects. Recently, mitragynine has been shown to exert conditioned place preference (CPP), indicating the rewarding and motivational properties of M. speciosa. Here, the involvement of GABA B receptors in mediating mitragynine reward is studied using a CPP paradigm in rats. First, we examined the effects of GABA B receptor agonist baclofen (1.25, 2.5 and 5 mg/kg) on the acquisition of mitragynine (10 mg/kg)-induced CPP. Second, the involvement of GABA B receptors in the expression of mitragynine-induced CPP was tested. We found that the acquisition of mitragynine-induced CPP could be blocked by higher doses (2.5 and 5 mg/kg) of baclofen. Baclofen at a high dose inhibited locomotor activity and caused a CPP. Furthermore, we found that baclofen (2.5 and 5 mg/kg) also blocked the expression of mitragynine-induced CPP. These findings suggest that both, the acquisition and expression of mitragynine's reinforcing properties is controlled by the GABA B receptor. Copyright © 2018 Elsevier B.V. All rights reserved.

The GABA-A benzodiazepine receptor complex: Role of pet and spect in neurology and psychiatry

International Nuclear Information System (INIS)

Juengling, F.D.; Schaefer, M.; Heinz, A.

2002-01-01

Nuclear medicine imaging techniques such as positron emission tomography (PET) and single photon emission tomography (SPECT) for selective depiction of GABA-A-benzodiazepine receptor (GBZR) binding are complementary investigations in the diagnostic process of neurological and psychiatric disorders. This review summarizes the current knowledge about options and limitations of PET and SPECT for in vivo diagnostics in neurology and psychiatry. The growing importance of GBZR-imaging for the understanding of pathophysiology and pharmacological treatment in different psychiatric syndromes is discussed. (orig.) [de

Increased GABA(A) inhibition of the RVLM after hindlimb unloading in rats

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Moffitt, Julia A.; Heesch, Cheryl M.; Hasser, Eileen M.

2002-01-01

Attenuated baroreflex-mediated increases in renal sympathetic nerve activity (RSNA) in hindlimb unloaded (HU) rats apparently are due to changes within the central nervous system. We hypothesized that GABA(A) receptor-mediated inhibition of the rostral ventrolateral medulla (RVLM) is increased after hindlimb unloading. Responses to bilateral microinjection of the GABA(A) antagonist (-)-bicuculline methiodide (BIC) into the RVLM were examined before and during caudal ventrolateral medulla (CVLM) inhibition in Inactin-anesthetized control and HU rats. Increases in mean arterial pressure (MAP), heart rate (HR), and RSNA in response to BIC in the RVLM were significantly enhanced in HU rats. Responses to bilateral CVLM blockade were not different. When remaining GABA(A) inhibition in the RVLM was blocked by BIC during CVLM inhibition, the additional increases in MAP and RSNA were significantly greater in HU rats. These data indicate that GABA(A) receptor-mediated inhibition of RVLM neurons is augmented after hindlimb unloading. Effects of input from the CVLM were unaltered. Thus, after cardiovascular deconditioning in rodents, the attenuated increase in sympathetic nerve activity in response to hypotension is associated with greater GABA(A) receptor-mediated inhibition of RVLM neurons originating at least in part from sources other than the CVLM.

Glutamate and GABA in lateral hypothalamic mechanisms controlling food intake.

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Stanley, B G; Urstadt, K R; Charles, J R; Kee, T

2011-07-25

By the 1990s a convergence of evidence had accumulated to suggest that neurons within the lateral hypothalamus (LH) play important roles in the stimulation of feeding behavior. However, there was little direct evidence demonstrating that neurotransmitters in the LH could, like electrical stimulation, elicit feeding in satiated animals. The present paper is a brief review in honor of Bartley Hoebel's scientific contributions, emphasizing the evidence from my lab that the excitatory neurotransmitter glutamate and the inhibitory neurotransmitter gamma aminobutyric acid (GABA) in the LH mediate feeding stimulation and feeding inhibition respectively. Specifically, we summarize evidence that LH injection of glutamate, or agonists of its N-methyl-D-aspartate (NMDA) and non-NMDA receptors, elicits feeding in satiated rats, that NMDA receptor antagonists block the eating elicited by NMDA and, more importantly, that NMDA blockade suppresses natural feeding and can reduce body weight. Conversely, GABA(A) agonists injected into the LH suppress feeding and can also reduce body weight, while GABA(A) receptor antagonists actually elicit eating when injected into the LH of satiated rats. It is suggested that natural feeding may reflect the moment-to-moment balance in the activity of glutamate and GABA within the LH. Copyright © 2011 Elsevier Inc. All rights reserved.

The dynamics of GABA signaling: Revelations from the circadian pacemaker in the suprachiasmatic nucleus

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Albers, H. Elliott; Walton, James C.; Gamble, Karen L.; McNeill, John K.; Hummer, Daniel L.

2016-01-01

Virtually every neuron within the suprachiasmatic nucleus (SCN) communicates via GABAergic signaling. The extracellular levels of GABA within the SCN are determined by a complex interaction of synthesis and transport, as well as synaptic and non-synaptic release. The response to GABA is mediated by GABAA receptors that respond to both phasic and tonic GABA release and that can produce excitatory as well as inhibitory cellular responses. GABA also influences circadian control through the exclusively inhibitory effects of GABAB receptors. Both GABA and neuropeptide signaling occur within the SCN, although the functional consequences of the interactions of these signals are not well understood. This review considers the role of GABA in the circadian pacemaker, in the mechanisms responsible for the generation of circadian rhythms, in the ability of non-photic stimuli to reset the phase of the pacemaker, and in the ability of the day-night cycle to entrain the pacemaker. PMID:27894927

Desensitization of γ-aminobutyric acid receptor from rat brain: two distinguishable receptors on the same membrane

International Nuclear Information System (INIS)

Cash, D.J.; Subbarao, K.

1987-01-01

Transmembrane chloride flux mediated by γ-aminobutyric acid (GABA) receptor can be measured with a mammalian brain homogenate preparation containing sealed membrane vesicles. The preparation can be mixed rapidly with solutions of defined composition. Influx of 36 Cl - tracer initiated by mixing with GABA was rapidly terminated by mixing with bicuculline methiodide. The decrease in the isotope influx measurement due to prior incubation of the vesicle preparation with GABA, which increased with preincubation time and GABA concentration, was attributed to desensitization of the GABA receptor. By varying the time of preincubation with GABA between 10 ms and 50 s with quench-flow technique, the desensitization rates could be measured over their whole time course independently of the chloride ion flux rate. Most of the receptor activity decreased in a fast phase of desensitization complete in 200 ms at saturation with GABA. Remaining activity was desensitized in a few seconds. These two phases of desensitization were each kinetically first order and were shown to correspond with two distinguishable GABA receptors on the same membrane. The receptor activities could be estimated, and the faster desensitizing receptor was the predominant one, giving on average ca. 80% of the total activity. The half-response concentrations were similar, 150 and 114 μM for the major and minor receptors, respectively. The dependence on GABA concentration indicated that desensitization is mediated by two GABA binding sites. The fast desensitization rate was approximately 20-fold faster than previously reported rates while the slower desensitization rate was slightly faster than previously reported rates

Linking GABA(A) receptor subunits to alcohol-induced conditioned taste aversion and recovery from acute alcohol intoxication.

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Blednov, Y A; Benavidez, J M; Black, M; Chandra, D; Homanics, G E; Rudolph, U; Harris, R A

2013-04-01

GABA type A receptors (GABA(A)-R) are important for ethanol actions and it is of interest to link individual subunits with specific ethanol behaviors. We studied null mutant mice for six different GABA(A)-R subunits (α1, α2, α3, α4, α5 and δ). Only mice lacking the α2 subunit showed reduction of conditioned taste aversion (CTA) to ethanol. These results are in agreement with data from knock-in mice with mutation of the ethanol-sensitive site in the α2-subunit (Blednov et al., 2011). All together, they indicate that aversive property of ethanol is dependent on ethanol action on α2-containing GABA(A)-R. Deletion of the α2-subunit led to faster recovery whereas absence of the α3-subunit slowed recovery from ethanol-induced incoordination (rotarod). Deletion of the other four subunits did not affect this behavior. Similar changes in this behavior for the α2 and α3 null mutants were found for flurazepam motor incoordination. However, no differences in recovery were found in motor-incoordinating effects of an α1-selective modulator (zolpidem) or an α4-selective agonist (gaboxadol). Therefore, recovery of rotarod incoordination is under control of two GABA(A)-R subunits: α2 and α3. For motor activity, α3 null mice demonstrated higher activation by ethanol (1 g/kg) whereas both α2 (-/-) and α3 (-/Y) knockout mice were less sensitive to ethanol-induced reduction of motor activity (1.5 g/kg). These studies demonstrate that the effects of ethanol at GABAergic synapses containing α2 subunit are important for specific behavioral effects of ethanol which may be relevant to the genetic linkage of the α2 subunit with human alcoholism. Copyright © 2012 Elsevier Ltd. All rights reserved.

GABA-ergic neurons in the leach central nervous system

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Cline, H.T.

1985-01-01

GABA is a candidate for an inhibitory neurotransmitter in the leech central nervous system because of the well-documented inhibitory action of GABA in other invertebrates. To demonstrate that GABA meets the criteria used to identify a substance as a neurotransmitter, the author examined GABA metabolism and synaptic interactions of inhibitory motor neurons in two leech species, Hirudo medicinalis and Haementeria ghilianii. Segmental ganglia of the leech ventral nerve cord and identified inhibitors have the capacity to synthesize GABA when incubated in the presence of the precursor glutamate. Application of GABA to cell bodies of excitatory motor neurons or muscle fibers innervated by the inhibitors hyperpolarizes the membrane potential of the target cell and activates a chloride ion conductance channel, similar to the inhibitory membrane response following intracellular stimulation of the inhibitor. Bicuculline methiodide (5 x 10 -5 M), GABA receptor antagonist, blocks reversibly the response to applied GABA and the inhibitory synaptic inputs onto the postsynaptic neurons or muscle fibers without interfering with their excitatory inputs. Furthermore, the inhibitors are included among approximately 25 neurons per segmental ganglion that take up GABA by a high affinity uptake system, as revealed by 3 H-GABA-autoradiography. The development of the capacities to synthesize and to take up GABA were examined in leech embryos. The embryos are able to synthesize GABA at early stages of the development of the nervous system, before any neurons have extended neutrites

Effects of electroacupuncture on the levels of retinal gamma-aminobutyric acid and its receptors in a guinea pig model of lens-induced myopia.

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Sha, F; Ye, X; Zhao, W; Xu, C-L; Wang, L; Ding, M-H; Bi, A-L; Wu, J-F; Jiang, W-J; Guo, D-D; Guo, J-G; Bi, H-S

2015-02-26

Gamma-aminobutyric acid (GABA) is a major inhibitory neurotransmitter of the retina and affects myopic development. Electroacupuncture (EA) is widely utilized to treat myopia in clinical settings. However, there are few reports on whether EA affects the level of retinal GABA during myopic development. To study this issue, in the present study, we explored the changes of retinal GABA content and the expression of its receptor subtypes, and the effects of EA stimulation on them in a guinea pig model with lens-induced myopia (LIM). Our results showed that the content of GABA and the expression of GABAA and GABAC receptors of retina were up-regulated during the development of myopia, and this up-regulation was inhibited by applying EA to Hegu (LI4) and Taiyang (EX-HN5) acupoints. Moreover, these effects of EA show a positional specificity. While applying EA at a sham acupoint, no apparent change of myopic retinal GABA and its receptor subtypes was observed. Taken together, our findings suggest that LIM is effective to up-regulate the level of retinal GABA, GABAA and GABAC receptors in guinea pigs and the effect may be inhibited by EA stimulation at LI4 and EX-HN5 acupoints. Copyright © 2014 IBRO. Published by Elsevier Ltd. All rights reserved.

Waking action of ursodeoxycholic acid (UDCA involves histamine and GABAA receptor block.

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Yevgenij Yanovsky

Full Text Available Since ancient times ursodeoxycholic acid (UDCA, a constituent of bile, is used against gallstone formation and cholestasis. A neuroprotective action of UDCA was demonstrated recently in models of Alzheimer's disease and retinal degeneration. The mechanisms of UDCA action in the nervous system are poorly understood. We show now that UDCA promotes wakefulness during the active period of the day, lacking this activity in histamine-deficient mice. In cultured hypothalamic neurons UDCA did not affect firing rate but synchronized the firing, an effect abolished by the GABA(AR antagonist gabazine. In histaminergic neurons recorded in slices UDCA reduced amplitude and duration of spontaneous and evoked IPSCs. In acutely isolated histaminergic neurons UDCA inhibited GABA-evoked currents and sIPSCs starting at 10 µM (IC(50 = 70 µM and did not affect NMDA- and AMPA-receptor mediated currents at 100 µM. Recombinant GABA(A receptors composed of α1, β1-3 and γ2L subunits expressed in HEK293 cells displayed a sensitivity to UDCA similar to that of native GABA(A receptors. The mutation α1V256S, known to reduce the inhibitory action of pregnenolone sulphate, reduced the potency of UDCA. The mutation α1Q241L, which abolishes GABA(AR potentiation by several neurosteroids, had no effect on GABA(AR inhibition by UDCA. In conclusion, UDCA enhances alertness through disinhibition, at least partially of the histaminergic system via GABA(A receptors.

Quantitative autoradiographic characterization of GA-BAB receptors in mammalian central nervous system

International Nuclear Information System (INIS)

Chu, D.Chin-Mei.

1989-01-01

The inhibitory effects of the amino acid neurotransmitter γ-aminobutyric acid (GABA) within the nervous system appear to be mediated through two distinct classes of receptors: GABA A and GABA B receptors. A quantitative autoradiographic method with 3 H-GABA was developed to examine the hypotheses that GABA A and GABA B sites have distinct anatomical distributions, pharmacologic properties, and synaptic localizations within the rodent nervous system. The method was also applied to a comparative study of these receptors in postmortem human brain from individuals afflicted with Alzheimer's disease and those without neurologic disease. The results indicated that GABA B receptors occur in fewer numbers and have a lower affinity for GABA than GABA A receptors in both rodent and human brain. Within rodent brain, the distribution of these two receptor populations were clearly distinct. GABA B receptors were enriched in the medial habenula, interpeduncular nucleus, cerebellar molecular layer and olfactory glomerular layer. After selective lesions of postsynaptic neurons of the corticostriatal and perforant pathway, both GABA B and GABA A receptors were significantly decreased in number. Lesions of the presynaptic limbs of the perforant but not the corticostriatal pathway resulted in upregulation of both GABA receptors in the area of innervation. GABA B receptors were also upregulated in CA3 dendritic regions after destruction of dentate granule neurons

GABAA receptor subunit gene expression in human prefrontal cortex: comparison of schizophrenics and controls

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Akbarian, S.; Huntsman, M. M.; Kim, J. J.; Tafazzoli, A.; Potkin, S. G.; Bunney, W. E. Jr; Jones, E. G.; Bloom, F. E. (Principal Investigator)

1995-01-01

The prefrontal cortex of schizophrenics is hypoactive and displays changes related to inhibitory, GABAergic neurons, and GABAergic synapses. These changes include decreased levels of glutamic acid decarboxylase (GAD), the enzyme for GABA synthesis, upregulation of muscimol binding, and downregulation of benzodiazepine binding to GABAA receptors. Studies in the visual cortex of nonhuman primates have demonstrated that gene expression for GAD and for several GABAA receptor subunit polypeptides is under control of neuronal activity, raising the possibility that similar mechanisms in the hypoactive prefrontal cortex of schizophrenics may explain the abnormalities in GAD and in GABAA receptor regulation. In the present study, which is the first of its type on human cerebral cortex, levels of mRNAs for six GABAA receptor subunits (alpha 1, alpha 2, alpha 5, beta 1, beta 2, gamma 2) and their laminar expression patterns were analyzed in the prefrontal cortex of schizophrenics and matched controls, using in situ hybridization histochemistry and densitometry. Three types of laminar expression pattern were observed: mRNAs for the alpha 1, beta 2, and gamma 2 subunits, which are the predominant receptor subunits expressed in the mature cortex, were expressed at comparatively high levels by cells of all six cortical layers, but most intensely by cells in lower layer III and layer IV. mRNAs for the alpha 2, alpha 5, and beta 1 subunits were expressed at lower levels; alpha 2 and beta 1 were expressed predominantly by cells in layers II, III, and IV; alpha 5 was expressed predominantly in layers IV, V, and VI. There were no significant changes in overall mRNA levels for any of the receptor subunits in the prefrontal cortex of schizophrenics, and the laminar expression pattern of all six receptor subunit mRNAs did not differ between schizophrenics and controls. Because gene expression for GABAA receptor subunits is not consistently altered in the prefrontal cortex of

Anxiolytic-like actions of the hexane extract from leaves of Annona cherimolia in two anxiety paradigms: possible involvement of the GABA/benzodiazepine receptor complex.

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López-Rubalcava, C; Piña-Medina, B; Estrada-Reyes, R; Heinze, G; Martínez-Vázquez, M

2006-01-11

A hexane extract of leaves of Annona cherimolia produced anxiolytic-like actions when administered to mice and tested in two animal models of anxiety: the mouse avoidance exploratory behavior and the burying behavior tests. In order to discard unspecific drug-actions on general activity, all treatments studied in the anxiety paradigms were also analyzed in the open field test. Results showed that A. cherimolia induced anxiolytic-like actions at the doses of 6.25, 12.5, 25.0 and 50.0 mg/kg. Picrotoxin (0.25 mg/kg), a GABA-gated chloride ion channel blocker, antagonized the anxiolytic-like actions of A. cherimolia, while a sub-effective dose of muscimol (0.5 mg/kg), a selective GABA(A) receptor agonist, facilitated the effects of a sub-optimal dose of A. cherimolia (3.12 mg/kg). Thus, the involvement of the GABA(A) receptor complex in the anxiolytic-like actions of A. cherimolia hexane extract is suggested. In addition the extract was also able to enhance the duration of sodium pentobarbital induced sleeping time. Taken together, results indicate that the hexane extract of A. cherimolia has depressant activity on the Central Nervous System and could interact with the GABA(A) receptor complex. On the other hand, the chromatographic separation of this extract led to the isolation of palmitone, and beta-sitosterol as major constituents. In addition a GC-MS study of some fractions revealed the presence of several compounds such beta-cariophyllene, beta-selinene, alpha-cubebene, and linalool that have been reported to show effects on behavior that could explain some of the extract effects.

Glutamate AMPA/kainate receptors, not GABA(A) receptors, mediate estradiol-induced sex differences in the hypothalamus.

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Todd, Brigitte J; Schwarz, Jaclyn M; Mong, Jessica A; McCarthy, Margaret M

2007-02-15

Sex differences in brain morphology underlie physiological and behavioral differences between males and females. During the critical perinatal period for sexual differentiation in the rat, gonadal steroids act in a regionally specific manner to alter neuronal morphology. Using Golgi-Cox impregnation, we examined several parameters of neuronal morphology in postnatal day 2 (PN2) rats. We found that in the ventromedial nucleus of the hypothalamus (VMN) and in areas just dorsal and just lateral to the VMN that there was a sex difference in total dendritic spine number (males greater) that was abolished by treating female neonates with exogenous testosterone. Dendritic branching was similarly sexually differentiated and hormonally modulated in the VMN and dorsal to the VMN. We then used spinophilin, a protein that positively correlates with the amount of dendritic spines, to investigate the mechanisms underlying these sex differences. Estradiol, which mediates most aspects of masculinization and is the aromatized product of testosterone, increased spinophilin levels in female PN2 rats to that of males. Muscimol, an agonist at GABA(A) receptors, did not affect spinophilin protein levels in either male or female neonates. Kainic acid, an agonist at glutamatergic AMPA/kainate receptors, mimicked the effect of estradiol in females. Antagonizing AMPA/kainate receptors with NBQX prevented the estradiol-induced increase in spinophilin in females but did not affect spinophilin level in males. (c) 2007 Wiley Periodicals, Inc.

Is GABA neurotransmission enhanced in auditory thalamus relative to inferior colliculus?

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Cai, Rui; Kalappa, Bopanna I.; Brozoski, Thomas J.; Ling, Lynne L.

2013-01-01

Gamma-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the central auditory system. Sensory thalamic structures show high levels of non-desensitizing extrasynaptic GABAA receptors (GABAARs) and a reduction in the redundancy of coded information. The present study compared the inhibitory potency of GABA acting at GABAARs between the inferior colliculus (IC) and the medial geniculate body (MGB) using quantitative in vivo, in vitro, and ex vivo experimental approaches. In vivo single unit studies compared the ability of half maximal inhibitory concentrations of GABA to inhibit sound-evoked temporal responses, and found that GABA was two to three times (P GABA levels and suggested a trend towards higher GABA concentrations in MGB than in IC. Collectively, these studies suggest that, per unit GABA, high affinity extrasynaptic and synaptic GABAARs confer a significant inhibitory GABAAR advantage to MGB neurons relative to IC neurons. This increased GABA sensitivity likely underpins the vital filtering role of auditory thalamus. PMID:24155003

Pyrethroid insecticides and radioligand displacement from the GABA receptor chloride ionophore complex

International Nuclear Information System (INIS)

Crofton, K.M.; Reiter, L.W.; Mailman, R.B.

1987-01-01

Radioligand binding displacement studies were conducted to determine the effects of Type I and II pyrethroids on 3 H-flunitrazepam (FLU), 3 H-muscimol (MUS), and ( 35 S-t-butylbicyclophosphorothionate (TBPS) binding. Competition experiments with 3 H-FLU and 3 H-MUS indicate a lack of competition for binding by the pyrethroids. Type I pyrethroids failed to compete for the binding of ( 35 S-TBPS at concentrations as high as 50 pM. Type II pyrethroids inhibited ( 35 S-TBPS binding to rat brain synaptosomes with Ki values ranging from 5-10 pM. The data presented suggest that the interaction of Type II pyrethroids with the GABA receptor-ionophore complex is restricted to a site near the TBPS/picrotoxinin binding site

Channel opening of γ-aminobutyric acid receptor from rat brain: molecular mechanisms of the receptor responses

International Nuclear Information System (INIS)

Cash, D.J.; Subbarao, K.

1987-01-01

The function of γ-aminobutyric acid (GABA) receptors, which mediate transmembrane chloride flux, can be studied by use of 36 Cl - isotope tracer with membrane from mammalian brain by quench-flow technique, with reaction times that allow resolution of the receptor desensitization rates from the ion flux rates. The rates of chloride exchange into the vesicles in the absence and presence of GABA were characterized with membrane from rat cerebral cortex. Unspecific 36 Cl - influx was completed in three phases of ca. 3% (t/sub 1/2/ = 0.6 s), 56% (t/sub 1/2 = 82 s), and 41% (t/sub 1/2 = 23 min). GABA-mediated, specific chloride exchange occurred with 6.5% of the total vesicular internal volume. The GABA-dependent 36 Cl - influx proceeded in two phases, each progressively slowed by desensitization. The measurements supported the presence of two distinguishable active GABA receptors on the same membrane mediating chloride exchange into the vesicles. The half-response concentrations were similar for both receptors. The two receptors were present in the activity ratio of ca. 4/1, similar to the ratio of low affinity to high-affinity GABA sites found in ligand binding experiments. The desensitization rates have a different dependence on GABA concentration than the channel-opening equilibria. For both receptors, the measurements over a 2000-fold GABA concentration range required a minimal mechanism involving the occupation of both of the two GABA binding sites for significant channel opening; then the receptors were ca. 80% open. Similarly for both receptors, desensitization was mediated by a different pair of binding sites, although desensitization with only one ligand molecule bound could occur at a 20-fold slower rate

Axonal GABAA receptors.

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Trigo, Federico F; Marty, Alain; Stell, Brandon M

2008-09-01

Type A GABA receptors (GABA(A)Rs) are well established as the main inhibitory receptors in the mature mammalian forebrain. In recent years, evidence has accumulated showing that GABA(A)Rs are prevalent not only in the somatodendritic compartment of CNS neurons, but also in their axonal compartment. Evidence for axonal GABA(A)Rs includes new immunohistochemical and immunogold data: direct recording from single axonal terminals; and effects of local applications of GABA(A)R modulators on action potential generation, on axonal calcium signalling, and on neurotransmitter release. Strikingly, whereas presynaptic GABA(A)Rs have long been considered inhibitory, the new studies in the mammalian brain mostly indicate an excitatory action. Depending on the neuron that is under study, axonal GABA(A)Rs can be activated by ambient GABA, by GABA spillover, or by an autocrine action, to increase either action potential firing and/or transmitter release. In certain neurons, the excitatory effects of axonal GABA(A)Rs persist into adulthood. Altogether, axonal GABA(A)Rs appear as potent neuronal modulators of the mammalian CNS.

Pharmacological Characterisation of Nicotinic Acetylcholine Receptors Expressed in Human iPSC-Derived Neurons.

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Anna Chatzidaki

Full Text Available Neurons derived from human induced pluripotent stem cells (iPSCs represent a potentially valuable tool for the characterisation of neuronal receptors and ion channels. Previous studies on iPSC-derived neuronal cells have reported the functional characterisation of a variety of receptors and ion channels, including glutamate receptors, γ-aminobutyric acid (GABA receptors and several voltage-gated ion channels. In the present study we have examined the expression and functional properties of nicotinic acetylcholine receptors (nAChRs in human iPSC-derived neurons. Gene expression analysis indicated the presence of transcripts encoding several nAChR subunits, with highest levels detected for α3-α7, β1, β2 and β4 subunits (encoded by CHRNA3-CHRNA7, CHRNB1, CHRNB2 and CHRNB4 genes. In addition, similarly high transcript levels were detected for the truncated dupα7 subunit transcript, encoded by the partially duplicated gene CHRFAM7A, which has been associated with psychiatric disorders such as schizophrenia. The functional properties of these nAChRs have been examined by calcium fluorescence and by patch-clamp recordings. The data obtained suggest that the majority of functional nAChRs expressed in these cells have pharmacological properties typical of α7 receptors. Large responses were induced by a selective α7 agonist (compound B, in the presence of the α7-selective positive allosteric modulator (PAM PNU-120596, which were blocked by the α7-selective antagonist methyllycaconitine (MLA. In addition, a small proportion of the neurons express nAChRs with properties typical of heteromeric (non-α7 containing nAChR subtypes. These cells therefore represent a great tool to advance our understanding of the properties of native human nAChRs, α7 in particular.

The effects of intraperitoneal administration of the GABA(B) receptor agonist baclofen on food intake in CFLP and C57BL/6 mice.

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Ebenezer, Ivor S; Prabhaker, Monika

2007-08-13

The effects of the GABA(B) receptor agonist baclofen were investigated on food intake in non-deprived CFLP and C57BL/6 mice. In Experiment 1, baclofen (1-8 mg /kg) administered i.p. to CFLP mice, produced a dose-related increase in food intake. The 4 and 8 mg/kg doses produced significant increases in cumulative feeding when measure 120 min after administration (at least P GABA(B) agonist baclofen produces an increase in food consumption in two different strains of mice and extend previous observations made in rat to another rodent species.

The GABA-A benzodiazepine receptor complex: Role of pet and spect in neurology and psychiatry; Der GABA-A-benzodiazepinrezeptorkomplex: Rolle von PET und SPECT in Neurologie und Psychiatrie

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Juengling, F.D. [Abt. fuer Nuklearmedizin, Radiologie III, Universitaetsklinik Ulm (Germany); Schaefer, M.; Heinz, A. [Klinik fuer Psychiatrie und Psychotherapie, Charite, Humboldt-Univ. zu Berlin (Germany)

2002-09-01

Nuclear medicine imaging techniques such as positron emission tomography (PET) and single photon emission tomography (SPECT) for selective depiction of GABA-A-benzodiazepine receptor (GBZR) binding are complementary investigations in the diagnostic process of neurological and psychiatric disorders. This review summarizes the current knowledge about options and limitations of PET and SPECT for in vivo diagnostics in neurology and psychiatry. The growing importance of GBZR-imaging for the understanding of pathophysiology and pharmacological treatment in different psychiatric syndromes is discussed. (orig.) [German] Mit der Entwicklung selektiver Liganden fuer den GABA-A-Benzodiazepinrezeptorkomplex (GBZR) hat die nuklearmedizinische Bildgebung mittels positronen-emissionstomographie (PET) und single-photon-emissionscomputertomographie (SPECT) einen festen Stellenwert fuer Klinik und Forschung in der Neurologie und Psychiatrie erlangt. Die vorliegende Ueberblicksarbeit fasst den aktuellen Wissensstand von Anwendungsmoeglichkeiten und -grenzen der nuklearmedizinischen Bildgebung der GBZR in vivo zusammen und beleuchtet ihren klinischen Nutzen. Die wachsende Bedeutung fuer das Verstaendnis der Pathophysiologie und pharmakotherapeutischer Konzepte unterschiedlicher psychiatrischer Erkrankungen wird herausgestellt. (orig.)

GABA-BZD Receptor Modulating Mechanism of Panax quinquefolius against 72-hours Sleep Deprivation Induced Anxiety like Behavior: Possible Roles of Oxidative Stress, Mitochondrial Dysfunction and Neuroinflammation

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Priyanka eChanana

2016-03-01

Full Text Available ABSTRACTRationale- Panax quinquefolius (American Ginseng is known for its therapeutic potential against various neurological disorders, but its plausible mechanism of action still remains undeciphered. GABA (Gamma Amino Butyric Acid plays an important role in sleep wake cycle homeostasis. Thus there exists rationale in exploring the GABA-ergic potential of Panax quinquefolius as neuroprotective strategy in sleep deprivation induced secondary neurological problems.Objective- The present study was designed to explore the possible GABA-ergic mechanism in the neuro-protective effect of Panax quinquefolius against 72-hours sleep deprivation induced anxiety like behaviour, oxidative stress, mitochondrial dysfunction, HPA-axis activation and neuroinflammation.Materials and Methods- Male laca mice were sleep deprived for 72-hours by using Grid suspended over water method. Panax quinquefolius (American Ginseng 50, 100 and 200 mg/kg was administered alone and in combination with GABA modulators (GABA Cl- channel inhibitor, GABA-benzodiazepine receptor inhibitor and GABAA agonist for 8 days, starting five days prior to 72-hours sleep deprivation period. Various behavioural (locomotor activity, mirror chamber test, biochemical (lipid peroxidation, reduced glutathione, catalase, nitrite levels, mitochondrial complexes, neuroinflammation marker (Tumour Necrosis Factor, TNF-alpha, serum corticosterone, and histopathological sections of brains were assessed. Results- 72-hours sleep deprivation significantly impaired locomotor activity, caused anxiety-like behaviour, conditions of oxidative stress, alterations in mitochondrial enzyme complex activities, raised serum corticosterone levels, brain TNFα levels and led to neuroinflammation like signs in discrete brain areas as compared to naive group. Panax quinquefolius (100 and 200 mg/kg treatment restored the behavioural, biochemical, mitochondrial, molecular and histopathological alterations. Pre-treatment of

HSF1 transcriptional activity mediates alcohol induction of Vamp2 expression and GABA release

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Florence P. Varodayan

2013-12-01

Full Text Available Many central synapses are highly sensitive to alcohol, and it is now accepted that short-term alterations in synaptic function may lead to longer term changes in circuit function. The regulation of postsynaptic receptors by alcohol has been well studied, but the mechanisms underlying the effects of alcohol on the presynaptic terminal are relatively unexplored. To identify a pathway by which alcohol regulates neurotransmitter release, we recently investigated the mechanism by which ethanol induces the Vamp2 gene, but not Vamp1, in mouse primary cortical cultures. These two genes encode isoforms of synaptobrevin, a vesicular soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE protein required for synaptic vesicle fusion. We found that alcohol activates the transcription factor heat shock factor 1 (HSF1 to induce Vamp2 gene expression, while Vamp1 mRNA levels remain unaffected. As the Vamp2 gene encodes a SNARE protein, we then investigated whether ethanol exposure and HSF1 transcriptional activity alter neurotransmitter release using electrophysiology. We found that alcohol increased the frequency of γ-aminobutyric acid (GABA-mediated miniature IPSCs via HSF1, but had no effect on mEPSCs. Overall, these data indicate that alcohol induces HSF1 transcriptional activity to trigger a specific coordinated adaptation in GABAergic presynaptic terminals. This mechanism could explain some of the changes in synaptic function that occur soon after alcohol exposure, and may underlie some of the more enduring effects of chronic alcohol intake on local circuit function.

Zolpidem, a clinical hypnotic that affects electronic transfer, alters synaptic activity through potential GABA receptors in the nervous system without significant free radical generation.

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Kovacic, Peter; Somanathan, Ratnasamy

2009-01-01

Zolpidem (trade name Ambien) has attracted much interest as a sleep-inducing agent and also in research. Attention has been centered mainly on receptor binding and electrochemistry in the central nervous system which are briefly addressed herein. A novel integrated approach to mode of action is presented. The pathways to be discussed involve basicity, reduction potential, electrostatics, cell signaling, GABA receptor binding, electron transfer (ET), pharmacodynamics, structure activity relationships (SAR) and side effects. The highly conjugated pyridinium salt formed by protonation of the amidine moiety is proposed to be the active form acting as an ET agent. Extrapolation of reduction potentials for related compounds supports the premise that zolpidem may act as an ET species in vivo. From recent literature reports, electrostatics is believed to play a significant role in drug action. The pyridinium cation displays molecular electrostatic potential which may well play a role energetically or as a bridging mechanism. An SAR analysis points to analogy with other physiologically active xenobiotics, namely benzodiazepines and paraquat in the conjugated iminium category. Inactivity of metabolites indicates that the parent is the active form of zolpidem. Absence of reactive oxygen species and oxidative stress is in line with minor side effects. In contrast, generally, the prior literature contains essentially no discussion of these fundamental biochemical relationships. Pharmacodynamics may play an important role. Concerning behavior at the blood-brain barrier, useful insight can be gained from investigations of the related cationic anesthetics that are structurally related to acetyl choline. Evidently, the neutral form of the drug penetrates the neuronal membrane, with the salt form operating at the receptor. The pathways of zolpidem have several clinical implications since the agent affects sedation, electroencephalographic activity, oxidative metabolites and

The role of GABA in the hypoxia tolerance of the epaulette shark

International Nuclear Information System (INIS)

Wise, G.; Mulvey, J.; Renshaw, G.M.C.; Dodd, P.R.

1998-01-01

Full text: The epaulette shark responds to hypoxia with brain hypometabolism which is correlated with increased levels of gamma-aminobutyric acid (GABA). We examined GABA-like immunoreactivity (GABA-IR) and the density and binding characteristics of GABA A receptors in the Epaulette shark brainstem. These studies were conducted to investigate changes in response to hypoxia. Experimental animals were exposed to eight cycles of an extreme hypoxic regimen (5% of normoxia). Animals were anaesthetised with 80mg/L of MS222 and the brain was dissected and processed either for immunohistochemistry or receptor ligand binding. Membranes were prepared at 4 deg C according to a previously reported protocol and the binding characteristics of [ 3 H]flunitrazeparn ([ 3 H]FNZ) were examined using an in vitro centrifugation assay. We report on the effect of hypoxia on specific [ 3 H]FNZ binding characteristics. GABA-IR was detected using a primary antibody dilution of 1:15 000 and the Vector ABC method. We report that an overall increase in the optical density of GABA-IR occurs with significant increases in three out of the four brainstem nuclei examined in experimental animals. The results of these studies are discussed in conjunction with the hypoxia-tolerance .of the epaulette shark. Copyright (1998) Australian Neuroscience Society

Genetic manipulation of the γ-aminobutyric acid (GABA) shunt in rice: overexpression of truncated glutamate decarboxylase (GAD2) and knockdown of γ-aminobutyric acid transaminase (GABA-T) lead to sustained and high levels of GABA accumulation in rice kernels.

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Shimajiri, Yasuka; Oonishi, Takayuki; Ozaki, Kae; Kainou, Kumiko; Akama, Kazuhito

2013-06-01

Gamma-aminobutyric acid (GABA) is a non-protein amino acid commonly present in all organisms. Because cellular levels of GABA in plants are mainly regulated by synthesis (glutamate decarboxylase, GAD) and catabolism (GABA-transaminase, GABA-T), we attempted seed-specific manipulation of the GABA shunt to achieve stable GABA accumulation in rice. A truncated GAD2 sequence, one of five GAD genes, controlled by the glutelin (GluB-1) or rice embryo globulin promoters (REG) and GABA-T-based trigger sequences in RNA interference (RNAi) cassettes controlled by one of these promoters as well, was introduced into rice (cv. Koshihikari) to establish stable transgenic lines under herbicide selection using pyriminobac. T₁ and T₂ generations of rice lines displayed high GABA concentrations (2-100 mg/100 g grain). In analyses of two selected lines from the T₃ generation, there was a strong correlation between GABA level and the expression of truncated GAD2, whereas the inhibitory effect of GABA-T expression was relatively weak. In these two lines both with two T-DNA copies, their starch, amylose, and protein levels were slightly lower than non-transformed cv. Koshihikari. Free amino acid analysis of mature kernels of these lines demonstrated elevated levels of GABA (75-350 mg/100 g polished rice) and also high levels of several amino acids, such as Ala, Ser, and Val. Because these lines of seeds could sustain their GABA content after harvest (up to 6 months), the strategy in this study could lead to the accumulation GABA and for these to be sustained in the edible parts. © 2013 Society for Experimental Biology, Association of Applied Biologists and John Wiley & Sons Ltd.

Effects of GABA-B receptor positive modulator on ketamine-induced psychosis-relevant behaviors and hippocampal electrical activity in freely moving rats.

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Ma, Jingyi; Stan Leung, L

2017-10-01

Decreased GABA B receptor function is proposed to mediate some symptoms of schizophrenia. In this study, we tested the effect of CGP7930, a GABA B receptor positive allosteric modulator, on ketamine-induced psychosis-relevant behaviors and hippocampal electrical activity in behaving rats. Electrodes were bilaterally implanted into the hippocampus, and cannulae were placed into the lateral ventricles of Long-Evans rats. CGP7930 or vehicle was injected intraperitoneally (i.p.) or intracerebroventricularly (i.c.v.), alone or 15 min prior to ketamine (3 mg/kg, subcutaneous) injection. Paired click auditory evoked potentials in the hippocampus (AEP), prepulse inhibition (PPI), and locomotor activity were recorded before and after drug injection. CGP7930 at doses of 1 mg/kg (i.p.) prevented ketamine-induced deficit of PPI. CGP7930 (1 mg/kg i.p.) also prevented the decrease in gating of hippocampal AEP and the increase in hippocampal gamma (65-100 Hz) waves induced by ketamine. Unilateral i.c.v. infusion of CGP7930 (0.3 mM/1 μL) also prevented the decrease in gating of hippocampal AEP induced by ketamine. Ketamine-induced behavioral hyperlocomotion was suppressed by 5 mg/kg i.p. CGP7930. CGP7930 alone, without ketamine, did not significantly affect integrated PPI, locomotion, gating of hippocampal AEP, or gamma waves. CGP7930 (1 mg/kg i.p.) increased heterosynaptically mediated paired pulse depression in the hippocampus, a measure of GABA B receptor function in vivo. CGP7930 reduces the behavioral and electrophysiological disruptions induced by ketamine in animals, and the hippocampus may be one of the neural targets where CGP7930 exerts its actions.

Reversed synaptic effects of hypocretin and NPY mediated by excitatory GABA-dependent synaptic activity in developing MCH neurons.

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Li, Ying; Xu, Youfen; van den Pol, Anthony N

2013-03-01

In mature neurons, GABA is the primary inhibitory neurotransmitter. In contrast, in developing neurons, GABA exerts excitatory actions, and in some neurons GABA-mediated excitatory synaptic activity is more prevalent than glutamate-mediated excitation. Hypothalamic neuropeptides that modulate cognitive arousal and energy homeostasis, hypocretin/orexin and neuropeptide Y (NPY), evoked reversed effects on synaptic actions that were dependent on presynaptic GABA release onto melanin-concentrating hormone (MCH) neurons. MCH neurons were identified by selective green fluorescent protein (GFP) expression in transgenic mice. In adults, hypocretin increased GABA release leading to reduced excitation. In contrast, in the developing brain as studied here with analysis of miniature excitatory postsynaptic currents, paired-pulse ratios, and evoked potentials, hypocretin acted presynaptically to enhance the excitatory actions of GABA. The ability of hypocretin to enhance GABA release increases inhibition in adult neurons but paradoxically enhances excitation in developing MCH neurons. In contrast, NPY attenuation of GABA release reduced inhibition in mature neurons but enhanced inhibition during development by attenuating GABA excitation. Both hypocretin and NPY also evoked direct actions on developing MCH neurons. Hypocretin excited MCH cells by activating a sodium-calcium exchanger and by reducing potassium currents; NPY reduced activity by increasing an inwardly rectifying potassium current. These data for the first time show that both hypocretin and NPY receptors are functional presynaptically during early postnatal hypothalamic development and that both neuropeptides modulate GABA actions during development with a valence of enhanced excitation or inhibition opposite to that of the adult state, potentially allowing neuropeptide modulation of use-dependent synapse stabilization.

Relative Neurotoxicity of Ivermectin and Moxidectin in Mdr1ab (−/−) Mice and Effects on Mammalian GABA(A) Channel Activity

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Ménez, Cécile; Sutra, Jean-François; Prichard, Roger; Lespine, Anne

2012-01-01

The anthelmintics ivermectin (IVM) and moxidectin (MOX) display differences in toxicity in several host species. Entrance into the brain is restricted by the P-glycoprotein (P-gp) efflux transporter, while toxicity is mediated through the brain GABA(A) receptors. This study compared the toxicity of IVM and MOX in vivo and their interaction with GABA(A) receptors in vitro. Drug toxicity was assessed in Mdr1ab(−/−) mice P-gp-deficient after subcutaneous administration of increasing doses (0.11–2.0 and 0.23–12.9 µmol/kg for IVM and MOX in P-gp-deficient mice and half lethal doses (LD50) in wild-type mice). Survival was evaluated over 14-days. In Mdr1ab(−/−) mice, LD50 was 0.46 and 2.3 µmol/kg for IVM and MOX, respectively, demonstrating that MOX was less toxic than IVM. In P-gp-deficient mice, MOX had a lower brain-to-plasma concentration ratio and entered into the brain more slowly than IVM. The brain sublethal drug concentrations determined after administration of doses close to LD50 were, in Mdr1ab(−/−) and wild-type mice, respectively, 270 and 210 pmol/g for IVM and 830 and 740–1380 pmol/g for MOX, indicating that higher brain concentrations are required for MOX toxicity than IVM. In rat α1β2γ2 GABA channels expressed in Xenopus oocytes, IVM and MOX were both allosteric activators of the GABA-induced response. The Hill coefficient was 1.52±0.45 for IVM and 0.34±0.56 for MOX (p<0.001), while the maximum potentiation caused by IVM and MOX relative to GABA alone was 413.7±66.1 and 257.4±40.6%, respectively (p<0.05), showing that IVM causes a greater potentiation of GABA action on this receptor. Differences in the accumulation of IVM and MOX in the brain and in the interaction of IVM and MOX with GABA(A) receptors account for differences in neurotoxicity seen in intact and Mdr1-deficient animals. These differences in neurotoxicity of IVM and MOX are important in considering their use in humans. PMID:23133688

Virus-mediated swapping of zolpidem-insensitive with zolpidem-sensitive GABA(A) receptors in cortical pyramidal cells.

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Sumegi, Mate; Fukazawa, Yugo; Matsui, Ko; Lorincz, Andrea; Eyre, Mark D; Nusser, Zoltan; Shigemoto, Ryuichi

2012-04-01

Recently developed pharmacogenetic and optogenetic approaches, with their own advantages and disadvantages, have become indispensable tools in modern neuroscience. Here, we employed a previously described knock-in mouse line (GABA(A)Rγ2(77I)lox) in which the γ2 subunit of the GABA(A) receptor (GABA(A)R) was mutated to become zolpidem insensitive (γ2(77I)) and used viral vectors to swap γ2(77I) with wild-type, zolpidem-sensitive γ2 subunits (γ2(77F)). The verification of unaltered density and subcellular distribution of the virally introduced γ2 subunits requires their selective labelling. For this we generated six N- and six C-terminal-tagged γ2 subunits, with which cortical cultures of GABA(A)Rγ2(−/−) mice were transduced using lentiviruses. We found that the N-terminal AU1 tag resulted in excellent immunodetection and unimpaired synaptic localization. Unaltered kinetic properties of the AU1-tagged γ2 ((AU1)γ2(77F)) channels were demonstrated with whole-cell patch-clamp recordings of spontaneous IPSCs from cultured cells. Next, we carried out stereotaxic injections of lenti- and adeno-associated viruses containing Cre-recombinase and the (AU1)γ2(77F) subunit (Cre-2A-(AU1)γ2(77F)) into the neocortex of GABA(A)Rγ2(77I)lox mice. Light microscopic immunofluorescence and electron microscopic freeze-fracture replica immunogold labelling demonstrated the efficient immunodetection of the AU1 tag and the normal enrichment of the (AU1)γ2(77F) subunits in perisomatic GABAergic synapses. In line with this,miniature and action potential-evoked IPSCs whole-cell recorded from transduced cells had unaltered amplitudes, kinetics and restored zolpidem sensitivity. Our results obtained with a wide range of structural and functional verification methods reveal unaltered subcellular distributions and functional properties of γ2(77I) and (AU1)γ2(77F) GABA(A)Rs in cortical pyramidal cells. This transgenic–viral pharmacogenetic approach has the advantage that it

Neuroimaging studies of GABA in schizophrenia: a systematic review with meta-analysis.

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Egerton, A; Modinos, G; Ferrera, D; McGuire, P

2017-06-06

Data from animal models and from postmortem studies suggest that schizophrenia is associated with brain GABAergic dysfunction. The extent to which this is reflected in data from in vivo studies of GABA function in schizophrenia is unclear. The Medline database was searched to identify articles published until 21 October 2016. The search terms included GABA, proton magnetic resonance spectroscopy ( 1 H-MRS), positron emission tomography (PET), single photon emission computed tomography (SPECT), schizophrenia and psychosis. Sixteen GABA 1 H-MRS studies (538 controls, 526 patients) and seven PET/SPECT studies of GABA A /benzodiazepine receptor (GABA A /BZR) availability (118 controls, 113 patients) were identified. Meta-analyses of 1 H-MRS GABA in the medial prefrontal cortex (mPFC), parietal/occipital cortex (POC) and striatum did not show significant group differences (mFC: g=-0.3, 409 patients, 495 controls, 95% confidence interval (CI): -0.6 to 0.1; POC: g=-0.3, 139 patients, 111 controls, 95% CI: -0.9 to 0.3; striatum: g=-0.004, 123 patients, 95 controls, 95% CI: -0.7 to 0.7). Heterogeneity across studies was high (I 2 >50%), and this was not explained by subsequent moderator or meta-regression analyses. There were insufficient PET/SPECT receptor availability studies for meta-analyses, but a systematic review did not suggest replicable group differences in regional GABA A /BZR availability. The current literature does not reveal consistent alterations in in vivo GABA neuroimaging measures in schizophrenia, as might be hypothesized from animal models and postmortem data. The analysis highlights the need for further GABA neuroimaging studies with improved methodology and addressing potential sources of heterogeneity.

An Electrostatic Funnel in the GABA-Binding Pathway.

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Timothy S Carpenter

2016-04-01

Full Text Available The γ-aminobutyric acid type A receptor (GABAA-R is a major inhibitory neuroreceptor that is activated by the binding of GABA. The structure of the GABAA-R is well characterized, and many of the binding site residues have been identified. However, most of these residues are obscured behind the C-loop that acts as a cover to the binding site. Thus, the mechanism by which the GABA molecule recognizes the binding site, and the pathway it takes to enter the binding site are both unclear. Through the completion and detailed analysis of 100 short, unbiased, independent molecular dynamics simulations, we have investigated this phenomenon of GABA entering the binding site. In each system, GABA was placed quasi-randomly near the binding site of a GABAA-R homology model, and atomistic simulations were carried out to observe the behavior of the GABA molecules. GABA fully entered the binding site in 19 of the 100 simulations. The pathway taken by these molecules was consistent and non-random; the GABA molecules approach the binding site from below, before passing up behind the C-loop and into the binding site. This binding pathway is driven by long-range electrostatic interactions, whereby the electrostatic field acts as a 'funnel' that sweeps the GABA molecules towards the binding site, at which point more specific atomic interactions take over. These findings define a nuanced mechanism whereby the GABAA-R uses the general zwitterionic features of the GABA molecule to identify a potential ligand some 2 nm away from the binding site.

Cockroach GABAB receptor subtypes: molecular characterization, pharmacological properties and tissue distribution.

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Blankenburg, S; Balfanz, S; Hayashi, Y; Shigenobu, S; Miura, T; Baumann, O; Baumann, A; Blenau, W

2015-01-01

γ-aminobutyric acid (GABA) is the predominant inhibitory neurotransmitter in the central nervous system (CNS). Its effects are mediated by either ionotropic GABAA receptors or metabotropic GABAB receptors. GABAB receptors regulate, via Gi/o G-proteins, ion channels, and adenylyl cyclases. In humans, GABAB receptor subtypes are involved in the etiology of neurologic and psychiatric disorders. In arthropods, however, these members of the G-protein-coupled receptor family are only inadequately characterized. Interestingly, physiological data have revealed important functions of GABAB receptors in the American cockroach, Periplaneta americana. We have cloned cDNAs coding for putative GABAB receptor subtypes 1 and 2 of P. americana (PeaGB1 and PeaGB2). When both receptor proteins are co-expressed in mammalian cells, activation of the receptor heteromer with GABA leads to a dose-dependent decrease in cAMP production. The pharmacological profile differs from that of mammalian and Drosophila GABAB receptors. Western blot analyses with polyclonal antibodies have revealed the expression of PeaGB1 and PeaGB2 in the CNS of the American cockroach. In addition to the widespread distribution in the brain, PeaGB1 is expressed in salivary glands and male accessory glands. Notably, PeaGB1-like immunoreactivity has been detected in the GABAergic salivary neuron 2, suggesting that GABAB receptors act as autoreceptors in this neuron. Copyright © 2014 Elsevier Ltd. All rights reserved.

Paracrine GABA and insulin regulate pancreatic alpha cell proliferation in a mouse model of type 1 diabetes.

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Feng, Allen L; Xiang, Yun-Yan; Gui, Le; Kaltsidis, Gesthika; Feng, Qingping; Lu, Wei-Yang

2017-06-01

This study aimed to elucidate the mechanism of increased proliferation of alpha cells in recent-onset type 1 diabetes. Pancreatic beta cells express GAD and produce γ-aminobutyric acid (GABA), which inhibits alpha cell secretion of glucagon. We explored the roles of GABA in alpha cell proliferation in conditions corresponding to type 1 diabetes in a mouse model and in vitro. Type 1 diabetes was induced by injecting the mice with streptozotocin (STZ). Some of the STZ-injected mice were treated with GABA (10 mg/kg daily) for 12 days. Isolated pancreatic islets were treated with STZ or STZ together with GABA for 2 days. The effects of GABA treatment on STZ-induced alpha cell proliferation in vivo and in vitro were assessed. The effect of muscimol, a GABA receptor agonist, on αTC1-6 cell proliferation was also examined. STZ injection substantially decreased levels of GAD, GABA and insulin in pancreatic beta cells 12 h after injection; this was followed by an upsurge of phosphorylated mechanistic target of rapamycin (p-mTOR) in the alpha cells at day 1, and a significant increase in alpha cell mass at day 3. Treating STZ-injected mice with GABA largely restored the immunodetectable levels of insulin and GAD in the beta cells and significantly decreased the number of aldehyde dehydrogenase 1 family, member A3 (ALDH1a3)-positive cells, alpha cell mass and hyperglucagonaemia. STZ treatment also increased alpha cell proliferation in isolated islets, which was reversed by co-treatment with GABA. Muscimol, together with insulin, significantly lowered the level of cytosolic Ca 2+ and p-mTOR, and decreased the proliferation rate of αTC1-6 cells. GABA signalling critically controls the alpha cell population in pancreatic islets. Low intraislet GABA may contribute to alpha cell hyperplasia in early type 1 diabetes.

Presynaptic nicotinic α7 and non-α7 receptors stimulate endogenous GABA release from rat hippocampal synaptosomes through two mechanisms of action.

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Stefania Zappettini

Full Text Available BACKGROUND: Although converging evidence has suggested that nicotinic acetylcholine receptors (nAChR play a role in the modulation of GABA release in rat hippocampus, the specific involvement of different nAChR subtypes at presynaptic level is still a matter of debate. In the present work we investigated, using selective α7 and α4β2 nAChR agonists, the presence of different nAChR subtypes on hippocampal GABA nerve endings to assess to what extent and through which mechanisms they stimulate endogenous GABA release. METHODOLOGY/FINDINGS: All agonists elicited GABA overflow. Choline (Ch-evoked GABA overflow was dependent to external Ca(2+, but unaltered in the presence of Cd(2+, tetrodotoxin (TTX, dihydro-β-erythroidine (DHβE and 1-(4,4-Diphenyl-3-butenyl-3-piperidinecarboxylic acid hydrochloride SKF 89976A. The effect of Ch was blocked by methyllycaconitine (MLA, α-bungarotoxin (α-BTX, dantrolene, thapsigargin and xestospongin C, suggesting that GABA release might be triggered by Ca(2+ entry into synaptosomes through the α7 nAChR channel with the involvement of calcium from intracellular stores. Additionally, 5-Iodo-A-85380 dihydrochloride (5IA85380 elicited GABA overflow, which was Ca(2+ dependent, blocked by Cd(2+, and significantly inhibited by TTX and DHβE, but unaffected by MLA, SKF 89976A, thapsigargin and xestospongin C and dantrolene. These findings confirm the involvement of α4β2 nAChR in 5IA85380-induced GABA release that seems to occur following membrane depolarization and opening calcium channels. CONCLUSIONS/SIGNIFICANCE: Rat hippocampal synaptosomes possess both α7 and α4β2 nAChR subtypes, which can modulate GABA release via two distinct mechanisms of action. The finding that GABA release evoked by the mixture of sub-maximal concentration of 5IA85380 plus sub-threshold concentrations of Ch was significantly larger than that elicited by the sum of the effects of the two agonists is compatible with the possibility that

Perinatal intermittent hypoxia alters γ-aminobutyric acid: a receptor levels in rat cerebellum.

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Pae, Eung-Kwon; Yoon, Audrey J; Ahuja, Bhoomika; Lau, Gary W; Nguyen, Daniel D; Kim, Yong; Harper, Ronald M

2011-12-01

Perinatal hypoxia commonly causes brain injury in infants, but the time course and mechanisms underlying the preferential male injury are unclear. Intermittent hypoxia disturbs cerebellar γ-aminobutyric (GABA)-A receptor profiles during the perinatal period, possibly responding to transient excitatory processes associated with GABA(A) receptors. We examined whether hypoxic insults were particularly damaging to the male rodent cerebellum during a specific developmental time window. We evaluated cerebellar injury and GABA(A) receptor profiles following 5-h intermittent hypoxia (IH: 20.8% and 10.3% ambient oxygen, switched every 240s) or room-air control in groups of male and female rat pups on postnatal d 1-2, wk 1, or wk 3. The cerebella were harvested and compared between groups. The mRNA levels of GABA(A) receptors α6, normalized to a house-keeping gene GAPDH, and assessed using real-time reverse-transcriptase PCR assays were up-regulated by IH at wk 1, more extensively in male rats, with sex influencing the regulatory time-course. In contrast, GABA(A) α6 receptor protein expression levels, assessed using Western blot assays, reached a nadir at wk 1 in both male and female rats, possibly indicating involvement of a post-transcriptional mechanism. The extent of cerebellar damage and level of apoptosis, assessed by DNA fragmentation, were greatest in the wk 3 IH-exposed group. The findings suggest partial protection for female rats against early hypoxic insult in the cerebellum, and that down-regulation of GABA(A) receptors, rather than direct neural injury assessed by DNA fragmentation may modify cerebellar function, with potential later motor and other deficits. Copyright © 2011 ISDN. Published by Elsevier Ltd. All rights reserved.

Phospho-dependent binding of the clathrin AP2 adaptor complex to GABAA receptors regulates the efficacy of inhibitory synaptic transmission.

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Kittler, Josef T; Chen, Guojun; Honing, Stephan; Bogdanov, Yury; McAinsh, Kristina; Arancibia-Carcamo, I Lorena; Jovanovic, Jasmina N; Pangalos, Menelas N; Haucke, Volker; Yan, Zhen; Moss, Stephen J

2005-10-11

The efficacy of synaptic inhibition depends on the number of gamma-aminobutyric acid type A receptors (GABA(A)Rs) expressed on the cell surface of neurons. The clathrin adaptor protein 2 (AP2) complex is a critical regulator of GABA(A)R endocytosis and, hence, surface receptor number. Here, we identify a previously uncharacterized atypical AP2 binding motif conserved within the intracellular domains of all GABA(A)R beta subunit isoforms. This AP2 binding motif (KTHLRRRSSQLK in the beta3 subunit) incorporates the major sites of serine phosphorylation within receptor beta subunits, and phosphorylation within this site inhibits AP2 binding. Furthermore, by using surface plasmon resonance, we establish that a peptide (pepbeta3) corresponding to the AP2 binding motif in the GABA(A)R beta3 subunit binds to AP2 with high affinity only when dephosphorylated. Moreover, the pepbeta3 peptide, but not its phosphorylated equivalent (pepbeta3-phos), enhanced the amplitude of miniature inhibitory synaptic current and whole cell GABA(A)R current. These effects of pepbeta3 on GABA(A)R current were occluded by inhibitors of dynamin-dependent endocytosis supporting an action of pepbeta3 on GABA(A)R endocytosis. Therefore phospho-dependent regulation of AP2 binding to GABA(A)Rs provides a mechanism to specify receptor cell surface number and the efficacy of inhibitory synaptic transmission.

Identification and cloning of a gamma 3 subunit splice variant of the human GABA(A) receptor.

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Poulsen, C F; Christjansen, K N; Hastrup, S; Hartvig, L

2000-05-31

cDNA sequences encoding two forms of the GABA(A) gamma 3 receptor subunit were cloned from human hippocampus. The nucleotide sequences differ by the absence (gamma 3S) or presence (gamma 3L) of 18 bp located in the presumed intracellular loop between transmembrane region (TM) III and IV. The extra 18 bp in the gamma 3L subunit generates a consensus site for phosphorylation by protein kinase C (PKC). Analysis of human genomic DNA encoding the gamma 3 subunit reveals that the 18 bp insert is contiguous with the upstream proximal exon.

Differentiated human midbrain-derived neural progenitor cells express excitatory strychnine-sensitive glycine receptors containing α2β subunits.

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Florian Wegner

Full Text Available BACKGROUND: Human fetal midbrain-derived neural progenitor cells (NPCs may deliver a tissue source for drug screening and regenerative cell therapy to treat Parkinson's disease. While glutamate and GABA(A receptors play an important role in neurogenesis, the involvement of glycine receptors during human neurogenesis and dopaminergic differentiation as well as their molecular and functional characteristics in NPCs are largely unknown. METHODOLOGY/PRINCIPAL FINDINGS: Here we investigated NPCs in respect to their glycine receptor function and subunit expression using electrophysiology, calcium imaging, immunocytochemistry, and quantitative real-time PCR. Whole-cell recordings demonstrate the ability of NPCs to express functional strychnine-sensitive glycine receptors after differentiation for 3 weeks in vitro. Pharmacological and molecular analyses indicate a predominance of glycine receptor heteromers containing α2β subunits. Intracellular calcium measurements of differentiated NPCs suggest that glycine evokes depolarisations mediated by strychnine-sensitive glycine receptors and not by D-serine-sensitive excitatory glycine receptors. Culturing NPCs with additional glycine, the glycine-receptor antagonist strychnine, or the Na(+-K(+-Cl(- co-transporter 1 (NKCC1-inhibitor bumetanide did not significantly influence cell proliferation and differentiation in vitro. CONCLUSIONS/SIGNIFICANCE: These data indicate that NPCs derived from human fetal midbrain tissue acquire essential glycine receptor properties during neuronal maturation. However, glycine receptors seem to have a limited functional impact on neurogenesis and dopaminergic differentiation of NPCs in vitro.

GABA promotes elastin synthesis and elastin fiber formation in normal human dermal fibroblasts (HDFs).

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Uehara, Eriko; Hokazono, Hideki; Hida, Mariko; Sasaki, Takako; Yoshioka, Hidekatsu; Matsuo, Noritaka

2017-06-01

The multiple physiological effects of γ-aminobutyric acid (GABA) as a functional food component have been recently reported. We previously reported that GABA upregulated the expression of type I collagen in human dermal fibroblasts (HDFs), and that oral administration of GABA significantly increased skin elasticity. However, details of the regulatory mechanism still remain unknown. In this study, we further examined the effects of GABA on elastin synthesis and elastin fiber formation in HDFs. Real-time PCR indicated that GABA significantly increased the expression of tropoelastin transcript in a dose-dependent manner. Additionally, the expression of fibrillin-1, fibrillin-2, and fibulin-5/DANCE, but not lysyl oxidase and latent transforming factor-β-binding protein 4, were also significantly increased in HDFs. Finally, immunohistochemical analysis confirmed that treatment with GABA dramatically increased the formation of elastic fibers in HDFs. Taken together, our results showed that GABA improves skin elasticity in HDFs by upregulating elastin synthesis and elastin fiber formation.

GABA from reactive astrocytes impairs memory in mouse models of Alzheimer's disease.

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Jo, Seonmi; Yarishkin, Oleg; Hwang, Yu Jin; Chun, Ye Eun; Park, Mijeong; Woo, Dong Ho; Bae, Jin Young; Kim, Taekeun; Lee, Jaekwang; Chun, Heejung; Park, Hyun Jung; Lee, Da Yong; Hong, Jinpyo; Kim, Hye Yun; Oh, Soo-Jin; Park, Seung Ju; Lee, Hyo; Yoon, Bo-Eun; Kim, YoungSoo; Jeong, Yong; Shim, Insop; Bae, Yong Chul; Cho, Jeiwon; Kowall, Neil W; Ryu, Hoon; Hwang, Eunmi; Kim, Daesoo; Lee, C Justin

2014-08-01

In Alzheimer's disease (AD), memory impairment is the most prominent feature that afflicts patients and their families. Although reactive astrocytes have been observed around amyloid plaques since the disease was first described, their role in memory impairment has been poorly understood. Here, we show that reactive astrocytes aberrantly and abundantly produce the inhibitory gliotransmitter GABA by monoamine oxidase-B (Maob) and abnormally release GABA through the bestrophin 1 channel. In the dentate gyrus of mouse models of AD, the released GABA reduces spike probability of granule cells by acting on presynaptic GABA receptors. Suppressing GABA production or release from reactive astrocytes fully restores the impaired spike probability, synaptic plasticity, and learning and memory in the mice. In the postmortem brain of individuals with AD, astrocytic GABA and MAOB are significantly upregulated. We propose that selective inhibition of astrocytic GABA synthesis or release may serve as an effective therapeutic strategy for treating memory impairment in AD.

CXCL12 chemokine and GABA neurotransmitter systems crosstalk and their putative roles

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Guyon eAlice

2014-04-01

Full Text Available Since CXCL12 and its receptors, CXCR4 and CXCR7, have been found in the brain, the role of this chemokine has been expanded from chemoattractant in the immune system to neuromodulatory in the brain. Several pieces of evidence suggest that this chemokine system could crosstalk with the GABAergic system, known to be the main inhibitory neurotransmitter system in the brain. Indeed, GABA and CXCL12 as well as their receptors are colocalized in many cell types including neurons and there are several examples in which these two systems interact. Several mechanisms can be proposed to explain how these systems interact, including receptor-receptor interactions, crosstalk at the level of second messenger cascades, or direct pharmacological interactions, as GABA and GABAB receptor agonists/antagonists have been shown to be allosteric modulators of CXCR4.The interplay between CXCL12/CXCR4-CXCR7 and GABA/GABAA-GABAB receptors systems could have many physiological implications in neurotransmission, cancer and inflammation. In addition, the GABAB agonist baclofen is currently used in medicine to treat spasticity in patients with spinal cord injury, cerebral palsy, traumatic brain injury, multiple sclerosis and other disorders. More recently it has also been used in the treatment of alcohol dependence and withdrawal. The allosteric effects of this agent on CXCR4 could contribute to these beneficial effects or at the opposite, to its side effects.

Chloride ions in the pore of glycine and GABA channels shape the time course and voltage dependence of agonist currents

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Moroni, Mirko; Biro, Istvan; Giugliano, Michele; Vijayan, Ranjit; Biggin, Philip C.; Beato, Marco; Sivilotti, Lucia G.

2011-01-01

In the vertebrate CNS, fast synaptic inhibition is mediated by GABA and glycine receptors. We recently reported that the time course of these synaptic currents is slower when intracellular chloride is high. Here we extend these findings to measure the effects of both extracellular and intracellular chloride on the deactivation of glycine and GABA currents at both negative and positive holding potentials. Currents were elicited by fast agonist application to outside-out patches from HEK293 cells expressing rat glycine or GABA receptors. The slowing effect of high extracellular chloride on current decay was detectable only in low intracellular chloride (4 mM). Our main finding is that glycine and GABA receptors “sense” chloride concentrations because of interactions between the M2 pore-lining domain and the permeating ions. This hypothesis is supported by the observation that the sensitivity of channel gating to intracellular chloride is abolished if the channel is engineered to become cation-selective, or if positive charges in the external pore vestibule are eliminated by mutagenesis. The appropriate interaction between permeating ions and channel pore is also necessary to maintain the channel voltage sensitivity of gating, which prolongs current decay at depolarized potentials. Voltage-dependence is abolished by the same mutations that suppress the effect of intracellular chloride and also by replacing chloride with another permeant ion, thiocyanate. These observations suggest that permeant chloride affects gating by a foot-in-the-door effect, binding to a channel site with asymmetrical access from the intracellular and extracellular sides of the membrane. PMID:21976494

The GABA[subscript A] Receptor Agonist Muscimol Induces an Age- and Region-Dependent Form of Long-Term Depression in the Mouse Striatum

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Zhang, Xiaoqun; Yao, Ning; Chergui, Karima

2016-01-01

Several forms of long-term depression (LTD) of glutamatergic synaptic transmission have been identified in the dorsal striatum and in the nucleus accumbens (NAc). Such experience-dependent synaptic plasticity might play important roles in reward-related learning. The GABA[subscript A] receptor agonist muscimol was recently found to trigger a…

Zolpidem, a clinical hypnotic that affects electronic transfer, alters synaptic activity through potential GABA receptors in the nervous system without significant free radical generation

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Kovacic, Peter; Somanathan, Ratnasamy

2009-01-01

Zolpidem (trade name Ambien) has attracted much interest as a sleep-inducing agent and also in research. Attention has been centered mainly on receptor binding and electrochemistry in the central nervous system which are briefly addressed herein. A novel integrated approach to mode of action is presented. The pathways to be discussed involve basicity, reduction potential, electrostatics, cell signaling, GABA receptor binding, electron transfer (ET), pharmacodynamics, structure activity relati...

A fluorescence-coupled assay for gamma aminobutyric acid (GABA reveals metabolic stress-induced modulation of GABA content in neuroendocrine cancer.

Directory of Open Access Journals (Sweden)

Joseph E Ippolito

Full Text Available Pathways involved in the synthesis of the neurotransmitter gamma-aminobutyric acid (GABA have been implicated in the pathogenesis of high grade neuroendocrine (NE neoplasms as well as neoplasms from a non-NE lineage. Using The Cancer Genome Atlas, overexpression of the GABA synthetic enzyme, glutamate decarboxylase 1 (GAD1, was found to be associated with decreased disease free-survival in prostate adenocarcinoma and decreased overall survival in clear cell renal cell carcinomas. Furthermore, GAD1 was found to be expressed in castrate-resistant prostate cancer cell lines, but not androgen-responsive cell lines. Using a novel fluorescence-coupled enzymatic microplate assay for GABA mediated through reduction of resazurin in a prostate neuroendocrine carcinoma (PNEC cell line, acid microenvironment-induced stress increased GABA levels while alkaline microenvironment-induced stress decreased GABA through modulation of GAD1 and glutamine synthetase (GLUL activities. Moreover, glutamine but not glucose deprivation decreased GABA through modulation of GLUL. Consistent with evidence in prokaryotic and eukaryotic organisms that GABA synthesis mediated through GAD1 may play a crucial role in surviving stress, GABA may be an important mediator of stress survival in neoplasms. These findings identify GABA synthesis and metabolism as a potentially important pathway for regulating cancer cell stress response as well as a potential target for therapeutic strategies.

Presynaptic Dopamine D2 Receptors Modulate [3H]GABA Release at StriatoPallidal Terminals via Activation of PLC → IP3 → Calcineurin and Inhibition of AC → cAMP → PKA Signaling Cascades.

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Jijón-Lorenzo, Rafael; Caballero-Florán, Isaac Hiram; Recillas-Morales, Sergio; Cortés, Hernán; Avalos-Fuentes, José Arturo; Paz-Bermúdez, Francisco Javier; Erlij, David; Florán, Benjamín

2018-02-21

Striatal dopamine D2 receptors activate the PLC → IP3 → Calcineurin-signaling pathway to modulate the neural excitability of En+ Medium-sized Spiny GABAergic neurons (MSN) through the regulation of L-type Ca 2+ channels. Presynaptic dopaminergic D2 receptors modulate GABA release at striatopallidal terminals through L-type Ca 2+ channels as well, but their signaling pathway is still undetermined. Since D2 receptors are Gi/o-coupled and negatively modulate adenylyl cyclase (AC), we investigated whether presynaptic D2 receptors modulate GABA release through the same signaling cascade that controls excitability in the striatum or by the inhibition of AC and decreased PKA activity. Activation of D2 receptors stimulated formation of [ 3 H]IP 1 and decreased Forskolin-stimulated [ 3 H]cAMP accumulation in synaptosomes from rat Globus Pallidus. D2 receptor activation with Quinpirole in the presence of L 745,870 decreased, in a dose-dependent manner, K + -induced [ 3 H]GABA release in pallidal slices. The effect was prevented by the pharmacological blockade of Gi/o βγ subunit effects with Gallein, PLC with U 73122, IP3 receptor activation with 4-APB, Calcineurin with FK506. In addition, when release was stimulated with Forskolin to activate AC, D2 receptors also decreased K + -induced [ 3 H]GABA release, an effect occluded with the effect of the blockade of PKA with H89 or stimulation of release with the cAMP analog 8-Br-cAMP. These data indicate that D2 receptors modulate [ 3 H]GABA release at striatopallidal terminals by activating the PLC → IP3 → Calcineurin-signaling cascade, the same one that modulates excitability in soma. Additionally, D2 receptors inhibit release when AC is active. Both mechanisms appear to converge to regulate the activity of presynaptic L-type Ca 2+ channels. Copyright © 2018 IBRO. Published by Elsevier Ltd. All rights reserved.

Channel opening of gamma-aminobutyric acid receptor from rat brain: molecular mechanisms of the receptor responses.

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Cash, D J; Subbarao, K

1987-12-01

The function of gamma-aminobutyric acid (GABA) receptors, which mediate transmembrane chloride flux, can be studied by use of 36Cl- isotope tracer with membrane from mammalian brain by quench-flow technique, with reaction times that allow resolution of the receptor desensitization rates from the ion flux rates. The rates of chloride exchange into the vesicles in the absence and presence of GABA were characterized with membrane from rat cerebral cortex. Unspecific 36Cl- influx was completed in three phases of ca. 3% (t 1/2 = 0.6 s), 56% (t 1/2 = 82 s), and 41% (t 1/2 = 23 min). GABA-mediated, specific chloride exchange occurred with 6.5% of the total vesicular internal volume. The GABA-dependent 36Cl- influx proceeded in two phases, each progressively slowed by desensitization. The measurements supported the presence of two distinguishable active GABA receptors on the same membrane mediating chloride exchange into the vesicles with initial first-order rate constants of 9.5 s-1 and 2.3 s-1 and desensitizing with first-order rate constants of 21 s-1 and 1.4 s-1, respectively, at saturation. The half-response concentrations were similar for both receptors, 150 microM and 114 microM GABA for desensitization and 105 microM and 82 microM for chloride exchange, for the faster and slower desensitizing receptors, respectively. The two receptors were present in the activity ratio of ca. 4/1, similar to the ratio of "low-affinity" to "high-affinity" GABA sites found in ligand binding experiments. The desensitization rates have a different dependence on GABA concentration than the channel-opening equilibria.(ABSTRACT TRUNCATED AT 250 WORDS)

Cortical Gene Expression After a Conditional Knockout of 67 kDa Glutamic Acid Decarboxylase in Parvalbumin Neurons.

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Georgiev, Danko; Yoshihara, Toru; Kawabata, Rika; Matsubara, Takurou; Tsubomoto, Makoto; Minabe, Yoshio; Lewis, David A; Hashimoto, Takanori

2016-07-01

In the cortex of subjects with schizophrenia, expression of glutamic acid decarboxylase 67 (GAD67), the enzyme primarily responsible for cortical GABA synthesis, is reduced in the subset of GABA neurons that express parvalbumin (PV). This GAD67 deficit is accompanied by lower cortical levels of other GABA-associated transcripts, including GABA transporter-1, PV, brain-derived neurotrophic factor (BDNF), tropomyosin receptor kinase B, somatostatin, GABAA receptor α1 subunit, and KCNS3 potassium channel subunit mRNAs. In contrast, messenger RNA (mRNA) levels for glutamic acid decarboxylase 65 (GAD65), another enzyme for GABA synthesis, are not altered. We tested the hypothesis that this pattern of GABA-associated transcript levels is secondary to the GAD67 deficit in PV neurons by analyzing cortical levels of these GABA-associated mRNAs in mice with a PV neuron-specific GAD67 knockout. Using in situ hybridization, we found that none of the examined GABA-associated transcripts had lower cortical expression in the knockout mice. In contrast, PV, BDNF, KCNS3, and GAD65 mRNA levels were higher in the homozygous mice. In addition, our behavioral test battery failed to detect a change in sensorimotor gating or working memory, although the homozygous mice exhibited increased spontaneous activities. These findings suggest that reduced GAD67 expression in PV neurons is not an upstream cause of the lower levels of GABA-associated transcripts, or of the characteristic behaviors, in schizophrenia. In PV neuron-specific GAD67 knockout mice, increased levels of PV, BDNF, and KCNS3 mRNAs might be the consequence of increased neuronal activity secondary to lower GABA synthesis, whereas increased GAD65 mRNA might represent a compensatory response to increase GABA synthesis. © The Author 2016. Published by Oxford University Press on behalf of the Maryland Psychiatric Research Center. All rights reserved. For permissions, please email: journals.permissions@oup.com.

GABAA receptor endocytosis in the basolateral amygdala is critical to the reinstatement of fear memory measured by fear-potentiated startle.

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Lin, Hui-Ching; Tseng, Yu-Chou; Mao, Sheng-Chun; Chen, Po-See; Gean, Po-Wu

2011-06-15

Reinstatement represents a phenomenon that may be used to model the effects of retraumatization observed in patients with posttraumatic stress disorder (PTSD). In this study, we found intraperitoneal injection of the β-adrenergic receptor antagonist propranolol (10 mg/kg) 1 h before reinstatement training attenuated reinstatement of fear memory in rats. Conversely, reinstatement was facilitated by intra-amygdalar administration of β-adrenergic receptor agonist isoproterenol (Iso; 2 μg per side) 30 min before reinstatement training. The frequency and amplitude of the miniature IPSC (mIPSC) and the surface expression of the β3 and γ2 subunits of the GABA(A) receptor (GABA(A)R) were significantly lower in reinstated than in extinction rats, whereas the AMPA/NMDA ratio and the surface expression of GluR1 and GluR2 in the amygdala did not differ between groups. In amygdala slices, Iso-induced decrease in the surface β3 subunit of GABA(A) receptor was blocked by a Tat-conjugated dynamin function-blocking peptide (Tat-P4) pretreatment (10 μm for 30 min). By contrast, Tat-scramble peptide had no effect. Intravenous injection (3 μmol/kg) or intra-amygdalar infusion (30 pmol per side) of Tat-P4 interfered with reinstatement. Reinstatement increased the association between protein phosphatase 2A (PP2A) and the β3 subunit of the GABA(A)R, which was abolished by PP1/PP2A inhibitors okadaic acid and calyculin A. These results suggest the involvement of β-adrenergic receptor activation and GABA(A) receptor endocytosis in the amygdala for the reinstatement in fear memory.

GABA transaminases from Saccharomyces cerevisiae and Arabidopsis thaliana complement function in cytosol and mitochondria.

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Cao, Juxiang; Barbosa, Jose M; Singh, Narendra; Locy, Robert D

2013-07-01

GABA transaminase (GABA-T) catalyses the conversion of GABA to succinate semialdehyde (SSA) in the GABA shunt pathway. The GABA-T from Saccharomyces cerevisiae (ScGABA-TKG) is an α-ketoglutarate-dependent enzyme encoded by the UGA1 gene, while higher plant GABA-T is a pyruvate/glyoxylate-dependent enzyme encoded by POP2 in Arabidopsis thaliana (AtGABA-T). The GABA-T from A. thaliana is localized in mitochondria and mediated by an 18-amino acid N-terminal mitochondrial targeting peptide predicated by both web-based utilities TargetP 1.1 and PSORT. Yeast UGA1 appears to lack a mitochondrial targeting peptide and is localized in the cytosol. To verify this bioinformatic analysis and examine the significance of ScGABA-TKG and AtGABA-T compartmentation and substrate specificity on physiological function, expression vectors were constructed to modify both ScGABA-TKG and AtGABA-T, so that they express in yeast mitochondria and cytosol. Physiological function was evaluated by complementing yeast ScGABA-TKG deletion mutant Δuga1 with AtGABA-T or ScGABA-TKG targeted to the cytosol or mitochondria for the phenotypes of GABA growth defect, thermosensitivity and heat-induced production of reactive oxygen species (ROS). This study demonstrates that AtGABA-T is functionally interchangeable with ScGABA-TKG for GABA growth, thermotolerance and limiting production of ROS, regardless of location in mitochondria or cytosol of yeast cells, but AtGABA-T is about half as efficient in doing so as ScGABA-TKG. These results are consistent with the hypothesis that pyruvate/glyoxylate-limited production of NADPH mediates the effect of the GABA shunt in moderating heat stress in Saccharomyces. Copyright © 2013 John Wiley & Sons, Ltd.

Defining Subpopulations of Arcuate Nucleus GABA Neurons in Male, Female, and Prenatally Androgenized Female Mice.

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Marshall, Christopher J; Desroziers, Elodie; McLennan, Timothy; Campbell, Rebecca E

2017-01-01

Arcuate nucleus (ARN) γ-aminobutyric acid (GABA) neurons are implicated in many critical homeostatic mechanisms, from food intake to fertility. To determine the functional relevance of ARN GABA neurons, it is essential to define the neurotransmitters co-expressed with and potentially co-released from ARN GABA neurons. The present study investigated the expression of markers of specific signaling molecules by ARN GABA neurons in brain sections from male, female, and, in some cases, prenatally androgen-treated (PNA) female, vesicular GABA transporter (VGaT)-ires-Cre/tdTomato reporter mice. Immunofluorescence for kisspeptin, β-endorphin, neuropeptide Y (NPY), tyrosine hydroxylase (TH) and neuronal nitric oxide synthase (nNOS) was detected by confocal microscopy, and co-localization with tdTomato VGaT reporter expression throughout the ARN was quantified. GABA neurons rarely co-localized with kisspeptin (95%) co-localized with VGaT across groups. Both TH and nNOS labeling was co-localized with ∼10% of ARN GABA neurons. The proportion of TH neurons co-localized with VGaT was significantly greater in males than either control or PNA females, and the proportion of nNOS neurons co-localizing VGaT was higher in control and PNA females compared with males. These data highlight NPY as a significant subpopulation of ARN GABA neurons, demonstrate no significant impact of PNA on signal co-expression, and, for the first time, show sexually dimorphic co-expression patterns of TH and nNOS with ARN GABA neurons. © 2016 S. Karger AG, Basel.

[Local GABA-ergic modulation of serotonergic neuron activity in the nucleus raphe magnus].

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Iniushkin, A N; Merkulova, N A; Orlova, A O; Iniushkina, E M

2009-07-01

In voltage-clamp experimental on slices of the rat brainstem the effects of 5-HT and GABA on serotonergic neurons of nucleus raphe magnus were investigated. Local applications of 5-HT induced an increase in IPCSs frequency and amplitude in 45% of serotonergic cells. The effect suppressed by the blocker of fast sodium channels tetradotoxin. Antagonist of GABA receptor gabazine blocked IPSCs in neurons both sensitive and non-sensitive to 5-HT action. Applications of GABA induced a membrane current (I(GABA)), which was completely blocked by gabazine. The data suggest self-control of the activity of serotonergic neurons in nucleus raphe magnus by negative feedback loop via local GABAergic interneurons.

Different effects of long-term haloperidol administration on GABA/sub A/ and benzodiazepine receptors in various parts of the brain

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Vasar, Oe.Oe.; Nurk, A.M.; Maimets, M.O.; Soosaar, A.H.; Allikmets, L.H.

1986-01-01

The data described in this paper are evidence that long-term administration of haloperidol has an opposite effect on the density of GABA/sub A/ and benzodiazepine receptors in the fore- and hindbrain. These changes are reflected at the molecular level as reversal of behavioral effect of the GABA/sub A/ agonist muscimol and the benzodiazepine agonist Ro15-1788. By means of parallel behavioral tests, binding of 3 H-muscimol in the fore- and hindbrain of rats was investigated in experiments in vitro. 3 H-flunitrazepam binding experiments were carried out in vivo on mice. Parallel with reversal of the behavioral effects of muscimol and Ro15-1788, the number of binding sites both for 3 H-muscimol and for 3 H-flunitrazepam in the forebrain was reduced; in the hindbrain the opposite process took place

Impaired expression of GABA transporters in the human Alzheimer's disease hippocampus, subiculum, entorhinal cortex and superior temporal gyrus.

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Fuhrer, Tessa E; Palpagama, Thulani H; Waldvogel, Henry J; Synek, Beth J L; Turner, Clinton; Faull, Richard L; Kwakowsky, Andrea

2017-05-20

Gamma-aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the brain and plays an important role in regulating neuronal excitability. GABA reuptake from the synapse is dependent on specific transporters - mainly GAT-1, GAT-3 and BGT-1 (GATs). This study is the first to show alterations in the expression of the GATs in the Alzheimer's disease (AD) hippocampus, entorhinal cortex and superior temporal gyrus. We found a significant increase in BGT-1 expression associated with AD in all layers of the dentate gyrus, in the stratum oriens of the CA2 and CA3 and the superior temporal gyrus. In AD there was a significant decrease in GAT-1 expression in the entorhinal cortex and superior temporal gyrus. We also found a significant decrease in GAT-3 immunoreactivity in the stratum pyramidale of the CA1 and CA3, the subiculum and entorhinal cortex. These observations indicate that the expression of the GATs shows brain-region- and layer-specific alterations in AD, suggesting a complex activation pattern of different GATs during the course of the disease. Copyright © 2017 IBRO. Published by Elsevier Ltd. All rights reserved.

Effect of GABA receptor agonists or antagonists injected spinally on the blood glucose level in mice.

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Sim, Yun-Beom; Park, Soo-Hyun; Kang, Yu-Jung; Kim, Sung-Su; Kim, Chea-Ha; Kim, Su-Jin; Jung, Jun-Sub; Ryu, Ohk-Hyun; Choi, Moon-Gi; Suh, Hong-Won

2013-05-01

The possible roles of gamma-amino butyric acid (GABA) receptors located in the spinal cord for the regulation of the blood glucose level were studied in ICR mice. We found in the present study that intrathecal (i.t.) injection with baclofen (a GABAB receptor agonist; 1-10 μg/5 μl) or bicuculline (a GABAA receptor antagonist; 1-10 μg/5 μl) caused an elevation of the blood glucose level in a dose-dependent manner. The hyperglycemic effect induced by baclofen was more pronounced than that induced by bicuculline. However, muscimol (a GABAA receptor agonist; 1-5 μg/5 μl) or phaclofen (a GABAB receptor antagonist; 5-10 μg/5 μl) administered i.t. did not affect the blood glucose level. Baclofen-induced elevation of the blood glucose was dose-dependently attenuated by phaclofen. Furthermore, i.t. pretreatment with pertussis toxin (PTX; 0.05 or 0.1 μg/5 μl) for 6 days dose-dependently reduced the hyperglycemic effect induced by baclofen. Our results suggest that GABAB receptors located in the spinal cord play important roles for the elevation of the blood glucose level. Spinally located PTX-sensitive G-proteins appear to be involved in hyperglycemic effect induced by baclofen. Furthermore, inactivation of GABAA receptors located in the spinal cord appears to be responsible for tonic up-regulation of the blood glucose level.

Altered cortical GABA neurotransmission in schizophrenia: insights into novel therapeutic strategies.

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Stan, Ana D; Lewis, David A

2012-06-01

Altered markers of cortical GABA neurotransmission are among the most consistently observed abnormalities in postmortem studies of schizophrenia. The altered markers are particularly evident between the chandelier class of GABA neurons and their synaptic targets, the axon initial segment (AIS) of pyramidal neurons. For example, in the dorsolateral prefrontal cortex of subjects with schizophrenia immunoreactivity for the GABA membrane transporter is decreased in presynaptic chandelier neuron axon terminals, whereas immunoreactivity for the GABAA receptor α2 subunit is increased in postsynaptic AIS. Both of these molecular changes appear to be compensatory responses to a presynaptic deficit in GABA synthesis, and thus could represent targets for novel therapeutic strategies intended to augment the brain's own compensatory mechanisms. Recent findings that GABA inputs from neocortical chandelier neurons can be powerfully excitatory provide new ideas about the role of these neurons in the pathophysiology of cortical dysfunction in schizophrenia, and consequently in the design of pharmacological interventions.

Fiat lux! Phylogeny and bioinformatics shed light on GABA functions in plants.

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Renault, Hugues

2013-06-01

The non-protein amino acid γ-aminobutyric acid (GABA) accumulates in plants in response to a wide variety of environmental cues. Recent data point toward an involvement of GABA in tricarboxylic acid (TCA) cycle activity and respiration, especially in stressed roots. To gain further insights into potential GABA functions in plants, phylogenetic and bioinformatic approaches were undertaken. Phylogenetic reconstruction of the GABA transaminase (GABA-T) protein family revealed the monophyletic nature of plant GABA-Ts. However, this analysis also pointed to the common origin of several plant aminotransferases families, which were found more similar to plant GABA-Ts than yeast and human GABA-Ts. A computational analysis of AtGABA-T co-expressed genes was performed in roots and in stress conditions. This second approach uncovered a strong connection between GABA metabolism and glyoxylate cycle during stress. Both in silico analyses open new perspectives and hypotheses for GABA metabolic functions in plants.

Effect of THIP and SL 76002, two clinically experimented GABA-mimetic compounds, on anterior pituitary GABA receptors and prolactin secretion in the rat

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Apud, J.A.; Masotto, C.; Racagni, G.

1987-01-01

In the present study, the ability of three direct GABA agonists, muscimol, THIP and SL 76002 to displace 3 H-GABA binding from anterior pituitary and medio-basal hypothalamus membranes was evaluated. Further, the effect of both THIP and SL 76002 on baseline prolactin levels or after stimulation of hormone release with haloperidol has been also studied. Either muscimol, THIP or SL 76002 have shown to posses 7-, 7- and 3-fold higher affinity, respectively, for the central nervous system than for the anterior pituitary 3 H-GABA binding sites. Moreover, THIP and SL 76002 have demonstrated to be respectively, 25- and 1000- fold less potent than muscimol in inhibiting 3 H- GABA binding at the level of the anterior pituitary and about 25- and 2700-fold less potent at the level of the medio-basal hypothalamus. Under basal conditions, either THIP or SL 76002 were ineffective to reduce prolactin release. However, after stimulation of prolactin secretion through blockade of the dopaminergic neurotransmission with haloperidol (0.1 mg/kg), both THIP (10 mg/kg) and SL 76002 (200 mg/kg) significantly counteracted the neuroleptic-induced prolactin rise with a potency which is in line with their ability to inhibit 3 H-GABA binding in the anterior pituitary. The present results indicate that both compounds inhibit prolactin release under specific experimental situations probably through a GABAergic mechanism. In view of the endocrine effects of these GABA-mimetic compounds, the possibility arises for an application of these type of drugs in clinical neuroendocrinology. 35 references, 3 figures, 2 tables

Systematic study of association of four GABAergic genes: glutamic acid decarboxylase 1 gene, glutamic acid decarboxylase 2 gene, GABA(B) receptor 1 gene and GABA(A) receptor subunit beta2 gene, with schizophrenia using a universal DNA microarray.

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Zhao, Xu; Qin, Shengying; Shi, Yongyong; Zhang, Aiping; Zhang, Jing; Bian, Li; Wan, Chunling; Feng, Guoyin; Gu, Niufan; Zhang, Guangqi; He, Guang; He, Lin

2007-07-01

Several studies have suggested the dysfunction of the GABAergic system as a risk factor in the pathogenesis of schizophrenia. In the present study, case-control association analysis was conducted in four GABAergic genes: two glutamic acid decarboxylase genes (GAD1 and GAD2), a GABA(A) receptor subunit beta2 gene (GABRB2) and a GABA(B) receptor 1 gene (GABBR1). Using a universal DNA microarray procedure we genotyped a total of 20 SNPs on the above four genes in a study involving 292 patients and 286 controls of Chinese descent. Statistically significant differences were observed in the allelic frequencies of the rs187269C/T polymorphism in the GABRB2 gene (P=0.0450, chi(2)=12.40, OR=1.65) and the -292A/C polymorphism in the GAD1 gene (P=0.0450, chi(2)=14.64 OR=1.77). In addition, using an electrophoretic mobility shift assay (EMSA), we discovered differences in the U251 nuclear protein binding to oligonucleotides representing the -292 SNP on the GAD1 gene, which suggests that the -292C allele has reduced transcription factor binding efficiency compared with the 292A allele. Using the multifactor-dimensionality reduction method (MDR), we found that the interactions among the rs187269C/T polymorphism in the GABRB2 gene, the -243A/G polymorphism in the GAD2 gene and the 27379C/T and 661C/T polymorphisms in the GAD1 gene revealed a significant association with schizophrenia (Pschizophrenia in the Chinese population.

Immunoreactivity for GABA, GAD65, GAD67 and Bestrophin-1 in the meninges and the choroid plexus: implications for non-neuronal sources for GABA in the developing mouse brain.

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Tochitani, Shiro; Kondo, Shigeaki

2013-01-01

Neural progenitors in the developing neocortex, neuroepithelial cells and radial glial cells, have a bipolar shape with a basal process contacting the basal membrane of the meninge and an apical plasma membrane facing the lateral ventricle, which the cerebrospinal fluid is filled with. Recent studies revealed that the meninges and the cerebrospinal fluid have certain roles to regulate brain development. γ-aminobutyric acid (GABA) is a neurotransmitter which appears first during development and works as a diffusible factor to regulate the properties of neural progenitors. In this study, we examined whether GABA can be released from the meninges and the choroid plexus in the developing mouse brain. Immunohistochemical analyses showed that glutamic acid decarboxylase 65 and 67 (GAD65 and GAD67), both of which are GABA-synthesizing enzymes, are expressed in the meninges. The epithelial cells in the choroid plexus express GAD65. GABA immunoreactivity could be observed beneath the basal membrane of the meninge and in the epithelial cells of the choroid plexus. Expression analyses on Bestrophin-1, which is known as a GABA-permeable channel in differentiated glial cells, suggested that the cells in the meninges and the epithelial cells in the choroid plexus have the channels able to permeate non-synaptic GABA into the extracellular space. Further studies showed that GAD65/67-expressing meningeal cells appear in a manner with rostral to caudal and lateral to dorsal gradient to cover the entire neocortex by E14.5 during development, while the cells in the choroid plexus in the lateral ventricle start to express GAD65 on E11-E12, the time when the choroid plexus starts to develop in the developing brain. These results totally suggest that the meninges and the choroid plexus can work as non-neuronal sources for ambient GABA which can modulate the properties of neural progenitors during neocortical development.

The Relevance of AgRP Neuron-Derived GABA Inputs to POMC Neurons Differs for Spontaneous and Evoked Release.

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Rau, Andrew R; Hentges, Shane T

2017-08-02

Hypothalamic agouti-related peptide (AgRP) neurons potently stimulate food intake, whereas proopiomelanocortin (POMC) neurons inhibit feeding. Whether AgRP neurons exert their orexigenic actions, at least in part, by inhibiting anorexigenic POMC neurons remains unclear. Here, the connectivity between GABA-releasing AgRP neurons and POMC neurons was examined in brain slices from male and female mice. GABA-mediated spontaneous IPSCs (sIPSCs) in POMC neurons were unaffected by disturbing GABA release from AgRP neurons either by cell type-specific deletion of the vesicular GABA transporter or by expression of botulinum toxin in AgRP neurons to prevent vesicle-associated membrane protein 2-dependent vesicle fusion. Additionally, there was no difference in the ability of μ-opioid receptor (MOR) agonists to inhibit sIPSCs in POMC neurons when MORs were deleted from AgRP neurons, and activation of the inhibitory designer receptor hM4Di on AgRP neurons did not affect sIPSCs recorded from POMC neurons. These approaches collectively indicate that AgRP neurons do not significantly contribute to the strong spontaneous GABA input to POMC neurons. Despite these observations, optogenetic stimulation of AgRP neurons reliably produced evoked IPSCs in POMC neurons, leading to the inhibition of POMC neuron firing. Thus, AgRP neurons can potently affect POMC neuron function without contributing a significant source of spontaneous GABA input to POMC neurons. Together, these results indicate that the relevance of GABAergic inputs from AgRP to POMC neurons is state dependent and highlight the need to consider different types of transmitter release in circuit mapping and physiologic regulation. SIGNIFICANCE STATEMENT Agouti-related peptide (AgRP) neurons play an important role in driving food intake, while proopiomelanocortin (POMC) neurons inhibit feeding. Despite the importance of these two well characterized neuron types in maintaining metabolic homeostasis, communication between these

Inflammatory mediators potentiate high affinity GABA(A) currents in rat dorsal root ganglion neurons.

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Lee, Kwan Yeop; Gold, Michael S

2012-06-19

Following acute tissue injury action potentials may be initiated in afferent processes terminating in the dorsal horn of the spinal cord that are propagated back out to the periphery, a process referred to as a dorsal root reflex (DRR). The DRR is dependent on the activation of GABA(A) receptors. The prevailing hypothesis is that DRR is due to a depolarizing shift in the chloride equilibrium potential (E(Cl)) following an injury-induced activation of the Na(+)-K(+)-Cl(-)-cotransporter. Because inflammatory mediators (IM), such as prostaglandin E(2) are also released in the spinal cord following tissue injury, as well as evidence that E(Cl) is already depolarized in primary afferents, an alternative hypothesis is that an IM-induced increase in GABA(A) receptor mediated current (I(GABA)) could underlie the injury-induced increase in DRR. To test this hypothesis, we explored the impact of IM (prostaglandin E(2) (1 μM), bradykinin (10 μM), and histamine (1 μM)) on I(GABA) in dissociated rat dorsal root ganglion (DRG) neurons with standard whole cell patch clamp techniques. IM potentiated I(GABA) in a subpopulation of medium to large diameter capsaicin insensitive DRG neurons. This effect was dependent on the concentration of GABA, manifest only at low concentrations (emergence of injury-induced DRR. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Involvement of Gaba and Cannabinoid Receptors in Central Food Intake Regulation in Neonatal Layer Chicks: Role of CB1 and Gabaa Receptors

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M Zendehdel

Full Text Available ABSTRACT Feeding behavior is regulated via a complex network which interacts via diverse signals from central and peripheral tissues. Endocannabinoids modulate release of GABA in a variety of regions of the central nervous system. Endocannabinoids and GABAergic system have an important role in the central regulation of appetite. Thus, the present study examines the possible interaction of central canabinoidergic and GABAergic systems on food intake in 3-h food-deprived (FD3 neonatal layer-type chicks. The results of this study showed that intracerebroventricular (ICV injection of 2-AG (2-Arachidonoylglycerol, selective CB1 receptors agonist, 2µg significantly increased food intake and this effect of 2-AG was attenuated by Picrotoxin (GABAA antagonist, 0.5µg (P0.05. Also, hyperphagic effect of CB65 (CB2 receptors agonist, 1.25µg was not affected by Picrotoxin or CGP54626 (p>0.05. Moreover, the food intake of chicks was significantly increased by ICV injection of GABAA agonist (Gaboxadol, 0.2 µg and SR141716A (CB1 receptors antagonist, 6.25µg significantly decreased Gaboxadol-induced hyperphagia (P0.05. These data showed there might be an interaction between central cannabinoidergic and GABAergic systems via CB1 and GABAA receptors in control of food intake in neonatal layer chicks.

Molecular and functional characterization of GAD67-expressing, newborn granule cells in mouse dentate gyrus

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Carolina eCabezas

2013-04-01

Full Text Available Dentate gyrus granule cells (GCs have been suggested to synthesize both GABA and glutamate immediately after birth and under pathological conditions in the adult. Expression of the GABA synthesizing enzyme GAD67 by GCs during the first few weeks of postnatal development may then allow for transient GABA synthesis and synaptic release from these cells. Here, using the GAD67-EGFP transgenic strain G42, we explored the phenotype of GAD67-expressing GCs in the mouse dentate gyrus. We report a transient, GAD67-driven EGFP expression in differentiating GCs throughout ontogenesis. EGFP expression correlates with the expression of GAD and molecular markers of GABA release and uptake in 2-4 weeks postmitotic GCs. These rather immature cells are able to fire action potentials and are synaptically integrated in the hippocampal network. Yet they show physiological properties that differentiate them from mature GCs. Finally, GAD67-expressing GCs express a specific complement of GABAA receptor subunits as well as distinctive features of synaptic and tonic GABA signaling. Our results reveal that GAD67 expression in dentate gyrus granule cells is a transient marker of late differentiation that persists throughout life and the G42 strain may be used to visualize newborn GCs at a specific, well-defined differentiation stage.

Linking γ-aminobutyric acid A receptor to epidermal growth factor receptor pathways activation in human prostate cancer.

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Wu, Weijuan; Yang, Qing; Fung, Kar-Ming; Humphreys, Mitchell R; Brame, Lacy S; Cao, Amy; Fang, Yu-Ting; Shih, Pin-Tsen; Kropp, Bradley P; Lin, Hsueh-Kung

2014-03-05

Neuroendocrine (NE) differentiation has been attributed to the progression of castration-resistant prostate cancer (CRPC). Growth factor pathways including the epidermal growth factor receptor (EGFR) signaling have been implicated in the development of NE features and progression to a castration-resistant phenotype. However, upstream molecules that regulate the growth factor pathway remain largely unknown. Using androgen-insensitive bone metastasis PC-3 cells and androgen-sensitive lymph node metastasis LNCaP cells derived from human prostate cancer (PCa) patients, we demonstrated that γ-aminobutyric acid A receptor (GABA(A)R) ligand (GABA) and agonist (isoguvacine) stimulate cell proliferation, enhance EGF family members expression, and activate EGFR and a downstream signaling molecule, Src, in both PC-3 and LNCaP cells. Inclusion of a GABA(A)R antagonist, picrotoxin, or an EGFR tyrosine kinase inhibitor, Gefitinib (ZD1839 or Iressa), blocked isoguvacine and GABA-stimulated cell growth, trans-phospohorylation of EGFR, and tyrosyl phosphorylation of Src in both PCa cell lines. Spatial distributions of GABAAR α₁ and phosphorylated Src (Tyr416) were studied in human prostate tissues by immunohistochemistry. In contrast to extremely low or absence of GABA(A)R α₁-positive immunoreactivity in normal prostate epithelium, elevated GABA(A)R α₁ immunoreactivity was detected in prostate carcinomatous glands. Similarly, immunoreactivity of phospho-Src (Tyr416) was specifically localized and limited to the nucleoli of all invasive prostate carcinoma cells, but negative in normal tissues. Strong GABAAR α₁ immunoreactivity was spatially adjacent to the neoplastic glands where strong phospho-Src (Tyr416)-positive immunoreactivity was demonstrated, but not in adjacent to normal glands. These results suggest that the GABA signaling is linked to the EGFR pathway and may work through autocrine or paracine mechanism to promote CRPC progression. Copyright © 2013 Elsevier

Stimulation of accumbal GABAA receptors inhibits delta2-, but not delta1-, opioid receptor-mediated dopamine efflux in the nucleus accumbens of freely moving rats.

Science.gov (United States)

Aono, Yuri; Kiguchi, Yuri; Watanabe, Yuriko; Waddington, John L; Saigusa, Tadashi

2017-11-15

The nucleus accumbens contains delta-opioid receptors that may reduce inhibitory neurotransmission. Reduction in GABA A receptor-mediated inhibition of accumbal dopamine release due to delta-opioid receptor activation should be suppressed by stimulating accumbal GABA A receptors. As delta-opioid receptors are divided into delta2- and delta1-opioid receptors, we analysed the effects of the GABA A receptor agonist muscimol on delta2- and delta1-opioid receptor-mediated accumbal dopamine efflux in freely moving rats using in vivo microdialysis. Drugs were administered intracerebrally through the dialysis probe. Doses of compounds indicate total amount administered (mol) during 25-50min infusions. The delta2-opioid receptor agonist deltorphin II (25.0nmol)- and delta1-opioid receptor agonist DPDPE (5.0nmol)-induced increases in dopamine efflux were inhibited by the delta2-opioid receptor antagonist naltriben (1.5nmol) and the delta1-opioid receptor antagonist BNTX (150.0pmol), respectively. Muscimol (250.0pmol) inhibited deltorphin II (25.0nmol)-induced dopamine efflux. The GABA A receptor antagonist bicuculline (50.0pmol), which failed to affect deltorphin II (25.0nmol)-induced dopamine efflux, counteracted the inhibitory effect of muscimol on deltorphin II-induced dopamine efflux. Neither muscimol (250.0pmol) nor bicuculline (50.0 and 500.0pmol) altered DPDPE (5.0nmol)-induced dopamine efflux. The present results show that reduction in accumbal GABA A receptor-mediated inhibition of dopaminergic activity is necessary to produce delta2-opioid receptor-induced increase in accumbal dopamine efflux. This study indicates that activation of delta2- but not delta1-opioid receptors on the cell bodies and/or terminals of accumbal GABAergic interneurons inhibits GABA release and, accordingly, decreases GABA A receptor-mediated inhibition of dopaminergic terminals, resulting in enhanced accumbal dopamine efflux. Copyright © 2017 Elsevier B.V. All rights reserved.

The anticonvulsant gabapentin (neurontin) does not act through gamma-aminobutyric acid-B receptors

DEFF Research Database (Denmark)

Jensen, Anders A.; Mosbacher, Johannes; Elg, Susanne

2002-01-01

The actions of the anticonvulsant gabapentin [1-(aminomethyl)cyclohexaneacetic acid, Neurontin] have been somewhat enigmatic until recently, when it was claimed to be a gamma-aminobutyric acid-B (GABA(B)) receptor agonist acting exclusively at a heterodimeric complex containing the GABA(B(1a...... in vitro assays. In light of these results, we find it highly questionable that gabapentin is a GABA(B) receptor agonist. Hence, the anticonvulsive effects of the compound have to arise from GABA(B) receptor-independent mechanisms. This also implies that the first GABA(B) receptor splice variant...

Differential Modulation of GABAA and NMDA Receptors by an α7-nicotinic Acetylcholine Receptor Agonist in Chronic Glaucoma

Directory of Open Access Journals (Sweden)

Xujiao Zhou

2017-12-01

Full Text Available Presynaptic modulation of γ-aminobutyric acid (GABA release by an alpha7 nicotinic acetylcholine receptor (α7-nAChR agonist promotes retinal ganglion cell (RGC survival and function, as suggested by a previous study on a chronic glaucomatous model from our laboratory. However, the role of excitatory and inhibitory amino acid receptors and their interaction with α7-nAChR in physiological and glaucomatous events remains unknown. In this study, we investigated GABAA and N-methyl-D-aspartate (NMDA receptor activity in control and glaucomatous retinal slices and the regulation of amino acid receptor expression and function by α7-nAChR. Whole-cell patch-clamp recordings from RGCs revealed that the α7-nAChR specific agonist PNU-282987 enhanced the amplitude of currents elicited by GABA and reduced the amplitude of currents elicited by NMDA. The positive modulation of GABAA receptor and the negative modulation of NMDA receptor (NMDAR by PNU-282987-evoked were prevented by pre-administration of the α7-nAChR antagonist methyllycaconitine (MLA. The frequency and the amplitude of glutamate receptor-mediated miniature glutamatergic excitatory postsynaptic currents (mEPSCs were not significantly different between the control and glaucomatous RGCs. Additionally, PNU-282987-treated slices showed no alteration in the frequency or amplitude of mEPSCs relative to control RGCs. Moreover, we showed that expression of the α1 subunit of the GABAA receptor was downregulated and the expression of the NMDAR NR2B subunit was upregulated by intraocular pressure (IOP elevation, and the changes of high IOP were blocked by PNU-282987. In conclusion, retina GABAA and NMDARs are modulated positively and negatively, respectively, by activation of α7-nAChR in in vivo chronic glaucomatous models.

Uptake and release of [14C] GABA from rabbit retina synaptosomes

International Nuclear Information System (INIS)

Redburn, D.A.

1977-01-01

A partial separation of two synaptosomal fractions was achieved using modifications of conventional homogenization and centrifugation techniques. The two fractions contained morphologically distinct synaptosomal populations, receptor cell synaptosomes (large synaptosomes, P 1 ), and synaptosomes from the other cell types (smaller, conventional-sized synaptosomes, P 2 ). [ 14 C]GABA was bound and released from subcellular fractions from retina under conditions which support its role as a neurotransmitter in retina. On the other hand, [ 3 H]leucine, which is very likely a non-transmitter compound, was bound by retinal fractions but not released to the appropriate stimulation. [ 14 C]GABA binding and release sites were more prevalent in P 2 fractions. [ 14 C]GABA was bound by P 1 fractions containing photoreceptor synaptosomes; however, the K + stimulated release of [ 14 C]GABA appeared to be insensitive to external Ca 2+ . Possible mechanisms are discussed. (author)

Mutation of the inhibitory ethanol site in GABAA ρ1 receptors promotes tolerance to ethanol-induced motor incoordination.

Science.gov (United States)

Blednov, Yuri A; Borghese, Cecilia M; Ruiz, Carlos I; Cullins, Madeline A; Da Costa, Adriana; Osterndorff-Kahanek, Elizabeth A; Homanics, Gregg E; Harris, R Adron

2017-09-01

Genes encoding the ρ1/2 subunits of GABA A receptors have been associated with alcohol (ethanol) dependence in humans, and ρ1 was also shown to regulate some of the behavioral effects of ethanol in animal models. Ethanol inhibits GABA-mediated responses in wild-type (WT) ρ1, but not ρ1(T6'Y) mutant receptors expressed in Xenopus laevis oocytes, indicating the presence of an inhibitory site for ethanol in the second transmembrane helix. In this study, we found that ρ1(T6'Y) receptors expressed in oocytes display overall normal responses to GABA, the endogenous GABA modulator (zinc), and partial agonists (β-alanine and taurine). We generated ρ1 (T6'Y) knockin (KI) mice using CRISPR/Cas9 to test the behavioral importance of the inhibitory actions of ethanol on this receptor. Both ρ1 KI and knockout (KO) mice showed faster recovery from acute ethanol-induced motor incoordination compared to WT mice. Both KI and KO mutant strains also showed increased tolerance to motor impairment produced by ethanol. The KI mice did not differ from WT mice in other behavioral actions, including ethanol intake and preference, conditioned taste aversion to ethanol, and duration of ethanol-induced loss of righting reflex. WT and KI mice did not differ in levels of ρ1 or ρ2 mRNA in cerebellum or in ethanol clearance. Our findings indicate that the inhibitory site for ethanol in GABA A ρ1 receptors regulates acute functional tolerance to moderate ethanol intoxication. We note that low sensitivity to alcohol intoxication has been linked to risk for development of alcohol dependence in humans. Copyright © 2017 Elsevier Ltd. All rights reserved.

Stress-restress evokes sustained iNOS activity and altered GABA levels and NMDA receptors in rat hippocampus

DEFF Research Database (Denmark)

Harvey, Brian H; Oosthuizen, Frasia; Brand, Linda

2004-01-01

. The NOS isoform involved, and the role of stress-mediated corticosterone release in NOS activation, was verified with the administration of selective iNOS and nNOS inhibitors, aminoguanidine (50 mg/kg/day i.p.) and 7-nitroindazole (12.5 mg/kg/day i.p.), and the steroid synthesis inhibitor, ketoconazole...... (24 mg/kg/day i.p.), administered for 21 days prior to and during the stress procedure. RESULTS: Stress evoked a sustained increase in NOS activity, but reduced NMDA receptor density and total GABA levels. Aminoguanidine or ketoconazole, but not 7-nitroindazole or saline, blocked stress-induced NOS...

Circadian modulation of GABA function in the rat suprachiasmatic nucleus: excitatory effects during the night phase.

NARCIS (Netherlands)

De Jeu, M.T.G.; Pennartz, C.M.A.

2002-01-01

Gramicidin-perforated patch-clamp recordings were made from slices of the suprachiasmatic nucleus (SCN) of adult rats to characterize the role of gamma-amino butyric acid (GABA) in the circadian timing system. During the day, activation of GABA(A) receptors hyperpolarized the membrane of SCN

Decreased surface expression of the δ subunit of the GABAA receptor contributes to reduced tonic inhibition in dentate granule cells in a mouse model of fragile X syndrome.

Science.gov (United States)

Zhang, Nianhui; Peng, Zechun; Tong, Xiaoping; Lindemeyer, A Kerstin; Cetina, Yliana; Huang, Christine S; Olsen, Richard W; Otis, Thomas S; Houser, Carolyn R

2017-11-01

While numerous changes in the GABA system have been identified in models of Fragile X Syndrome (FXS), alterations in subunits of the GABA A receptors (GABA A Rs) that mediate tonic inhibition are particularly intriguing. Considering the key role of tonic inhibition in controlling neuronal excitability, reduced tonic inhibition could contribute to FXS-associated disorders such as hyperactivity, hypersensitivity, and increased seizure susceptibility. The current study has focused on the expression and function of the δ subunit of the GABA A R, a major subunit involved in tonic inhibition, in granule cells of the dentate gyrus in the Fmr1 knockout (KO) mouse model of FXS. Electrophysiological studies of dentate granule cells revealed a marked, nearly four-fold, decrease in tonic inhibition in the Fmr1 KO mice, as well as reduced effects of two δ subunit-preferring pharmacological agents, THIP and DS2, supporting the suggestion that δ subunit-containing GABA A Rs are compromised in the Fmr1 KO mice. Immunohistochemistry demonstrated a small but statistically significant decrease in δ subunit labeling in the molecular layer of the dentate gyrus in Fmr1 KO mice compared to wildtype (WT) littermates. The discrepancy between the large deficits in GABA-mediated tonic inhibition in granule cells in the Fmr1 KO mice and only modest reductions in immunolabeling of the δ subunit led to studies of surface expression of the δ subunit. Cross-linking experiments followed by Western blot analysis demonstrated a small, non-significant decrease in total δ subunit protein in the hippocampus of Fmr1 KO mice, but a four-fold decrease in surface expression of the δ subunit in these mice. No significant changes were observed in total or surface expression of the α4 subunit protein, a major partner of the δ subunit in the forebrain. Postembedding immunogold labeling for the δ subunit demonstrated a large, three-fold, decrease in the number of symmetric synapses with

The effects of elevated endogenous GABA levels on movement-related network oscillations.

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Muthukumaraswamy, S D; Myers, J F M; Wilson, S J; Nutt, D J; Lingford-Hughes, A; Singh, K D; Hamandi, K

2013-02-01

The EEG/MEG signal is generated primarily by the summation of the post-synaptic potentials of cortical principal cells. At a microcircuit level, these glutamatergic principal cells are reciprocally connected to GABAergic interneurons and cortical oscillations are thought to be dependent on the balance of excitation and inhibition between these cell types. To investigate the dependence of movement-related cortical oscillations on excitation-inhibition balance, we pharmacologically manipulated the GABA system using tiagabine, which blocks GABA Transporter 1(GAT-1), the GABA uptake transporter and increases endogenous GABA activity. In a blinded, placebo-controlled, crossover design, in 15 healthy participants we administered either 15mg of tiagabine or a placebo. We recorded whole-head magnetoencephalograms, while the participants performed a movement task, prior to, one hour post, three hour post and five hour post tiagabine ingestion. Using time-frequency analysis of beamformer source reconstructions, we quantified the baseline level of beta activity (15-30Hz), the post-movement beta rebound (PMBR), beta event-related desynchronisation (beta-ERD) and movement-related gamma synchronisation (MRGS) (60-90Hz). Our results demonstrated that tiagabine, and hence elevated endogenous GABA levels causes, an elevation of baseline beta power, enhanced beta-ERD and reduced PMBR, but no modulation of MRGS. Comparing our results to recent literature (Hall et al., 2011) we suggest that beta-ERD may be a GABAA receptor mediated process while PMBR may be GABAB receptor mediated. Copyright © 2012 Elsevier Inc. All rights reserved.

GABA-A receptor beta3 and alpha5 subunit gene cluster on chromosome 15q11-q13 and bipolar disorder: a genetic association study.

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Papadimitriou, G N; Dikeos, D G; Karadima, G; Avramopoulos, D; Daskalopoulou, E G; Stefanis, C N

2001-05-08

There is accumulated evidence that the genes coding for the receptor of gamma aminobutyric acid (GABA), the most important inhibitory neurotransmitter in the CNS, may be involved in the pathogenesis of affective disorders. In a previous study, we have found a genetic association between the GABA-A receptor alpha5 subunit gene locus (GABRA5) on chromosome 15q11-of 13 and bipolar affective disorder. The aim of the present study was to examine the same subjects to see if there exists a genetic association between bipolar affective disorder and the GABA receptor beta3 subunit gene (GABRB3), which is located within 100 kb from GABRA5. The sample consisted of 48 bipolar patients compared to 44 controls (blood donors). All subjects were Greek, unrelated, and personally interviewed. Diagnosis was based on DSM-IV and ICD-10 criteria. The marker used was a dinucleotide (CA) repeat polymorphism with 12 alleles 179 to 201 bp long; genotyping was successful in all patients and 43 controls. The distribution of GABRB3 genotypes among the controls did not deviate significantly from the Hardy-Weinberg equilibrium. No differences in allelic frequencies between bipolar patients and controls were found for GABRB3, while this locus and GABRA5 did not seem to be in significant linkage disequilibrium. In conclusion, the GABRB3 CA-repeat polymorphism we investigated does not present the observed association between bipolar affective illness and GABRA5. This could be due to higher mutation rate in the GABRB3 CA-repeat polymorphism, but it might also signify that GABRA5 is the gene actually associated with the disease. Copyright 2001 Wiley-Liss, Inc.

Human α1β3γ2L gamma-aminobutyric acid type A receptors: High-level production and purification in a functional state.

Science.gov (United States)

Dostalova, Zuzana; Zhou, Xiaojuan; Liu, Aiping; Zhang, Xi; Zhang, Yinghui; Desai, Rooma; Forman, Stuart A; Miller, Keith W

2014-02-01

Gamma-aminobutyric acid type A receptors (GABA(A)Rs) are the most important inhibitory chloride ion channels in the central nervous system and are major targets for a wide variety of drugs. The subunit compositions of GABA(A)Rs determine their function and pharmacological profile. GABAA Rs are heteropentamers of subunits, and (α1)2 (β3)2 (γ2L)1 is a common subtype. Biochemical and biophysical studies of GABA(A)Rs require larger quantities of receptors of defined subunit composition than are currently available. We previously reported high-level production of active human α1β3 GABA(A)R using tetracycline-inducible stable HEK293 cells. Here we extend the strategy to receptors containing three different subunits. We constructed a stable tetracycline-inducible HEK293-TetR cell line expressing human (N)-FLAG-α1β3γ2L-(C)-(GGS)3 GK-1D4 GABA(A)R. These cells achieved expression levels of 70-90 pmol [(3)H]muscimol binding sites/15-cm plate at a specific activity of 15-30 pmol/mg of membrane protein. Incorporation of the γ2 subunit was confirmed by the ratio of [(3)H]flunitrazepam to [(3)H]muscimol binding sites and sensitivity of GABA-induced currents to benzodiazepines and zinc. The α1β3γ2L GABA(A)Rs were solubilized in dodecyl-D-maltoside, purified by anti-FLAG affinity chromatography and reconstituted in CHAPS/asolectin at an overall yield of ∼ 30%. Typical purifications yielded 1.0-1.5 nmoles of [(3)H]muscimol binding sites/60 plates. Receptors with similar properties could be purified by 1D4 affinity chromatography with lower overall yield. The composition of the purified, reconstituted receptors was confirmed by ligand binding, Western blot, and proteomics. Allosteric interactions between etomidate and [(3)H]muscimol binding were maintained in the purified state. © 2013 The Protein Society.

Gaba mediated long-term depression (LTD) in the rat medial vestibular nuclei.

Science.gov (United States)

Grassi, S; Della Torre, G; Zampolini, M; Pettorossi, V E

1995-01-01

As previously demonstrated, high frequency stimulation (HFS) of the primary vestibular afferents always induces a clear, long lasting depression of the polysynaptic (N2) component of the field potentials recorded in the dorsal portion of the medial vestibular nuclei (MVN). The induction of the HFS effect was mediated by the activation of glutamate NMDA receptors, since it was blocked by AP5. The mechanisms at the basis of such a depression were studied. Our results demonstrate that Gaba, acting on both GabaA and GabaB receptors, is involved in mediating this phenomenon. In fact, HFS applied during Bicuculline and Saclofen perfusion, was no longer able to induce an N2 depression, but provoked a slight potentiation. However, the N2 depression clearly emerged after drug wash-out. Furthermore, Bicuculline and Saclofen fully abolished the N2 depression and highlighted the potentiation, when administered after HFS. The possibility that the N2 depression is the result of a homosynaptic LTD can be excluded on the basis of our results. On the contrary, our findings suggest that the depression is due to an enhancement of the Gaba inhibitory effect due to an HFS dependent increase in gabaergic interneuron activity, which resets vestibular neuron excitability at a lower level.

Immunoreactivity for GABA, GAD65, GAD67 and Bestrophin-1 in the meninges and the choroid plexus: implications for non-neuronal sources for GABA in the developing mouse brain.

Directory of Open Access Journals (Sweden)

Shiro Tochitani

Full Text Available Neural progenitors in the developing neocortex, neuroepithelial cells and radial glial cells, have a bipolar shape with a basal process contacting the basal membrane of the meninge and an apical plasma membrane facing the lateral ventricle, which the cerebrospinal fluid is filled with. Recent studies revealed that the meninges and the cerebrospinal fluid have certain roles to regulate brain development. γ-aminobutyric acid (GABA is a neurotransmitter which appears first during development and works as a diffusible factor to regulate the properties of neural progenitors. In this study, we examined whether GABA can be released from the meninges and the choroid plexus in the developing mouse brain. Immunohistochemical analyses showed that glutamic acid decarboxylase 65 and 67 (GAD65 and GAD67, both of which are GABA-synthesizing enzymes, are expressed in the meninges. The epithelial cells in the choroid plexus express GAD65. GABA immunoreactivity could be observed beneath the basal membrane of the meninge and in the epithelial cells of the choroid plexus. Expression analyses on Bestrophin-1, which is known as a GABA-permeable channel in differentiated glial cells, suggested that the cells in the meninges and the epithelial cells in the choroid plexus have the channels able to permeate non-synaptic GABA into the extracellular space. Further studies showed that GAD65/67-expressing meningeal cells appear in a manner with rostral to caudal and lateral to dorsal gradient to cover the entire neocortex by E14.5 during development, while the cells in the choroid plexus in the lateral ventricle start to express GAD65 on E11-E12, the time when the choroid plexus starts to develop in the developing brain. These results totally suggest that the meninges and the choroid plexus can work as non-neuronal sources for ambient GABA which can modulate the properties of neural progenitors during neocortical development.

Molecular Mechanisms Underlying γ-Aminobutyric Acid (GABA) Accumulation in Giant Embryo Rice Seeds.

Science.gov (United States)

Zhao, Guo-Chao; Xie, Mi-Xue; Wang, Ying-Cun; Li, Jian-Yue

2017-06-21

To uncover the molecular mechanisms underlying GABA accumulation in giant embryo rice seeds, we analyzed the expression levels of GABA metabolism genes and contents of GABA and GABA metabolic intermediates in developing grains and germinated brown rice of giant embryo rice 'Shangshida No. 5' and normal embryo rice 'Chao2-10' respectively. In developing grains, the higher GABA contents in 'Shangshida No. 5' were accompanied with upregulation of gene transcripts and intermediate contents in the polyamine pathway and downregulation of GABA catabolic gene transcripts, as compared with those in 'Chao2-10'. In germinated brown rice, the higher GABA contents in 'Shangshida No. 5' were parallel with upregulation of OsGAD and polyamine pathway gene transcripts and Glu and polyamine pathway intermediate contents and downregulation of GABA catabolic gene transcripts. These results are the first to indicate that polyamine pathway and GABA catabolic genes play a crucial role in GABA accumulation in giant embryo rice seeds.

Effects of cocaine history on postsynaptic GABA receptors on dorsal raphe serotonin neurons in a stress-induced relapse model in rats.

Science.gov (United States)

Li, Chen; Kirby, Lynn G

2016-01-01

The serotonin (5-hydroxytryptamine, 5-HT) system plays an important role in stress-related psychiatric disorders and substance abuse. Stressors and stress hormones can inhibit the dorsal raphe nucleus (DRN)-5-HT system, which composes the majority of forebrain-projecting 5-HT. This inhibition is mediated via stimulation of GABA synaptic activity at DRN-5-HT neurons. Using swim stress-induced reinstatement of morphine conditioned place-preference, recent data from our laboratory indicate that morphine history sensitizes DRN-5-HT neurons to GABAergic inhibitory effects of stress. Moreover, GABAA receptor-mediated inhibition of the serotonergic DRN is required for this reinstatement. In our current experiment, we tested the hypothesis that GABAergic sensitization of DRN-5-HT neurons is a neuroadaptation elicited by multiple classes of abused drugs across multiple models of stress-induced relapse by applying a chemical stressor (yohimbine) to induce reinstatement of previously extinguished cocaine self-administration in Sprague-Dawley rats. Whole-cell patch-clamp recordings of GABA synaptic activity in DRN-5-HT neurons were conducted after the reinstatement. Behavioral data indicate that yohimbine triggered reinstatement of cocaine self-administration. Electrophysiology data indicate that 5-HT neurons in the cocaine group exposed to yohimbine had increased amplitude of inhibitory postsynaptic currents compared to yoked-saline controls exposed to yohimbine or unstressed animals in both drug groups. These data, together with previous findings, indicate that interaction between psychostimulant or opioid history and chemical or physical stressors may increase postsynaptic GABA receptor density and/or sensitivity in DRN-5-HT neurons. Such mechanisms may result in serotonergic hypofunction and consequent dysphoric mood states which confer vulnerability to stress-induced drug reinstatement. Copyright © 2015 Elsevier B.V. and ECNP. All rights reserved.

Leptin signaling in GABA neurons, but not glutamate neurons, is required for reproductive function.

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Zuure, Wieteke A; Roberts, Amy L; Quennell, Janette H; Anderson, Greg M

2013-11-06

The adipocyte-derived hormone leptin acts in the brain to modulate the central driver of fertility: the gonadotropin releasing hormone (GnRH) neuronal system. This effect is indirect, as GnRH neurons do not express leptin receptors (LEPRs). Here we test whether GABAergic or glutamatergic neurons provide the intermediate pathway between the site of leptin action and the GnRH neurons. Leptin receptors were deleted from GABA and glutamate neurons using Cre-Lox transgenics, and the downstream effects on puberty onset and reproduction were examined. Both mouse lines displayed the expected increase in body weight and region-specific loss of leptin signaling in the hypothalamus. The GABA neuron-specific LEPR knock-out females and males showed significantly delayed puberty onset. Adult fertility observations revealed that these knock-out animals have decreased fecundity. In contrast, glutamate neuron-specific LEPR knock-out mice displayed normal fertility. Assessment of the estrogenic hypothalamic-pituitary-gonadal axis regulation in females showed that leptin action on GABA neurons is not necessary for estradiol-mediated suppression of tonic luteinizing hormone secretion (an indirect measure of GnRH neuron activity) but is required for regulation of a full preovulatory-like luteinizing hormone surge. In conclusion, leptin signaling in GABAergic (but not glutamatergic neurons) plays a critical role in the timing of puberty onset and is involved in fertility regulation throughout adulthood in both sexes. These results form an important step in explaining the role of central leptin signaling in the reproductive system. Limiting the leptin-to-GnRH mediators to GABAergic cells will enable future research to focus on a few specific types of neurons.

Paradoxical effects of GABA-A modulators may explain sex steroid induced negative mood symptoms in some persons

NARCIS (Netherlands)

Bäckström, T.; Haage, D.; Löfgren, M.; Johansson, I. M.; Strömberg, J.; Nyberg, S.; Andréen, L.; Ossewaarde, L.; van Wingen, G. A.; Turkmen, S.; Bengtsson, S. K.

2011-01-01

Some women have negative mood symptoms, caused by progestagens in hormonal contraceptives or sequential hormone therapy or by progesterone in the luteal phase of the menstrual cycle, which may be attributed to metabolites acting on the GABA-A receptor. The GABA system is the major inhibitory system

Differential Compartmentalization and Distinct Functions of GABA(B) Receptor Variants

Czech Academy of Sciences Publication Activity Database

Vigot, B.; Barbieri, S.; Bräuner-Osborne, H.; Tureček, Rostislav; Shigemoto, R.; Zhang, Y.P.; Luján, R.; Jacobson, L.H.; Biermann, B.; Fritschy, J.M.; Vacher, C.M.; Müller, M.; Sansing, G.; Guetg, N.; Cryan, J.F.; Kaupmann, K.; Gassmann, M.; Oertner, T.G.; Bettler, B.

2006-01-01

Roč. 50, - (2006), s. 589-601 ISSN 0896-6273 R&D Projects: GA ČR GA309/03/1158 Institutional research plan: CEZ:AV0Z50390512 Keywords : GABA(B) Subject RIV: FH - Neurology Impact factor: 13.894, year: 2006

VMAT2-mediated neurotransmission from midbrain leptin receptor neurons in feeding regulation

Science.gov (United States)

Leptin receptors (LepRs) expressed in the midbrain contribute to the action of leptin on feeding regulation. The midbrain neurons release a variety of neurotransmitters including dopamine (DA), glutamate and GABA. However, which neurotransmitter mediates midbrain leptin action on feeding remains unc...

Restoration of GABA production machinery in Lactobacillus brevis by accessible carbohydrates, anaerobiosis and early acidification.

Science.gov (United States)

Wu, Qinglong; Shah, Nagendra P

2018-02-01

Lactobacillus brevis is an efficient cell factory for producing bioactive γ-aminobutyric acid (GABA) by its gad operon-encoded glutamic acid decarboxylase (GAD) system. However, little mechanistic insights have been reported on the effects of carbohydrate, oxygen and early acidification on GABA production machinery in Lb. brevis. In the present study, GABA production from Lb. brevis was enhanced by accessible carbohydrates. Fast growth of this organism was stimulated by maltose and xylose. However, its GABA production was highly suppressed by oxygen exposure, but was fully restored by anaerobiosis that up-regulated the expression of gad operon in Lb. brevis cells. Although the level of cytosolic acidity was suitable for the functioning of GadA and GadB, early acidification of the medium (ipH 5 and ipH 4) restored GABA synthesis strictly in aerated cells of Lb. brevis because the expression of gad operon was not up-regulated in them. We conclude that GABA production machinery in Lb. brevis could be restored by accessible carbohydrates, anaerobiosis and early acidification. This will be of interest for controlling fermentation for synthesis of GABA and manufacturing GABA-rich fermented vegetables. Copyright © 2017. Published by Elsevier Ltd.

Expression of Glutamate and GABA during the Process of Rat Retinal Synaptic Plasticity Induced by Acute High Intraocular Pressure

International Nuclear Information System (INIS)

Zhou, Lihong; Huang, Jufang; Wang, Hui; Luo, Jia; Zeng, Leping; Xiong, Kun; Chen, Dan

2013-01-01

Acute high intraocular pressure (HIOP) can induce plastic changes of retinal synapses during which the expression of the presynaptic marker synaptophysin (SYN) has a distinct spatiotemporal pattern from the inner plexiform layer to the outer plexiform layer. We identified the types of neurotransmitters in the retina that participated in this process and determined the response of these neurotransmitters to HIOP induction. The model of acute HIOP was established by injecting normal saline into the anterior chamber of the rat eye. We found that the number of glutamate-positive cells increased successively from the inner part to the outer part of the retina (from the ganglion cell layer to the inner nuclear layer to the outer nuclear layer) after HIOP, which was similar to the spatiotemporal pattern of SYN expression (internally to externally) following HIOP. However, the distribution and intensity of GABA immunoreactivity in the retina did not change significantly at different survival time post injury and had no direct correlation with SYN expression. Our results suggested that the excitatory neurotransmitter glutamate might participate in the plastic process of retinal synapses following acute HIOP, but no evidence was found for the role of the inhibitory neurotransmitter GABA

Transition from androgenic to neurosteroidal action of 5α-androstane-3α, 17β-diol through the type A γ-aminobutyric acid receptor in prostate cancer progression.

Science.gov (United States)

Xia, Ding; Lai, Doan V; Wu, Weijuan; Webb, Zachary D; Yang, Qing; Zhao, Lichao; Yu, Zhongxin; Thorpe, Jessica E; Disch, Bryan C; Ihnat, Michael A; Jayaraman, Muralidharan; Dhanasekaran, Danny N; Stratton, Kelly L; Cookson, Michael S; Fung, Kar-Ming; Lin, Hsueh-Kung

2018-04-01

Androgen ablation is the standard of care prescribed to patients with advanced or metastatic prostate cancer (PCa) to slow down disease progression. Unfortunately, a majority of PCa patients under androgen ablation progress to castration-resistant prostate cancer (CRPC). Several mechanisms including alternative intra-prostatic androgen production and androgen-independent androgen receptor (AR) activation have been proposed for CRPC progression. Aldo-keto reductase family 1 member C3 (AKR1C3), a multi-functional steroid metabolizing enzyme, is specifically expressed in the cytoplasm of PCa cells; and positive immunoreactivity of the type A γ-aminobutyric acid receptor (GABA A R), an ionotropic receptor and ligand-gated ion channel, is detected on the membrane of PCa cells. We studied a total of 72 radical prostatectomy cases by immunohistochemistry, and identified that 21 cases exhibited positive immunoreactivities for both AKR1C3 and GABA A R. In the dual positive cancer cases, AKR1C3 and GABA A R subunit α 1 were either expressed in the same cells or in neighboring cells. Among several possible substrates, AKR1C3 reduces 5α-dihydrotesterone (DHT) to form 5α-androstane-3α, 17β-diol (3α-diol). 3α-diol is a neurosteroid that acts as a positive allosteric modulator of the GABA A R in the central nervous system (CNS). We examined the hypothesis that 3α-diol-regulated pathological effects in the prostate are GABA A R-dependent, but are independent of the AR. In GABA A R-positive, AR-negative human PCa PC-3 cells, 3α-diol significantly stimulated cell growth in culture and the in ovo chorioallantoic membrane (CAM) xenograft model. 3α-diol also up-regulated expression of the epidermal growth factor (EGF) family of growth factors and activation of EGF receptor (EGFR) and Src as measured by quantitative polymerase chain reaction and immunoblotting, respectively. Inclusion of GABA A R antagonists reversed 3α-diol-stimulated tumor cell growth, expression of EGF

Opposing roles for GABAA and GABAC receptors in short-term memory formation in young chicks.

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Gibbs, M E; Johnston, G A R

2005-01-01

The inhibitory neurotransmitter GABA has both inhibitory and enhancing effects on short-term memory for a bead discrimination task in the young chick. Low doses of GABA (1-3 pmol/hemisphere) injected into the multimodal association area of the chick forebrain, inhibit strongly reinforced memory, whereas higher doses (30-100 pmol/hemisphere) enhance weakly reinforced memory. The effect of both high and low doses of GABA is clearly on short-term memory in terms of both the time of injection and in the time that the memory loss occurs. We argue on the basis of relative sensitivities to GABA and to selective GABA receptor antagonists that low doses of GABA act at GABAC receptors (EC50 approximately 1 microM) and the higher doses of GABA act via GABAA receptors (EC50 approximately 10 microM). The selective GABAA receptor antagonist bicuculline inhibited strongly reinforced memory in a dose and time dependent manner, whereas the selective GABAC receptor antagonists TPMPA and P4MPA enhanced weakly reinforced in a dose and time dependent manner. Confirmation that different levels of GABA affect different receptor subtypes was demonstrated by the shift in the GABA dose-response curves to the selective antagonists. It is clear that GABA is involved in the control of short-term memory formation and its action, enhancing or inhibiting, depends on the level of GABA released at the time of learning.

Distinct interneuron types express m2 muscarinic receptor immunoreactivity on their dendrites or axon terminals in the hippocampus.

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Hájos, N; Papp, E C; Acsády, L; Levey, A I; Freund, T F

1998-01-01

In previous studies m2 muscarinic acetylcholine receptor-immunoreactive interneurons and various types of m2-positive axon terminals have been described in the hippocampal formation. The aim of the present study was to identify the types of interneurons expressing m2 receptor and to examine whether the somadendritic and axonal m2 immunostaining labels the same or distinct cell populations. In the CA1 subfield, neurons immunoreactive for m2 have horizontal dendrites, they are located at the stratum oriens/alveus border and have an axon that project to the dendritic region of pyramidal cells. In the CA3 subfield and the hilus, m2-positive neurons are multipolar and are scattered in all layers except stratum lacunosum-moleculare. In stratum pyramidale of the CA1 and CA3 regions, striking axon terminal staining for m2 was observed, surrounding the somata and axon initial segments of pyramidal cells in a basket-like manner. The co-localization of m2 with neurochemical markers and GABA was studied using the "mirror" technique and fluorescent double-immunostaining at the light microscopic level and with double-labelling using colloidal gold-conjugated antisera and immunoperoxidase reaction (diaminobenzidine) at the electron microscopic level. GABA was shown to be present in the somata of most m2-immunoreactive interneurons, as well as in the majority of m2-positive terminals in all layers. The calcium-binding protein parvalbumin was absent from practically all m2-immunoreactive cell bodies and dendrites. In contrast, many of the terminals synapsing on pyramidal cell somata and axon initial segments co-localized parvalbumin and m2, suggesting a differential distribution of m2 receptor immunoreactivity on the axonal and somadendritic membrane of parvalbumin-containing basket and axo-axonic cells. The co-existence of m2 receptors with the calcium-binding protein calbindin and the neuropeptides cholecystokinin and vasoactive intestinal polypeptide was rare throughout the

Differential association of GABAB receptors with their effector ion channels in Purkinje cells.

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Luján, Rafael; Aguado, Carolina; Ciruela, Francisco; Cózar, Javier; Kleindienst, David; de la Ossa, Luis; Bettler, Bernhard; Wickman, Kevin; Watanabe, Masahiko; Shigemoto, Ryuichi; Fukazawa, Yugo

2018-04-01

Metabotropic GABA B receptors mediate slow inhibitory effects presynaptically and postsynaptically through the modulation of different effector signalling pathways. Here, we analysed the distribution of GABA B receptors using highly sensitive SDS-digested freeze-fracture replica labelling in mouse cerebellar Purkinje cells. Immunoreactivity for GABA B1 was observed on presynaptic and, more abundantly, on postsynaptic compartments, showing both scattered and clustered distribution patterns. Quantitative analysis of immunoparticles revealed a somato-dendritic gradient, with the density of immunoparticles increasing 26-fold from somata to dendritic spines. To understand the spatial relationship of GABA B receptors with two key effector ion channels, the G protein-gated inwardly rectifying K + (GIRK/Kir3) channel and the voltage-dependent Ca 2+ channel, biochemical and immunohistochemical approaches were performed. Co-immunoprecipitation analysis demonstrated that GABA B receptors co-assembled with GIRK and Ca V 2.1 channels in the cerebellum. Using double-labelling immunoelectron microscopic techniques, co-clustering between GABA B1 and GIRK2 was detected in dendritic spines, whereas they were mainly segregated in the dendritic shafts. In contrast, co-clustering of GABA B1 and Ca V 2.1 was detected in dendritic shafts but not spines. Presynaptically, although no significant co-clustering of GABA B1 and GIRK2 or Ca V 2.1 channels was detected, inter-cluster distance for GABA B1 and GIRK2 was significantly smaller in the active zone than in the dendritic shafts, and that for GABA B1 and Ca V 2.1 was significantly smaller in the active zone than in the dendritic shafts and spines. Thus, GABA B receptors are associated with GIRK and Ca V 2.1 channels in different subcellular compartments. These data provide a better framework for understanding the different roles played by GABA B receptors and their effector ion channels in the cerebellar network.

Alternative-splicing in the exon-10 region of GABA(A receptor beta(2 subunit gene: relationships between novel isoforms and psychotic disorders.

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Cunyou Zhao

Full Text Available BACKGROUND: Non-coding single nucleotide polymorphisms (SNPs in GABRB2, the gene for beta(2-subunit of gamma-aminobutyric acid type A (GABA(A receptor, have been associated with schizophrenia (SCZ and quantitatively correlated to mRNA expression and alternative splicing. METHODS AND FINDINGS: Expression of the Exon 10 region of GABRB2 from minigene constructs revealed this region to be an "alternative splicing hotspot" that readily gave rise to differently spliced isoforms depending on intron sequences. This led to a search in human brain cDNA libraries, and the discovery of two novel isoforms, beta(2S1 and beta(2S2, bearing variations in the neighborhood of Exon-10. Quantitative real-time PCR analysis of postmortem brain samples showed increased beta(2S1 expression and decreased beta(2S2 expression in both SCZ and bipolar disorder (BPD compared to controls. Disease-control differences were significantly correlated with SNP rs187269 in BPD males for both beta(2S1 and beta(2S2 expressions, and significantly correlated with SNPs rs2546620 and rs187269 in SCZ males for beta(2S2 expression. Moreover, site-directed mutagenesis indicated that Thr(365, a potential phosphorylation site in Exon-10, played a key role in determining the time profile of the ATP-dependent electrophysiological current run-down. CONCLUSION: This study therefore provided experimental evidence for the importance of non-coding sequences in the Exon-10 region in GABRB2 with respect to beta(2-subunit splicing diversity and the etiologies of SCZ and BPD.

Alterations of cortical GABA neurons and network oscillations in schizophrenia.

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Gonzalez-Burgos, Guillermo; Hashimoto, Takanori; Lewis, David A

2010-08-01

The hypothesis that alterations of cortical inhibitory gamma-aminobutyric acid (GABA) neurons are a central element in the pathology of schizophrenia has emerged from a series of postmortem studies. How such abnormalities may contribute to the clinical features of schizophrenia has been substantially informed by a convergence with basic neuroscience studies revealing complex details of GABA neuron function in the healthy brain. Importantly, activity of the parvalbumin-containing class of GABA neurons has been linked to the production of cortical network oscillations. Furthermore, growing knowledge supports the concept that gamma band oscillations (30-80 Hz) are an essential mechanism for cortical information transmission and processing. Herein we review recent studies further indicating that inhibition from parvalbumin-positive GABA neurons is necessary to produce gamma oscillations in cortical circuits; provide an update on postmortem studies documenting that deficits in the expression of glutamic acid decarboxylase67, which accounts for most GABA synthesis in the cortex, are widely observed in schizophrenia; and describe studies using novel, noninvasive approaches directly assessing potential relations between alterations in GABA, oscillations, and cognitive function in schizophrenia.

GABA Levels Are Decreased After Stroke and GABA Changes During Rehabilitation Correlate With Motor Improvement

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Blicher, Jakob Udby; Near, Jamie; Næss-Schmidt, Erhard; Stagg, Charlotte J.; Johansen-Berg, Heidi; Nielsen, Jørgen Feldbæk; Østergaard, Leif; Ho, Yi-Ching Lynn

2017-01-01

Background and Objective γ-Aminobutyric acid (GABA) is the dominant inhibitory neurotransmitter in the brain and is important in motor learning. We aimed to measure GABA content in primary motor cortex poststroke (using GABA-edited magnetic resonance spectroscopy [MRS]) and in relation to motor recovery during 2 weeks of constraint-induced movement therapy (CIMT). Methods Twenty-one patients (3-12 months poststroke) and 20 healthy subjects were recruited. Magnetic resonance imaging structural T1 and GABA-edited MRS were performed at baseline and after CIMT, and once in healthy subjects. GABA:creatine (GABA:Cr) ratio was measured by GABA-edited MRS. Motor function was measured using Wolf Motor Function Test (WMFT). Results Baseline comparison between stroke patients (n = 19) and healthy subjects showed a significantly lower GABA:Cr ratio in stroke patients (P GABA relative to N-acetylaspartic acid (NAA; P = .03). After 2 weeks of CIMT patients improved significantly on WMFT, but no consistent change across the group was observed for the GABA:Cr ratio (n = 17). However, the extent of improvement on WMFT correlated significantly with the magnitude of GABA:Cr changes (P GABA:Cr ratio being associated with better improvements in motor function. Conclusions In patients 3 to 12 months poststroke, GABA levels are lower in the primary motor cortex than in healthy subjects. The observed association between GABA and recovery warrants further studies on the potential use of GABA MRS as a biomarker in poststroke recovery. PMID:25055837

Inhibition of GABA A receptor improved special memory impairment in the local model of demyelination in rat hippocampus.

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Mousavi Majd, Alireza; Ebrahim Tabar, Forough; Afghani, Arghavan; Ashrafpour, Sahand; Dehghan, Samaneh; Gol, Mohammad; Ashrafpour, Manouchehr; Pourabdolhossein, Fereshteh

2018-01-15

Cognitive impairment and memory deficit are common features in multiple Sclerosis patients. The mechanism of memory impairment in MS is unknown, but neuroimaging studies suggest that hippocampal demyelination is involved. Here, we investigate the role of GABA A receptor on spatial memory in the local model of hippocampal demyelination. Demyelination was induced in male Wistar rats by bilaterally injection of lysophosphatidylcholine (LPC) 1% into the CA1 region of the hippocampus. The treatment groups were received daily intraventricular injection of bicuculline (0.025, 0.05μg/2μl/animal) or muscimol (0.1, 0.2μg/2μl/animal) 5days after LPC injection. Morris Water Maze was used to evaluate learning and memory in rats. We used Luxol fast blue staining and qPCR to assess demyelination extention and MBP expression level respectively. Immunohistochemistry (IHC) for CD45 and H&E staining were performed to assess inflammatory cells infiltration. Behavioral study revealed that LPC injection in the hippocampus impaired learning and memory function. Animals treated with both doses of bicuculline improved spatial learning and memory function; however, muscimol treatment had no effect. Histological and MBP expression studies confirmed that demylination in LPC group was maximal. Bicuculline treatment significantly reduced demyelination extension and increased the level of MBP expression. H&E and IHC results showed that bicuculline reduced inflammatory cell infiltration in the lesion site. Bicuculline improved learning and memory and decreased demyelination extention in the LPC-induced hippocampal demyelination model. We conclude that disruption of GABAergic homeostasis in hippocampal demyelination context may be involved in memory impairment with the implications for both pathophysiology and therapy. Copyright © 2017. Published by Elsevier B.V.

Concentration-dependent activation of dopamine receptors differentially modulates GABA release onto orexin neurons.

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Linehan, Victoria; Trask, Robert B; Briggs, Chantalle; Rowe, Todd M; Hirasawa, Michiru

2015-08-01

Dopamine (DA) and orexin neurons play important roles in reward and food intake. There are anatomical and functional connections between these two cell groups: orexin peptides stimulate DA neurons in the ventral tegmental area and DA inhibits orexin neurons in the hypothalamus. However, the cellular mechanisms underlying the action of DA on orexin neurons remain incompletely understood. Therefore, the effect of DA on inhibitory transmission to orexin neurons was investigated in rat brain slices using the whole-cell patch-clamp technique. We found that DA modulated the frequency of spontaneous and miniature IPSCs (mIPSCs) in a concentration-dependent bidirectional manner. Low (1 μM) and high (100 μM) concentrations of DA decreased and increased IPSC frequency, respectively. These effects did not accompany a change in mIPSC amplitude and persisted in the presence of G-protein signaling inhibitor GDPβS in the pipette, suggesting that DA acts presynaptically. The decrease in mIPSC frequency was mediated by D2 receptors whereas the increase required co-activation of D1 and D2 receptors and subsequent activation of phospholipase C. In summary, our results suggest that DA has complex effects on GABAergic transmission to orexin neurons, involving cooperation of multiple receptor subtypes. The direction of dopaminergic influence on orexin neurons is dependent on the level of DA in the hypothalamus. At low levels DA disinhibits orexin neurons whereas at high levels it facilitates GABA release, which may act as negative feedback to curb the excitatory orexinergic output to DA neurons. These mechanisms may have implications for consummatory and motivated behaviours. © 2015 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

Synchronization by Food Access Modifies the Daily Variations in Expression and Activity of Liver GABA Transaminase

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De Ita-Pérez, Dalia; Méndez, Isabel; Vázquez-Martínez, Olivia; Villalobos-Leal, Mónica; Díaz-Muñoz, Mauricio

2014-01-01

Daytime restricted feeding (DRF) is an experimental protocol that influences the circadian timing system and underlies the expression of a biological clock known as the food entrained oscillator (FEO). Liver is the organ that reacts most rapidly to food restriction by adjusting the functional relationship between the molecular circadian clock and the metabolic networks. γ-Aminobutyric acid (GABA) is a signaling molecule in the liver, and able to modulate the cell cycle and apoptosis. This stu...

Quantitative autoradiography of hippocampal GABAB and GASAA receptor changes in Alzheimer's disease

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Chu, D.C.M.; Penney, J.B. Jr.; Young, A.B.

1987-01-01

GABA B and GABA A receptors were examined by quantitative [ 3 H] GABA autoradiography in postmortem human hippocampus from 6 histopathologically verified cases of dementia of the Alzheimer type (DAT) and 6 normal controls. Significant decrements in the B max for both types of GABA receptors were observed in DAT hippocampus as compared to normal controls. No significant differences in K d values were revealed. As compared to controls, DAT hippocampus exhibited fewer GABA B receptors in stratum moleculare of the denate gyrus, stratum lacunosum-molecular and stratum pyramidale of CA 1 . Significant loss of GABA A receptors in DAT hippocampus was also observed in the CA 1 pyramidal cell region. These changes could not be correlated with differences in age nor in postmortem delay between the two groups. These findings may reflect the neuronal pathologies in CA 1 region in dentate gyrus, and in projections from the entorhinal cortex which are associated with the memory impairment of DAT. 29 refs. (Author)

Turnover and release of GABA in rat cortical slices: effect of a GABA-T inhibitor, gabaculine

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Szerb, J.C.

1982-01-01

The turnover and release of endogenous and labeled GABA were followed in rat cortical slices after incubation with [ 3 H]GABA. High performance liquid chromatography was used to measure endogenous GABA and to separate [ 3 H]GABA from its metabolites. During superfusion with 3 mM K + the slices rapidly lost their [ 3 H]GABA content while maintaining constant GABA levels. Exposure to 50 mM K + for 25 min caused an initial rapid rise in the release of both endogenous and [ 3 H]GABA followed by a more rapid decline in the release of the latter. The specific activity of released GABA was two to four times higher than that in the slices. Depolarization lead to a net synthesis of GABA. The GABA -T inhibitor, gabaculine, (5 micrometers) in vitro arrested the metabolism of [ 3 H]GABA and rapidly doubled the GABA content but did not significantly increase the high K + evoked release of endogenous GABA. In vivo pretreatment with 0.5 mM/kg gabaculine quadrupled GABA content and increased both the spontaneous and evoked release of endogenous GABA but while its Ca 2 + -dependent release increased by 50%, the Ca 2 + -independent release was enhanced sevenfold. This large Ca 2 + -independent release of GABA is likely to have different functional significance from the normal Ca 2 + -dependent release

GABAA Receptors, Anesthetics and Anticonvulsants in Brain Development

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Henschel, Oliver; Gipson, Keith E.; Bordey, Angelique

2008-01-01

GABA, acting via GABAA receptors, is well-accepted as the main inhibitory neurotransmitter of the mature brain, where it dampens neuronal excitability. The receptor's properties have been studied extensively, yielding important information about its structure, pharmacology, and regulation that are summarized in this review. Several GABAergic drugs have been commonly used as anesthetics, sedatives, and anticonvulsants for decades. However, findings that GABA has critical functions in brain development, in particular during the late embryonic and neonatal period, raise worthwhile questions regarding the side effects of GABAergic drugs that may lead to long-term cognitive deficits. Here, we will review some of these drugs in parallel with the control of CNS development that GABA exerts via activation of GABAA receptors. This review aims to provide a basic science and clinical perspective on the function of GABA and related pharmaceuticals acting at GABAA receptors. PMID:18537647

Induction of the GABA cell phenotype: an in vitro model for studying neurodevelopmental disorders.

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Sivan Subburaju

Full Text Available Recent studies of the hippocampus have suggested that a network of genes is associated with the regulation of the GAD₆₇ (GAD1 expression and may play a role in γ-amino butyric acid (GABA dysfunction in schizophrenia (SZ and bipolar disorder (BD. To obtain a more detailed understanding of how GAD₆₇ regulation may result in GABAergic dysfunction, we have developed an in vitro model in which GABA cells are differentiated from the hippocampal precursor cell line, HiB5. Growth factors, such as PDGF, and BDNF, regulate the GABA phenotype by inducing the expression of GAD₆₇ and stimulating the growth of cellular processes, many with growth cones that form appositions with the cell bodies and processes of other GAD₆₇-positive cells. These changes are associated with increased expression of acetylated tubulin, microtubule-associated protein 2 (MAP2 and the post-synaptic density protein 95 (PSD95. The addition of BDNF, together with PDGF, increases the levels of mRNA and protein for GAD₆₇, as well as the high affinity GABA uptake protein, GAT1. These changes are associated with increased concentrations of GABA in the cytoplasm of "differentiated" HiB5 neurons. In the presence of Ca²⁺ and K⁺, newly synthesized GABA is released extracellularly. When the HiB5 cells appear to be fully differentiated, they also express GAD₆₅, parvalbumin and calbindin, and GluR subtypes as well as HDAC1, DAXX, PAX5, Runx2, associated with GAD₆₇ regulation. Overall, these results suggest that the HiB5 cells can differentiate into functionally mature GABA neurons in the presence of gene products that are associated with GAD₆₇ regulation in the adult hippocampus.

Sleep-promoting effects of a GABA/5-HTP mixture: Behavioral changes and neuromodulation in an invertebrate model.

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Hong, Ki-Bae; Park, Yooheon; Suh, Hyung Joo

2016-04-01

This study was to investigate the sleep promoting effects of combined γ-aminobutyric acid (GABA) and 5-hydroxytryptophan (5-HTP), by examining neuronal processes governing mRNA level alterations, as well as assessing neuromodulator concentrations, in a fruit fly model. Behavioral assays were applied to investigate subjective nighttime activity, sleep episodes, and total duration of subjective nighttime sleep of two amino acids and GABA/5-HTP mixture with caffeine treated flies. Also, real-time PCR and HPLC analysis were applied to analyze the signaling pathway. Subjective nighttime activity and sleep patterns of individual flies significantly decreased with 1% GABA treatment in conjunction with 0.1% 5-HTP treatment (pGABA/5-HTP mixture resulted in significant differences between groups related to sleep patterns (40%, plevels of the GABAB receptor (GABAB-R1) and serotonin receptor (5-HT1A), compared to the control group. In addition, GABA/5-HTP mixture significantly increased GABA levels 1h and 12h following treatment (2.1 fold and 1.2 fold higher than the control, respectively) and also increased 5-HTP levels (0 h: 1.01 μg/protein, 12h: 3.45 μg/protein). In this regard, we successfully demonstrated that using a GABA/5-HTP mixture modulates subjective nighttime activity, sleep episodes, and total duration of subjective nighttime sleep to a greater extent than single administration of each amino acid, and that this modulation occurs via GABAergic and serotonergic signaling. Copyright © 2016 Elsevier Inc. All rights reserved.

Structural determinants for antagonist pharmacology that distinguish the rho1 GABAC receptor from GABAA receptors.

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Zhang, Jianliang; Xue, Fenqin; Chang, Yongchang

2008-10-01

GABA receptor (GABAR) types C (GABACR) and A (GABAAR) are both GABA-gated chloride channels that are distinguished by their distinct competitive antagonist properties. The structural mechanism underlying these distinct properties is not well understood. In this study, using previously identified binding residues as a guide, we made individual or combined mutations of nine binding residues in the rho1 GABACR subunit to their counterparts in the alpha1beta2gamma2 GABAAR or reverse mutations in alpha1 or beta2 subunits. The mutants were expressed in Xenopus laevis oocytes and tested for sensitivities of GABA-induced currents to the GABAA and GABAC receptor antagonists. The results revealed that bicuculline insensitivity of the rho1 GABACR was mainly determined by Tyr106, Phe138 and Phe240 residues. Gabazine insensitivity of the rho1 GABACR was highly dependent on Tyr102, Tyr106, and Phe138. The sensitivity of the rho1 GABACR to 3-aminopropyl-phosphonic acid and its analog 3-aminopropyl-(methyl)phosphinic acid mainly depended on residues Tyr102, Val140, FYS240-242, and Phe138. Thus, the residues Tyr102, Tyr106, Phe138, and Phe240 in the rho1 GABACR are major determinants for its antagonist properties distinct from those in the GABAAR. In addition, Val140 in the GABACR contributes to 3-APA binding. In conclusion, we have identified the key structural elements underlying distinct antagonist properties for the GABACR. The mechanistic insights were further extended and discussed in the context of antagonists docking to the homology models of GABAA or GABAC receptors.

Temperature dependence and GABA modulation of [3H]triazolam binding in the rat brain

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Earle, M.E.; Concas, A.; Wamsley, J.K.; Yamamura, H.I.

1987-01-01

The hypnotic triazolam (TZ), a triazolobenzodiazepine displays a short physiological half life and has been used for the treatment of insomnia related to anxiety states. The authors major objectives were the direct measurement of the temperature dependence and the gamma-aminobutyric acid (GABA) effect of [ 3 H]TZ binding in the rat brain. Saturation studies showed a shift to lower affinity with increasing temperatures (K/sub d/ = 0.27 +/- 08 nM at 0 0 C; K/sub d/ = 1.96 +/- 0.85 nM at 37 0 C) while the B/sub max/ values remained unchanged (1220 +/- 176 fmoles/mg protein at 0 0 C and 1160 +/- 383 fmoles/mg protein at 37 0 C). Saturation studies of [ 3 H]TZ binding in the presence or absence of GABA (100μM) showed a GABA-shift. At 0 0 C the K/sub d/ values were (K/sub d/ = 0.24 +/- 0.03 nM/-GABA; K/sub d/ = 0.16 +/- 0.04/+GABA) and at 37 0 C the K/sub d/ values were (K/sub d/ = 1.84 +/- 0.44 nM/-GABA; K/sub d/ = 0.95 +/- 0.29 nM/+GABA). In contrast to reported literature, the authors findings show that TZ interacts with benzodiazepine receptors with a temperature dependence and GABA-shift consistent with predicted behavior for benzodiazepine agonists. 20 references, 3 tables

Enhanced phasic GABA inhibition during the repair phase of stroke: a novel therapeutic target.

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Hiu, Takeshi; Farzampour, Zoya; Paz, Jeanne T; Wang, Eric Hou Jen; Badgely, Corrine; Olson, Andrew; Micheva, Kristina D; Wang, Gordon; Lemmens, Robin; Tran, Kevin V; Nishiyama, Yasuhiro; Liang, Xibin; Hamilton, Scott A; O'Rourke, Nancy; Smith, Stephen J; Huguenard, John R; Bliss, Tonya M; Steinberg, Gary K

2016-02-01

Ischaemic stroke is the leading cause of severe long-term disability yet lacks drug therapies that promote the repair phase of recovery. This repair phase of stroke occurs days to months after stroke onset and involves brain remapping and plasticity within the peri-infarct zone. Elucidating mechanisms that promote this plasticity is critical for the development of new therapeutics with a broad treatment window. Inhibiting tonic (extrasynaptic) GABA signalling during the repair phase was reported to enhance functional recovery in mice suggesting that GABA plays an important function in modulating brain repair. While tonic GABA appears to suppress brain repair after stroke, less is known about the role of phasic (synaptic) GABA during the repair phase. We observed an increase in postsynaptic phasic GABA signalling in mice within the peri-infarct cortex specific to layer 5; we found increased numbers of α1 receptor subunit-containing GABAergic synapses detected using array tomography, and an associated increased efficacy of spontaneous and miniature inhibitory postsynaptic currents in pyramidal neurons. Furthermore, we demonstrate that enhancing phasic GABA signalling using zolpidem, a Food and Drug Administration (FDA)-approved GABA-positive allosteric modulator, during the repair phase improved behavioural recovery. These data identify potentiation of phasic GABA signalling as a novel therapeutic strategy, indicate zolpidem's potential to improve recovery, and underscore the necessity to distinguish the role of tonic and phasic GABA signalling in stroke recovery. © The Author (2015). Published by Oxford University Press on behalf of the Guarantors of Brain.

GABA in nucleus tractus solitarius participates in electroacupuncture modulation of cardiopulmonary bradycardia reflex.

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Tjen-A-Looi, Stephanie C; Guo, Zhi-Ling; Longhurst, John C

2014-12-01

Phenylbiguanide (PBG) stimulates cardiopulmonary receptors and cardiovascular reflex responses, including decreases in blood pressure and heart rate mediated by the brain stem parasympathetic cardiac neurons in the nucleus ambiguus and nucleus tractus solitarius (NTS). Electroacupuncture (EA) at P5-6 stimulates sensory fibers in the median nerve and modulates these reflex responses. Stimulation of median nerves reverses bradycardia through action of γ-aminobutyric acid (GABA) in the nucleus ambiguus, important in the regulation of heart rate. We do not know whether the NTS or the neurotransmitter mechanisms in this nucleus participate in these modulatory actions by acupuncture. We hypothesized that somatic nerve stimulation during EA (P5-6) modulates cardiopulmonary inhibitory responses through a GABAergic mechanism in the NTS. Anesthetized and ventilated cats were examined during either PBG or direct vagal afferent stimulation while 30 min of EA was applied at P5-6. Reflex heart rate and blood pressure responses and NTS-evoked discharge were recorded. EA reduced the PBG-induced depressor and bradycardia reflexes by 67% and 60%, respectively. Blockade of GABAA receptors in the NTS reversed EA modulation of bradycardia but not the depressor response. During EA, gabazine reversed the vagally evoked discharge activity of cardiovascular NTS neurons. EA modulated the vagal-evoked cardiovascular NTS cellular activity for 60 min. Immunohistochemistry using triple labeling showed GABA immunoreactive fibers juxtaposed to glutamatergic nucleus ambiguus-projecting NTS neurons in rats. These glutamatergic neurons expressed GABAA receptors. These findings suggest that EA inhibits PBG-evoked bradycardia and vagally evoked NTS activity through a GABAergic mechanism, likely involving glutamatergic nucleus ambiguus-projecting NTS neurons. Copyright © 2014 the American Physiological Society.

New Pharmacotherapy Targeting Cognitive Dysfunction of Schizophrenia via Modulation of GABA Neuronal Function.

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Uehara, Takashi; Sumiyoshi, Tomiki; Kurachi, Masayoshi

2015-01-01

Schizophrenia is considered a neurodevelopmental and neurodegenerative disorder. Cognitive impairment is a core symptom in patients with the illness, and has been suggested a major predictor of functional outcomes. Reduction of parvalbumin (PV)-positive γ-aminobutyric acid (GABA) interneurons has been associated with the pathophysiology of schizophrenia, in view of the link between the abnormality of GABA neurons and cognitive impairments of the disease. It is assumed that an imbalance of excitatory and inhibitory (E-I) activity induced by low activity of glutamatergic projections and PV-positive GABA interneurons in the prefrontal cortex resulted in sustained neural firing and gamma oscillation, leading to impaired cognitive function. Therefore, it is important to develop novel pharmacotherapy targeting GABA neurons and their activities. Clinical evidence suggests serotonin (5-HT) 1A receptor agonist improves cognitive disturbances of schizophrenia, consistent with results from preclinical studies, through mechanism that corrects E-I imbalance via the suppression of GABA neural function. On the other hand, T-817MA, a novel neurotrophic agent, ameliorated loss of PV-positive GABA neurons in the medial prefrontal cortex and reduction of gamma-band activity, as well as cognitive dysfunction in animal model of schizophrenia. In conclusion, a pharmacotherapy to alleviate abnormalities in GABA neurons through 5-HT1A agonists and T-817MA is expected to prevent the onset and/or progression of schizophrenia.

Regulation of Arterial Pressure By The Paraventricular Nucleus in Conscious Rats: Interactions Among Glutamate, GABA, and Nitric Oxide

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Marli Cardoso Martins-Pinge

2013-01-01

Full Text Available The paraventricular nucleus (PVN of the hypothalamus is an important site for autonomic and neuroendocrine regulation. Experiments in anesthetized animals and in vitro indicate an interaction among gamma-aminobutyric acid (GABA, nitric oxide (NO and glutamate in the PVN. The cardiovascular role of the PVN and interactions of these neurotransmitters in conscious animals have not been evaluated fully. In chronically instrumented conscious rats, mean arterial pressure (MAP and heart rate (HR responses to microinjections (100 nl in the region of the PVN were tested. Bilateral blockade of ionotropic excitatory amino acid (EAA receptors (kynurenic acid, Kyn in the PVN produced small but significant decreases in MAP and HR. GABAA receptor blockade (bicuculline, Bic, and inhibition of NO synthase (N-(G-monomethyl-L-arginine, L-NMMA each increased MAP and HR. The NO donor sodium nitroprusside (SNP produced depressor responses that were attenuated by Bic. NO synthase inhibition potentiated both pressor responses to the selective EAA agonist, N-methyl-D-aspartic acid (NMDA, and depressor responses to Kyn. Increases in MAP and HR due to Bic were blunted by prior blockade of EAA receptors. Thus, pressor responses to GABA blockade require EAA receptors and GABA neurotransmission contributes to NO inhibition. Tonic excitatory effects of glutamate in the PVN are tonically attenuated by NO. These data demonstrate that, in the PVN of conscious rats, GABA, glutamate and NO interact in a complex fashion to regulate arterial pressure and heart rate under normal conditions.

Gad1 mRNA as a reliable indicator of altered GABA release from orexigenic neurons in the hypothalamus.

Science.gov (United States)

Dicken, Matthew S; Hughes, Alexander R; Hentges, Shane T

2015-11-01

The strength of γ-aminobutyric acid (GABA)-mediated inhibitory synaptic input is a principle determinant of neuronal activity. However, because of differences in the number of GABA afferent inputs and the sites of synapses, it is difficult to directly assay for altered GABA transmission between specific cells. The present study tested the hypothesis that the level of mRNA for the GABA synthetic enzyme glutamate decarboxylase (GAD) can provide a reliable proxy for GABA release. This was tested in a mouse hypothalamic circuit important in the regulation of energy balance. Fluorescent in situ hybridization results show that the expression of Gad1 mRNA (encoding the GAD67 enzyme) was increased in hypothalamic neuropeptide Y/agouti-related peptide (NPY/AgRP) neurons after an overnight fast, consistent with the ability of GABA from these neurons to stimulate food intake. Optogenetic studies confirmed that the observed increase in Gad1 mRNA correlated with an increase in the probability of GABA release from NPY/AgRP neurons onto downstream proopiomelanocortin neurons. Likewise, there was an increase in the readily releasable pool of GABA in NPY/AgRP neurons. Selective inhibition of GAD activity in NPY/AgRP neurons decreased GABA release, indicating that GAD67 activity, which is largely dictated by expression level, is a key determinant of GABA release. Altogether, it appears that Gad expression may be a reliable proxy of altered GABAergic transmission. Examining changes in Gad mRNA as a proxy for GABA release may be particularly helpful when the downstream targets are not known or when limited tools exist for detecting GABA release at a particular synapse. © 2015 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

γ-aminobutyric acidA (GABAA) receptor regulates ERK1/2 phosphorylation in rat hippocampus in high doses of Methyl Tert-Butyl Ether (MTBE)-induced impairment of spatial memory

International Nuclear Information System (INIS)

Zheng Gang; Zhang Wenbin; Zhang Yun; Chen Yaoming; Liu Mingchao; Yao Ting; Yang Yanxia; Zhao Fang; Li Jingxia; Huang Chuanshu; Luo Wenjing; Chen Jingyuan

2009-01-01

Experimental and occupational exposure to Methyl Tert-Butyl Ether (MTBE) has been reported to induce neurotoxicological and neurobehavioral effects, such as headache, nausea, dizziness, and disorientation, etc. However, the molecular mechanisms involved in MTBE-induced neurotoxicity are still not well understood. In the present study, we investigated the effects of MTBE on spatial memory and the expression and function of GABA A receptor in the hippocampus. Our results demonstrated that intraventricular injection of MTBE impaired the performance of the rats in a Morris water maze task, and significantly increased the expression of GABA A receptor α1 subunit in the hippocampus. The phosphorylation of ERK1/2 decreased after the MTBE injection. Furthermore, the decreased ability of learning and the reduction of phosphorylated ERK1/2 level of the MTBE-treated rats was partly reversed by bicuculline injected 30 min before the training. These results suggested that MTBE exposure could result in impaired spatial memory. GABA A receptor may play an important role in the MTBE-induced impairment of learning and memory by regulating the phosphorylation of ERK in the hippocampus.

Positive modulation of delta-subunit containing GABAA receptors in mouse neurons

DEFF Research Database (Denmark)

Vardya, Irina; Hoestgaard-Jensen, Kirsten; Nieto-Gonzalez, Jose Luis

2012-01-01

δ-subunit containing extrasynaptic GABA(A) receptors are potential targets for modifying neuronal activity in a range of brain disorders. With the aim of gaining more insight in synaptic and extrasynaptic inhibition, we used a new positive modulator, AA29504, of δ-subunit containing GABA(A) recep......δ-subunit containing extrasynaptic GABA(A) receptors are potential targets for modifying neuronal activity in a range of brain disorders. With the aim of gaining more insight in synaptic and extrasynaptic inhibition, we used a new positive modulator, AA29504, of δ-subunit containing GABA......(A) receptors in mouse neurons in vitro and in vivo. Whole-cell patch-clamp recordings were carried out in the dentate gyrus in mouse brain slices. In granule cells, AA29504 (1 μM) caused a 4.2-fold potentiation of a tonic current induced by THIP (1 μM), while interneurons showed a potentiation of 2.6-fold......-free environment using Ca²⁺ imaging in cultured neurons, AA29504 showed GABA(A) receptor agonism in the absence of agonist. Finally, AA29504 exerted dose-dependent stress-reducing and anxiolytic effects in mice in vivo. We propose that AA29504 potentiates δ-containing GABA(A) receptors to enhance tonic inhibition...

Cell and Receptor Type-Specific Alterations in Markers of GABA Neurotransmission in the Prefrontal Cortex of Subjects with Schizophrenia

OpenAIRE

Lewis, David A.; Hashimoto, Takanori; Morris, Harvey M.

2008-01-01

Impairments in cognitive control, such as those involved in working memory, are associated with dysfunction of the dorsolateral prefrontal cortex (DLPFC) in individuals with schizophrenia. This dysfunction appears to result, at least in part, from abnormalities in GABA-mediated neurotransmission. In this paper, we review recent findings indicating that the altered DLPFC circuitry in subjects with schizophrenia reflects changes in the expression of genes that encode selective presynaptic and p...

Neuroprotection of ebselen against ischemia/reperfusion injury involves GABA shunt enzymes.

Science.gov (United States)

Seo, Jeong Yeol; Lee, Choong Hyun; Cho, Jun Hwi; Choi, Jung Hoon; Yoo, Ki-Yeon; Kim, Dae Won; Park, Ok Kyu; Li, Hua; Choi, Soo Young; Hwang, In Koo; Won, Moo-Ho

2009-10-15

Seleno-organic compound, ebselen (2-phenyl-1,2-benzisoselenazol-3(2H)-one), is a substrate with radical-scavenging activity. In this study, we observed the neuroprotective effects of ebselen against ischemic damage and on GABA shunt enzymes such as glutamic acid decarboxylase 67 (GAD67), GABA transaminse (GABA-T) and succinic semialdehyde dehydrogenase (SSADH) in the hippocampal CA1 region after 5 min of transient forebrain ischemia in gerbils. For this, vehicle (physiological saline) or ebselen was administered 30 min before or after ischemia/reperfusion and sacrificed 4 days after ischemia/reperfusion. The administration of ebselen significantly reduced the neuronal death in the CA1 region induced by ischemia/reperfusion. In addition, treatment with ebselen markedly elevated GAD67, GABA-T and SSADH immunoreactivity and their protein levels compared to that in the vehicle-treated group, respectively. These results suggest that ebselen protects neurons from ischemic damage via control of the expressions of GABA shunt enzymes to enter the TCA cycle.

GABA shapes the dynamics of bistable perception.

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van Loon, Anouk M; Knapen, Tomas; Scholte, H Steven; St John-Saaltink, Elexa; Donner, Tobias H; Lamme, Victor A F

2013-05-06

Sometimes, perception fluctuates spontaneously between two distinct interpretations of a constant sensory input. These bistable perceptual phenomena provide a unique window into the neural mechanisms that create the contents of conscious perception. Models of bistable perception posit that mutual inhibition between stimulus-selective neural populations in visual cortex plays a key role in these spontaneous perceptual fluctuations. However, a direct link between neural inhibition and bistable perception has not yet been established experimentally. Here, we link perceptual dynamics in three distinct bistable visual illusions (binocular rivalry, motion-induced blindness, and structure from motion) to measurements of gamma-aminobutyric acid (GABA) concentrations in human visual cortex (as measured with magnetic resonance spectroscopy) and to pharmacological stimulation of the GABAA receptor by means of lorazepam. As predicted by a model of neural interactions underlying bistability, both higher GABA concentrations in visual cortex and lorazepam administration induced slower perceptual dynamics, as reflected in a reduced number of perceptual switches and a lengthening of percept durations. Thus, we show that GABA, the main inhibitory neurotransmitter, shapes the dynamics of bistable perception. These results pave the way for future studies into the competitive neural interactions across the visual cortical hierarchy that elicit conscious perception. Copyright © 2013 Elsevier Ltd. All rights reserved.

Alterations in GABA-related transcriptome in the dorsolateral prefrontal cortex of subjects with schizophrenia

OpenAIRE

Hashimoto, T; Arion, D; Unger, T; Maldonado-Avilés, JG; Morris, HM; Volk, DW; Mirnics, K; Lewis, DA

2007-01-01

In subjects with schizophrenia, impairments in working memory are associated with dysfunction of the dorsolateral prefrontal cortex (DLPFC). This dysfunction appears to be due, at least in part, to abnormalities in γ-aminobutyric acid (GABA)-mediated inhibitory circuitry. To test the hypothesis that altered GABA-mediated circuitry in the DLPFC of subjects with schizophrenia reflects expression changes of genes that encode selective presynaptic and postsynaptic components of GABA neurotransmis...

Mechanism of action of the insecticides, lindane and fipronil, on glycine receptor chloride channels.

Science.gov (United States)

Islam, Robiul; Lynch, Joseph W

2012-04-01

Docking studies predict that the insecticides, lindane and fipronil, block GABA(A) receptors by binding to 6' pore-lining residues. However, this has never been tested at any Cys-loop receptor. The neurotoxic effects of these insecticides are also thought to be mediated by GABA(A) receptors, although a recent morphological study suggested glycine receptors mediated fipronil toxicity in zebrafish. Here we investigated whether human α1, α1β, α2 and α3 glycine receptors were sufficiently sensitive to block by either compound as to represent possible neurotoxicity targets. We also investigated the mechanisms by which lindane and fipronil inhibit α1 glycine receptors. Glycine receptors were recombinantly expressed in HEK293 cells and insecticide effects were studied using patch-clamp electrophysiology. Both compounds completely inhibited all tested glycine receptor subtypes with IC(50) values ranging from 0.2-2 µM, similar to their potencies at vertebrate GABA(A) receptors. Consistent with molecular docking predictions, both lindane and fipronil interacted with 6' threonine residues via hydrophobic interactions and hydrogen bonds. In contrast with predictions, we found no evidence for lindane interacting at the 2' level. We present evidence for fipronil binding in a non-blocking mode in the anaesthetic binding pocket, and for lindane as an excellent pharmacological tool for identifying the presence of β subunits in αβ heteromeric glycine receptors. This study implicates glycine receptors as novel vertebrate toxicity targets for fipronil and lindane. Furthermore, lindane interacted with pore-lining 6' threonine residues, whereas fipronil may have both pore and non-pore binding sites. © 2011 The Authors. British Journal of Pharmacology © 2011 The British Pharmacological Society.