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Sample records for acting opioid-receptor antagonist

  1. Identification of short-acting κ-opioid receptor antagonists with anxiolytic-like activity.

    Peters, Matthew F; Zacco, Anna; Gordon, John; Maciag, Carla M; Litwin, Linda C; Thompson, Carolann; Schroeder, Patricia; Sygowski, Linda A; Piser, Timothy M; Brugel, Todd A

    2011-07-01

    The κ-opioid receptor plays a central role in mediating the response to stressful life events. Inhibiting κ-opioid receptor signaling is proposed as a mechanism for treating stress-related conditions such as depression and anxiety. Preclinical testing consistently confirms that disruption of κ-opioid signaling is efficacious in animal models of mood disorders. However, concerns about the feasibility of developing antagonists into drugs stem from an unusual pharmacodynamic property of prototypic κ-opioid receptor-selective antagonists; they inhibit receptor signaling for weeks to months after a single dose. Several fundamental questions include - is it possible to identify short-acting antagonists; is long-lasting inhibition necessary for efficacy; and is it safe to develop long-acting antagonists in the clinic. Here, we test representative compounds (AZ-ECPC, AZ-MTAB, and LY-DMPF) from three new chemical series of κ-opioid receptor ligands for long-lasting inhibition. Each compound dose-dependently reversed κ-opioid agonist-induced diuresis. However, unlike the prototypic antagonist, nBNI, which fully inhibited evoked diuresis for at least four weeks, the new compounds showed no inhibition after one week. The two compounds with greater potency and selectivity were tested in prenatally-stressed rats on the elevated plus maze, an exploration-based model of anxiety. Spontaneous exploration of open arms in the elevated plus maze was suppressed by prenatal stress and restored with both compounds. These findings indicate that persistent inhibition is not an inherent property of κ-opioid-selective antagonists and that post-stress dosing with transient inhibitors can be effective in a mood disorder model. This further supports κ-opioid receptor as a promising target for developing novel psychiatric medications. PMID:21539838

  2. μ Opioid receptor: novel antagonists and structural modeling

    Kaserer, Teresa; Lantero, Aquilino; Schmidhammer, Helmut; Spetea, Mariana; Schuster, Daniela

    2016-02-01

    The μ opioid receptor (MOR) is a prominent member of the G protein-coupled receptor family and the molecular target of morphine and other opioid drugs. Despite the long tradition of MOR-targeting drugs, still little is known about the ligand-receptor interactions and structure-function relationships underlying the distinct biological effects upon receptor activation or inhibition. With the resolved crystal structure of the β-funaltrexamine-MOR complex, we aimed at the discovery of novel agonists and antagonists using virtual screening tools, i.e. docking, pharmacophore- and shape-based modeling. We suggest important molecular interactions, which active molecules share and distinguish agonists and antagonists. These results allowed for the generation of theoretically validated in silico workflows that were employed for prospective virtual screening. Out of 18 virtual hits evaluated in in vitro pharmacological assays, three displayed antagonist activity and the most active compound significantly inhibited morphine-induced antinociception. The new identified chemotypes hold promise for further development into neurochemical tools for studying the MOR or as potential therapeutic lead candidates.

  3. The kappa opioid receptor antagonist JDTic attenuates alcohol seeking and withdrawal anxiety

    Schank, Jesse R.; Goldstein, Andrea L.; Rowe, Kelly E.; King, Courtney E.; Marusich, Julie A.; Wiley, Jenny L; Carroll, F. Ivy; Thorsell, Annika; Heilig, Markus

    2012-01-01

    The role of kappa-opioid receptors (KOR) in regulation of alcohol-related behaviors is not completely understood. For example, alcohol consumption has been reported to increase following treatment with KOR antagonists in rats, but was decreased in mice with genetic deletion of KOR. Recent studies have further suggested that KOR antagonists may selectively decrease alcohol self-administration in rats following a history of dependence. We assessed the effects of the KOR antagonist JDTic on alco...

  4. Crystal structure of the[mu]-opioid receptor bound to a morphinan antagonist

    Manglik, Aashish; Kruse, Andrew C.; Kobilka, Tong Sun; Thian, Foon Sun; Mathiesen, Jesper M.; Sunahara, Roger K.; Pardo, Leonardo; Weis, William I.; Kobilka, Brian K.; Granier, Sébastien (Michigan-Med); (Stanford-MED); (UAB, Spain)

    2012-06-27

    Opium is one of the world's oldest drugs, and its derivatives morphine and codeine are among the most used clinical drugs to relieve severe pain. These prototypical opioids produce analgesia as well as many undesirable side effects (sedation, apnoea and dependence) by binding to and activating the G-protein-coupled {mu}-opioid receptor ({mu}-OR) in the central nervous system. Here we describe the 2.8 {angstrom} crystal structure of the mouse {mu}-OR in complex with an irreversible morphinan antagonist. Compared to the buried binding pocket observed in most G-protein-coupled receptors published so far, the morphinan ligand binds deeply within a large solvent-exposed pocket. Of particular interest, the {mu}-OR crystallizes as a two-fold symmetrical dimer through a four-helix bundle motif formed by transmembrane segments 5 and 6. These high-resolution insights into opioid receptor structure will enable the application of structure-based approaches to develop better drugs for the management of pain and addiction.

  5. Differential involvement of the opioid receptor antagonist naloxone in motivational and hedonic aspects of reward.

    Schneider, Miriam; Heise, Verena; Spanagel, Rainer

    2010-04-01

    In the present study dose-dependent effects of the opioid receptor antagonist naloxone were investigated on the rewarding effects of sweetened condensed milk (SCM) in four behavioral paradigms addressing hedonic, consummatory as well as motivational aspects of a reward: odour-conditioned pleasure attenuation of the acoustic startle response (PAS), conditioned place preference (CPP), voluntary consumption in a limited access paradigm, as well as break point determination in a progressive ratio (PR) task. A dose-dependent reduction in reward-related behavior was observed in all paradigms, with exception of the break point in the PR task, which was not affected by naloxone at all. CPP for SCM was only affected by the highest dose of naloxone. The present results indicate that naloxone is more effective in suppressing the hedonic than motivational aspects of reward, further supporting the involvement of the endogenous opioid system in the mediation of hedonic properties of food reward. PMID:20035797

  6. The kappa opioid receptor antagonist JDTic attenuates alcohol seeking and withdrawal anxiety.

    Schank, Jesse R; Goldstein, Andrea L; Rowe, Kelly E; King, Courtney E; Marusich, Julie A; Wiley, Jenny L; Carroll, F Ivy; Thorsell, Annika; Heilig, Markus

    2012-05-01

    The role of kappa-opioid receptors (KOR) in the regulation of alcohol-related behaviors is not completely understood. For example, alcohol consumption has been reported to increase following treatment with KOR antagonists in rats, but was decreased in mice with genetic deletion of KOR. Recent studies have further suggested that KOR antagonists may selectively decrease alcohol self-administration in rats following a history of dependence. We assessed the effects of the KOR antagonist JDTic on alcohol self-administration, reinstatement of alcohol seeking induced by alcohol-associated cues or stress, and acute alcohol withdrawal-induced anxiety ('hangover anxiety'). JDTic dose-dependently reversed hangover anxiety when given 48 hours prior to testing, a time interval corresponding to the previously demonstrated anxiolytic efficacy of this drug. In contrast, JDTic decreased alcohol self-administration and cue-induced reinstatement of alcohol seeking when administered 2 hours prior to testing, but not at longer pre-treatment times. For comparison, we determined that the prototypical KOR antagonist nor-binaltorphimine can suppress self-administration of alcohol at 2 hours pre-treatment time, mimicking our observations with JDTic. The effects of JDTic were behaviorally specific, as it had no effect on stress-induced reinstatement of alcohol seeking, self-administration of sucrose, or locomotor activity. Further, we demonstrate that at a 2 hours pre-treatment time JDTic antagonized the antinociceptive effects of the KOR agonist U50,488H but had no effect on morphine-induced behaviors. Our results provide additional evidence for the involvement of KOR in regulation of alcohol-related behaviors and provide support for KOR antagonists, including JDTic, to be evaluated as medications for alcoholism. PMID:22515275

  7. Development of displacement binding and GTPgammaS scintillation proximity assays for the identification of antagonists of the micro-opioid receptor.

    Rodgers, George; Hubert, Cassandra; McKinzie, Jamie; Suter, Todd; Statnick, Michael; Emmerson, Paul; Stancato, Louis

    2003-10-01

    This article describes the development of micro-opioid receptor (MOR) binding and GTPgammaS functional SPAs as improved screening tools for the identification of MOR antagonists. Opioid receptors are members of the seven-transmembrane G protein-coupled receptor (GPCR) family and are involved in the control of various aspects of human physiology, including pain, stress, reward, addiction, respiration, gastric motility, and pituitary hormone secretion. Activation of the MOR initiates intracellular signaling pathways leading to a reduction in intracellular cyclic AMP levels, inhibition of calcium channels, and activation of potassium channels resulting in a reduction of the excitability of neurons. Characterization of opioid receptor ligand binding has traditionally been accomplished through the use of low throughput filtration-based binding assays, whereas functional activity has been based upon cyclic AMP measurements or filtration-based GTPgammaS functional assays. This report describes the development of a MOR displacement binding SPA using the radiolabeled antagonist [(3)H]diprenorphine ((3)H-DPN). The assay was optimized using statistical experimental design and demonstrates the stability and robustness necessary for HTS. The assay was biased toward the identification of MOR antagonists through the addition of Na(+). Our assay conditions also minimized the phenomenon of ligand depletion, a problem commonly observed in low-volume assays using high receptor-expressing cell lines. The optimized procedure revealed (3)H-DPN affinity constants at the MOR that were consistent with results obtained using filtration methods (K(D) (SPA) = 1.89 +/- 0.24 nM, K(D) (filtration) = 1.88 +/- 0.35 nM). The binding SPA identified known opioid receptor modulators contained within the Library of Pharmacological Active Compounds (LOPAC) cassette, and the GTPgammaS scintillation proximity assay (SPA) was used to confirm the functional activity of the LOPAC antagonists acting at the

  8. Combination cannabinoid and opioid receptor antagonists improves metabolic outcomes in obese mice.

    Lockie, Sarah H; Stefanidis, Aneta; Tschöp, Matthias H; Oldfield, Brian J

    2015-12-01

    The CB1 receptor antagonist, rimonabant, causes weight loss but also produces undesirable psychiatric side effects. We investigated using a combination of rimonabant with the opioid receptor antagonists naloxone and norBNI to treat the metabolic sequelae of long-term high fat diet feeding in mice. This combination has previously been shown to have positive effects on both weight loss and mood related behaviour. Diet-induced obese mice were treated chronically with either low dose rimonabant (1 mg/kg) or the combination of rimonabant, naloxone and norBNI (rim nal BNI). After 6 days of treatment, glucose and insulin tolerance tests were performed and body composition analysed using DEXA. Changes in BAT thermogenesis were assessed using implantable radio telemetry probes. Behavioural responses to acute rimonabant or rim nal BNI were examined in the forced swim test and elevated plus maze. Separately, we assessed shifts in Fos immunoreactivity in response to rimonabant or rim nal BNI. Rim nal BNI was significantly better than rimonabant treatment alone at reducing body weight and food intake. In addition, it improved fasting blood glucose and fat mass. Acute low dose rimonabant did not alter behaviour in either the forced swim test or elevated plus maze. Combination rim nal BNI reversed the behavioural effects of high dose (10 mg/kg) rimonabant in obese mice. Rim nal BNI altered Rimonabant-induced Fos in a number of nuclei, with particular shifts in expression in the central and basolateral amygdala, and insular cortex. This study demonstrates that the combination of rimonabant, naloxone and norBNI is effective at producing weight loss over a sustained period of time without altering performance in standardised mouse behaviour tests. Fos expression patterns offer insight into the neuroanatomical substrates subserving these physiological and behavioural changes. These results indicate that CB1-targeted drugs for weight loss may still be feasible. PMID:26360587

  9. Selective κ opioid antagonists nor-BNI, GNTI and JDTic have low affinities for non-opioid receptors and transporters.

    Thomas A Munro

    Full Text Available BACKGROUND: Nor-BNI, GNTI and JDTic induce selective κ opioid antagonism that is delayed and extremely prolonged, but some other effects are of rapid onset and brief duration. The transient effects of these compounds differ, suggesting that some of them may be mediated by other targets. RESULTS: In binding assays, the three antagonists showed no detectable affinity (K(i≥10 µM for most non-opioid receptors and transporters (26 of 43 tested. There was no non-opioid target for which all three compounds shared detectable affinity, or for which any two shared sub-micromolar affinity. All three compounds showed low nanomolar affinity for κ opioid receptors, with moderate selectivity over μ and δ (3 to 44-fold. Nor-BNI bound weakly to the α(2C-adrenoceptor (K(i = 630 nM. GNTI enhanced calcium mobilization by noradrenaline at the α(1A-adrenoceptor (EC₅₀ = 41 nM, but did not activate the receptor, displace radioligands, or enhance PI hydrolysis. This suggests that it is a functionally-selective allosteric enhancer. GNTI was also a weak M₁ receptor antagonist (K(B = 3.7 µM. JDTic bound to the noradrenaline transporter (K(i = 54 nM, but only weakly inhibited transport (IC₅₀ = 1.1 µM. JDTic also bound to the opioid-like receptor NOP (K(i = 12 nM, but gave little antagonism even at 30 µM. All three compounds exhibited rapid permeation and active efflux across Caco-2 cell monolayers. CONCLUSIONS: Across 43 non-opioid CNS targets, only GNTI exhibited a potent functional effect (allosteric enhancement of α(1A-adrenoceptors. This may contribute to GNTI's severe transient effects. Plasma concentrations of nor-BNI and GNTI may be high enough to affect some peripheral non-opioid targets. Nonetheless, κ opioid antagonism persists for weeks or months after these transient effects dissipate. With an adequate pre-administration interval, our results therefore strengthen the evidence that nor-BNI, GNTI and JDTic are highly

  10. Kinetic modeling of 11C-LY2795050, a novel antagonist radiotracer for PET imaging of the kappa opioid receptor in humans

    Naganawa, Mika; Zheng, Ming-Qiang; Nabulsi, Nabeel; Tomasi, Giampaolo; Henry, Shannan; Lin, Shu-fei; Ropchan, Jim; Labaree, David; Tauscher, Johannes; Neumeister, Alexander; Carson, Richard E.; Huang, Yiyun

    2014-01-01

    11C-LY2795050 is a novel kappa opioid receptor (KOR) antagonist tracer for positron emission tomography (PET) imaging. The purpose of this first-in-human study was to determine the optimal kinetic model for analysis of 11C-LY2795050 imaging data. Sixteen subjects underwent baseline scans and blocking scans after oral naltrexone. Compartmental modeling and multilinear analysis-1 (MA1) were applied using the arterial input functions. Two-tissue compartment model and MA1 were found to be the bes...

  11. Dopamine D2/3- and μ-opioid receptor antagonists reduce cue-induced responding and reward impulsivity in humans.

    Weber, S C; Beck-Schimmer, B; Kajdi, M-E; Müller, D; Tobler, P N; Quednow, B B

    2016-01-01

    Increased responding to drug-associated stimuli (cue reactivity) and an inability to tolerate delayed gratification (reward impulsivity) have been implicated in the development and maintenance of drug addiction. Whereas data from animal studies suggest that both the dopamine and opioid system are involved in these two reward-related processes, their role in humans is less clear. Moreover, dopaminergic and opioidergic drugs have not been directly compared with regard to these functions, even though a deeper understanding of the underlying mechanisms might inform the development of specific treatments for elevated cue reactivity and reward impulsivity. In a randomized, double-blind, between-subject design we administered the selective dopamine D2/D3 receptor antagonist amisulpride (400 mg, n=41), the unspecific opioid receptor antagonist naltrexone (50 mg, n=40) or placebo (n=40) to healthy humans and measured cue-induced responding with a Pavlovian-instrumental transfer task and reward impulsivity with a delay discounting task. Mood was assessed using a visual analogue scale. Compared with placebo, amisulpride significantly suppressed cue-induced responding and reward impulsivity. The effects of naltrexone were similar, although less pronounced. Both amisulpride and naltrexone decreased average mood ratings compared with placebo. Our results demonstrate that a selective blockade of dopamine D2/D3 receptors reduces cue-induced responding and reward impulsivity in healthy humans. Antagonizing μ-opioid receptors has similar effects for cue-induced responding and to a lesser extent for reward impulsivity. PMID:27378550

  12. COCAINE REWARD AND HYPERACTIVITY IN THE RAT: SITES OF MU OPIOID RECEPTOR MODULATION

    Soderman, Avery R.; Unterwald, Ellen M.

    2008-01-01

    Opioid receptor agonists and antagonists have profound effects on cocaine-induced hyperactivity and conditioned reward. Recently, the role specifically of the mu opioid receptor has been demonstrated based on the finding that intracerebroventricular administration of the selective mu opioid receptor antagonist, CTAP, can attenuate cocaine-induced behaviors. The purpose of the present study was to determine the location of mu opioid receptors that are critical for cocaine-induced reward and hy...

  13. Differential effects of LY235959, a competitive antagonist of the NMDA receptor on kappa-opioid receptor agonist induced responses in mice and rats.

    Bhargava, H N; Thorat, S N

    1997-02-01

    The effects of the competitive antagonist of the N-methyl-D-aspartate (NMDA) receptor, LY235959, were determined on the analgesic and hypothermic effects as well as on the development of tolerance to these effects of U-50,488H, a kappa-opioid receptor agonist in mice and rats. In the mouse, a single injection of LY235959 given 10 min prior to U-50,488H did not modify the analgesic action of the latter. Similarly, chronic administration of LY235959 twice a day for 4 days did not modify U-50,488H-induced analgesia in mice. Repeated pretreatment of mice with LY235959 dose-dependently attenuated the development of tolerance to the analgesic actions of U-50,488H. In the rat, LY235959 by itself produced a significant analgesia and prior treatment of rats with LY235959 enhanced the analgesic action of U-50,488H. Similar effects were seen with the hypothermic action. Pretreatment of rats with LY235959 attenuated the development of tolerance to the analgesic but not to the hypothermic action of U-50,488H. These results provide evidence that LY235959 produces differential actions on nociception and thermic responses by itself and when given acutely with U-50,488H in mice and rats. However, when the animals are pretreated with LY235959, similar inhibitory effects are observed on the development of tolerance to the analgesic action of U-50,488H in both the species. These studies demonstrate an involvement of the NMDA receptor in the development of kappa-opioid tolerance and suggest that the biochemical consequences of an opioid's interaction with the opioid receptor are not the only factors that contribute to the acute and chronic actions of opioid analgesic drugs. PMID:9045999

  14. Kinetic modeling of (11)C-LY2795050, a novel antagonist radiotracer for PET imaging of the kappa opioid receptor in humans.

    Naganawa, Mika; Zheng, Ming-Qiang; Nabulsi, Nabeel; Tomasi, Giampaolo; Henry, Shannan; Lin, Shu-Fei; Ropchan, Jim; Labaree, David; Tauscher, Johannes; Neumeister, Alexander; Carson, Richard E; Huang, Yiyun

    2014-11-01

    (11)C-LY2795050 is a novel kappa opioid receptor (KOR) antagonist tracer for positron emission tomography (PET) imaging. The purpose of this first-in-human study was to determine the optimal kinetic model for analysis of (11)C-LY2795050 imaging data. Sixteen subjects underwent baseline scans and blocking scans after oral naltrexone. Compartmental modeling and multilinear analysis-1 (MA1) were applied using the arterial input functions. Two-tissue compartment model and MA1 were found to be the best models to provide reliable measures of binding parameters. The rank order of (11)C-LY2795050 distribution volume (VT) matched the known regional KOR densities in the human brain. Blocking scans with naltrexone indicated no ideal reference region for (11)C-LY2795050. Three methods for calculation of the nondisplaceable distribution volume (VND) were assessed: (1) individual VND estimated from naltrexone occupancy plots, (2) mean VND across subjects, and (3) a fixed fraction of cerebellum VT. Approach (3) produced the lowest intersubject variability in the calculation of binding potentials (BPND, BPF, and BPP). Therefore, binding potentials of (11)C-LY2795050 can be determined if the specific binding fraction in the cerebellum is presumed to be unchanged by diseases and experimental conditions. In conclusion, results from the present study show the suitability of (11)C-LY2795050 to image and quantify KOR in humans. PMID:25182664

  15. Effects of the kappa opioid receptor antagonist nor-binaltorphimine (nor-BNI) on cocaine versus food choice and extended-access cocaine intake in rhesus monkeys.

    Hutsell, Blake A; Cheng, Kejun; Rice, Kenner C; Negus, Sidney Stevens; Banks, Matthew L

    2016-03-01

    The dynorphin/kappa opioid receptor (KOR) system has been implicated as one potential neurobiological modulator of the abuse-related effects of cocaine and as a potential target for medications development. This study determined effects of the KOR antagonist nor-binaltorphimine (nor-BNI) on cocaine self-administration under a novel procedure that featured two daily components: (1) a 2-hour 'choice' component (9:00-11:00 am) when monkeys could choose between food pellets and cocaine injections (0-0.1 mg/kg per injection, intravenous) and (2) a 20-hour 'extended-access' component (noon to 8:00 am) when cocaine (0.1 mg/kg per injection) was available under a fixed-ratio schedule to promote high daily cocaine intakes. Rhesus monkeys (n = 4) were given 14 days of exposure to the choice + extended-access procedure then treated with nor-BNI (3.2 or 10.0 mg/kg, intramuscular), and cocaine choice and extended-access cocaine intake were evaluated for an additional 14 days. Consistent with previous studies, cocaine maintained both a dose-dependent increase in cocaine choice during choice components and a high level of cocaine intake during extended-access components. Neither 3.2 nor 10 mg/kg nor-BNI significantly altered cocaine choice or extended-access cocaine intake. In two additional monkeys, nor-BNI also had no effect on cocaine choice or extended-access cocaine intake when it was administered at the beginning of exposure to the extended-access components. Overall, these results do not support a major role for the dynorphin/KOR system in modulating cocaine self-administration under these conditions in non-human primates nor do they support the clinical utility of KOR antagonists as a pharmacotherapeutic strategy for cocaine addiction. PMID:25581305

  16. Tumor Targeting and Pharmacokinetics of a Near-Infrared Fluorescent-Labeled δ-Opioid Receptor Antagonist Agent, Dmt-Tic-Cy5.

    Huynh, Amanda Shanks; Estrella, Veronica; Stark, Valerie E; Cohen, Allison S; Chen, Tingan; Casagni, Todd J; Josan, Jatinder S; Lloyd, Mark C; Johnson, Joseph; Kim, Jongphil; Hruby, Victor J; Vagner, Josef; Morse, David L

    2016-02-01

    Fluorescence molecular imaging can be employed for the development of novel cancer targeting agents. Herein, we investigated the pharmacokinetics (PK) and cellular uptake of Dmt-Tic-Cy5, a delta-opioid receptor (δOR) antagonist-fluorescent dye conjugate, as a tumor-targeting molecular imaging agent. δOR expression is observed normally in the CNS, and pathologically in some tumors, including lung liver and breast cancers. In vitro, in vivo, and ex vivo experiments were conducted to image and quantify the fluorescence signal associated with Dmt-Tic-Cy5 over time using in vitro and intravital fluorescence microscopy and small animal fluorescence imaging of tumor-bearing mice. We observed specific retention of Dmt-Tic-Cy5 in tumors with maximum uptake in δOR-expressing positive tumors at 3 h and observable persistence for >96 h; clearance from δOR nonexpressing negative tumors by 6 h; and systemic clearance from normal organs by 24 h. Live-cell and intravital fluorescence microscopy demonstrated that Dmt-Tic-Cy5 had sustained cell-surface binding lasting at least 24 h with gradual internalization over the initial 6 h following administration. Dmt-Tic-Cy5 is a δOR-targeted agent that exhibits long-lasting and specific signal in δOR-expressing tumors, is rapidly cleared from systemic circulation, and is not retained in non-δOR-expressing tissues. Hence, Dmt-Tic-Cy5 has potential as a fluorescent tumor imaging agent. PMID:26713599

  17. Endothelin B receptors exert antipruritic effects via peripheral κ-opioid receptors

    Ji, Wenjin; Liang, Jiexian; Zhang, Zhiwei

    2012-01-01

    Endothelin B receptor agonists exert antipruritic effects on itching induced via endothelin-1 (ET-1) and compound 48/80. Peripheral µ- and κ-opioid receptors (MORs and KORs, respectively) are reported to be involved in the anti-nociceptive properties triggered by ETB agonists. Therefore, we investigated the role of peripheral opioid receptors in the scratching response induced by ET-1. ETA and ETB antagonists and non-selective and selective opioid receptor antagonists were co-injected with ET...

  18. Zyklophin, a short-acting kappa opioid antagonist, induces scratching in mice

    DiMattio, K.M.; T.V. Yakovleva; Aldrich, J V; Cowan, A; Liu-Chen, L.Y.

    2014-01-01

    It has been shown previously that norbinaltorphimine (norBNI) and 5΄-guanidinonaltrindole (5΄-GNTI), long-acting kappa opioid receptor (KOPR) antagonists, cause frenzied scratching in mice [1;2]. In the current study, we examined if zyklophin, a short-acting cyclic peptide KOPR antagonist, also elicited scratching behavior. When injected s.c. in the nape of the neck of male Swiss-Webster mice, zyklophin at doses of 0.1, 0.3 and 1 mg/kg induced dose-related hindleg scratching of the neck betwe...

  19. Modulation of Opioid Receptor Ligand Affinity and Efficacy Using Active and Inactive State Receptor Models

    Anand, Jessica P.; Purington, Lauren C.; Pogozheva, Irina D.; Traynor, John R.; Mosberg, Henry I.

    2012-01-01

    Mu opioid receptor (MOR) agonists are widely used for the treatment of pain; however chronic use results in the development of tolerance and dependence. It has been demonstrated that co-administration of a MOR agonist with a delta opioid receptor (DOR) antagonist maintains the analgesia associated with MOR agonists, but with reduced negative side effects. Using our newly refined opioid receptor models for structure-based ligand design, we have synthesized several pentapeptides with tailored a...

  20. Functional modulation of human delta opioid receptor by neuropeptide FF

    Panula Pertti

    2005-04-01

    Full Text Available Abstract Background Neuropeptide FF (NPFF plays a role in physiological pain sensation and opioid analgesia. For example, NPFF potentiates opiate-induced analgesia and the delta opioid receptor antagonist naltrindole inhibits NPFF-induced antinociception. The nature of the interactions between NPFF and opioid receptors seems to be complex and the molecular mechanisms behind the observed physiological effects are not known. Results We used a stable Chinese hamster ovary cell line expressing c-MYC-tagged human delta opioid receptor to study the interactions at the molecular level. Our results imply that NPFF can directly modulate the activation of delta opioid receptor in the absence of NPFF receptors. The modulatory effect, though only moderate, was consistently detected with several methods. The agonist-induced receptor trafficking was changed in the presence of (1DMeNPYF, a stable NPFF-analogue. (1DMeNPYF enhanced the receptor activation and recovery; opioid antagonists inhibited the effects, indicating that they were delta opioid receptor-mediated. The binding experiments with a novel ligand, Terbium-labeled deltorphin I, showed that (1DMeNPYF modulated the binding of delta opioid receptor ligands. The levels of phosphorylated mitogen-activated protein kinase and intracellular cAMP were studied to clarify the effects of NPFF on the opioid signaling mechanisms. Application of (1DMeNPYF together with a delta opioid receptor agonist enhanced the signaling via both pathways studied. Concomitantly to the receptor trafficking, the time-course of the activation of the signaling was altered. Conclusion In addition to working via indirect mechanisms on the opioid systems, NPFF may exert a direct modulatory effect on the delta opioid receptor. NPFF may be a multi-functional neuropeptide that regulates several neuronal systems depending on the site of action.

  1. Redoubling the ring size of an endomorphin-2 analog transforms a centrally acting mu-opioid receptor agonist into a pure peripheral analgesic.

    Piekielna, Justyna; De Marco, Rossella; Gentilucci, Luca; Cerlesi, Maria Camilla; Calo', Girolamo; Tömböly, Csaba; Artali, Roberto; Janecka, Anna

    2016-05-01

    The study reports the synthesis and biological evaluation of two opioid analogs, a monomer and a dimer, obtained as products of the solid-phase, side-chain to side-chain cyclization of the pentapeptide Tyr-d-Lys-Phe-Phe-AspNH2 . The binding affinities to the mu, delta, and kappa opioid receptors, as well as results obtained in a calcium mobilization functional assay are reported. Tyr-[d-Lys-Phe-Phe-Asp]2 -NH2 1 was a potent and selective full agonist of mu with sub-nanomolar affinity, while the dimer (Tyr-[d-Lys-Phe-Phe-Asp]2 -NH2 )2 2 showed a significant mixed mu/kappa affinity, acting as an agonist at the mu. Molecular docking computations were utilized to explain the ability of the dimeric cyclopeptide 2 to interact with the receptor. Interestingly, in spite of the increased ring size, the higher flexibility allowed 2 to fold and fit into the mu receptor binding pocket. Both cyclopeptides were shown to elicit strong antinociceptive activity after intraventricular injection but only cyclomonomer 1 was able to cross the blood-brain barrier. However, the cyclodimer 2 displayed a potent peripheral antinociceptive activity in a mouse model of visceral inflammatory pain. © 2016 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 106: 309-317, 2016. PMID:27038094

  2. κ-Opioid receptor participates of NSAIDs peripheral antinociception.

    Silva, Lívia Caroline Resende; Castor, Marina Gomes Miranda E; Navarro, Larissa Caldeira; Romero, Thiago Roberto Lima; Duarte, Igor Dimitri Gama

    2016-05-27

    NSAIDs represent some of the most widely prescribed drugs for relief of short-term fever, pain and inflammation. The participation of the opioid system in the peripheral is poorly understood. The aim of this study was evaluate the role of opioid system in the peripheral antinociception by diclofenac and dipyrone. To test this hypothesis, opioid receptor antagonists were evaluated using the rat paw pressure test, in which pain sensitivity is increased by intraplantar injection of prostaglandin E2 (PGE2, 2μg). Diclofenac (20μg/paw) and Dipyrone (40μg/paw) administered locally into the right paw elicited an antinociceptive effect. It was used naloxone (50μg/paw), a non-selective opioid receptor antagonist, which antagonized peripheral antinociception induced by diclofenac and dipyrone. Selectively, it was evaluated the μ-, δ- and κ-opioid receptor antagonists, respectively, clocinnamox (40μg/paw), naltrindole (50μg/paw) and nor-binaltorphimine (20, 40 and 80μg/paw). Our data indicated that only the κ-opioid antagonist was capable to reverse the peripheral antinociception by NSAIDs. The present results provide evidence that the opioid system participated in the diclofenac and dipyrone-induced peripheral antinociception by indirect activation of κ-opioid receptor probable by release of endogenous opioids such as dynorphins. PMID:27091501

  3. Involvement of mu-opioid receptors in antinociception and inhibition of gastrointestinal transit induced by 7-hydroxymitragynine, isolated from Thai herbal medicine Mitragyna speciosa.

    Matsumoto, Kenjiro; Hatori, Yoshio; Murayama, Toshihiko; Tashima, Kimihito; Wongseripipatana, Sumphan; Misawa, Kaori; Kitajima, Mariko; Takayama, Hiromitsu; Horie, Syunji

    2006-11-01

    7-hydroxymitragynine, a constituent of the Thai herbal medicine Mitragyna speciosa, has been found to have a potent opioid antinociceptive effect. In the present study, we investigated the mechanism of antinociception and the inhibitory effect on gastrointestinal transit of 7-hydroxymitragynine, and compared its effects with those of morphine. When administered subcutaneously to mice, 7-hydroxymitragynine produced antinociceptive effects about 5.7 and 4.4 times more potent than those of morphine in the tail-flick (ED50=0.80 mg/kg) and hot-plate (ED50=0.93 mg/kg) tests, respectively. The antinociceptive effect of 7-hydroxymitragynine was significantly blocked by the mu1/mu2-opioid receptor antagonist beta-funaltrexamine hydrochloride (beta-FNA) and the mu1-opioid receptor-selective antagonist naloxonazine in both tests. Thus, 7-hydroxymitragynine acts predominantly on mu-opioid receptors, especially on mu1-opioid receptors. Isolated tissue studies further supported its specificity for the mu-opioid receptors. Further, 7-hydroxymintragynine dose-dependently (ED50=1.19 mg/kg, s.c.) and significantly inhibited gastrointestinal transit in mice, as morphine does. The inhibitory effect was significantly antagonized by beta-FNA pretreatment, but slightly antagonized by naloxonazine. The ED50 value of 7-hydroxymitragynine on gastrointestinal transit was larger than its antinociceptive ED50 value. On the other hand, morphine significantly inhibits gastrointestinal transit at a much smaller dose than its antinociceptive dose. These results suggest that mu-opioid receptor mechanisms mediate the antinociceptive effect and inhibition of gastrointestinal transit. This compound induced more potent antinociceptive effects and was less constipating than morphine. PMID:16978601

  4. The Roles of Opioid Receptors and agonists in health and disease Conditions

    A.O. Ibegbu

    Full Text Available Opioid receptors are found in the central nervous system (CNS and are classified as mu (µ, kappa (κ, delta (δ and sigma (σ opioid receptors. Opioid receptors belong to the large family of G protein coupled receptors (GPCRs, and have diverse and important physiological roles. Opioid receptors are not uniformly distributed in the CNS and are found in areas concerned with pain, with the highest concentration in the cerebral cortex, followed by the amygdala, septum, thalamus, hypothalamus, midbrain and spinal cord. Activated delta opioid receptors are coupled to Gi1 while activated mu opioid receptors are coupled to Gi3 in neuroblastoma cells. Mu opioid receptors are activated by mu receptor agonists and are coupled through the Gαi1 and GαoA. Both mu and kappa opioid receptors are coupled via both Gi and Gz and opioid receptors are important targets for thousands of pharmacological agents. GPCRs typically require activation by agonists for their signalling activity to be initiated but some of the GPCRs may display basal or spontaneous signalling activity in the absence of an agonist. The stimulation of these receptors triggers analgesic effects and affects the function of the nervous system, gastrointestinal tract and other body systems. Hundreds of analogs of opioid peptides have been synthesized in an effort to make the compounds more active, selective, and resistant to biodegradation than the endogenous ligands. All these modifications resulted in obtaining very selective agonists and antagonists with high affinity at mu-, delta-, and kappa-opioid receptors, which are useful in further studies on the pharmacology of opioid receptors in a mammalian organism.

  5. Structure of the [delta]-opioid receptor bound to naltrindole

    Granier, Sébastien; Manglik, Aashish; Kruse, Andrew C.; Kobilka, Tong Sun; Thian, Foon Sun; Weis, William I.; Kobilka, Brian K. (Stanford-MED)

    2012-07-11

    The opioid receptor family comprises three members, the {mu}-, {delta}- and {kappa}-opioid receptors, which respond to classical opioid alkaloids such as morphine and heroin as well as to endogenous peptide ligands like endorphins. They belong to the G-protein-coupled receptor (GPCR) superfamily, and are excellent therapeutic targets for pain control. The {delta}-opioid receptor ({delta}-OR) has a role in analgesia, as well as in other neurological functions that remain poorly understood. The structures of the {mu}-OR and {kappa}-OR have recently been solved. Here we report the crystal structure of the mouse {delta}-OR, bound to the subtype-selective antagonist naltrindole. Together with the structures of the {mu}-OR and {kappa}-OR, the {delta}-OR structure provides insights into conserved elements of opioid ligand recognition while also revealing structural features associated with ligand-subtype selectivity. The binding pocket of opioid receptors can be divided into two distinct regions. Whereas the lower part of this pocket is highly conserved among opioid receptors, the upper part contains divergent residues that confer subtype selectivity. This provides a structural explanation and validation for the 'message-address' model of opioid receptor pharmacology, in which distinct 'message' (efficacy) and 'address' (selectivity) determinants are contained within a single ligand. Comparison of the address region of the {delta}-OR with other GPCRs reveals that this structural organization may be a more general phenomenon, extending to other GPCR families as well.

  6. C7β-Methyl Analogues of the Orvinols: The Discovery of Kappa Opioid Antagonists with Nociceptin/Orphanin FQ Peptide (NOP) Receptor Partial Agonism and Low, or Zero, Efficacy at Mu Opioid Receptors

    Cueva, Juan Pablo; Roche, Christopher; Ostovar, Mehrnoosh; Kumar, Vinod; Clark, Mary J.; Hillhouse, Todd M.; Lewis, John W.; Traynor, John R.; Husbands, Stephen. M.

    2015-01-01

    Buprenorphine is a successful analgesic and treatment for opioid abuse, with both activities relying on its partial agonist activity at mu opioid receptors. However, there is substantial interest in its activities at the kappa opioid and nociceptin/orphanin FQ peptide receptors. This has led to an interest in developing compounds with a buprenorphine-like pharmacological profile but with lower efficacy at mu opioid receptors. The present article describes aryl ring analogues of buprenorphine ...

  7. Dissociation of μ-opioid receptor and CRF-R1 antagonist effects on escalated ethanol consumption and mPFC serotonin in C57BL/6J mice.

    Hwa, Lara S; Shimamoto, Akiko; Kayyali, Tala; Norman, Kevin J; Valentino, Rita J; DeBold, Joseph F; Miczek, Klaus A

    2016-01-01

    Both the opioid antagonist naltrexone and corticotropin-releasing factor type-1 receptor (CRF-R1) antagonists have been investigated for the treatment of alcoholism. The current study examines the combination of naltrexone and CP154526 to reduce intermittent access ethanol drinking [intermittent access to alcohol (IAA)] in C57BL/6J male mice, and if these compounds reduce drinking via serotonergic mechanisms in the dorsal raphe nucleus (DRN). Systemic injections and chronic intracerebroventricular infusions of naltrexone, CP154526 or CP376395 transiently decreased IAA drinking. Immunohistochemistry revealed CRF-R1 or μ-opioid receptor immunoreactivity was co-localized in tryptophan hydroxylase (TPH)-immunoreactive neurons as well as non-TPH neurons in the DRN. Mice with a history of IAA or continuous access to alcohol were microinjected with artificial cerebral spinal fluid, naltrexone, CP154526 or the combination into the DRN or the median raphe nucleus (MRN). Either intra-DRN naltrexone or CP154526 reduced IAA in the initial 2 hours of fluid access, but the combination did not additively suppress IAA, suggesting a common mechanism via which these two compounds affect intermittent drinking. These alcohol-reducing effects were localized to the DRN of IAA drinkers, as intra-MRN injections only significantly suppressed water drinking, and continuous access drinkers were not affected by CRF-R1 antagonism. Extracellular serotonin was measured in the medial prefrontal cortex (mPFC) using in vivo microdialysis after intra-DRN microinjections in another group of mice. Intra-DRN CP154526 increased serotonin impulse flow to the mPFC while naltrexone did not. This suggests the mPFC may not be an essential location to intermittent drinking, as evidenced by different effects on serotonin signaling to the forebrain yet similar behavioral findings. PMID:25262980

  8. Delta opioid receptor on equine sperm cells: subcellular localization and involvement in sperm motility analyzed by computer assisted sperm analyzer (CASA

    Lacalandra Giovanni M

    2010-06-01

    Full Text Available Abstract Background Opioid receptors and endogenous opioid peptides act not only in the control of nociceptive pathways, indeed several reports demonstrate the effects of opiates on sperm cell motility and morphology suggesting the importance of these receptors in the modulation of reproduction in mammals. In this study we investigated the expression of delta opioid receptors on equine spermatozoa by western blot/indirect immunofluorescence and its relationship with sperm cell physiology. Methods We analyzed viability, motility, capacitation, acrosome reaction and mitochondrial activity in the presence of naltrindole and DPDPE by means of a computer assisted sperm analyzer and a fluorescent confocal microscope. The evaluation of viability, capacitation and acrosome reaction was carried out by the double CTC/Hoechst staining, whereas mitochondrial activity was assessed by means of MitoTracker Orange dye. Results We showed that in equine sperm cells, delta opioid receptor is expressed as a doublet of 65 and 50 kDa molecular mass and is localized in the mid piece of tail; we also demonstrated that naltrindole, a delta opioid receptor antagonist, could be utilized in modulating several physiological parameters of the equine spermatozoon in a dose-dependent way. We also found that low concentrations of the antagonist increase sperm motility whereas high concentrations show the opposite effect. Moreover low concentrations hamper capacitation, acrosome reaction and viability even if the percentage of cells with active mitochondria seems to be increased; the opposite effect is exerted at high concentrations. We have also observed that the delta opioid receptor agonist DPDPE is scarcely involved in affecting the same parameters at the employed concentrations. Conclusions The results described in this paper add new important details in the comprehension of the mammalian sperm physiology and suggest new insights for improving reproduction and for

  9. Analgesic effect of interferon-alpha via mu opioid receptor in the rat.

    Jiang, C L; Son, L X; Lu, C L; You, Z D; Wang, Y X; Sun, L Y; Cui, R Y; Liu, X Y

    2000-03-01

    Using the tail-flick induced by electro-stimulation as a pain marker, it was found that pain threshold (PT) was significantly increased after injecting interferon-alpha (IFN alpha) into the lateral ventricle of rats. This effect was dosage-dependent and abolished by monoclonal antibody (McAb) to IFN alpha. Naloxone could inhibit the analgesic effect of IFN alpha, suggesting that the analgesic effect of IFN alpha be related to the opioid receptors. Beta-funaltrexamine (beta-FNA), the mu specific receptor antagonist could completely block the analgesic effect of IFN alpha. The selective delta-opioid receptor antagonist, ICI174,864 and the kappa-opioid receptor antagonist, nor-BNI both failed to prevent the analgesic effect of IFN alpha. IFN alpha could significantly inhibit the production of the cAMP stimulated by forskolin in SK-N-SH cells expressing the mu-opioid receptor, not in NG108-15 cells expressing the delta-opioid receptor uniformly. The results obtained provide further evidence for opioid activity of IFN alpha and suggest that this effect is mediated by central opioid receptors of the mu subtype. The evidence is consistent with the hypothesis that multiple actions of cytokines, such as immunoregulatory and neuroregulatory effects, might be mediated by distinct domains of cytokines interacting with different receptors. PMID:10676852

  10. Discovery of the First Small-Molecule Opioid Pan Antagonist with Nanomolar Affinity at Mu, Delta, Kappa, and Nociceptin Opioid Receptors

    Zaveri, Nurulain T.; Journigan, V. Blair; Polgar, Willma E.

    2015-01-01

    The trans-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine scaffold is a known pharmacophore for mu opioid (MOP), kappa opioid (KOP), and delta opioid (DOP) receptor antagonists; however, it has not been explored in nociceptin opioid (NOP/ORL-1) receptor ligands. We recently found that the selective KOP antagonist JDTic, (3R)-7-hydroxy-N-((1S)-1-{[(3R,4R)-4-(3-hydroxyphenyl)-3,4-dimethyl-1-piperidinyl]methyl}-2-methylpropyl)-1,2,3,4-tetrahydro-3-isoquinolinecarboxamide, containing this opioid a...

  11. Antinociceptive action of isolated mitragynine from Mitragyna Speciosa through activation of opioid receptor system.

    Shamima, Abdul Rahman; Fakurazi, Sharida; Hidayat, Mohamad Taufik; Hairuszah, Ithnin; Moklas, Mohamad Aris Mohd; Arulselvan, Palanisamy

    2012-01-01

    Cannabinoids and opioids systems share numerous pharmacological properties and antinociception is one of them. Previous findings have shown that mitragynine (MG), a major indole alkaloid found in Mitragyna speciosa (MS) can exert its antinociceptive effects through the opioids system. In the present study, the action of MG was investigated as the antinociceptive agent acting on Cannabinoid receptor type 1 (CB1) and effects on the opioids receptor. The latency time was recorded until the mice showed pain responses such as shaking, licking or jumping and the duration of latency was measured for 2 h at every 15 min interval by hot plate analysis. To investigate the beneficial effects of MG as antinociceptive agent, it was administered intraperitoneally 15 min prior to pain induction with a single dosage (3, 10, 15, 30, and 35 mg/kg b.wt). In this investigation, 35 mg/kg of MG showed significant increase in the latency time and this dosage was used in the antagonist receptor study. The treated groups were administered with AM251 (cannabinoid receptor-1 antagonist), naloxone (non-selective opioid antagonist), naltrindole (δ-opioid antagonist) naloxonazine (μ(1)-receptor antagonist) and norbinaltorpimine (κ-opioid antagonist) respectively, prior to administration of MG (35 mg/kg). The results showed that the antinociceptive effect of MG was not antagonized by AM251; naloxone and naltrindole were effectively blocked; and norbinaltorpimine partially blocked the antinociceptive effect of MG. Naloxonazine did inhibit the effect of MG, but it was not statistically significant. These results demonstrate that CB1 does not directly have a role in the antinociceptive action of MG where the effect was observed with the activation of opioid receptor. PMID:23109863

  12. Antinociceptive Action of Isolated Mitragynine from Mitragyna Speciosa through Activation of Opioid Receptor System

    Mohamad Aris Mohd Moklas

    2012-09-01

    Full Text Available Cannabinoids and opioids systems share numerous pharmacological properties and antinociception is one of them. Previous findings have shown that mitragynine (MG, a major indole alkaloid found in Mitragyna speciosa (MS can exert its antinociceptive effects through the opioids system. In the present study, the action of MG was investigated as the antinociceptive agent acting on Cannabinoid receptor type 1 (CB1 and effects on the opioids receptor. The latency time was recorded until the mice showed pain responses such as shaking, licking or jumping and the duration of latency was measured for 2 h at every 15 min interval by hot plate analysis. To investigate the beneficial effects of MG as antinociceptive agent, it was administered intraperitoneally 15 min prior to pain induction with a single dosage (3, 10, 15, 30, and 35 mg/kg b.wt. In this investigation, 35 mg/kg of MG showed significant increase in the latency time and this dosage was used in the antagonist receptor study. The treated groups were administered with AM251 (cannabinoid receptor-1 antagonist, naloxone (non-selective opioid antagonist, naltrindole (δ-opioid antagonist naloxonazine (µ1-receptor antagonist and norbinaltorpimine (κ-opioid antagonist respectively, prior to administration of MG (35 mg/kg. The results showed that the antinociceptive effect of MG was not antagonized by AM251; naloxone and naltrindole were effectively blocked; and norbinaltorpimine partially blocked the antinociceptive effect of MG. Naloxonazine did inhibit the effect of MG, but it was not statistically significant. These results demonstrate that CB1 does not directly have a role in the antinociceptive action of MG where the effect was observed with the activation of opioid receptor.

  13. Opioid receptor activation triggering downregulation of cAMP improves effectiveness of anti-cancer drugs in treatment of glioblastoma

    Friesen, Claudia; Hormann, Inis; Roscher, Mareike; Fichtner, Iduna; Alt, Andreas; Hilger, Ralf; Debatin, Klaus-Michael; Miltner, Erich

    2014-01-01

    Glioblastoma are the most frequent and malignant human brain tumors, having a very poor prognosis. The enhanced radio- and chemoresistance of glioblastoma and the glioblastoma stem cells might be the main reason why conventional therapies fail. The second messenger cyclic AMP (cAMP) controls cell proliferation, differentiation, and apoptosis. Downregulation of cAMP sensitizes tumor cells for anti-cancer treatment. Opioid receptor agonists triggering opioid receptors can activate inhibitory Gi proteins, which, in turn, block adenylyl cyclase activity reducing cAMP. In this study, we show that downregulation of cAMP by opioid receptor activation improves the effectiveness of anti-cancer drugs in treatment of glioblastoma. The µ-opioid receptor agonist D,L-methadone sensitizes glioblastoma as well as the untreatable glioblastoma stem cells for doxorubicin-induced apoptosis and activation of apoptosis pathways by reversing deficient caspase activation and deficient downregulation of XIAP and Bcl-xL, playing critical roles in glioblastomas’ resistance. Blocking opioid receptors using the opioid receptor antagonist naloxone or increasing intracellular cAMP by 3-isobutyl-1-methylxanthine (IBMX) strongly reduced opioid receptor agonist-induced sensitization for doxorubicin. In addition, the opioid receptor agonist D,L-methadone increased doxorubicin uptake and decreased doxorubicin efflux, whereas doxorubicin increased opioid receptor expression in glioblastomas. Furthermore, opioid receptor activation using D,L-methadone inhibited tumor growth significantly in vivo. Our findings suggest that opioid receptor activation triggering downregulation of cAMP is a promising strategy to inhibit tumor growth and to improve the effectiveness of anti-cancer drugs in treatment of glioblastoma and in killing glioblastoma stem cells. PMID:24626197

  14. Dopamine D1 and opioid receptor antagonists differentially reduce the acquisition and expression of fructose-conditioned flavor preferences in BALB/c and SWR mice.

    Kraft, Tamar T; Yakubov, Yakov; Huang, Donald; Fitzgerald, Gregory; Natanova, Elona; Sclafani, Anthony; Bodnar, Richard J

    2015-11-01

    Sugar appetite is influenced by unlearned and learned preferences in rodents. The present study examined whether dopamine (DA) D1 (SCH23390: SCH) and opioid (naltrexone: NTX) receptor antagonists differentially altered the expression and acquisition of fructose-conditioned flavor preferences (CFPs) in BALB/c and SWR mice. In expression experiments, food-restricted mice alternately (10 sessions, 1h) consumed a flavored (e.g., cherry) 8% fructose+0.2% saccharin solution (CS+) and a differently-flavored (e.g., grape) 0.2% saccharin solution (CS-). Two-bottle CS choice tests (1h) occurred 0.5h following vehicle: SCH (200 or 800 nmol/kg) or NTX (1 or 5mg/kg). SCH, but not NTX significantly reduced CS+ preference in both strains. In acquisition experiments, 0.5h prior to 10 acquisition training sessions, vehicle, SCH (50 nmol/kg), NTX (1 mg/kg) or Limited Control vehicle treatments were administered, followed by two-bottle CS choice tests without injections. SCH and NTX reduced training intakes in both strains. BALB/c mice displayed hastened extinction of the fructose-CFP following training with SCH, but not NTX. SCH eliminated fructose-CFP acquisition in SWR mice, whereas NTX hastened extinction of the CFP. These results are compared to previous drug findings obtained with sucrose-CFPs in SWR and BALB/c mice, and are discussed in terms of differential effects of these sugars on oral and post-oral conditioning. PMID:26220464

  15. AB260. Role of µ, κ, and δ opioid receptors in tibial inhibition of bladder overactivity in cats

    Zhang, Zhaocun; JIANG, XUEWEN; Shang, Zhenhua; Chen, Shouzhen; Tai, Changfeng; Shi, Benkang

    2016-01-01

    Background To study the impact of µ, κ, and δ opioid receptors on tibial inhibition of bladder overactivity in cats Methods In α-chloralose anesthetized cats we examined the role of opioid receptor (OR) subtypes (µ, κ, and δ) intibialnerve stimulation (TNS) induced inhibition of bladder overactivity elicited by intravesical infusion of 0.25% acetic acid (AA). The sensitivity of TNS inhibition to cumulative intravenous doses of selective OR antagonists (cyprodime for µ, nor-binaltorphimine for...

  16. Molecular Physiology of Enteric Opioid Receptors

    Galligan, James J.; Akbarali, Hamid I.

    2014-01-01

    Opioid drugs have powerful antidiarrheal effects and many patients taking these drugs for chronic pain relief experience chronic constipation that can progress to opioid-induced bowel dysfunction. Three classes of opioid receptors are expressed by enteric neurons: μ-, δ-, and κ-opioid receptors (MOR, DOR, and KOR). MOR and DOR couple to inhibition of adenylate cylase and nerve terminal Ca2+ channels and activation of K+ channels. These effects reduce neuronal activity and neurotransmitter rel...

  17. Molecular physiology of enteric opioid receptors.

    Galligan, James J; Akbarali, Hamid I

    2014-09-10

    Opioid drugs have powerful antidiarrheal effects and many patients taking these drugs for chronic pain relief experience chronic constipation that can progress to opioid-induced bowel dysfunction. Three classes of opioid receptors are expressed by enteric neurons: μ-, δ-, and κ-opioid receptors (MOR, DOR, and KOR). MOR and DOR couple to inhibition of adenylate cylase and nerve terminal Ca(2+) channels and activation of K(+) channels. These effects reduce neuronal activity and neurotransmitter release. KOR couples to inhibition of Ca(2+) channels and inhibition of neurotransmitter release. In the human gastrointestinal tract, MOR, DOR, and KOR link to inhibition of acetylcholine release from enteric interneurons and purine/nitric oxide release from inhibitory motorneurons. These actions inhibit propulsive motility. MOR and DOR also link to inhibition of submucosal secretomotor neurons, reducing active Cl(-) secretion and passive water movement into the colonic lumen. These effects account for the constipation caused by opioid receptor agonists. Tolerance develops to the analgesic effects of opioid receptor agonists but not to the constipating actions. This may be due to differential β-arrestin-2-dependent opioid receptor desensitization and internalization in enteric nerves in the colon compared with the small intestine and in neuronal pain pathways. Further studies of differential opioid receptor desensitization and tolerance in subsets of enteric neurons may identify new drugs or other treatment strategies of opioid-induced bowel dysfunction. PMID:25207608

  18. Pharmacological evidence for the mediation of the panicolytic effect of fluoxetine by dorsal periaqueductal gray matter μ-opioid receptors.

    Roncon, Camila Marroni; Almada, Rafael Carvalho; Maraschin, Jhonatan Christian; Audi, Elisabeth Aparecida; Zangrossi, Hélio; Graeff, Frederico Guilherme; Coimbra, Norberto Cysne

    2015-12-01

    Previously reported results have shown that the inhibitory effect of fluoxetine on escape behavior, interpreted as a panicolytic-like effect, is blocked by pretreatment with either the opioid receptor antagonist naloxone or the 5-HT1A receptor (5-HT1A-R) antagonist WAY100635 via injection into the dorsal periaqueductal gray matter (dPAG). Additionally, reported evidence indicates that the μ-opioid receptor (MOR) interacts with the 5-HT1A-R in the dPAG. In the present work, pretreatment of the dPAG with the selective MOR blocker CTOP antagonized the anti-escape effect of chronic fluoxetine (10 mg/kg, i.p., daily, for 21 days), as measured in the elevated T-maze (ETM) test, indicating mediation of this effect by the MOR. In addition, the combined administration of sub-effective doses of the selective MOR agonist DAMGO (intra-dPAG) and sub-effective doses of chronic as well as subchronic (7 days) fluoxetine increased avoidance and escape latencies, suggesting that the activation of MORs may facilitate and accelerate the effects of fluoxetine. The current observation that MORs located in the dPAG mediate the anti-escape effect of fluoxetine may open new perspectives for the development of more efficient and fast-acting panic-alleviating drugs. PMID:26320545

  19. The Analgesic Efficacy of Fentanyl: Relationship to Tolerance and μ-Opioid Receptor Regulation

    Sirohi, Sunil; Dighe, Shveta V.; Walker, Ellen A; Yoburn, Byron C.

    2008-01-01

    This study determined if fentanyl analgesic efficacy predicts the magnitude of tolerance and μ-opioid receptor regulation. To estimate efficacy, mice were injected i.p. with saline or clocinnamox (CCAM), an irreversible μ-opioid receptor antagonist, (0.32 – 25.6 mg/kg) and 24 hr later fentanyl cumulative dose response studies were conducted. CCAM dose dependently shifted the fentanyl dose-response function to the right. The apparent efficacy (τ) of fentanyl, based on the operational model of ...

  20. [11C]-MeJDTic: a novel radioligand for κ-opioid receptor positron emission tomography imaging

    Introduction: Radiopharmaceuticals that can bind selectively the κ-opioid receptor may present opportunities for staging clinical brain disorders and evaluating the efficiency of new therapies related to stroke, neurodegenerative diseases or opiate addiction. The N-methylated derivative of JDTic (named MeJDTic), which has been recently described as a potent and selective antagonist of κ-opioid receptor in vitro, was labeled with carbon-11 and evaluated for in vivo imaging the κ-opioid receptor in mice. Methods: [11C]-MeJDTic was prepared by methylation of JDTic with [11C]-methyl triflate. The binding of [11C]-MeJDTic to κ-opioid receptor was investigated ex vivo by biodistribution and competition studies using nonfasted male CD1 mice. Results: [11C]-MeJDTic exhibited a high and rapid distribution in peripheral organs. The uptake was maximal in lung where the κ receptor is largely expressed. [11C]-MeJDTic rapidly crossed the blood-brain barrier and accumulated in the brain regions of interest (hypothalamus). The parent ligand remained the major radioactive compound in brain during the experiment. Chase studies with U50,488 (a κ referring agonist), morphine (a μ agonist) and naltrindole (a δ antagonist) demonstrated that this uptake was the result of specific binding to the κ-opioid receptor. Conclusion: These findings suggested that [11C]-MeJDTic appeared to be a promising selective 'lead' radioligand for κ-opioid receptor PET imaging

  1. Antinociceptive Interactions between the Imidazoline I2 Receptor Agonist 2-BFI and Opioids in Rats: Role of Efficacy at the μ-Opioid Receptor.

    Siemian, Justin N; Obeng, Samuel; Zhang, Yan; Zhang, Yanan; Li, Jun-Xu

    2016-06-01

    Although μ-opioids have been reported to interact favorably with imidazoline I2 receptor (I2R) ligands in animal models of chronic pain, the dependence on the μ-opioid receptor ligand efficacy on these interactions had not been previously investigated. This study systematically examined the interactions between the selective I2 receptor ligand 2-(2-benzofuranyl)-2-imidazoline hydrochloride (2-BFI) and three μ-opioid receptor ligands of varying efficacies: fentanyl (high efficacy), buprenorphine (medium-low efficacy), and 17-cyclopropylmethyl-3,14β-dihydroxy-4,5α-epoxy-6α-[(3'-isoquinolyl) acetamido] morphine (NAQ; very low efficacy). The von Frey test of mechanical nociception and Hargreaves test of thermal nociception were used to examine the antihyperalgesic effects of drug combinations in complete Freund's adjuvant-induced inflammatory pain in rats. Food-reinforced schedule-controlled responding was used to examine the rate-suppressing effects of each drug combination. Dose-addition and isobolographical analyses were used to characterize the nature of drug-drug interactions in each assay. 2-BFI and fentanyl fully reversed both mechanical and thermal nociception, whereas buprenorphine significantly reversed thermal but only slightly reversed mechanical nociception. NAQ was ineffective in both nociception assays. When studied in combination with fentanyl, NAQ acted as a competitive antagonist (apparent pA2 value: 6.19). 2-BFI/fentanyl mixtures produced additive to infra-additive analgesic interactions, 2-BFI/buprenorphine mixtures produced supra-additive to infra-additive interactions, and 2-BFI/NAQ mixtures produced supra-additive to additive interactions in the nociception assays. The effects of all combinations on schedule-controlled responding were generally additive. Results consistent with these were found in experiments using female rats. These findings indicate that lower-efficacy μ-opioid receptor agonists may interact more favorably with I2R

  2. Antidepressant-like Effects of Buprenorphine are Mediated by Kappa Opioid Receptors.

    Falcon, Edgardo; Browne, Caroline A; Leon, Rosa M; Fleites, Vanessa C; Sweeney, Rachel; Kirby, Lynn G; Lucki, Irwin

    2016-08-01

    Previous studies have identified potential antidepressant effects of buprenorphine (BPN), a drug with high affinity for mu opioid receptor (MORs) and kappa opioid receptors (KORs) and some affinity at delta opioid receptor (DOR) and opioid receptor-like 1 (ORL-1) receptors. Therefore, these studies examined which opioid receptors were involved in BPN's effects on animal behavior tests sensitive to antidepressant drugs. The acute effects of BPN were tested in the forced swim test (FST) using mice with genetic deletion of individual opioid receptors or after pharmacological blockade of receptors. For evaluating the effects of BPN on chronic stress, separate groups of mice were exposed to unpredictable chronic mild stress (UCMS) for 3 weeks and treated with BPN for at least 7 days before behavioral assessment and subsequent measurement of Oprk1, Oprm1, and Pdyn mRNA expression in multiple brain regions. BPN did not reduce immobility in mice with KOR deletion or after pretreatment with norbinaltorphimine, even though desipramine remained effective. In contrast, BPN reduced immobility in MOR and DOR knockout mice and in mice pretreated with the ORL-1 antagonist JTC-801. UCMS reduced sucrose preference, decreased time in the light side of the light/dark box, increased immobility in the FST and induced region-specific alterations in Oprk1, Oprm1, and PDYN mRNA expression in the frontal cortex and striatum. All of these changes were normalized following BPN treatment. The KOR was identified as a key player mediating the effects of BPN in tests sensitive to antidepressant drugs in mice. These studies support further development of BPN as a novel antidepressant. PMID:26979295

  3. Modulation of brain opioid receptors by zinc and histidine

    The effect of zinc and several trace elements was studied on the binding of the opioid receptor antagonist [3H]-naloxone and the agonists [3H]-DAGO, [3H]-DSTLE, and [3H]-EKC, specific for the mu, delta and kappa receptors, respectively, in several areas of the rat brain. Physiological concentrations of zinc were inhibitory to the binding of naloxone, DAGO, and EKC, whereas delta receptors were insensitive to this inhibition. Copper, cadmium, and mercury also inhibited the binding of all the ligands studied to their receptors. Histidine was most effective in preventing the inhibitory effects of zinc and copper, whereas it was less effective on cadmium, and without any effect on the inhibit was less effective on cadmium, and without any effect on the inhibition caused by mercury. Its metabolites histamine and imidazoleacetic acid, and also citrate were ineffective. Magnesium and manganese were stimulatory to opioid receptor binding, whereas cobalt and nickel had dual effects. Concentrations of zinc less that its IC50 totally prevented the stimulatory effects of magnesium and manganese on the mu and delta receptors on which zinc alone had no effects. The reducing reagents dithiothreitol and B-mercaptoethanol partially protected against zinc inhibition, and the oxidizing reagent dithiobisnitrobenzoic acid even potentiated the inhibitory effects of zinc on DSTLE and DAGO binding, although to different extents

  4. Modulation of brain opioid receptors by zinc and histidine

    Hanissian, S.H.

    1988-01-01

    The effect of zinc and several trace elements was studied on the binding of the opioid receptor antagonist ({sup 3}H)-naloxone and the agonists ({sup 3}H)-DAGO, ({sup 3}H)-DSTLE, and ({sup 3}H)-EKC, specific for the mu, delta and kappa receptors, respectively, in several areas of the rat brain. Physiological concentrations of zinc were inhibitory to the binding of naloxone, DAGO, and EKC, whereas delta receptors were insensitive to this inhibition. Copper, cadmium, and mercury also inhibited the binding of all the ligands studied to their receptors. Histidine was most effective in preventing the inhibitory effects of zinc and copper, whereas it was less effective on cadmium, and without any effect on the inhibit was less effective on cadmium, and without any effect on the inhibition caused by mercury. Its metabolites histamine and imidazoleacetic acid, and also citrate were ineffective. Magnesium and manganese were stimulatory to opioid receptor binding, whereas cobalt and nickel had dual effects. Concentrations of zinc less that its IC{sub 50} totally prevented the stimulatory effects of magnesium and manganese on the mu and delta receptors on which zinc alone had no effects. The reducing reagents dithiothreitol and B-mercaptoethanol partially protected against zinc inhibition, and the oxidizing reagent dithiobisnitrobenzoic acid even potentiated the inhibitory effects of zinc on DSTLE and DAGO binding, although to different extents.

  5. Opioid receptor types involved in the development of nicotine physical dependence in an invertebrate (Planaria) model.

    Raffa, Robert B; Baron, Steve; Bhandal, Jaspreet S; Brown, Tevin; Song, Kevin; Tallarida, Christopher S; Rawls, Scott M

    2013-11-01

    Recent data suggest that opioid receptors are involved in the development of nicotine physical dependence in mammals. Evidence in support of a similar involvement in an invertebrate (Planaria) is presented using the selective opioid receptor antagonist naloxone, and the more receptor subtype-selective antagonists CTAP (D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH2) (μ, MOR), naltrindole (δ, DOR), and nor-BNI (norbinaltorphimine) (κ, KOR). Induction of physical dependence was achieved by 60-min pre-exposure of planarians to nicotine and was quantified by abstinence-induced withdrawal (reduction in spontaneous locomotor activity). Known MOR and DOR subtype-selective opioid receptor antagonists attenuated the withdrawal, as did the non-selective antagonist naloxone, but a KOR subtype-selective antagonist did not. An involvement of MOR and DOR, but not KOR, in the development of nicotine physical dependence or in abstinence-induced withdrawal was thus demonstrated in a sensitive and facile invertebrate model. PMID:24084318

  6. Involvement of multiple µ-opioid receptor subtypes on the presynaptic or postsynaptic inhibition of spinal pain transmission.

    Mizoguchi, Hirokazu; Takagi, Hirokazu; Watanabe, Chizuko; Yonezawa, Akihiko; Sato, Takumi; Sakurada, Tsukasa; Sakurada, Shinobu

    2014-01-01

    The involvement of the μ-opioid receptor subtypes on the presynaptic or postsynaptic inhibition of spinal pain transmission was characterized in ddY mice using endomorphins. Intrathecal treatment with capsaicin, N-methyl-d-aspartate (NMDA) or substance P elicited characteristic nociceptive behaviors that consisted primarily of vigorous biting and/or licking with some scratching. Intrathecal co-administration of endogenous μ-opioid peptide endomorphin-1 or endomorphin-2 resulted in a potent antinociceptive effect against the nociceptive behaviors induced by capsaicin, NMDA or substance P, which was eliminated by i.t. co-administration of the μ-opioid receptor antagonist D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH2 (CTOP). The antinociceptive effect of endomorphin-1 was significantly suppressed by i.t.-co-administration of the μ2-opioid receptor antagonist Tyr-D-Pro-Trp-Phe-NH2 (D-Pro2-endomorphin-1) but not the μ1-opioid receptor antagonist Tyr-D-Pro-Phe-Phe-NH2 (D-Pro2-endomorphin-2) on capsaicin- or NMDA-elicited nociceptive behaviors. In contrast, the antinociceptive effect of endomorphin-2 was significantly suppressed by i.t.-co-administration of D-Pro2-endomorphin-2 but not D-Pro2-endomorphin-1 on capsaicin-, NMDA- or substance P-elicited nociceptive behaviors. Interestingly, regarding substance P-elicited nociceptive behaviors, the antinociceptive effect of endomorphin-1 was significantly suppressed by i.t.-co-administration of another μ2-opioid receptor antagonist, Tyr-D-Pro-Trp-Gly-NH2 (D-Pro2-Tyr-W-MIF-1), but not D-Pro2-endomorphin-1 or D-Pro2-endomorphin-2. The present results suggest that the multiple μ-opioid receptor subtypes are involved in the presynaptic or postsynaptic inhibition of spinal pain transmission. PMID:24512946

  7. Computer Modeling of Human Delta Opioid Receptor

    Tatyana Dzimbova

    2013-04-01

    Full Text Available The development of selective agonists of δ-opioid receptor as well as the model of interaction of ligands with this receptor is the subjects of increased interest. In the absence of crystal structures of opioid receptors, 3D homology models with different templates have been reported in the literature. The problem is that these models are not available for widespread use. The aims of our study are: (1 to choose within recently published crystallographic structures templates for homology modeling of the human δ-opioid receptor (DOR; (2 to evaluate the models with different computational tools; and (3 to precise the most reliable model basing on correlation between docking data and in vitro bioassay results. The enkephalin analogues, as ligands used in this study, were previously synthesized by our group and their biological activity was evaluated. Several models of DOR were generated using different templates. All these models were evaluated by PROCHECK and MolProbity and relationship between docking data and in vitro results was determined. The best correlations received for the tested models of DOR were found between efficacy (erel of the compounds, calculated from in vitro experiments and Fitness scoring function from docking studies. New model of DOR was generated and evaluated by different approaches. This model has good GA341 value (0.99 from MODELLER, good values from PROCHECK (92.6% of most favored regions and MolProbity (99.5% of favored regions. Scoring function correlates (Pearson r = -0.7368, p-value = 0.0097 with erel of a series of enkephalin analogues, calculated from in vitro experiments. So, this investigation allows suggesting a reliable model of DOR. Newly generated model of DOR receptor could be used further for in silico experiments and it will give possibility for faster and more correct design of selective and effective ligands for δ-opioid receptor.

  8. The Effect of Opioid Receptor Blockade on the Neural Processing of Thermal Stimuli

    Eszter D Schoell; Ulrike Bingel; Falk Eippert; Juliana Yacubian; Kerrin Christiansen; Hilke Andresen; Arne May; Christian Buechel

    2010-01-01

    The endogenous opioid system represents one of the principal systems in the modulation of pain. This has been demonstrated in studies of placebo analgesia and stress-induced analgesia, where anti-nociceptive activity triggered by pain itself or by cognitive states is blocked by opioid antagonists. The aim of this study was to characterize the effect of opioid receptor blockade on the physiological processing of painful thermal stimulation in the absence of cognitive manipulation. We therefore...

  9. OPIOID RECEPTORS IN THE BASOLATERAL AMYGDALA BUT NOT DORSAL HIPPOCAMPUS MEDIATE CONTEXT-INDUCED ALCOHOL SEEKING

    Marinelli, Peter W.; Funk, Douglas; Juzytsch, Walter; Lê, A.D.

    2010-01-01

    Contexts associated with the availability of alcohol can induce craving in humans and alcohol seeking in rats. The opioid antagonist naltrexone attenuates context-induced reinstatement (renewal) of alcohol seeking and suppresses neuronal activation in the basolateral amygdaloid complex and dorsal hippocampus induced by such reinstatement. The objective of this study was to determine whether pharmacological blockade of opioid receptors in the basolateral amygdala or dorsal hippocampus would at...

  10. Morphine Induces Hyperalgesia without Involvement of μ-Opioid Receptor or Morphine-3-glucuronide

    Swartjes, Maarten; Mooren, René A G; Waxman, Amanda R.; Arout, Caroline; van de Wetering, Koen; den Hartigh, Jan; Beijnen, Jos H.; Kest, Benjamin; Dahan, Albert

    2012-01-01

    Opioid-induced hyperalgesia (OIH) is a paradoxical increase in pain perception that may manifest during opioid treatment. For morphine, the metabolite morphine-3-glucuronide (M3G) is commonly believed to underlie this phenomenon. Here, in three separate studies, we empirically assess the role of M3G in morphine-induced hyperalgesia. In the first study, CD-1 mice injected with morphine (15 mg/kg subcutaneously) after pretreatment with the opioid receptor antagonist naltrexone (NTX) (15 mg/kg) ...

  11. Synthetic and Receptor Signaling Explorations of the Mitragyna Alkaloids: Mitragynine as an Atypical Molecular Framework for Opioid Receptor Modulators.

    Kruegel, Andrew C; Gassaway, Madalee M; Kapoor, Abhijeet; Váradi, András; Majumdar, Susruta; Filizola, Marta; Javitch, Jonathan A; Sames, Dalibor

    2016-06-01

    Mu-opioid receptor agonists represent mainstays of pain management. However, the therapeutic use of these agents is associated with serious side effects, including potentially lethal respiratory depression. Accordingly, there is a longstanding interest in the development of new opioid analgesics with improved therapeutic profiles. The alkaloids of the Southeast Asian plant Mitragyna speciosa, represented by the prototypical member mitragynine, are an unusual class of opioid receptor modulators with distinct pharmacological properties. Here we describe the first receptor-level functional characterization of mitragynine and related natural alkaloids at the human mu-, kappa-, and delta-opioid receptors. These results show that mitragynine and the oxidized analogue 7-hydroxymitragynine, are partial agonists of the human mu-opioid receptor and competitive antagonists at the kappa- and delta-opioid receptors. We also show that mitragynine and 7-hydroxymitragynine are G-protein-biased agonists of the mu-opioid receptor, which do not recruit β-arrestin following receptor activation. Therefore, the Mitragyna alkaloid scaffold represents a novel framework for the development of functionally biased opioid modulators, which may exhibit improved therapeutic profiles. Also presented is an enantioselective total synthesis of both (-)-mitragynine and its unnatural enantiomer, (+)-mitragynine, employing a proline-catalyzed Mannich-Michael reaction sequence as the key transformation. Pharmacological evaluation of (+)-mitragynine revealed its much weaker opioid activity. Likewise, the intermediates and chemical transformations developed in the total synthesis allowed the elucidation of previously unexplored structure-activity relationships (SAR) within the Mitragyna scaffold. Molecular docking studies, in combination with the observed chemical SAR, suggest that Mitragyna alkaloids adopt a binding pose at the mu-opioid receptor that is distinct from that of classical opioids. PMID

  12. The multiple facets of opioid receptor function: implications for addiction

    Lutz, Pierre-Eric; Kieffer, Brigitte L.

    2013-01-01

    Addiction is characterized by altered reward processing, disrupted emotional responses and poor decision-making. Beyond a central role in drug reward, increasing evidence indicate that opioid receptors are more generally involved in all these processes. Recent studies establish the mu opioid receptor as a main player in social reward, which attracts increasing attention in psychiatric research. There is growing interest in blocking the kappa opioid receptor to prevent relapse, and alleviate t...

  13. Inhibition of Opioid Transmission at the μ-Opioid Receptor Prevents Both Food Seeking and Binge-Like Eating

    Giuliano, Chiara; Robbins, Trevor W.; Nathan, Pradeep J; Bullmore, Edward T.; Everitt, Barry J.

    2012-01-01

    Endogenous opioids, and in particular μ-opioid receptors, have been linked to hedonic and rewarding mechanisms engaged during palatable food intake. The aim of this study was to investigate the effects of GSK1521498, a novel μ-opioid receptor antagonist, on food-seeking behavior and on binge-like eating of a highly preferred chocolate diet. Food seeking was measured in rats trained to respond for chocolate under a second-order schedule of reinforcement, in which prolonged periods of food-seek...

  14. Opioid receptors: Structural and mechanistic insights into pharmacology and signaling.

    Shang, Yi; Filizola, Marta

    2015-09-15

    Opioid receptors are important drug targets for pain management, addiction, and mood disorders. Although substantial research on these important subtypes of G protein-coupled receptors has been conducted over the past two decades to discover ligands with higher specificity and diminished side effects, currently used opioid therapeutics remain suboptimal. Luckily, recent advances in structural biology of opioid receptors provide unprecedented insights into opioid receptor pharmacology and signaling. We review here a few recent studies that have used the crystal structures of opioid receptors as a basis for revealing mechanistic details of signal transduction mediated by these receptors, and for the purpose of drug discovery. PMID:25981301

  15. Biphalin preferentially recruits peripheral opioid receptors to facilitate analgesia in a mouse model of cancer pain - A comparison with morphine.

    Lesniak, Anna; Bochynska-Czyz, Marta; Sacharczuk, Mariusz; Benhye, Sandor; Misicka, Aleksandra; Bujalska-Zadrozny, Magdalena; Lipkowski, Andrzej W

    2016-06-30

    The search for new drugs for cancer pain management has been a long-standing goal in basic and clinical research. Classical opioid drugs exert their primary antinociceptive effect upon activating opioid receptors located in the central nervous system. A substantial body of evidence points to the relevance of peripheral opioid receptors as potential targets for cancer pain treatment. Peptides showing limited blood-brain-barrier permeability promote peripheral analgesia in many pain models. In the present study we examined the peripheral and central analgesic effect of intravenously administered biphalin - a dimeric opioid peptide in a mouse skin cancer pain model, developed by an intraplantar inoculation of B16F0 melanoma cells. The effect of biphalin was compared with morphine - a golden standard in cancer pain management. Biphalin produced profound, dose-dependent and naloxone sensitive spinal analgesia. Additionally, the effect in the tumor-bearing paw was largely mediated by peripheral opioid receptors, as it was readily attenuated by the blood-brain-barrier-restricted opioid receptor antagonist - naloxone methiodide. On the contrary, morphine facilitated its analgesic effect primarily by activating spinal opioid receptors. Both drugs induced tolerance in B16F0 - implanted paws after chronic treatment, however biphalin as opposed to morphine, showed little decrease in its activity at the spinal level. Our results indicate that biphalin may be considered a future alternative drug in cancer pain treatment due to an enhanced local analgesic activity as well as lower tolerance liability compared with morphine. PMID:27094782

  16. [{sup 11}C]-MeJDTic: a novel radioligand for {kappa}-opioid receptor positron emission tomography imaging

    Poisnel, Geraldine; Oueslati, Farhana; Dhilly, Martine; Delamare, Jerome [Groupe de Developpements Methodologiques en Tomographie par Emission de Positons, DSV/DRM UMR CEA 2E, Universite de Caen-Basse Normandie, Centre Cyceron, 14074 Caen Cedex (France); Perrio, Cecile [Groupe de Developpements Methodologiques en Tomographie par Emission de Positons, DSV/DRM UMR CEA 2E, Universite de Caen-Basse Normandie, Centre Cyceron, 14074 Caen Cedex (France)], E-mail: perrio@cyceron.fr; Debruyne, Daniele [Groupe de Developpements Methodologiques en Tomographie par Emission de Positons, DSV/DRM UMR CEA 2E, Universite de Caen-Basse Normandie, Centre Cyceron, 14074 Caen Cedex (France)], E-mail: debruyne@cyceron.fr; Barre, Louisa [Groupe de Developpements Methodologiques en Tomographie par Emission de Positons, DSV/DRM UMR CEA 2E, Universite de Caen-Basse Normandie, Centre Cyceron, 14074 Caen Cedex (France)

    2008-07-15

    Introduction: Radiopharmaceuticals that can bind selectively the {kappa}-opioid receptor may present opportunities for staging clinical brain disorders and evaluating the efficiency of new therapies related to stroke, neurodegenerative diseases or opiate addiction. The N-methylated derivative of JDTic (named MeJDTic), which has been recently described as a potent and selective antagonist of {kappa}-opioid receptor in vitro, was labeled with carbon-11 and evaluated for in vivo imaging the {kappa}-opioid receptor in mice. Methods: [{sup 11}C]-MeJDTic was prepared by methylation of JDTic with [{sup 11}C]-methyl triflate. The binding of [{sup 11}C]-MeJDTic to {kappa}-opioid receptor was investigated ex vivo by biodistribution and competition studies using nonfasted male CD1 mice. Results: [{sup 11}C]-MeJDTic exhibited a high and rapid distribution in peripheral organs. The uptake was maximal in lung where the {kappa} receptor is largely expressed. [{sup 11}C]-MeJDTic rapidly crossed the blood-brain barrier and accumulated in the brain regions of interest (hypothalamus). The parent ligand remained the major radioactive compound in brain during the experiment. Chase studies with U50,488 (a {kappa} referring agonist), morphine (a {mu} agonist) and naltrindole (a {delta} antagonist) demonstrated that this uptake was the result of specific binding to the {kappa}-opioid receptor. Conclusion: These findings suggested that [{sup 11}C]-MeJDTic appeared to be a promising selective 'lead' radioligand for {kappa}-opioid receptor PET imaging.

  17. On the role of cannabinoid CB1- and µ-opioid receptors in nicotine-induced motor impulsivity

    TommyPattij

    2012-06-01

    Full Text Available Previous studies using a rat 5-choice serial reaction time task (5-CSRTT have established a critical role for dopamine D2 receptors in regulating increments in motor impulsivity induced by acute administration of the psychostimulant drugs amphetamine and nicotine. Here we investigated whether cannabinoid CB1 and/or µ-opioid receptors are involved in nicotine-induced impulsivity, given recent findings indicating that both receptor systems mediate amphetamine-induced motor impulsivity. Results showed that the cannabinoid CB1 receptor antagonist SR141716A, but not the opioid receptor antagonist naloxone, reduced nicotine-induced premature responding. In contrast, SR141716A did not affect impulsivity following a challenge with the dopamine transporter inhibitor GBR 12909, a form of drug-induced impulsivity that was previously found to be dependent on µ-opioid receptor activation. Finally, unlike SR141716A and the dopamine D2 receptor antagonist eticlopride, naloxone did not affect impulsivity when the intertrial interval was lengthened from 5 to 7s, i.e. under conditions of heightened cognitive load resulting in higher levels of premature responding. Together, these findings indicate that nicotine-induced motor impulsivity is cannabinoid, but not opioid receptor-dependent. These data confirm that the endogenous cannabinoid, dopamine, and opioid systems each play important, but distinct roles in regulating motor impulsivity. The rather complex interplay between these neurotransmitter systems modulating impulsivity will be discussed in terms of the differential involvement of mesocortical and mesolimbic neurocircuitry.

  18. Behavioral and Cellular Pharmacology Characterization of 17-cyclopropylmethyl-3,14β-dihydroxy-4,5α-epoxy-6α-(isoquinoline-3′-carboxamido)morphinan (NAQ) as a Mu Opioid Receptor Selective Ligand

    Zhang, Yan; Braithwaite, Amanda; Yuan, Yunyun; Streicher, John M.; Bilsky, Edward J.

    2014-01-01

    Mu opioid receptor (MOR) selective antagonists and partial agonists have been used for the treatment of opioid abuse and addiction. Our recent efforts on the identification of MOR antagonists have provided several novel leads displaying interesting pharmacological profiles. Among them, 17-cyclopropylmethyl-3,14β-dihydroxy-4,5α-epoxy-6α-[(3'-isoquinolyl)acetamido]morphinan (NAQ) showed sub-nanomolar binding affinity to the MOR with significant selectivity over the delta opioid receptor (DOR) a...

  19. PET imaging of human cardiac opioid receptors

    The presence of opioid peptides and receptors and their role in the regulation of cardiovascular function has been previously demonstrated in the mammalian heart. The aim of this study was to image μ and δ opioid receptors in the human heart using positron emission tomography (PET). Five subjects (three females, two males, 65±8 years old) underwent PET scanning of the chest with [11C]carfentanil ([11C]CFN) and [11C]-N-methyl-naltrindole ([11C]MeNTI) and the images were analyzed for evidence of opioid receptor binding in the heart. Either [11C]CFN or [11C]MeNTI (20 mCi) was injected i.v. with subsequent dynamic acquisitions over 90 min. For the blocking studies, either 0.2 mg/kg or 1 mg/kg of naloxone was injected i.v. 5 min prior to the injection of [11C]CFN and [11C]MeNTI, respectively. Regions of interest were placed over the left ventricle, left ventricular chamber, lung and skeletal muscle. Graphical analysis demonstrated average baseline myocardial binding potentials (BP) of 4.37±0.91 with [11C]CFN and 3.86±0.60 with [11C]MeNTI. Administration of 0.2 mg/kg naloxone prior to [11C]CFN produced a 25% reduction in BP in one subject in comparison with baseline values, and a 19% decrease in myocardial distribution volume (DV). Administration of 1 mg/kg of naloxone before [11C]MeNTI in another subject produced a 14% decrease in BP and a 21% decrease in the myocardial DV. These results demonstrate the ability to image these receptors in vivo by PET. PET imaging of cardiac opioid receptors may help to better understand their role in cardiovascular pathophysiology and the effect of abuse of opioids and drugs on heart function. (orig.)

  20. Mu Opioid Receptor Actions in the Lateral Habenula

    Margolis, Elyssa B.; Fields, Howard L.

    2016-01-01

    Increased activity of lateral habenula (LHb) neurons is correlated with aversive states including pain, opioid abstinence, rodent models of depression, and failure to receive a predicted reward. Agonists at the mu opioid receptor (MOR) are among the most powerful rewarding and pain relieving drugs. Injection of the MOR agonist morphine directly into the habenula produces analgesia, raising the possibility that MOR acts locally within the LHb. Consequently, we examined the synaptic actions of MOR agonists in the LHb using whole cell patch clamp recording. We found that the MOR selective agonist DAMGO inhibits a subset of LHb neurons both directly and by inhibiting glutamate release onto these cells. Paradoxically, DAMGO also presynaptically inhibited GABA release onto most LHb neurons. The behavioral effect of MOR activation will thus depend upon both the level of intrinsic neuronal activity in the LHb and the balance of activity in glutamate and GABA inputs to different LHb neuronal populations. PMID:27427945

  1. Mu Opioid Receptor Actions in the Lateral Habenula.

    Margolis, Elyssa B; Fields, Howard L

    2016-01-01

    Increased activity of lateral habenula (LHb) neurons is correlated with aversive states including pain, opioid abstinence, rodent models of depression, and failure to receive a predicted reward. Agonists at the mu opioid receptor (MOR) are among the most powerful rewarding and pain relieving drugs. Injection of the MOR agonist morphine directly into the habenula produces analgesia, raising the possibility that MOR acts locally within the LHb. Consequently, we examined the synaptic actions of MOR agonists in the LHb using whole cell patch clamp recording. We found that the MOR selective agonist DAMGO inhibits a subset of LHb neurons both directly and by inhibiting glutamate release onto these cells. Paradoxically, DAMGO also presynaptically inhibited GABA release onto most LHb neurons. The behavioral effect of MOR activation will thus depend upon both the level of intrinsic neuronal activity in the LHb and the balance of activity in glutamate and GABA inputs to different LHb neuronal populations. PMID:27427945

  2. Mu Opioid Receptor Actions in the Lateral Habenula.

    Elyssa B Margolis

    Full Text Available Increased activity of lateral habenula (LHb neurons is correlated with aversive states including pain, opioid abstinence, rodent models of depression, and failure to receive a predicted reward. Agonists at the mu opioid receptor (MOR are among the most powerful rewarding and pain relieving drugs. Injection of the MOR agonist morphine directly into the habenula produces analgesia, raising the possibility that MOR acts locally within the LHb. Consequently, we examined the synaptic actions of MOR agonists in the LHb using whole cell patch clamp recording. We found that the MOR selective agonist DAMGO inhibits a subset of LHb neurons both directly and by inhibiting glutamate release onto these cells. Paradoxically, DAMGO also presynaptically inhibited GABA release onto most LHb neurons. The behavioral effect of MOR activation will thus depend upon both the level of intrinsic neuronal activity in the LHb and the balance of activity in glutamate and GABA inputs to different LHb neuronal populations.

  3. Mu opioid receptor up-regulation and participation in excitability of hippocampal pyramidal cell electrophysiology

    Chronic administration of opiate antagonists to rats results in up-regulation of their brain opioid receptors. Using subcellular fractionation techniques, brain opioid receptors were resolved into two membrane populations, one associated with synaptic plasma membranes (SPM) and the other enriched in smooth endoplasmic reticulum and Golgi (microsomes). This study addressed in part the question of whether an antagonist induces up-regulation uniformly in these two populations. Rats were administered naltrexone by subcutaneously implanted osmotic minipumps. Forebrain mu receptor levels were determined by homologous displacement of (3H)D-ala2-mePhe4-gly-ol5-enkephalin (DAGO) followed by computer estimation of binding parameters. Receptor levels in crude membranes rose 77% after treatment. Microsomes displayed a 92% increase, a two-fold greater change than in SPMs (51%). These results establish that naltrexone induces up-regulation of both membrane populations; and that microsomal and SPM receptors represent discrete populations of intracellular and cell surface sites, respectively. Binding experiments on isolated hippocampi also demonstrated up-regulation (71%) of mu receptors. To demonstrate up-regulation of opioid receptors electrophysiologically, hippocampal slices were prepared from rats which had been chronically treated with naltrexone. After superfusion with DAGO, these slices showed a 42% greater population spike output than controls in response to the same EPSP input. Hippocampi from animals treated for two weeks showed an additional increase in sensitivity. The results support a disinhibitory role for opioids in pyramidal cell hyper-excitability. More importantly, they demonstrate a significant physiological correlate to opioid receptor up-regulation

  4. Mu and delta opioid receptors oppositely regulate motor impulsivity in the signaled nose poke task.

    Mary C Olmstead

    Full Text Available Impulsivity is a primary feature of many psychiatric disorders, most notably attention deficit hyperactivity disorder and drug addiction. Impulsivity includes a number of processes such as the inability to delay gratification, the inability to withhold a motor response, or acting before all of the relevant information is available. These processes are mediated by neural systems that include dopamine, serotonin, norepinephrine, glutamate and cannabinoids. We examine, for the first time, the role of opioid systems in impulsivity by testing whether inactivation of the mu- (Oprm1 or delta- (Oprd1 opioid receptor gene alters motor impulsivity in mice. Wild-type and knockout mice were examined on either a pure C57BL6/J (BL6 or a hybrid 50% C57Bl/6J-50% 129Sv/pas (HYB background. Mice were trained to respond for sucrose in a signaled nose poke task that provides independent measures of associative learning (responses to the reward-paired cue and motor impulsivity (premature responses. Oprm1 knockout mice displayed a remarkable decrease in motor impulsivity. This was observed on the two genetic backgrounds and did not result from impaired associative learning, as responses to the cue signaling reward did not differ across genotypes. Furthermore, mutant mice were insensitive to the effects of ethanol, which increased disinhibition and decreased conditioned responding in wild-type mice. In sharp contrast, mice lacking the Oprd1 gene were more impulsive than controls. Again, mutant animals showed no deficit in associative learning. Ethanol completely disrupted performance in these animals. Together, our results suggest that mu-opioid receptors enhance, whereas delta-opioid receptors inhibit, motor impulsivity. This reveals an unanticipated contribution of endogenous opioid receptor activity to disinhibition. In a broader context, these data suggest that alterations in mu- or delta-opioid receptor function may contribute to impulse control disorders.

  5. Activation of µ-opioid receptors inhibits calcium-currents in the vestibular afferent neurons of the rat through a cAMP dependent mechanism

    Enrique Soto

    2014-03-01

    Full Text Available Opioid receptors are expressed in the vestibular endorgans (afferent neurons and hair cells and are activated by the efferent system, which modulates the discharge of action potentials in the vestibular afferent neurons (VANs. In mammals, the VANs mainly express the µ opioid-receptor, but the function of the opioid receptor activation and the cellular mechanisms by which they exert their actions in these neurons are poorly studied. To determine the actions of the µ opioid receptor (MOR and the cell signaling mechanisms in the VANs, we made perforated patch-clamp recordings of VANs that were obtained from postnatal days 7 to 10 (P7-10 rats and then maintained in primary culture. The MOR agonist [D-Ala2, N-Me-Phe4, Gly5-ol]-enkephalin (DAMGO inhibited the total voltage-gated outward current; this effect was prevented by the perfusion of a Ca2+-free extracellular solution. We then studied the voltage-gated calcium current (Ica and found that DAMGO Met-enkephalin or endomorphine-1 inhibited the ICa in a dose-response fashion. The effects of DAMGO were prevented by the MOR antagonist (CTAP or by the pertussis toxin (PTX. The use of specific calcium channel blockers showed that MOR activation inhibited the T-, L- and N-type ICa. The use of various enzyme activators and inhibitors and of cAMP analogs allowed us to demonstrate that the MOR acts through a cAMP dependent signaling mechanism. In the current clamp experiments, MOR activation increased the duration and decreased the amplitude of the action potentials and modulated the discharge to the current injection. Pre-incubation with PTX occluded all MOR activation effects observed in the current clamp experiments.\tWe conclude that MOR activation inhibits the T-, L- and N-type ICa through the activation of a Gi/o protein that involves a decrease in AC-cAMP-PKA activity. The modulation of ICa may have an impact on the synaptic integration, excitability and neurotransmitter release from the VANs.

  6. PET imaging of human cardiac opioid receptors

    Villemagne, Patricia S.R.; Dannals, Robert F. [Department of Radiology, The Johns Hopkins University School of Medicine, 605 N Caroline St., Baltimore, Maryland (United States); Department of Environmental Health Sciences, The Johns Hopkins University School of Medicine, Baltimore, Maryland (United States); Ravert, Hayden T. [Department of Radiology, The Johns Hopkins University School of Medicine, 605 N Caroline St., Baltimore, Maryland (United States); Frost, James J. [Department of Radiology, The Johns Hopkins University School of Medicine, 605 N Caroline St., Baltimore, Maryland (United States); Department of Environmental Health Sciences, The Johns Hopkins University School of Medicine, Baltimore, Maryland (United States); Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, Maryland (United States)

    2002-10-01

    The presence of opioid peptides and receptors and their role in the regulation of cardiovascular function has been previously demonstrated in the mammalian heart. The aim of this study was to image {mu} and {delta} opioid receptors in the human heart using positron emission tomography (PET). Five subjects (three females, two males, 65{+-}8 years old) underwent PET scanning of the chest with [{sup 11}C]carfentanil ([{sup 11}C]CFN) and [{sup 11}C]-N-methyl-naltrindole ([{sup 11}C]MeNTI) and the images were analyzed for evidence of opioid receptor binding in the heart. Either [{sup 11}C]CFN or [{sup 11}C]MeNTI (20 mCi) was injected i.v. with subsequent dynamic acquisitions over 90 min. For the blocking studies, either 0.2 mg/kg or 1 mg/kg of naloxone was injected i.v. 5 min prior to the injection of [{sup 11}C]CFN and [{sup 11}C]MeNTI, respectively. Regions of interest were placed over the left ventricle, left ventricular chamber, lung and skeletal muscle. Graphical analysis demonstrated average baseline myocardial binding potentials (BP) of 4.37{+-}0.91 with [{sup 11}C]CFN and 3.86{+-}0.60 with [{sup 11}C]MeNTI. Administration of 0.2 mg/kg naloxone prior to [{sup 11}C]CFN produced a 25% reduction in BP in one subject in comparison with baseline values, and a 19% decrease in myocardial distribution volume (DV). Administration of 1 mg/kg of naloxone before [{sup 11}C]MeNTI in another subject produced a 14% decrease in BP and a 21% decrease in the myocardial DV. These results demonstrate the ability to image these receptors in vivo by PET. PET imaging of cardiac opioid receptors may help to better understand their role in cardiovascular pathophysiology and the effect of abuse of opioids and drugs on heart function. (orig.)

  7. Cell death sensitization of leukemia cells by opioid receptor activation

    Friesen, Claudia; Roscher, Mareike; Hormann, Inis; Fichtner, Iduna; Alt, Andreas; Hilger, Ralf A.; Debatin, Klaus-Michael; Miltner, Erich

    2013-01-01

    Cyclic AMP (cAMP) regulates a number of cellular processes and modulates cell death induction. cAMP levels are altered upon stimulation of specific G-protein-coupled receptors inhibiting or activating adenylyl cyclases. Opioid receptor stimulation can activate inhibitory Gi-proteins which in turn block adenylyl cyclase activity reducing cAMP. Opioids such as D,L-methadone induce cell death in leukemia cells. However, the mechanism how opioids trigger apoptosis and activate caspases in leukemia cells is not understood. In this study, we demonstrate that downregulation of cAMP induced by opioid receptor activation using the opioid D,L-methadone kills and sensitizes leukemia cells for doxorubicin treatment. Enhancing cAMP levels by blocking opioid-receptor signaling strongly reduced D,L-methadone-induced apoptosis, caspase activation and doxorubicin-sensitivity. Induction of cell death in leukemia cells by activation of opioid receptors using the opioid D,L-methadone depends on critical levels of opioid receptor expression on the cell surface. Doxorubicin increased opioid receptor expression in leukemia cells. In addition, the opioid D,L-methadone increased doxorubicin uptake and decreased doxorubicin efflux in leukemia cells, suggesting that the opioid D,L-methadone as well as doxorubicin mutually increase their cytotoxic potential. Furthermore, we found that opioid receptor activation using D,L-methadone alone or in addition to doxorubicin inhibits tumor growth significantly in vivo. These results demonstrate that opioid receptor activation via triggering the downregulation of cAMP induces apoptosis, activates caspases and sensitizes leukemia cells for doxorubicin treatment. Hence, opioid receptor activation seems to be a promising strategy to improve anticancer therapies. PMID:23633472

  8. Antinociceptive Action of Isolated Mitragynine from Mitragyna Speciosa through Activation of Opioid Receptor System

    Mohamad Aris Mohd Moklas; Palanisamy Arulselvan; Ithnin Hairuszah; Mohamad Taufik Hidayat; Sharida Fakurazi; Abdul Rahman Shamima

    2012-01-01

    Cannabinoids and opioids systems share numerous pharmacological properties and antinociception is one of them. Previous findings have shown that mitragynine (MG), a major indole alkaloid found in Mitragyna speciosa (MS) can exert its antinociceptive effects through the opioids system. In the present study, the action of MG was investigated as the antinociceptive agent acting on Cannabinoid receptor type 1 (CB1) and effects on the opioids receptor. The latency time was recorded until the mice ...

  9. Hyaluronic acid induces activation of the κ-opioid receptor.

    Barbara Zavan

    Full Text Available INTRODUCTION: Nociceptive pain is one of the most common types of pain that originates from an injury involving nociceptors. Approximately 60% of the knee joint innervations are classified as nociceptive. The specific biological mechanism underlying the regulation of nociceptors is relevant for the treatment of symptoms affecting the knee joint. Intra-articular administration of exogenous hyaluronic acid (HA in patients with osteoarthritis (OA appears to be particularly effective in reducing pain and improving patient function. METHODS: We performed an in vitro study conducted in CHO cells that expressed a panel of opioid receptors and in primary rat dorsal root ganglion (DRG neurons to determine if HA induces the activation of opioid peptide receptors (OPr using both aequorin and the fluorescent dye Fura-2/AM. RESULTS: Selective agonists and antagonists for each OPr expressed on CHO cells were used to test the efficacy of our in vitro model followed by stimulation with HA. The results showed that HA induces stimulatory effects on the κ receptor (KOP. These effects of HA were also confirmed in rat DRG neurons, which express endogenously the OPr. CONCLUSIONS: HA activates the KOP receptor in a concentration dependent manner, with a pEC(50 value of 7.57.

  10. Positron Emission Tomography (PET) Imaging of Opioid Receptors

    van Waarde, Aren; Absalom, Anthony; Visser, Anniek; Dierckx, Rudi; Dierckx, Rudi AJO; Otte, Andreas; De Vries, Erik FJ; Van Waarde, Aren; Luiten, Paul GM

    2014-01-01

    The opioid system consists of opioid receptors (which mediate the actions of opium), their endogenous ligands (the enkephalins, endorphins, endomorphins, dynorphin, and nociceptin), and the proteins involved in opioid production, transport, and degradation. PET tracers for the various opioid recepto

  11. Analgesia produced by exposure to 2450-MHz radiofrequency radiation (RFR) is mediated by brain mu- and kappa-opioid receptors

    Salomon, G.; Park, E.J.; Quock, R.M. (Univ. of Illinois, Rockford (United States))

    1992-02-26

    This study was conducted to identify the opioid receptor subtype(s) responsible for RFR-induced analgesia. Male Swiss Webster mice, 20-25 g, were exposed to 20 mW/cm{sup 2} RFR in a 2,450-MHz waveguide system for 10 min, then tested 15 min later in the abdominal constriction paradigm which detects {mu}- and {kappa}-opioid activity. Immediately following RFR exposure, different groups of mice were pretreated intracerebroventricularly with different opioid receptor blockers with selectivity for {mu}- or {kappa}-opioid receptors. Results show that RFR-induced analgesia was attenuated by higher but not lower doses of the non-selective antagonist naloxone, but the selective {mu}-opioid antagonist {beta}-funaltrexamine and by the selective {kappa}-opioid antagonist norbinaltorphimine. RFR-induced analgesia was also reduced by subcutaneous pretreatment with 5.0 mg/kg of the {mu}-/{kappa}-opioid antagonist({minus})-5,9-diethyl-{alpha}-5,9-dialkyl-2{prime}-hydroxy-6,7-benzomorphan(MR-2266). These findings suggest that RFR-induced analgesia may be mediated by both {mu}- and {kappa}-opioid mechanisms.

  12. μ-Opioid receptor desensitization: Is morphine different?

    Connor, Mark; Osborne, Peregrine B.; Christie, MacDonald J.

    2004-01-01

    Opioid tolerance and dependence are important phenomena. The contribution of acute μ-opioid receptor regulatory mechanisms to the development of analgesic tolerance or physical dependence are unknown, and even the mechanisms underlying relatively rapid receptor desensitization in single cells are unresolved. To a large degree, the uncertainty surrounding the mechanisms and consequences of short-term regulation of μ-opioid receptors in single cells arises from the limitations in the experiment...

  13. Modulation of opioid receptor function by protein-protein interactions

    Alfaras-Melainis, Konstantinos; Gomes, Ivone; Rozenfeld, Raphael; Zachariou, Venetia; Devi, Lakshmi,

    2009-01-01

    Opioid receptors, MORP, DORP and KORP, belong to the family A of G protein coupled receptors (GPCR), and have been found to modulate a large number of physiological functions, including mood, stress, appetite, nociception and immune responses. Exogenously applied opioid alkaloids produce analgesia, hedonia and addiction. Addiction is linked to alterations in function and responsiveness of all three opioid receptors in the brain. Over the last few years, a large number of studies identified pr...

  14. Characterization of opioid receptors that modulate nociceptive neurotransmission in the trigeminocervical complex

    Storer, R J; Akerman, S; Goadsby, P J

    2003-01-01

    Opioid agonists have been used for many years to treat all forms of headache, including migraine. We sought to characterize opioid receptors involved in craniovascular nociceptive pathways by in vivo microiontophoresis of μ-receptor agonists and antagonists onto neurons in the trigeminocervical complex of the cat.Cats were anaesthetized with α-chloralose 60 mg kg−1, i.p. and 20 mg kg−1, i.v. supplements after induction and surgical preparation using halothane. Units were identified in the tri...

  15. Structural basis for bifunctional peptide recognition at human δ-opioid receptor.

    Fenalti, Gustavo; Zatsepin, Nadia A; Betti, Cecilia; Giguere, Patrick; Han, Gye Won; Ishchenko, Andrii; Liu, Wei; Guillemyn, Karel; Zhang, Haitao; James, Daniel; Wang, Dingjie; Weierstall, Uwe; Spence, John C H; Boutet, Sébastien; Messerschmidt, Marc; Williams, Garth J; Gati, Cornelius; Yefanov, Oleksandr M; White, Thomas A; Oberthuer, Dominik; Metz, Markus; Yoon, Chun Hong; Barty, Anton; Chapman, Henry N; Basu, Shibom; Coe, Jesse; Conrad, Chelsie E; Fromme, Raimund; Fromme, Petra; Tourwé, Dirk; Schiller, Peter W; Roth, Bryan L; Ballet, Steven; Katritch, Vsevolod; Stevens, Raymond C; Cherezov, Vadim

    2015-03-01

    Bifunctional μ- and δ-opioid receptor (OR) ligands are potential therapeutic alternatives, with diminished side effects, to alkaloid opiate analgesics. We solved the structure of human δ-OR bound to the bifunctional δ-OR antagonist and μ-OR agonist tetrapeptide H-Dmt-Tic-Phe-Phe-NH2 (DIPP-NH2) by serial femtosecond crystallography, revealing a cis-peptide bond between H-Dmt and Tic. The observed receptor-peptide interactions are critical for understanding of the pharmacological profiles of opioid peptides and for development of improved analgesics. PMID:25686086

  16. Involvement of dynorphin and kappa opioid receptor in yohimbine-induced reinstatement of heroin seeking in rats

    Zhou, Yan; Leri, Francesco; Grella, Stephanie; Aldrich, Jane V.; Kreek, Mary Jeanne

    2013-01-01

    Although kappa opioid receptor (KOP-r) antagonists are known to reduce reinstatement of cocaine, alcohol and nicotine seeking induced by a variety of stressors, the role of KOP-r in yohimbine-induced reinstatement of heroin seeking has not been investigated. Yohimbine, used as a stressor, increases the hypothalamic-pituitary-adrenal (HPA) hormones, causes anxiety and induces heroin craving in humans. The present experiments were undertaken to assess the effects of yohimbine on reinstatement o...

  17. Modulation of opioid receptor function by protein-protein interactions.

    Alfaras-Melainis, Konstantinos; Gomes, Ivone; Rozenfeld, Raphael; Zachariou, Venetia; Devi, Lakshmi

    2009-01-01

    Opioid receptors, MORP, DORP and KORP, belong to the family A of G protein coupled receptors (GPCR), and have been found to modulate a large number of physiological functions, including mood, stress, appetite, nociception and immune responses. Exogenously applied opioid alkaloids produce analgesia, hedonia and addiction. Addiction is linked to alterations in function and responsiveness of all three opioid receptors in the brain. Over the last few years, a large number of studies identified protein-protein interactions that play an essential role in opioid receptor function and responsiveness. Here, we summarize interactions shown to affect receptor biogenesis and trafficking, as well as those affecting signal transduction events following receptor activation. This article also examines protein interactions modulating the rate of receptor endocytosis and degradation, events that play a major role in opiate analgesia. Like several other GPCRs, opioid receptors may form homo or heterodimers. The last part of this review summarizes recent knowledge on proteins known to affect opioid receptor dimerization. PMID:19273296

  18. The effect of opioid receptor blockade on the neural processing of thermal stimuli.

    Eszter D Schoell

    Full Text Available The endogenous opioid system represents one of the principal systems in the modulation of pain. This has been demonstrated in studies of placebo analgesia and stress-induced analgesia, where anti-nociceptive activity triggered by pain itself or by cognitive states is blocked by opioid antagonists. The aim of this study was to characterize the effect of opioid receptor blockade on the physiological processing of painful thermal stimulation in the absence of cognitive manipulation. We therefore measured BOLD (blood oxygen level dependent signal responses and intensity ratings to non-painful and painful thermal stimuli in a double-blind, cross-over design using the opioid receptor antagonist naloxone. On the behavioral level, we observed an increase in intensity ratings under naloxone due mainly to a difference in the non-painful stimuli. On the neural level, painful thermal stimulation was associated with a negative BOLD signal within the pregenual anterior cingulate cortex, and this deactivation was abolished by naloxone.

  19. The effect of opioid receptor blockade on the neural processing of thermal stimuli.

    Schoell, Eszter D; Bingel, Ulrike; Eippert, Falk; Yacubian, Juliana; Christiansen, Kerrin; Andresen, Hilke; May, Arne; Buechel, Christian

    2010-01-01

    The endogenous opioid system represents one of the principal systems in the modulation of pain. This has been demonstrated in studies of placebo analgesia and stress-induced analgesia, where anti-nociceptive activity triggered by pain itself or by cognitive states is blocked by opioid antagonists. The aim of this study was to characterize the effect of opioid receptor blockade on the physiological processing of painful thermal stimulation in the absence of cognitive manipulation. We therefore measured BOLD (blood oxygen level dependent) signal responses and intensity ratings to non-painful and painful thermal stimuli in a double-blind, cross-over design using the opioid receptor antagonist naloxone. On the behavioral level, we observed an increase in intensity ratings under naloxone due mainly to a difference in the non-painful stimuli. On the neural level, painful thermal stimulation was associated with a negative BOLD signal within the pregenual anterior cingulate cortex, and this deactivation was abolished by naloxone. PMID:20811582

  20. G-receptor antagonists increased the activating effect of mastoparan on low Km GTPase of mouse PAG.

    Martínez-Peña, Y; Sánchez-Blázquez, P; Garzón, J

    1995-02-01

    Mastoparan activated in a concentration-dependent manner the low Km GTPase activity in P2 fractions from mouse periaquedultal grey matter (PAG). This peptide at 1-10 mM produced increases of 30-70% over the basal value of 90-120 pmol Pi/mg/min. A series of substances displaying antagonist activity at cellular receptors and not modifying the GTPase function, when used at nanomolar and micromolar concentrations enhanced the effect of mastoparan upon this enzyme. These included antagonists of receptors coupling G proteins: naloxone (non selective opioid antagonist), CTOP (m opioid receptors), ICI 174,864 (d opioid receptors), nor-BNI (k opioid receptors), sulpiride (D2 dopaminergic antagonist), idazoxan (a2 adrenergic antagonist). Bicuculline, antagonist of a receptor not linked to G proteins, GABAA, did not alter the effect of mastoparan on the GTPase. The m opioid agonist, DAMGO, prevented naloxone from increasing the function of the mastoparan-activated enzyme. Thus, mastoparan appears to act on Gi/Go proteins at a site not directly related to the receptor binding domain. PMID:7794687

  1. Opioid receptors and legal highs: Salvia divinorum and Kratom.

    Babu, Kavita M; McCurdy, Christopher R; Boyer, Edward W

    2008-02-01

    Salvia divinorum and Mitragyna speciosa ("Kratom"), two unscheduled dietary supplements whose active agents are opioid receptor agonists, have discrete psychoactive effects that have contributed to their increasing popularity. Salvia divinorum contains the highly selective kappa- opioid receptor agonist salvinorin A; this compound produces visual hallucinations and synesthesia. Mitragynine, the major alkaloid identified from Kratom, has been reported as a partial opioid agonist producing similar effects to morphine. An interesting minor alkaloid of Kratom, 7-hydroxymitragynine, has been reported to be more potent than morphine. Both Kratom alkaloids are reported to activate supraspinal mu- and delta- opioid receptors, explaining their use by chronic narcotics users to ameliorate opioid withdrawal symptoms. Despite their widespread Internet availability, use of Salvia divinorum and Kratom represents an emerging trend that escapes traditional methods of toxicologic monitoring. The purpose of this article is to familiarize toxicologists and poison control specialists with these emerging psychoactive dietary supplements. PMID:18259963

  2. Interaction of trimebutine and Jo-1196 (fedotozine) with opioid receptors in the canine ileum

    Receptor binding of the opioid receptor antagonist, [3H]diprenorphine, which has a similar affinity to the various opioid receptor subtypes, was characterized in subcellular fractions derived from either longitudinal or circular smooth muscle of the canine small intestine with their plexuses (myenteric plexus and deep muscular plexus, respectively) attached. The distribution of opioid binding activity showed a good correlation in the different fractions with the binding of the neuronal marker [3H]saxitoxin but no correlation to the smooth muscle plasma membrane marker 5'-nucleotidase. The saturation data (Kd = 0.12 +/- 0.04 nM and maximum binding = 400 +/- 20 fmol/mg) and the data from kinetic experiments (Kd = 0.08 nmol) in the myenteric plexus were in good agreement with results obtained previously from the circular muscle/deep muscular plexus preparation. Competition experiments using selective drugs for mu [morphiceptin-analog (N-MePhe3-D-Pro4)-morphiceptin], delta (D-Pen2,5-enkephalin) and kappa (dynorphin 1-13, U50488-H) ligands showed the existence of all three receptor subtypes. The existence of kappa receptors was confirmed in saturation experiments using [3H] ethylketocycloazocine as labeled ligand. Two putative opioid agonists, with effects on gastrointestinal motility, trimebutine and JO-1196 (fedotozin), were also examined. Trimebutine (Ki = 0.18 microM), Des-Met-trimebutine (Ki = 0.72 microM) and Jo-1196 (Ki = 0.19 microM) displaced specific opiate binding. The relative affinity for the opioid receptor subtypes was mu = 0.44, delta = 0.30 and kappa = 0.26 for trimebutine and mu = 0.25, delta = 0.22 and kappa = 0.52 for Jo-1196

  3. Morphine protects against methylmercury intoxication: a role for opioid receptors in oxidative stress?

    Allan Costa-Malaquias

    Full Text Available Mercury is an extremely dangerous environmental contaminant responsible for episodes of human intoxication throughout the world. Methylmercury, the most toxic compound of this metal, mainly targets the central nervous system, accumulating preferentially in cells of glial origin and causing oxidative stress. Despite studies demonstrating the current exposure of human populations, the consequences of mercury intoxication and concomitant use of drugs targeting the central nervous system (especially drugs used in long-term treatments, such as analgesics are completely unknown. Morphine is a major option for pain management; its global consumption more than quadrupled in the last decade. Controversially, morphine has been proposed to function in oxidative stress independent of the activation of the opioid receptors. In this work, a therapeutic concentration of morphine partially protected the cellular viability of cells from a C6 glioma cell line exposed to methylmercury. Morphine treatment also reduced lipid peroxidation and totally prevented increases in nitrite levels in those cells. A mechanistic study revealed no alteration in sulfhydryl groups or direct scavenging at this opioid concentration. Interestingly, the opioid antagonist naloxone completely eliminated the protective effect of morphine against methylmercury intoxication, pointing to opioid receptors as the major contributor to this action. Taken together, the experiments in the current study provide the first demonstration that a therapeutic concentration of morphine is able to reduce methylmercury-induced oxidative damage and cell death by activating the opioid receptors. Thus, these receptors may be a promising pharmacological target for modulating the deleterious effects of mercury intoxication. Although additional studies are necessary, our results support the clinical safety of using this opioid in methylmercury-intoxicated patients, suggesting that normal analgesic doses could

  4. Major Depressive Disorder and Kappa Opioid Receptor Antagonists

    Li, Wei; Sun, Huijiao; Chen, Hao; Yang, Xicheng; Xiao, Li; Liu, Renyu; Shao, Liming; Qiu, Zhuibai

    2016-01-01

    Major depressive disorder (MDD) is a common psychiatric disease worldwide. The clinical use of tricyclic antidepressants (TCAs), monoamine oxidase inhibitors (MAOIs) and selective serotonin reuptake inhibitors (SSRIs)/serotonin–norepinephrine reuptake inhibitor (SNRIs) for this condition have been widely accepted, but they were challenged by unacceptable side-effects, potential drug-drug interactions (DDIs) or slow onset/lack of efficacy. The endogenous opioid system is involved in stress and...

  5. Κ-opioid receptor stimulation improves endothelial function in hypoxic pulmonary hypertension.

    Qi Wu

    Full Text Available The present study was designed to investigate the effect of κ-opioid receptor stimulation with U50,488H on endothelial function and underlying mechanism in rats with hypoxic pulmonary hypertension (HPH. Chronic hypoxia-induced HPH was simulated by exposing the rats to 10% oxygen for 2 wk. After hypoxia, mean pulmonary arterial pressure (mPAP, right ventricular pressure (RVP and right ventricular hypertrophy index (RVHI were measured. Relaxation of pulmonary artery in response to acetylcholine (ACh was determined. Expression and activity of endothelial nitric oxide (NO synthase (eNOS and inducible NO synthase (iNOS with NO production, total antioxidant capacity (T-AOC, gp91(phox expression and nitrotyrosine content were measured. The effect of U50,488H administration during chronic hypoxia was investigated. Administration of U50,488H significantly decreased mPAP and right ventricular hypertrophy as evidenced by reduction in RVP and RVHI. These effects were mediated by κ-opioid receptor. In the meantime, treatment with U50,488H significantly improved endothelial function as evidenced by enhanced relaxation in response to ACh. Moreover, U50,488H resulted in a significant increase in eNOS phosphorylation, NO content in serum, and T-AOC in pulmonary artery of HPH rats. In addition, the activity of eNOS was enhanced, but the activity of iNOS was attenuated in the pulmonary artery of chronic hypoxic rats treated with U50,488H. On the other hand, U50,488H markedly blunted HPH-induced elevation of gp91(phox expression and nitrotyrosine content in pulmonary artery, and these effects were blocked by nor-BNI, a selective κ-opioid receptor antagonist. These data suggest that κ-opioid receptor stimulation with U50,488H improves endothelial function in rats with HPH. The mechanism of action might be attributed to the preservation of eNOS activity, enhancement of eNOS phosphorylation, downregulation of iNOS activity and its antioxidative/nitrative effect.

  6. Central delta-opioid receptor interactions and the inhibition of reflex urinary bladder contractions in the rat.

    Dray, A; Nunan, L; Wire, W

    1985-07-01

    The in vivo effects of a number of opioid agonists and antagonists were studied on the spontaneous reflex contractions of the urinary bladder recorded isometrically in the rat anesthetized with urethane. All substances were administered into the central nervous system by the intracereboventricular (i.c.v.) or spinal intrathecal (i.t.) route. The conformationally restricted enkephalin analogues [2-D-penicillamine, 5-L-cysteine] enkephalin (DPLCE), [2-D-penicillamine, 5-L-penicillamine] enkephalin (DPLPE) and [2-D-penicillamine, 5-D-penicillamine] enkephalin (DPDPE) produced dose-related inhibition of reflex bladder contractions when administered by the i.c.v. or i.t. route. Both the novel delta-opioid receptor antagonist ICI 154,129 (200-600 micrograms) [N,N-bisallyl-Tyr-Gly-Gly-Psi-(CH2S)-Phe-Leu-OH) and ICI 174,864 (1-3 micrograms) [N,N-dially-Tyr-Aib-Aib-Phe-Leu-OH: Aib = alpha-aminoisobutyric acid] attenuated or abolished the effects of DPLCE, DPLPE and DPDPE when administered by the i.c.v. or i.t. route. The antagonism observed was selective since the equipotent inhibition produced by the mu-opioid receptor agonist [D-Ala2, Me-Phe4, Gly(ol)5] enkephalin (DAGO) was unaffected. Overall, ICI 154,129 was considerably weaker than ICI 174,864 and both antagonists inhibited bladder activity at doses higher than those required to demonstrate delta-receptor antagonism. Further studies of the agonistic effect of ICI 174,864 showed that it was insensitive to low doses of naloxone (2 micrograms, i.c.v. or i.t.) but could be abolished by higher (10-15 micrograms) doses of naloxone. These observations suggested that the agonistic effect of ICI 174,864 was not mediated by mu-opioid receptor. beta-Endorphin (0.2-1.0 micrograms, i.c.v.) inhibited bladder contractions but following recovery from this effect, appeared to prevent the expression of delta-receptor antagonism by ICI 174,864. In addition a previously subthreshold dose of ICI 174,864 now exhibited marked agonistic

  7. Sucrose-induced analgesia in mice: Role of nitric oxide and opioid receptor-mediated system

    Abtin Shahlaee

    2013-01-01

    Full Text Available Background: The mechanism of action of sweet substance-induced analgesia is thought to involve activation of the endogenous opioid system. The nitric oxide (NO pathway has a pivotal role in pain modulation of analgesic compounds such as opioids. Objectives: We investigated the role of NO and the opioid receptor-mediated system in the analgesic effect of sucrose ingestion in mice. Materials and Methods: We evaluated the effect of intraperitoneal administration of 10 mg/kg of NO synthase inhibitor, N-nitro-L-arginine methyl ester (L-NAME and 20 mg/kg of opioid receptor antagonist, naltrexone on the tail flick response in sucrose ingesting mice. Results: Sucrose ingestion for 12 days induced a statistically significant increase in the latency of tail flick response which was unmodified by L-NAME, but partially inhibited by naltrexone administration. Conclusions: Sucrose-induced nociception may be explained by facilitating the release of endogenous opioid peptides. Contrary to some previously studied pain models, the NO/cyclic guanosine monophosphate (cGMP pathway had no role in thermal hyperalgesia in our study. We recommend further studies on the involvement of NO in other animals and pain models.

  8. The μ-opioid receptor gene and smoking initiation and nicotine dependence

    Kendler Kenneth S

    2006-08-01

    Full Text Available Abstract The gene encoding the mu-opioid receptor (OPRM1 is reported to be associated with a range of substance dependence. Experiments in knockout mice indicate that the mu-opioid receptor may mediate reinforcing effects of nicotine. In humans, opioid antagonist naltrexone may reduce the reinforcing effects of tobacco smoking. Additionally, the OPRM1 gene is located in a region showing linkage to nicotine dependence. The OPRM1 is thus a plausible candidate gene for smoking behavior. To investigate whether OPRM1 contributes to the susceptibility of smoking initiation and nicotine dependence, we genotyped 11 SNPs in the gene for 688 Caucasian subjects of lifetime smokers and nonsmokers. Three SNPs showed nominal significance for smoking initiation and one reached significance for nicotine dependence. The global test for three-marker (rs9479757-rs2075572-rs10485057 haplotypes was significant for smoking initiation (p = 0.0022. The same three-marker haplotype test was marginal (p = 0.0514 for nicotine dependence. These results suggest that OPRM1 may be involved in smoking initiation and nicotine dependence.

  9. Partial agonistic effect of 9-hydroxycorynantheidine on mu-opioid receptor in the guinea-pig ileum.

    Matsumoto, Kenjiro; Takayama, Hiromitsu; Ishikawa, Hayato; Aimi, Norio; Ponglux, Dhavadee; Watanabe, Kazuo; Horie, Syunji

    2006-04-01

    Mitragynine is an indole alkaloid isolated from the Thai medicinal plant Mitragyna speciosa that is reported to have opioid agonistic properties. The 9-demethyl analogue of mitragynine, 9-hydroxycorynantheidine, is synthesized from mitragynine. 9-Hydroxycorynantheidine inhibited electrically stimulated guinea-pig ileum contraction, but its maximum inhibition was weaker than that of mitragynine and its effect was antagonized by naloxone, suggesting that 9-hydroxycorynantheidine possesses partial agonist properties on opioid receptors. Receptor binding assays revealed that 9-hydroxycorynantheidine has high affinity for mu-opioid receptors. In an assay of the guinea-pig ileum, naloxone shifted the concentration-response curves for [D-Ala(2), N-MePhe(4), Gly-ol(5)]-enkephalin (DAMGO), (5alpha,7alpha,8beta)-(+)-N-Methyl-N-[7-(1-pyrrolidinyl)-1-oxaspiro[4.5]dec-8-yl]-benzeneacetamide (U69593) and 9-hydroxycorynantheidine to the right in a competitive manner. The pA(2) values of naloxone against 9-hydroxycorynantheidine and DAMGO were very similar, but not that against U69593. As indicated by the two assay systems, the opioid effect of 9-hydroxycorynantheidine is selective for the mu-opioid receptor. 9-Hydroxycorynantheidine shifted the concentration-response curve for DAMGO slightly to the right. Pretreatment with the mu-opioid selective and irreversible antagonist beta-funaltorexamine hydrochloride (beta-FNA) shifted the concentration-response curve for DAMGO to the right without affecting the maximum response. On the other hand, beta-FNA did not affect the curve for 9-hydroxycorynantheidine, but decreased the maximum response because of the lack of spare receptors. These studies suggest that 9-hydroxycorynantheidine has partial agonist properties on mu-opioid receptors in the guinea-pig ileum. PMID:16266723

  10. Mu opioid receptor modulation in the nucleus accumbens lowers voluntary wheel running in rats bred for high running motivation.

    Ruegsegger, Gregory N; Toedebusch, Ryan G; Will, Matthew J; Booth, Frank W

    2015-10-01

    The exact role of opioid receptor signaling in mediating voluntary wheel running is unclear. To provide additional understanding, female rats selectively bred for motivation of low (LVR) versus high voluntary running (HVR) behaviors were used. Aims of this study were 1) to identify intrinsic differences in nucleus accumbens (NAc) mRNA expression of opioid-related transcripts and 2) to determine if nightly wheel running is differently influenced by bilateral NAc injections of either the mu-opioid receptor agonist D-Ala2, NMe-Phe4, Glyo5-enkephalin (DAMGO) (0.25, 2.5 μg/side), or its antagonist, naltrexone (5, 10, 20 μg/side). In Experiment 1, intrinsic expression of Oprm1 and Pdyn mRNAs were higher in HVR compared to LVR. Thus, the data imply that line differences in opioidergic mRNA in the NAc could partially contribute to differences in wheel running behavior. In Experiment 2, a significant decrease in running distance was present in HVR rats treated with 2.5 μg DAMGO, or with 10 μg and 20 μg naltrexone between hours 0-1 of the dark cycle. Neither DAMGO nor naltrexone had a significant effect on running distance in LVR rats. Taken together, the data suggest that the high nightly voluntary running distance expressed by HVR rats is mediated by increased endogenous mu-opioid receptor signaling in the NAc, that is disturbed by either agonism or antagonism. In summary, our findings on NAc opioidergic mRNA expression and mu-opioid receptor modulations suggest HVR rats, compared to LVR rats, express higher running levels mediated by an increase in motivation driven, in part, by elevated NAc opioidergic signaling. PMID:26044640

  11. Site-specific effects of the nonsteroidal anti-inflammatory drug lysine clonixinate on rat brain opioid receptors.

    Ortí, E; Coirini, H; Pico, J C

    1999-04-01

    In addition to effects in the periphery through inhibition of prostaglandin synthesis, several lines of evidence suggest that nonsteroidal anti-inflammatory drugs (NSAIDs) act in the central nervous system. The possibility that the central action of NSAIDs involves regulation of opioid receptors was investigated by quantitative autoradiography of mu, delta, and kappa sites in rat brain slices. Increased (p lysine clonixinate. Labeling of delta receptors was lower in the lateral septum, and kappa sites decreased in thalamic nuclei. These effects were not mediated through direct interaction with opioid-binding sites, since receptor-binding assays using rat brain membranes confirmed that clonixinate up to 1 x 10(-4) mol/l does not inhibit mu, delta, and kappa receptor specific binding. Central effects of NSAIDs might, therefore, involve interaction with the opioid receptor system through indirect mechanisms. PMID:10077738

  12. Noribogaine is a G-protein biased κ-opioid receptor agonist.

    Maillet, Emeline L; Milon, Nicolas; Heghinian, Mari D; Fishback, James; Schürer, Stephan C; Garamszegi, Nandor; Mash, Deborah C

    2015-12-01

    Noribogaine is the long-lived human metabolite of the anti-addictive substance ibogaine. Noribogaine efficaciously reaches the brain with concentrations up to 20 μM after acute therapeutic dose of 40 mg/kg ibogaine in animals. Noribogaine displays atypical opioid-like components in vivo, anti-addictive effects and potent modulatory properties of the tolerance to opiates for which the mode of action remained uncharacterized thus far. Our binding experiments and computational simulations indicate that noribogaine may bind to the orthosteric morphinan binding site of the opioid receptors. Functional activities of noribogaine at G-protein and non G-protein pathways of the mu and kappa opioid receptors were characterized. Noribogaine was a weak mu antagonist with a functional inhibition constants (Ke) of 20 μM at the G-protein and β-arrestin signaling pathways. Conversely, noribogaine was a G-protein biased kappa agonist 75% as efficacious as dynorphin A at stimulating GDP-GTP exchange (EC50=9 μM) but only 12% as efficacious at recruiting β-arrestin, which could contribute to the lack of dysphoric effects of noribogaine. In turn, noribogaine functionally inhibited dynorphin-induced kappa β-arrestin recruitment and was more potent than its G-protein agonistic activity with an IC50 of 1 μM. This biased agonist/antagonist pharmacology is unique to noribogaine in comparison to various other ligands including ibogaine, 18-MC, nalmefene, and 6'-GNTI. We predict noribogaine to promote certain analgesic effects as well as anti-addictive effects at effective concentrations>1 μM in the brain. Because elevated levels of dynorphins are commonly observed and correlated with anxiety, dysphoric effects, and decreased dopaminergic tone, a therapeutically relevant functional inhibition bias to endogenously released dynorphins by noribogaine might be worthy of consideration for treating anxiety and substance related disorders. PMID:26302653

  13. Kappa-opioid receptor signaling and brain reward function

    Bruijnzeel, Adrie W.

    2009-01-01

    The dynorphin-like peptides have profound effects on the state of the brain reward system and human and animal behavior. The dynorphin-like peptides affect locomotor activity, food intake, sexual behavior, anxiety-like behavior, and drug intake. Stimulation of kappa-opioid receptors, the endogenous receptor for the dynorphin-like peptides, inhibits dopamine release in the striatum (nucleus accumbens and caudate putamen) and induces a negative mood state in humans and animals. The administrati...

  14. Effect of prenatal methadone and ethanol on opioid receptor development in rats

    Peters, M.A.; Braun, R.L. (Loma Linda Univ., CA (United States))

    1991-03-11

    The current literature shows that the offspring of female rats exposed to methadone or ethanol display similar neurochemical and neurobehavioral alterations, and suggests that these drugs may be operating through a common mechanism. If this hypothesis is true, their effect on the endogenous opioid systems should be qualitatively similar. In this study virgin females were treated with methadone or 10% ethanol oral solution starting prior to conception and continued throughout gestation. When the offspring had reached 15 or 30 days of age they were sacrificed, the brain was removed and prepared for opioid receptor binding studies. ({sup 3}H)DAGO and ({sup 3}H)DADLE were used as ligands for the mu and delta receptors, respectively. These studies show significant treatment-related differences in both the number of mu and delta binding sites as well as in apparent receptor affinity. Significant sex- and age-related differences between treatments were also observed. These data show that methadone and ethanol, while manifesting some similar neurochemical and behavioral effects, have unique effects on opioid receptor binding, suggesting that they may be acting by different mechanisms.

  15. Local analgesic effect of tramadol is not mediated by opioid receptors in early postoperative pain in rats

    Angela Maria Sousa

    2015-06-01

    Full Text Available BACKGROUND AND OBJECTIVES: Tramadol is known as a central acting analgesic drug, used for the treatment of moderate to severe pain. Local analgesic effect has been demonstrated, in part due to local anesthetic-like effect, but other mechanisms remain unclear. The role of peripheral opioid receptors in the local analgesic effect is not known. In this study, we examined role of peripheral opioid receptors in the local analgesic effect of tramadol in the plantar incision model. METHODS: Young male Wistar rats were divided into seven groups: control, intraplantar tramadol, intravenous tramadol, intravenous naloxone-intraplantar tramadol, intraplantar naloxone-intraplantar tramadol, intravenous naloxone-intravenous tramadol, and intravenous naloxone. After receiving the assigned drugs (tramadol 5 mg, naloxone 200 µg or 0.9% NaCl, rats were submitted to plantar incision, and withdrawal thresholds after mechanical stimuli with von Frey filaments were assessed at baseline, 10, 15, 30, 45 and 60 min after incision. RESULTS: Plantar incision led to marked mechanical hyperalgesia during the whole period of observation in the control group, no mechanical hyperalgesia were observed in intraplantar tramadol group, intraplantar naloxone-intraplantar tramadol group and intravenous naloxone-intraplantar tramadol. In the intravenous tramadol group a late increase in withdrawal thresholds (after 45 min was observed, the intravenous naloxone-intravenous tramadol group and intravenous naloxone remained hyperalgesic during the whole period. CONCLUSIONS: Tramadol presented an early local analgesic effect decreasing mechanical hyperalgesia induced by plantar incision. This analgesic effect was not mediated by peripheral opioid receptors.

  16. Role of Opioid Receptors Signaling in Remote Electrostimulation - Induced Protection against Ischemia/Reperfusion Injury in Rat Hearts

    Tsai, Hsin-Ju; Huang, Shiang-Suo; Tsou, Meng-Ting; Wang, Hsiao-Ting; Chiu, Jen-Hwey

    2015-01-01

    Aims Our previous studies demonstrated that remote electro-stimulation (RES) increased myocardial GSK3 phosphorylation and attenuated ischemia/ reperfusion (I/R) injury in rat hearts. However, the role of various opioid receptors (OR) subtypes in preconditioned RES-induced myocardial protection remains unknown. We investigated the role of OR subtype signaling in RES-induced cardioprotection against I/R injury of the rat heart. Methods & Results Male Spraque-Dawley rats were used. RES was performed on median nerves area with/without pretreatment with various receptors antagonists such as opioid receptor (OR) subtype receptors (KOR, DOR, and MOR). The expressions of Akt, GSK3, and PKCε expression were analyzed by Western blotting. When RES was preconditioned before the I/R model, the rat's hemodynamic index, infarction size, mortality and serum CK-MB were evaluated. Our results showed that Akt, GSK3 and PKCε expression levels were significantly increased in the RES group compared to the sham group, which were blocked by pretreatment with specific antagonists targeting KOR and DOR, but not MOR subtype. Using the I/R model, the duration of arrhythmia and infarct size were both significantly attenuated in RES group. The mortality rates of the sham RES group, the RES group, RES group + KOR antagonist, RES group + DOR/MOR antagonists (KOR left), RES group + DOR antagonist, and RES group + KOR/MOR antagonists (DOR left) were 50%, 20%, 67%, 13%, 50% and 55%, respectively. Conclusion The mechanism of RES-induced myocardial protection against I/R injury seems to involve multiple target pathways such as Akt, KOR and/or DOR signaling. PMID:26430750

  17. Role of Opioid Receptors Signaling in Remote Electrostimulation--Induced Protection against Ischemia/Reperfusion Injury in Rat Hearts.

    Hsin-Ju Tsai

    Full Text Available Our previous studies demonstrated that remote electro-stimulation (RES increased myocardial GSK3 phosphorylation and attenuated ischemia/ reperfusion (I/R injury in rat hearts. However, the role of various opioid receptors (OR subtypes in preconditioned RES-induced myocardial protection remains unknown. We investigated the role of OR subtype signaling in RES-induced cardioprotection against I/R injury of the rat heart.Male Spraque-Dawley rats were used. RES was performed on median nerves area with/without pretreatment with various receptors antagonists such as opioid receptor (OR subtype receptors (KOR, DOR, and MOR. The expressions of Akt, GSK3, and PKCε expression were analyzed by Western blotting. When RES was preconditioned before the I/R model, the rat's hemodynamic index, infarction size, mortality and serum CK-MB were evaluated. Our results showed that Akt, GSK3 and PKCε expression levels were significantly increased in the RES group compared to the sham group, which were blocked by pretreatment with specific antagonists targeting KOR and DOR, but not MOR subtype. Using the I/R model, the duration of arrhythmia and infarct size were both significantly attenuated in RES group. The mortality rates of the sham RES group, the RES group, RES group + KOR antagonist, RES group + DOR/MOR antagonists (KOR left, RES group + DOR antagonist, and RES group + KOR/MOR antagonists (DOR left were 50%, 20%, 67%, 13%, 50% and 55%, respectively.The mechanism of RES-induced myocardial protection against I/R injury seems to involve multiple target pathways such as Akt, KOR and/or DOR signaling.

  18. Optimized Proteomic Mass Spectrometry Characterization of Recombinant Human μ-Opioid Receptor Functionally Expressed in Pichia pastoris Cell Lines.

    Rosa, Mònica; Bech-Serra, Joan Josep; Canals, Francesc; Zajac, Jean Marie; Talmont, Franck; Arsequell, Gemma; Valencia, Gregorio

    2015-08-01

    Human μ-opioid receptor (hMOR) is a class-A G-protein-coupled receptor (GPCR), a prime therapeutic target for the management of moderate and severe pain. A chimeric form of the receptor has been cocrystallized with an opioid antagonist and resolved by X-ray diffraction; however, further direct structural analysis is still required to identify the active form of the receptor to facilitate the rational design of hMOR-selective agonist and antagonists with therapeutic potential. Toward this goal and in spite of the intrinsic difficulties posed by the highly hydrophobic transmembrane motives of hMOR, we have comprehensively characterized by mass spectrometry (MS) analysis the primary sequence of the functional hMOR. Recombinant hMOR was overexpressed as a C-terminal c-myc and 6-his tagged protein using an optimized expression procedure in Pichia pastoris cells. After membrane solubilization and metal-affinity chromatography purification, a procedure was devised to enhance the concentration of the receptor. Subsequent combinations of in-solution and in-gel digestions using either trypsin, chymotrypsin, or proteinase K, followed by matrix-assisted laser desorption ionization time-of-flight MS or nanoliquid chromatography coupled with tandem MS analyses afforded an overall sequence coverage of up to >80%, a level of description first attained for an opioid receptor and one of the six such high-coverage MS-based analyses of any GPCR. PMID:26090583

  19. Nociceptin Opioid Receptor (NOP) as a Therapeutic Target: Progress in Translation from Preclinical Research to Clinical Utility.

    Zaveri, Nurulain T

    2016-08-11

    In the two decades since the discovery of the nociceptin opioid receptor (NOP) and its ligand, nociceptin/orphaninFQ (N/OFQ), steady progress has been achieved in understanding the pharmacology of this fourth opioid receptor/peptide system, aided by genetic and pharmacologic approaches. This research spawned an explosion of small-molecule NOP receptor ligands from discovery programs in major pharmaceutical companies. NOP agonists have been investigated for their efficacy in preclinical models of anxiety, cough, substance abuse, pain (spinal and peripheral), and urinary incontinence, whereas NOP antagonists have been investigated for treatment of pain, depression, and motor symptoms in Parkinson's disease. Translation of preclinical findings into the clinic is guided by PET and receptor occupancy studies, particularly for NOP antagonists. Recent progress in preclinical NOP research suggests that NOP agonists may have clinical utility for pain treatment and substance abuse pharmacotherapy. This review discusses the progress toward validating the NOP-N/OFQ system as a therapeutic target. PMID:26878436

  20. [3H]naloxone as an opioid receptor label: Analysis of binding site heterogeneity and use for determination of opioid affinities of casomorphin analogues

    The nonselective antagonist [3H]naloxone was used to identify opioid receptors in rat brain membranes. The multiple naloxone binding sites were related to different opioid receptors by means of selective opiod ligands as well as various β-casomorphin analogues. Analysis of binding site heterogeneity was performed using several computer curve fitting methods. The results indicate that structurally modified casomorphin peptides are able to discriminate between μ1 and μ2 binding sites. The affinities to the μ sites obtained with [3H]naloxone as label are in a good agreement with those from experiments with the μ selective radioligand [3H]DAGO. The μ1 site affinities of these casomorphin derivatives are well correlated with their antinociceptive potencies. This finding suggests the mediation of the analgesic activity via the high-affinity μ1 subtype. (author)

  1. Proteasome involvement in agonist-induced down-regulation of mu and delta opioid receptors.

    Chaturvedi, K; Bandari, P; Chinen, N; Howells, R D

    2001-04-13

    This study investigated the mechanism of agonist-induced opioid receptor down-regulation. Incubation of HEK 293 cells expressing FLAG-tagged delta and mu receptors with agonists caused a time-dependent decrease in opioid receptor levels assayed by immunoblotting. Pulse-chase experiments using [(35)S]methionine metabolic labeling indicated that the turnover rate of delta receptors was accelerated 5-fold following agonist stimulation. Inactivation of functional G(i) and G(o) proteins by pertussis toxin-attenuated down-regulation of the mu opioid receptor, while down-regulation of the delta opioid receptor was unaffected. Pretreatment of cells with inhibitors of lysosomal proteases, calpain, and caspases had little effect on mu and delta opioid receptor down-regulation. In marked contrast, pretreatment with proteasome inhibitors attenuated agonist-induced mu and delta receptor down-regulation. In addition, incubation of cells with proteasome inhibitors in the absence of agonists increased steady-state mu and delta opioid receptor levels. Immunoprecipitation of mu and delta opioid receptors followed by immunoblotting with ubiquitin antibodies suggested that preincubation with proteasome inhibitors promoted accumulation of polyubiquitinated receptors. These data provide evidence that the ubiquitin/proteasome pathway plays a role in agonist-induced down-regulation and basal turnover of opioid receptors. PMID:11152677

  2. Involvement of opioid receptors in the systemic and peripheral antinociceptive actions of montelukast in the animal models of pain.

    Ghorbanzadeh, Behnam; Mansouri, Mohammad Taghi; Sahraei, Hedayat; Alboghobeish, Soheila

    2016-05-15

    This study aimed to investigate the involvement of opioid receptors in the systemic and peripheral antinociceptive activities of montelukast in different animal models of pain. Rats and mice were injected with montelukast to produce analgesia. The formalin and acetic acid-induced writhing tests were used to assess the nociceptive activity. The results showed that i.p. administration of montelukast (0.3-10mg/kg) dose-dependently reduced flinching behavior in both the first and second phases of formalin test with mean ED50 of 0.55 and 5.31mg/kg, respectively. Also, intraplantar administration of montelukast (3-30μg/paw) produced antinociception against the two phases of formalin assay in a dose-dependent way with mean ED30 of 2.92 and 8.11μg/paw, respectively. Furthermore, pre-treatment with naloxone (a non-selective opioid receptor antagonist) significantly inhibited both the systemic and also peripheral antinociceptive actions of montelukast in formalin test. In writhing test, the results showed that intraperitoneal administration of montelukast (3-10mg/kg) significantly reduced the writhe number induced by acetic acid in mice. Moreover, co-administration of non-effective doses of montelukast (0.3 and 1mg/kg; i.p.) and morphine (0.25mg/kg; i.p.) significantly decreased the writhes number induced by acetic acid. Also, this effect was naloxone-reversible. These findings suggest that the systemic and peripheral antinociception produced by montelukast were mediated through the opioid receptors in central and peripheral nervous systems. Moreover, combination of montelukast and morphine could be noted as a new strategy for pain relief. PMID:26948314

  3. Cutaneous nociceptors lack sensitisation, but reveal μ-opioid receptor-mediated reduction in excitability to mechanical stimulation in neuropathy

    Schmidt Yvonne

    2012-11-01

    Full Text Available Abstract Background Peripheral nerve injuries often trigger a hypersensitivity to tactile stimulation. Behavioural studies demonstrated efficient and side effect-free analgesia mediated by opioid receptors on peripheral sensory neurons. However, mechanistic approaches addressing such opioid properties in painful neuropathies are lacking. Here we investigated whether opioids can directly inhibit primary afferent neuron transmission of mechanical stimuli in neuropathy. We analysed the mechanical thresholds, the firing rates and response latencies of sensory fibres to mechanical stimulation of their cutaneous receptive fields. Results Two weeks following a chronic constriction injury of the saphenous nerve, mice developed a profound mechanical hypersensitivity in the paw innervated by the damaged nerve. Using an in vitro skin-nerve preparation we found no changes in the mechanical thresholds and latencies of sensory fibres from injured nerves. The firing rates to mechanical stimulation were unchanged or reduced following injury. Importantly, μ-opioid receptor agonist [D-Ala2,N-Me-Phe4,Gly5]-ol-enkephalin (DAMGO significantly elevated the mechanical thresholds of nociceptive Aδ and C fibres. Furthermore, DAMGO substantially diminished the mechanically evoked discharges of C nociceptors in injured nerves. These effects were blocked by DAMGO washout and pre-treatment with the selective μ-opioid receptor antagonist Cys2-Tyr3-Orn5-Pen7-amide. DAMGO did not alter the responses of sensory fibres in uninjured nerves. Conclusions Our findings suggest that behaviourally manifested neuropathy-induced mechanosensitivity does not require a sensitised state of cutaneous nociceptors in damaged nerves. Yet, nerve injury renders nociceptors sensitive to opioids. Prevention of action potential generation or propagation in nociceptors might represent a cellular mechanism underlying peripheral opioid-mediated alleviation of mechanical hypersensitivity in neuropathy.

  4. Addictive evaluation of cholic acid-verticinone ester, a potential cough therapeutic agent with agonist action of opioid receptor

    Jiu-liang ZHANG; Hui WANG; Chang CHEN; Hui-fang PI; Han-li RUAN; Peng ZHANG; Ji-zhou WU

    2009-01-01

    Aim: The purpose of this work was to search for potential drugs with potent antitussive and expectorant activities as well as a low toxicity, but without addictive properties. Cholic acid-verticinone ester (CA-Ver) was synthesized based on the clearly elucidated antitussive and expectorant activities of verticinone in bulbs of Fritillaria and different bile acids in Snake Bile. In our previous study, CA-Vet showed a much more potent activity than codeine phosphate. This study was carried out to investigate the central antitussive mechanism and the addictive evaluation of CA-Ver.Methods: Testing on a capsaicin-induced cough model of mice pretreated with naloxone, a non-selective opioid receptor antagonist, was performed for the observation of CA-Ver's central antitussive mechanism. We then took naloxone-induced withdrawal tests of mice for the judgment of CA-Ver's addiction. Lastly, we determined the opioid dependence of CA-Ver in the guinea pig ileum. Results: The test on the capsaicin-induced cough model showed that naloxone could block the antitussive effect of CA-Ver,suggesting the antitussive mechanism of CA-Ver was related to the central opioid receptors. The naloxone-urged withdrawal tests of the mice showed that CA-Ver was not addictive, and the test of the opioid dependence in the guinea pig ileum showed that CA-Ver had no withdrawal response.Conclusion: These findings suggested that CA-Ver deserved attention for its potent antitussive effects related to the central opioid receptors, but without addiction, and had a good development perspective.

  5. Does the kappa opioid receptor system contribute to pain aversion?

    Catherine M Cahill

    2014-11-01

    Full Text Available The kappa opioid receptor (KOR and the endogenous peptide-ligand dynorphin have received significant attention due the involvement in mediating a variety of behavioral and neurophysiological responses, including opposing the rewarding properties of drugs of abuse including opioids. Accumulating evidence indicates this system is involved in regulating states of motivation and emotion. Acute activation of the KOR produces an increase in motivational behavior to escape a threat, however, KOR activation associated with chronic stress leads to the expression of symptoms indicative of mood disorders. It is well accepted that KOR can produce analgesia and is engaged in chronic pain states including neuropathic pain. Spinal studies have revealed KOR-induced analgesia in reversing pain hypersensitivities associated with peripheral nerve injury. While systemic administration of KOR agonists attenuates nociceptive sensory transmission, this effect appears to be a stress-induced effect as anxiolytic agents, including delta opioid receptor agonists, mitigate KOR agonist-induced analgesia. Additionally, while the role of KOR and dynorphin in driving the dysphoric and aversive components of stress and drug withdrawal has been well characterized, how this system mediates the negative emotional states associated with chronic pain is relatively unexplored. This review provides evidence that dynorphin and the KOR system contribute to the negative affective component of pain and that this receptor system likely contributes to the high comorbidity of mood disorders associated with chronic neuropathic pain.

  6. Collybolide is a novel biased agonist of κ-opioid receptors with potent antipruritic activity.

    Gupta, Achla; Gomes, Ivone; Bobeck, Erin N; Fakira, Amanda K; Massaro, Nicholas P; Sharma, Indrajeet; Cavé, Adrien; Hamm, Heidi E; Parello, Joseph; Devi, Lakshmi A

    2016-05-24

    Among the opioid receptors, the κ-opioid receptor (κOR) has been gaining considerable attention as a potential therapeutic target for the treatment of complex CNS disorders including depression, visceral pain, and cocaine addiction. With an interest in discovering novel ligands targeting κOR, we searched natural products for unusual scaffolds and identified collybolide (Colly), a nonnitrogenous sesquiterpene from the mushroom Collybia maculata. This compound has a furyl-δ-lactone core similar to that of Salvinorin A (Sal A), another natural product from the plant Salvia divinorum Characterization of the molecular pharmacological properties reveals that Colly, like Sal A, is a highly potent and selective κOR agonist. However, the two compounds differ in certain signaling and behavioral properties. Colly exhibits 10- to 50-fold higher potency in activating the mitogen-activated protein kinase pathway compared with Sal A. Taken with the fact that the two compounds are equipotent for inhibiting adenylyl cyclase activity, these results suggest that Colly behaves as a biased agonist of κOR. Behavioral studies also support the biased agonistic activity of Colly in that it exhibits ∼10-fold higher potency in blocking non-histamine-mediated itch compared with Sal A, and this difference is not seen in pain attenuation by these two compounds. These results represent a rare example of functional selectivity by two natural products that act on the same receptor. The biased agonistic activity, along with an easily modifiable structure compared with Sal A, makes Colly an ideal candidate for the development of novel therapeutics targeting κOR with reduced side effects. PMID:27162327

  7. Characterization of opioid receptors that modulate nociceptive neurotransmission in the trigeminocervical complex.

    Storer, R J; Akerman, S; Goadsby, P J

    2003-01-01

    1. Opioid agonists have been used for many years to treat all forms of headache, including migraine. We sought to characterize opioid receptors involved in craniovascular nociceptive pathways by in vivo microiontophoresis of micro -receptor agonists and antagonists onto neurons in the trigeminocervical complex of the cat. 2. Cats were anaesthetized with alpha-chloralose 60 mg kg(-1), i.p. and 20 mg kg(-1), i.v. supplements after induction and surgical preparation using halothane. Units were identified in the trigeminocervical complex responding to supramaximal electrical stimulation of the superior sagittal sinus, and extracellular recordings of activity made. 3. Seven- or nine-barrelled glass micropipettes incorporating tungsten recording electrodes in their centre barrels were used for microiontophoresis of test substances onto cell bodies. 4. Superior sagittal sinus (SSS)-linked cells whose firing was evoked by microiontophoretic application of L-glutamate (n=8 cells) were reversibly inhibited by microiontophoresis of H(2)N-Tyr-D-Ala-Gly-N-Me-Phe-Gly-ol (DAMGO) (n=12), a selective micro -receptor agonist, in a dose dependent manner, but not by control ejection of sodium or chloride ions from a barrel containing saline. 5. The inhibition by DAMGO of SSS-linked neurons activated with L-glutamate could be antagonized by microiontophoresis of selective micro -receptor antagonists D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH(2) (CTOP) or D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH(2) (CTAP), or both, in all cells tested (n=4 and 6, respectively). 6. Local iontophoresis of DAMGO during stimulation of the superior sagittal sinus resulted in a reduction in SSS-evoked activity. This effect was substantially reversed 10 min after cessation of iontophoresis. The effect of DAMGO was markedly inhibited by co-iontophoresis of CTAP. 7. Thus, we found that micro -receptors modulate nociceptive input to the trigeminocervical complex. Characterizing the sub-types of opioid receptors that

  8. Kappa-opioid receptor from human placenta: hydrodynamic characteristics and evidence for its association with a G protein

    The kappa nature of opioid binding sites in a brush border membrane (BBM) fraction from human placenta has been confirmed: these sites display considerably higher apparent affinity for the kappa selective ligand U-50488 than they do for the μ and δ selective ligands enkephalin and enkephalyl-Thr, respectively. Two lines of evidence indicated that the placental kappa opioid receptor is capable of interacting with a guanine nucleotide regulatory (G) protein: (i) equilibrium binding of the angonist 3H-etorphine in the BBM fraction was clearly inhibited by 5'-guanylylimidodiphosphate (Gpp(NH)p), especially in the presence of Na+ ions while binding of the antagonist 3H-diprenorphine was significantly less so and (ii) the sedimentation velocity of the kappa opioid receptor was decreased down to about 10 S when the BBM fraction was prelabeled with radioligand in the presence of Gpp(NH)p prior to its solubilization with digitonin. The G protein that mediates the effect of Gpp(NH)p might be neither G/sub s/ nor G/sub i/ since no adenylate cyclase activity could be demonstrated in the BBM fraction from human placenta

  9. Involvement of opioid receptors in the CGRP8-37-induced inhibition of the activity of wide-dynamic-range neurons in the spinal dorsal horn of rats.

    Yan, Yi; Yu, Long-Chuan

    2004-07-01

    The present study was performed to explore the involvement of opioid receptors in the calcitonin gene-related peptide 8-37 (CGRP8-37, an antagonist of CGRP receptor)-induced inhibition of the activity of wide-dynamic-range (WDR) neurons in the spinal dorsal horn of rats. Extracellular recording was performed with a multibarrelled glass micropipette, and the chemicals were delivered by micro-iontophoresis. The discharge frequency of WDR neurons was evoked by subcutaneous electrical stimulation applied to the ipsilateral hindpaw. Iontophoretic application of CGRP8-37 by an ejection current of 160 nA induced significant inhibition of the discharge frequency of WDR neurons. The inhibitory effect of CGRP8-37 on the activity of WDR neurons was attenuated by later iontophoretic application of the opioid antagonist naloxone. Furthermore, the effect of CGRP8-37 was attenuated by either iontophoretic application of the kappa-receptor antagonist nor-binaltorphimine (nor-BNI) or the mu-receptor antagonist beta-funaltrexamine (beta-FNA) but not by the delta-receptor antagonist naltrindole. The results indicate that kappa- and mu-opioid receptors on the membrane of WDR neurons are involved in the modulation of CGRP8-37-induced antinociception in dorsal horn of the spinal cord in rats. PMID:15197748

  10. κ-Opioid Receptor Expression Defines a Phenotypically Distinct Subpopulation of Astroglia: Relationship to Ca2+ Mobilization, Development, and the Antiproliferative Effect of Opioids

    Gurwell, Julie A.; Duncan, Marilyn J.; Maderspach, Katalin; Stiene-Martin, Anne; Elde, Robert P.; Hauser, Kurt F.

    2016-01-01

    To assess the role of κ opioid receptors in astrocyte development, the effect of κ agonists on the growth of astroglia derived from 1–2 day-old mouse cerebra was examined in vitro. κ-Opioid receptor expression was assessed immunocytochemically (using KA8 and KOR1 antibodies), as well as functionally by examining the effect of κ receptor activation on intracellular calcium ([Ca2+]i) homeostasis and DNA synthesis. On days 6–7, as many as 50% of the astrocytes displayed κ receptor (KA8) immunoreactivity or exhibited increases in [Ca 2+]i in response to κ agonist treatment (U69,593 or U50,488H). Exposure to U69,593 (100 nM) for 72 h caused a significant reduction in number and proportion of glial fibrillary acidic protein-immunoreactive astrocytes incorporating bromodeoxyuridine (BrdU) that could be prevented by co-administering the κ antagonist, nor-binaltorphimine (300 nM). In contrast, on day 14, only 5 or 14%, respectively, of the astrocytes were κ opioid receptor (KA8) immunoreactive or displayed functional increases in [Ca2+]i. Furthermore, U69,593 (100 nM) treatment failed to inhibit BrdU incorporation at 9 days in vitro. Experimental manipulations showed that κ receptor activation increases astroglial [Ca 2+]i both through influx via L-type channels and through mobilization of intracellular stores (which is an important Ca2+ signaling pathway in cell division). Collectively, these results indicate that a subpopulation of developing astrocytes express κ opioid receptors in vitro, and suggest that the activation of κ receptors mobilizes [Ca 2+]i and inhibits cell proliferation. Moreover, the proportion of astrocytes expressing κ receptors was greatest during a period of rapid cell growth suggesting that they are preferentially expressed by proliferating astrocytes. PMID:8930364

  11. Mu opioid receptor polymorphism, early social adversity, and social traits.

    Carver, Charles S; Johnson, Sheri L; Kim, Youngmee

    2016-10-01

    A polymorphism in the mu opioid receptor gene OPRM1 (rs1799971) has been investigated for its role in sensitivity to social contexts. Evidence suggests that the G allele of this polymorphism is associated with higher levels of sensitivity. This study tested for main effects of the polymorphism and its interaction with a self-report measure of childhood adversity as an index of negative environment. Outcomes were several personality measures relevant to social connection. Significant interactions were obtained, such that the negative impact of childhood adversity on personality was greater among G carriers than among A homozygotes on measures of agreeableness, interdependence, anger proneness, hostility, authentic pride, life engagement, and an index of (mostly negative) feelings coloring one's world view. Findings support the role of OPRM1 in sensitivity to negative environments. Limitations are noted, including the lack of a measure of advantageous social environment to assess sensitivity to positive social contexts. PMID:26527429

  12. The role of κ-opioid receptor activation in mediating antinociception and addiction

    Wang, Yu-hua; Sun, Jian-feng; Tao, Yi-min; Chi, Zhi-Qiang; Liu, Jing-gen

    2010-01-01

    The κ-opioid receptor (KOR), a member of the opioid receptor family, is widely expressed in the central nervous system and peripheral tissues. Substantial evidence has shown that activation of KOR by agonists and endogenous opioid peptides in vivo may produce a strong analgesic effect that is free from the abuse potential and the adverse side effects of μ-opioid receptor (MOR) agonists, such as morphine. In addition, activation of the KOR has also been shown to exert an inverse effect on morp...

  13. Analgesic tone conferred by constitutively active mu opioid receptors in mice lacking β-arrestin 2

    Hales Tim G

    2011-04-01

    Full Text Available Abstract Hedonic reward, dependence and addiction are unwanted effects of opioid analgesics, linked to the phasic cycle of μ opioid receptor activation, tolerance and withdrawal. In vitro studies of recombinant G protein coupled receptors (GPCRs over expressed in cell lines reveal an alternative tonic signaling mechanism that is independent of agonist. Such studies demonstrate that constitutive GPCR signaling can be inhibited by inverse agonists but not by neutral antagonists. However, ligand-independent activity has been difficult to examine in vivo, at the systems level, due to relatively low levels of constitutive activity of most GPCRs including μ receptors, often necessitating mutagenesis or pharmacological manipulation to enhance basal signaling. We previously demonstrated that the absence of β-arrestin 2 (β-arr2 augments the constitutive coupling of μ receptors to voltage-activated Ca2+ channels in primary afferent dorsal root ganglion neurons from β-arr2-/- mice. We used this in vitro approach to characterize neutral competitive antagonists and inverse agonists of the constitutively active wild type μ receptors in neurons. We administered these agents to β-arr2-/- mice to explore the role of constitutive μ receptor activity in nociception and hedonic tone. This study demonstrates that the induction of constitutive μ receptor activity in vivo in β-arr2-/- mice prolongs tail withdrawal from noxious heat, a phenomenon that was reversed by inverse agonists, but not by antagonists that lack negative efficacy. By contrast, the aversive effects of inverse agonists were similar in β-arr2-/- and β-arr2+/+ mice, suggesting that hedonic tone was unaffected.

  14. Intact brain cells: a novel model system for studying opioid receptor binding

    Rogers, N.F.; El-Fakahany, E.E.

    1985-07-29

    The use of a novel tissue preparation to study opioid receptor binding in viable, intact cells derived from whole brains of adult rats is presented. Mechanically dissociated and sieved cells, which were not homogenized at any stage of the experimental protocol, and iso-osmotic physiological buffer were used in these experiments. This system was adapted in order to avoid mechanical and chemical disruption of cell membranes, cytoskeletal ultrastructure or receptor topography by homogenization or by the use of nonphysiological buffers, and to mimic in vivo binding conditions as much as possible. Using (/sup 3/H)naloxone as the radioligand, the studies showed saturable and stereospecific high-affinity binding of this opioid antagonist in intact cells, which in turn showed consistently high viability. (/sup 3/H)Naloxone binding was also linear over a wide range of tissue concentrations. This technique provides a very promising model for future studies of the binding of opioids and of many other classes of drugs to brain tissue receptors in a more physiologically relevant system than those commonly used to date.

  15. Ventral hippocampal kappa opioid receptors mediate the renewal of fear following extinction in the rat.

    Cole, Sindy; Richardson, Rick; McNally, Gavan P

    2013-01-01

    The hippocampus is part of a neural network which regulates the renewal of fear following extinction. Both the ventral (VH) and dorsal (DH) hippocampus have been shown to be necessary for renewal, however the critical receptors and neurotransmitters mediating these contributions are poorly understood. One candidate mechanism is the kappa opioid receptor (KOR) system, which has been implicated in fear learning and anxiety. Here we examined the effect of the KOR antagonist norbinaltorphamine hydrochloride (norBNI), infused into either the VH or DH, on the renewal of extinguished fear. We found that an infusion of norBNI into the VH significantly reduced the relapse of fear on test compared to that seen in saline controls (Experiment 1), while similar infusions of norBNI into the DH had no effect on renewal (Experiment 2). These findings show that hippocampal KORs are involved in fear renewal and also identify a dissociation in the contribution of VH and DH KORs to the expression of renewed fear. PMID:23675405

  16. Intact brain cells: a novel model system for studying opioid receptor binding

    The use of a novel tissue preparation to study opioid receptor binding in viable, intact cells derived from whole brains of adult rats is presented. Mechanically dissociated and sieved cells, which were not homogenized at any stage of the experimental protocol, and iso-osmotic physiological buffer were used in these experiments. This system was adapted in order to avoid mechanical and chemical disruption of cell membranes, cytoskeletal ultrastructure or receptor topography by homogenization or by the use of nonphysiological buffers, and to mimic in vivo binding conditions as much as possible. Using [3H]naloxone as the radioligand, the studies showed saturable and stereospecific high-affinity binding of this opioid antagonist in intact cells, which in turn showed consistently high viability. [3H]Naloxone binding was also linear over a wide range of tissue concentrations. This technique provides a very promising model for future studies of the binding of opioids and of many other classes of drugs to brain tissue receptors in a more physiologically relevant system than those commonly used to date

  17. The development of [18F]cyclofoxy as a ligand for imaging opioid receptors in the CNS of conscious humans

    Positron emission tomography (PET) is a unique, noninvasive technique applicable to real time visualization and quantitation of drug receptor occupancy in the brain of conscious humans. Such studies with the normal and abnormal human CNS can potentially provide insight into the biochemical basis of disease states and the effects of drug therapy. The (-)-enantiomer of cyclofoxy, a fluorinated, potent narcotic antagonist derived from naltrexone, has been developed at NIH as an agent for study of the opioid receptor-endorphin system using PET. The development and current status of this program is described, including application of the NIH Opiate Total Synthesis for production the pharmacologically inert (+)-[18F]cyclofoxy required for quantitation of receptor occupancy

  18. Reduced emotional and corticosterone responses to stress in μ-opioid receptor knockout mice

    Ide, Soichiro; Sora, Ichiro; Ikeda, Kazutaka; Minami, Masabumi; Uhl, George R; Ishihara, Kumatoshi

    2009-01-01

    The detailed mechanisms of emotional modulation in the nervous system by opioids remain to be elucidated, although the opioid system is well known to play important roles in the mechanisms of analgesia and drug dependence. In the present study, we conducted behavioral tests of anxiety and depression and measured corticosterone concentrations in both male and female μ-opioid receptor knockout (MOP-KO) mice to reveal the involvement of μ-opioid receptors in stress-induced emotional responses. M...

  19. A mu–delta opioid receptor brain atlas reveals neuronal co-occurrence in subcortical networks

    Erbs, Eric; Faget, Lauren; Scherrer, Gregory; Matifas, Audrey; Filliol, Dominique; Vonesch, Jean-Luc; Koch, Marc; Kessler, Pascal; Hentsch, Didier; Birling, Marie-Christine; Koutsourakis, Manoussos; Vasseur, Laurent; Veinante, Pierre; Kieffer, Brigitte L.; Massotte, Dominique

    2014-01-01

    Opioid receptors are G protein-coupled receptors (GPCRs) that modulate brain function at all levels of neural integration, including autonomic, sensory, emotional and cognitive processing. Mu (MOR) and delta (DOR) opioid receptors functionally interact in vivo, but whether interactions occur at circuitry, cellular or molecular levels remains unsolved. To challenge the hypothesis of MOR/DOR heteromerization in the brain, we generated redMOR/greenDOR double knock-in mice and report dual recepto...

  20. In vivo neuronal co-expression of mu and delta opioid receptors uncovers new therapeutic perspectives

    Erbs, Eric; Faget, Lauren; Veinante, Pierre; Kieffer, Brigitte L.; Massotte, Dominique

    2014-01-01

    Opioid receptors belong to the G protein coupled receptor family. They modulate brain function at all levels of neural integration and therefore impact on autonomous, sensory, emotional and cognitive processing. In vivo functional interaction between mu and delta opioid receptors are known to take place though it is still debated whether interactions occur at circuitry, cellular or molecular level. Also, the notion of receptor crosstalk via mu-delta heteromers is well documented in vitro but ...

  1. Inhibition of mu and delta opioid receptor ligand binding by the peptide aldehyde protease inhibitor, leupeptin.

    Christoffers, Keith H; Khokhar, Arshia; Chaturvedi, Kirti; Howells, Richard D

    2002-04-15

    We reported recently that the ubiquitin-proteasome pathway is involved in agonist-induced down regulation of mu and delta opioid receptors [J. Biol. Chem. 276 (2001) 12345]. While evaluating the effects of various protease inhibitors on agonist-induced opioid receptor down regulation, we observed that while the peptide aldehyde, leupeptin (acetyl-L-Leucyl-L-Leucyl-L-Arginal), did not affect agonist-induced down regulation, leupeptin at submillimolar concentrations directly inhibited radioligand binding to opioid receptors. In this study, the inhibitory activity of leupeptin on radioligand binding was characterized utilizing human embryonic kidney (HEK) 293 cell lines expressing transfected mu, delta, or kappa opioid receptors. The rank order of potency for leupeptin inhibition of [3H]bremazocine binding to opioid receptors was mu > delta > kappa. In contrast to the effect of leupeptin, the peptide aldehyde proteasome inhibitor, MG 132 (carbobenzoxy-L-Leucyl-L-Leucyl-L-Leucinal), had significantly less effect on bremazocine binding to mu, delta, or kappa opioid receptors. We propose that leupeptin inhibits ligand binding by reacting reversibly with essential sulfhydryl groups that are necessary for high-affinity ligand/receptor interactions. PMID:11853866

  2. Role of µ, κ, and δ opioid receptors in tibial inhibition of bladder overactivity in cats.

    Zhang, Zhaocun; Slater, Richard C; Ferroni, Matthew C; Kadow, Brian T; Lyon, Timothy D; Shen, Bing; Xiao, Zhiying; Wang, Jicheng; Kang, Audry; Roppolo, James R; de Groat, William C; Tai, Changfeng

    2015-11-01

    In α-chloralose anesthetized cats, we examined the role of opioid receptor (OR) subtypes (µ, κ, and δ) in tibial nerve stimulation (TNS)-induced inhibition of bladder overactivity elicited by intravesical infusion of 0.25% acetic acid (AA). The sensitivity of TNS inhibition to cumulative i.v. doses of selective OR antagonists (cyprodime for µ, nor-binaltorphimine for κ, or naltrindole for δ ORs) was tested. Naloxone (1 mg/kg, i.v., an antagonist for µ, κ, and δ ORs) was administered at the end of each experiment. AA caused bladder overactivity and significantly (P < 0.01) reduced bladder capacity to 21.1% ± 2.6% of the saline control. TNS at 2 or 4 times threshold (T) intensity for inducing toe movement significantly (P < 0.01) restored bladder capacity to 52.9% ± 3.6% or 57.4% ± 4.6% of control, respectively. Cyprodime (0.3-1.0 mg/kg) completely removed TNS inhibition without changing AA control capacity. Nor-binaltorphimine (3-10 mg/kg) also completely reversed TNS inhibition and significantly (P < 0.05) increased AA control capacity. Naltrindole (1-10 mg/kg) reduced (P < 0.05) TNS inhibition but significantly (P < 0.05) increased AA control capacity. Naloxone (1 mg/kg) had no effect in cyprodime pretreated cats, but it reversed the nor-binaltorphimine-induced increase in bladder capacity and eliminated the TNS inhibition remaining in naltrindole pretreated cats. These results indicate a major role of µ and κ ORs in TNS inhibition, whereas δ ORs play a minor role. Meanwhile, κ and δ ORs also have an excitatory role in irritation-induced bladder overactivity. PMID:26354994

  3. Early-Life Social Isolation Stress Increases Kappa Opioid Receptor Responsiveness and Downregulates the Dopamine System.

    Karkhanis, Anushree N; Rose, Jamie H; Weiner, Jeffrey L; Jones, Sara R

    2016-08-01

    Chronic early-life stress increases vulnerability to alcoholism and anxiety disorders during adulthood. Similarly, rats reared in social isolation (SI) during adolescence exhibit augmented ethanol intake and anxiety-like behaviors compared with group housed (GH) rats. Prior studies suggest that disruption of dopamine (DA) signaling contributes to SI-associated behaviors, although the mechanisms underlying these alterations are not fully understood. Kappa opioid receptors (KORs) have an important role in regulating mesolimbic DA signaling, and other kinds of stressors have been shown to augment KOR function. Therefore, we tested the hypothesis that SI-induced increases in KOR function contribute to the dysregulation of NAc DA and the escalation in ethanol intake associated with SI. Our ex vivo voltammetry experiments showed that the inhibitory effects of the kappa agonist U50,488 on DA release were significantly enhanced in the NAc core and shell of SI rats. Dynorphin levels in NAc tissue were observed to be lower in SI rats. Microdialysis in freely moving rats revealed that SI was also associated with reduced baseline DA levels, and pretreatment with the KOR antagonist nor-binaltorphimine (nor-BNI) increased DA levels selectively in SI subjects. Acute ethanol elevated DA in SI and GH rats and nor-BNI pretreatment augmented this effect in SI subjects, while having no effect on ethanol-stimulated DA release in GH rats. Together, these data suggest that KORs may have increased responsiveness following SI, which could lead to hypodopaminergia and contribute to an increased drive to consume ethanol. Indeed, SI rats exhibited greater ethanol intake and preference and KOR blockade selectively attenuated ethanol intake in SI rats. Collectively, the findings that nor-BNI reversed SI-mediated hypodopaminergic state and escalated ethanol intake suggest that KOR antagonists may represent a promising therapeutic strategy for the treatment of alcohol use disorders, particularly

  4. The kappa opioid receptor: from addiction to depression, and back

    Laurence eLalanne

    2014-12-01

    Full Text Available Comorbidity is a major issue in psychiatry that notably associates with more severe symptoms, longer illness duration and higher service utilization. Therefore, identifying key clusters of comorbidity and exploring the underlying pathophysiological mechanisms represent important steps towards improving mental health care. In the present review, we focus on the frequent association between addiction and depression. In particular, we summarize the large body of evidence from preclinical models indicating that the kappa opioid receptor (KOR, a member of the opioid neuromodulatory system, represents a central player in the regulation of both reward and mood processes. Current data suggest that the KOR modulates overlapping neuronal networks linking brainstem monoaminergic nuclei with forebrain limbic structures. Rewarding properties of both drugs of abuse and natural stimuli, as well as the neurobiological effects of stressful experiences, strongly interact at the level of KOR signalling. In addiction models, activity of the KOR is potentiated by stressors and critically controls drug-seeking and relapse. In depression paradigms, KOR signalling is responsive to a variety of stressors, and mediates despair-like responses. Altogether, the KOR represents a prototypical substrate of comorbidity, whereby life experiences converge upon common brain mechanisms to trigger behavioural dysregulation and increased risk for distinct but interacting psychopathologies.

  5. Binding-site analysis of opioid receptors using monoclonal anti-idiotypic antibodies

    Structural relatedness between the variable region of anti-ligand antibodies and opioid binding sites allowed the generation of anti-idiotypic antibodies which recognized opioid receptors. The IgG3k antibodies which bound to opioid receptors were obtained when an anti-morphine antiserum was the idiotype. Both antibodies bound to opioid receptors, but only one of these blocked the binding of [3H]naloxone. The antibody which did not inhibit the binding of [3H]naloxone was itself displaced from the receptor by opioid ligands. The unique binding properties displayed by this antibody indicated that anti-idiotypic antibodies are not always a perfect image of the original ligand, and therefore may be more useful than typical ligands as probes for the receptor. An auto-anti-idiotypic technique was successfully used to obtain anti-opioid receptor antibodies. Another IgG3k antibody that blocked the binding of [3H]naloxone to rat brain opioid receptors was obtained when a mouse was immunized with naloxone conjugated to bovine serum albumin. These data confirmed that an idiotype-anti-idiotype network which can generate an anti-receptor antibody normally functions when an opioid ligand is introduced into an animal in an immunogenic form

  6. Effects of imipramine treatment on delta-opioid receptors of the rat brain cortex and striatum.

    Varona, Adolfo; Gil, Javier; Saracibar, Gonzalo; Maza, Jose Luis; Echevarria, Enrique; Irazusta, Jon

    2003-01-01

    Imipramine (CAS 113-52-0) is being utilized widely for the treatment of major depression. In recent years, there has been evidence of the involvement of the endogenous opioid system in major depression and its treatment. There is some evidence indicating that opioid receptors could be involved in the antidepressant mechanism of action. Regarding this topic, mood-related behavior of endogenous enkephalins seems to be mediated by delta-opioid receptors. In this work, the effects of subacute (5 day) and chronic (15 day) treatments of imipramine on the density and the affinity of the delta-receptors in the striatum and in the parietal and frontal cortices of the rat brain are described. Studied parameters (Bmax and Kd) were calculated by a saturation binding assay with the delta-opioid agonists [3H]-DPDPE (tyrosyl-2,6-3H(N)-(2-D-penicillamine-5-D-penicillamine)-enkephalin) as specific ligand and DSLET ([D-serine2]-D-leucine-enkephalin-threonine) as non-radioactive competing ligand. It was found that 15 days treatment significantly decreased the delta-opioid receptor density,without changing the affinity, in the frontal cortex of the rat brain. That decrease was confirmed by delta-opioid receptor immunostaining. These results suggest that delta-opioid receptors could play a role in the chronic action mechanism of imipramine. PMID:12608010

  7. Binding-site analysis of opioid receptors using monoclonal anti-idiotypic antibodies

    Conroy, W.G.

    1988-01-01

    Structural relatedness between the variable region of anti-ligand antibodies and opioid binding sites allowed the generation of anti-idiotypic antibodies which recognized opioid receptors. The IgG{sub 3}k antibodies which bound to opioid receptors were obtained when an anti-morphine antiserum was the idiotype. Both antibodies bound to opioid receptors, but only one of these blocked the binding of ({sup 3}H)naloxone. The antibody which did not inhibit the binding of ({sup 3}H)naloxone was itself displaced from the receptor by opioid ligands. The unique binding properties displayed by this antibody indicated that anti-idiotypic antibodies are not always a perfect image of the original ligand, and therefore may be more useful than typical ligands as probes for the receptor. An auto-anti-idiotypic technique was successfully used to obtain anti-opioid receptor antibodies. Another IgG{sub 3}k antibody that blocked the binding of ({sup 3}H)naloxone to rat brain opioid receptors was obtained when a mouse was immunized with naloxone conjugated to bovine serum albumin. These data confirmed that an idiotype-anti-idiotype network which can generate an anti-receptor antibody normally functions when an opioid ligand is introduced into an animal in an immunogenic form.

  8. Mediation of buprenorphine analgesia by a combination of traditional and truncated mu opioid receptor splice variants.

    Grinnell, Steven G; Ansonoff, Michael; Marrone, Gina F; Lu, Zhigang; Narayan, Ankita; Xu, Jin; Rossi, Grace; Majumdar, Susruta; Pan, Ying-Xian; Bassoni, Daniel L; Pintar, John; Pasternak, Gavril W

    2016-10-01

    Buprenorphine has long been classified as a mu analgesic, although its high affinity for other opioid receptor classes and the orphanin FQ/nociceptin ORL1 receptor may contribute to its other actions. The current studies confirmed a mu mechanism for buprenorphine analgesia, implicating several subsets of mu receptor splice variants. Buprenorphine analgesia depended on the expression of both exon 1-associated traditional full length 7 transmembrane (7TM) and exon 11-associated truncated 6 transmembrane (6TM) MOR-1 variants. In genetic models, disruption of delta, kappa1 or ORL1 receptors had no impact on buprenorphine analgesia, while loss of the traditional 7TM MOR-1 variants in an exon 1 knockout (KO) mouse markedly lowered buprenorphine analgesia. Loss of the truncated 6TM variants in an exon 11 KO mouse totally eliminated buprenorphine analgesia. In distinction to analgesia, the inhibition of gastrointestinal transit and stimulation of locomotor activity were independent of truncated 6TM variants. Restoring expression of a 6TM variant with a lentivirus rescued buprenorphine analgesia in an exon 11 KO mouse that still expressed the 7TM variants. Despite a potent and robust stimulation of (35) S-GTPγS binding in MOR-1 expressing CHO cells, buprenorphine failed to recruit β-arrestin-2 binding at doses as high as 10 µM. Buprenorphine was an antagonist in DOR-1 expressing cells and an inverse agonist in KOR-1 cells. Buprenorphine analgesia is complex and requires multiple mu receptor splice variant classes but other actions may involve alternative receptors. PMID:27223691

  9. Androgen receptor transcriptionally regulates μ-opioid receptor expression in rat trigeminal ganglia.

    Lee, Ki Seok; Zhang, Youping; Asgar, Jamila; Auh, Q-Schick; Chung, Man-Kyo; Ro, Jin Y

    2016-09-01

    The involvement of testosterone in pain, inflammation, and analgesia has been reported, but the role of androgen receptor (AR), a steroid receptor for testosterone, is not well understood. We have previously shown that peripheral inflammation upregulates μ-opioid receptor (MOR) in rat trigeminal ganglia (TG) in a testosterone-dependent manner. In this study, we hypothesized that testosterone regulates MOR expression via transcriptional activities of AR in TG. We first examined whether AR is co-expressed with MOR in TG neurons. Our immunohistochemical experiment revealed that AR staining is detected in neurons of all sizes in TG and that a subset of AR is expressed in MOR as well as in TRPV1-positive neurons. We identified the promoter region of the rat MOR gene contains putative AR binding sites. Using chromatin immunoprecipitation assay, we demonstrated that AR directly binds to these sites in TG extracts. We confirmed with luciferase reporter assay that AR activated the MOR promoter in response to androgens in a human neuroblastoma cell line (5H-5YSY). These data demonstrated that AR functions as a transcriptional regulator of the MOR gene activity. Finally, we showed that flutamide, a specific AR antagonist, prevents complete Freund's adjuvant (CFA)-induced upregulation of MOR mRNA in TG, and that flutamide dose-dependently blocks the efficacy of DAMGO, a specific MOR agonist, on CFA-induced mechanical hypersensitivity. Our results expand the knowledge regarding the role of androgens and their receptor in pain and analgesia and have important clinical implications, particularly for inflammatory pain patients with low or compromised plasma testosterone levels. PMID:27320211

  10. Activation and Allosteric Modulation of Human μ Opioid Receptor in Molecular Dynamics.

    Bartuzi, Damian; Kaczor, Agnieszka A; Matosiuk, Dariusz

    2015-11-23

    Allosteric protein modulation has gained increasing attention in drug design. Its application as a mechanism of action could bring forth safer and more effective medicines. Targeting opioid receptors with allosteric modulators can result in better treatment of pain, depression, and respiratory and immune disorders. In this work we use recent reports on negative modulators of μ opioid receptor as a starting point for identification of allosteric sites and mechanisms of opioid receptor modulation using homology modeling and docking and molecular dynamics studies. An allosteric binding site description is presented. Results suggest a shared binding region for lipophilic allosteric ligands, reveal possible differences in the modulation mechanism between cannabinoids and salvinorin A, and show ambiguous properties of the latter. Also, they emphasize the importance of native-like environment in molecular dynamics simulations and uncover relationships between modulator and orthosteric ligand binding and receptor behavior. Relationships between ligands, transmission switch, and hydrophobic lock are analyzed. PMID:26517559

  11. Involvement of δ-and μ-opioid receptors in the delayed cerebral ischemic tolerance induced by repeated electroacupuncture preconditioning in rats

    XIONG Li-ze; YANG Jing; WANG Qiang; LU Zhi-hong

    2007-01-01

    Background Preconditioning with repeated electroacupuncture (EA) could mimic ischemic preconditioning to induce cerebral ischemic tolerance in rats. The present study was designed to investigate whether mu(μ)-, delta(δ)- or kappa(κ)-opioid receptors are involved in the neuroprotection induced by repeated EA preconditioning.Methods The rats were pretreated with naltrindole (NTI), nor-binaltorphimine (nor-BNI) or D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH2 (CTOP), which is a highly selective δ-, κ- or μ-opioid receptor antagonist respectively, before each EA preconditioning (30 minutes per day, 5 days). Twenty-four hours after the last EA treatment, the middle cerebral artery occlusion (MCAO) was induced for 120 minutes. The brain infarct volume was determined with 2,3,5-triphenyltetrazolium chloride staining at 24 hours after MCAO and compared with that in rats which only received EA preconditioning. In another experiment, the met-enkephalin-like immunoreactivity in rat brain was investigated by immunohistochemistry in both EA preconditioning and control rats.Results The EA preconditioning reduced brain infarct volume compared with the control rats (P=0.000). Administration of both NTI and CTOP attenuated the brain infarct volume reduction induced by EA preconditioning, presenting with larger infarct volume than that in the EA preconditioning rats (P<0.001). But nor-BNI administration did not block the infarct volume reduction induced by EA preconditioning, presenting with smaller infarct volume than the control group rats(P=0.000). The number of met-enkephalin-like immunoreactivity positive neurons in the EA preconditioning rats was more than that of the control rats (P=0.000).Conclusion Repeated EA preconditioning stimulates the release of enkephalins, which may bind δ- and μ-opioid receptors to induce the tolerance against focal cerebral ischemia.

  12. Kinetic analysis of transport and opioid receptor binding of [3H](-)-cyclofoxy in rat brain in vivo: Implications for human studies

    [3H]Cyclofoxy (CF: 17-cyclopropylmethyl-3,14-dihydroxy-4,5-alpha-epoxy-6-beta-fluoromorp hinan) is an opioid antagonist with affinity to both mu and kappa subtypes that was synthesized for quantitative evaluation of opioid receptor binding in vivo. Two sets of experiments in rats were analyzed. The first involved determining the metabolite-corrected blood concentration and tissue distribution of CF in brain 1 to 60 min after i.v. bolus injection. The second involved measuring brain washout for 15 to 120 s following intracarotid artery injection of CF. A physiologically based model and a classical compartmental pharmacokinetic model were compared. The models included different assumptions for transport across the blood-brain barrier (BBB); estimates of nonspecific tissue binding and specific binding to a single opiate receptor site were found to be essentially the same with both models. The nonspecific binding equilibrium constant varied modestly in different brain structures (Keq = 3-9), whereas the binding potential (BP) varied over a much broader range (BP = 0.6-32). In vivo estimates of the opioid receptor dissociation constant were similar for different brain structures (KD = 2.1-5.2 nM), whereas the apparent receptor density (Bmax) varied between 1 (cerebellum) and 78 (thalamus) pmol/g of brain. The receptor dissociation rate constants in cerebrum (k4 = 0.08-0.16 min-1; koff = 0.16-0.23 min-1) and brain vascular permeability (PS = 1.3-3.4 ml/min/g) are sufficiently high to achieve equilibrium conditions within a reasonable period of time. Graphical analysis of the data is inappropriate due to the high tissue-loss rate constant for CF in brain. From these findings, CF should be a very useful opioid receptor ligand for the estimation of the receptor binding parameters in human subjects using [18F]CF and positron emission tomography

  13. Effects of DPDPE (a specific delta-opioid receptor agonist) and naloxone on hypothalamic monoamine concentrations during the pre-ovulatory LH surge in the rat.

    Yilmaz, B; Gilmore, D P; Wilson, C A

    1998-11-01

    We have investigated the inter-relationship between the opioid and aminergic systems in the control of secretion of the pro-oestrous LH surge and the involvement of delta-opioid receptor subtypes in this process. Conscious female rats bearing a cannula in the femoral artery were injected i.p. with a selective delta-opioid receptor agonist (DPDPE) either alone or with the opioid antagonist (naloxone) at 1300 h on the day of pro-oestrus. Blood samples were collected hourly between 1500 h and 1900 h, and plasma LH levels were measured by RIA. At the end of this period (1900 h), the animals were autopsied and the concentrations of the amines (noradrenaline (NA), dopamine (DA), 5-hydroxytryptamine (5HT)) and their metabolites (dihydroxyphenolglycol (DHPG) and 5-hydroxyindoleacetic acid (5HIAA), metabolites of NA and 5HT respectively) were determined by HPLC with electrochemical detection in the medial preoptic area, suprachiasmatic nucleus, median eminence and arcuate nucleus. DPDPE abolished the LH surge and concomitantly decreased hypothalamic NA and DHPG concentrations in all the areas examined. The levels of DA, 5HT and 5HIAA were also reduced in all hypothalamic regions studied, except DA and 5HIAA in the suprachiasmatic nucleus. Naloxone reversed these inhibitory effects of the delta-agonist. We conclude that activation of delta-opioid receptors may exert an inhibitory effect on LH release. The effect is probably an indirect one mediated by the monoaminergic systems, as they are suppressed by DPDPE in nearly all the hypothalamic regions studied. PMID:9849821

  14. Identification of kappa opioid receptors in the immune system by indirect immunofluorescence.

    Lawrence, D M; el-Hamouly, W; Archer, S; Leary, J F; Bidlack, J M

    1995-01-01

    A method to visualize the kappa opioid receptor is described that uses a high-affinity fluorescein-conjugated opioid ligand and indirect immunofluorescence with the phycoerythrin fluorophore to amplify the signal. The mouse thymoma cell line R1E/TL8x.1.G1.OUAr.1 (R1EGO), which expresses the kappa 1 but not mu or delta opioid receptors, was used as a positive control for fluorescence labeling. A fluorescein isothiocyanate-conjugated arylacetamide (FITC-AA) compound displaying high affinity for...

  15. Motivational effects of cannabinoids are mediated by ??-opioid and k-opioid receptor

    Ghozland, Sandy; Matthes, Hans W.D.; Simonin, Frederic; Filliol, Dominique; Kieffer, Brigitte L.; Maldonado, Rafael

    2002-01-01

    Repeated THC administration produces motivational and somatic adaptive changes leading to dependence in rodents. To investigate the molecular basis for cannabinoid dependence and its possible relationship with the endogenous opioid system, we explored ??9-tetrahydrocannabinol (THC) activity in mice lacking ??-, ??- or ??-opioid receptor genes. Acute THCinduced hypothermia, antinociception, and ypolocomotion remained unaffected in these mice, whereas THC tolerance and withdrawal...

  16. A Facile Synthesis for Novel Loperamide Analogs as Potential μ Opioid Receptor Agonists

    Xiaofeng Bao

    2012-12-01

    Full Text Available A facile synthesis for novel loperamide analogs as potential μ opioid receptors is described. The synthetic procedure for compound 5, which contains two 4-phenyl piperidine scaffolds, was optimized, and this compound was synthesized in excellent yield. We also describe a mild and highly efficient protocol for the synthesis of compounds 6 and 7.

  17. Berberine Improves Intestinal Motility and Visceral Pain in the Mouse Models Mimicking Diarrhea-Predominant Irritable Bowel Syndrome (IBS-D Symptoms in an Opioid-Receptor Dependent Manner.

    Chunqiu Chen

    Full Text Available Berberine and its derivatives display potent analgesic, anti-inflammatory and anticancer activity. Here we aimed at characterizing the mechanism of action of berberine in the gastrointestinal (GI tract and cortical neurons using animal models and in vitro tests.The effect of berberine was characterized in murine models mimicking diarrhea-predominant irritable bowel syndrome (IBS-D symptoms. Then the opioid antagonists were used to identify the receptors involved. Furthermore, the effect of berberineon opioid receptors expression was established in the mouse intestine and rat fetal cortical neurons.In mouse models, berberine prolonged GI transit and time to diarrhea in a dose-dependent manner, and significantly reduced visceral pain. In physiological conditions the effects of berberine were mediated by mu- (MOR and delta- (DOR opioid receptors; hypermotility, excessive secretion and nociception were reversed by berberine through MOR and DOR-dependent action. We also found that berberine increased the expression of MOR and DOR in the mouse bowel and rat fetal cortical neurons.Berberine significantly improved IBS-D symptoms in animal models, possibly through mu- and delta- opioid receptors. Berberine may become a new drug candidate for the successful treatment of IBS-D in clinical conditions.

  18. The non-peptidic delta opioid receptor agonist TAN-67 enhances dopamine efflux in the nucleus accumbens of freely moving rats via a mechanism that involves both glutamate and free radicals.

    Fusa, K.; Takahashi, I.; Watanabe, S.; Aono, Y.; Ikeda, H.; Saigusa, T.; Nagase, H.; Suzuki, T.; Koshikawa, N.; Cools, A.R.

    2005-01-01

    The activation of the delta-opioid receptors in the nucleus accumbens is known to induce a large and rapid increase of accumbal dopamine efflux. (+/-)-TAN-67 (2-methyl-4a(alpha)-(3-hydroxyphenyl)-1,2,3,4,4a,5,12,12a(alpha)-octahydro -quinolino[2,3,3,-g]isoquinoline) is a centrally acting non-peptidi

  19. Effect of Iboga alkaloids on µ-opioid receptor-coupled G protein activation.

    Tamara Antonio

    Full Text Available OBJECTIVE: The iboga alkaloids are a class of small molecules defined structurally on the basis of a common ibogamine skeleton, some of which modify opioid withdrawal and drug self-administration in humans and preclinical models. These compounds may represent an innovative approach to neurobiological investigation and development of addiction pharmacotherapy. In particular, the use of the prototypic iboga alkaloid ibogaine for opioid detoxification in humans raises the question of whether its effect is mediated by an opioid agonist action, or if it represents alternative and possibly novel mechanism of action. The aim of this study was to independently replicate and extend evidence regarding the activation of μ-opioid receptor (MOR-related G proteins by iboga alkaloids. METHODS: Ibogaine, its major metabolite noribogaine, and 18-methoxycoronaridine (18-MC, a synthetic congener, were evaluated by agonist-stimulated guanosine-5´-O-(γ-thio-triphosphate ([(35S]GTPγS binding in cells overexpressing the recombinant MOR, in rat thalamic membranes, and autoradiography in rat brain slices. RESULTS AND SIGNIFICANCE: In rat thalamic membranes ibogaine, noribogaine and 18-MC were MOR antagonists with functional Ke values ranging from 3 uM (ibogaine to 13 uM (noribogaine and 18MC. Noribogaine and 18-MC did not stimulate [(35S]GTPγS binding in Chinese hamster ovary cells expressing human or rat MORs, and had only limited partial agonist effects in human embryonic kidney cells expressing mouse MORs. Ibogaine did not did not stimulate [(35S]GTPγS binding in any MOR expressing cells. Noribogaine did not stimulate [(35S]GTPγS binding in brain slices using autoradiography. An MOR agonist action does not appear to account for the effect of these iboga alkaloids on opioid withdrawal. Taken together with existing evidence that their mechanism of action also differs from that of other non-opioids with clinical effects on opioid tolerance and withdrawal, these

  20. Effects of acute and chronic social defeat stress are differentially mediated by the dynorphin/kappa-opioid receptor system.

    Donahue, Rachel J; Landino, Samantha M; Golden, Sam A; Carroll, F Ivy; Russo, Scott J; Carlezon, William A

    2015-10-01

    Accumulating evidence indicates that kappa-opioid receptors (KORs) and their endogenous ligand, dynorphin (DYN), can play important roles in regulating the effects of stress. Here, we examined the role of KOR systems in the molecular and behavioral effects of acute (1-day) and chronic (10-day) social defeat stress (SDS) in mice. We found that acute SDS increased DYN mRNA levels within the nucleus accumbens, a key element of brain dopamine (DA) systems. In contrast, chronic SDS produced long-lasting decreases in DYN mRNA levels. We then examined whether disruption of KOR function would affect development of SDS-induced depressive-like behaviors, as measured in the intracranial self-stimulation and social interaction tests. Ablation of KORs from DA transporter-expressing neurons delayed the development of SDS-induced anhedonia in the intracranial self-stimulation test, suggesting increased stress resilience. However, administration of the long-lasting KOR antagonist JDTic (30 mg/kg, intraperitoneally) before the SDS regimen did not affect anhedonia, suggesting that disruption of KOR function outside DA systems can oppose stress resilience. Social avoidance behavior measured after the 10-day SDS regimen was not altered by ablation of KORs in DA transporter-expressing neurons or by JDTic administration before testing. Our findings indicate that KORs expressed in DA systems regulate the effects of acute, but not chronic, social stress. PMID:26110224

  1. Anti-analgesic effect of the mu/delta opioid receptor heteromer revealed by ligand-biased antagonism.

    Laura Milan-Lobo

    Full Text Available Delta (DOR and mu opioid receptors (MOR can complex as heteromers, conferring functional properties in agonist binding, signaling and trafficking that can differ markedly from their homomeric counterparts. Because of these differences, DOR/MOR heteromers may be a novel therapeutic target in the treatment of pain. However, there are currently no ligands selective for DOR/MOR heteromers, and, consequently, their role in nociception remains unknown. In this study, we used a pharmacological opioid cocktail that selectively activates and stabilizes the DOR/MOR heteromer at the cell surface by blocking its endocytosis to assess its role in antinociception. We found that mice treated chronically with this drug cocktail showed a significant right shift in the ED50 for opioid-mediated analgesia, while mice treated with a drug that promotes degradation of the heteromer did not. Furthermore, promoting degradation of the DOR/MOR heteromer after the right shift in the ED50 had occurred, or blocking signal transduction from the stabilized DOR/MOR heteromer, shifted the ED50 for analgesia back to the left. Taken together, these data suggest an anti-analgesic role for the DOR/MOR heteromer in pain. In conclusion, antagonists selective for DOR/MOR heteromer could provide an avenue for alleviating reduced analgesic response during chronic pain treatment.

  2. Role of lateral parabrachial opioid receptors in exercise-induced modulation of the hypotensive hemorrhage response in conscious male rats.

    Ahlgren, Joslyn K; Hayward, Linda F

    2012-01-15

    Some of the benefits of exercise appear to be mediated through modulation of neuronal excitability in central autonomic control circuits. Previously, we identified that six weeks of voluntary wheel running had a protective effect during hemorrhage (HEM), limiting both the hypotensive phase of HEM and enhancing recovery. The present study was undertaken to evaluate the role of opioid release in the lateral parabrachial nucleus (LPBN) on the response to severe HEM in chronically exercised (EX, voluntary) versus sedentary (SED) controls. Male Sprague Dawley rats were allowed either free access to running wheels (EX) or normal cage conditions (SED). After 6 weeks of "training" animals were instrumented with a bilateral cannula directed toward the dorsolateral pons and arterial catheters. After a recovery period, animals underwent central microinjection of either vehicle (VEH; n=3/group) or the opioid receptor antagonist naloxone (NAL; n=6/group) followed by withdrawal of 30% of their total estimated blood volume. Following VEH injection, the drop in MAP during and following HEM was significantly attenuated in the EX vs SED animals. Alternatively, NAL microinjection in the dorsolateral pons (20 μM, 200-500 nl) reversed the beneficial effect of EX on the HEM response. NAL microinjection in SED rats did not significantly alter the response to HEM. These data suggest chronic voluntary EX has a beneficial effect on the autonomic response to severe HEM which is mediated, in part, via EX-induced plasticity of the opioid system within the dorsolateral pons. PMID:21985861

  3. CRITICAL ROLE OF NMDA BUT NOT OPIOID RECEPTORS IN THE ACQUISITION OF FAT-CONDITIONED FLAVOR PREFERENCES IN RATS

    Cruz, J.A.D. Dela; Bae, V.S.; Icaza-Cukali, D.; Sampson, C.; Bamshad, D.; Samra, A.; Singh, S.; Khalifa, N.; Touzani, K.; Sclafani, A.; Bodnar, R.J.

    2012-01-01

    -CFP. These data suggest a critical role for NMDA, but not opioid receptor signaling in the acquisition of a fat conditioned flavor preferences, and at best limited involvement of NMDA and opioid receptors in the expression of a previously learned preference. PMID:23103774

  4. Blocking opioid receptors alters short-term feed intake and oro-sensorial preferences in weaned calves.

    Montoro, C; Ipharraguerre, I R; Bach, A

    2012-05-01

    Opioid peptides may participate in the control of feed intake through mechanisms involving pleasure reward linked to consumption of palatable feed. The objective of this study was to determine whether blocking opioid receptors might void oro-sensorial preferences of calves, and affect circulating glucose, insulin, and anorexigenic hormones in fasted and fed calves. Two experiments involved 32 Holstein calves [body weight (BW)=86.5±1.73 kg, age=72±0.6 d]. In experiment 1, all calves received an ad libitum choice of the same feed either unflavored or flavored with a sweetener (Luctarom SFS-R, Lucta, Montornès del Vallès, Spain). Feed consumption was recorded every 2 h from 0800 to 1400 h for 3 consecutive days to verify the establishment of an oro-sensorial preference for sweet feed (SF). The SF was preferred over the control feed (CF) at all recorded times. In experiment 2, calves were subjected to a 2 × 2 factorial design to study the interaction between opioid activity and metabolic state. Half of the calves were fasted for 14 h (FAS), whereas the other half remained well fed (FED). Within each of these groups, at feeding time (0800 h), half of the calves received an i.v. injection of naloxone (NAL, an opioid receptor antagonist; 1 mg/kg of BW) and the other half was injected with saline solution (SAL; 0.9% NaCl). Therefore, treatments were FED-NAL, FED-SAL, FAS-NAL, and FAS-SAL. Blood samples were taken at -10, 20, 180, and 240 min relative to NAL or SAL injections. As expected, cumulative consumption of starter feed was greater in FAS than in FED calves. Total feed consumption 2 h after feeding was lower in NAL than in SAL calves. Calves in the FAS group did not discern between CF and SF during the first 4 h after feed offer. Preference for SF was greater in SAL than in NAL calves. Calves in the FED-SAL treatment preferred SF at 2 and 6 h after feed offer and tended to prefer SF at 4 h after feeding. However, FED-NAL calves did not discern between SF and CF

  5. Orphanin FQ in the mediobasal hypothalamus facilitates sexual receptivity through the deactivation of medial preoptic nucleus mu-opioid receptors

    Sanathara, Nayna M.; Moraes, Justine; Kanjiya, Shrey; Sinchak, Kevin

    2011-01-01

    Sexual receptivity, lordosis, can be induced by sequential estradiol and progesterone or extended exposure to high levels of estradiol in the female rat. In both cases estradiol initially inhibits lordosis through activation of β-endorphin (β-END) neurons of the arcuate nucleus of the hypothalamus (ARH) that activate μ-opioid receptors (MOP) in the medial preoptic nucleus (MPN). Subsequent progesterone or extended estradiol exposure deactivate MPN MOP to facilitate lordosis. Opioid receptor-l...

  6. Bidirectional effects of fentanyl on dendritic spines and AMPA receptors depend upon the internalization of mu opioid receptors

    Lin, Hang; Higgins, Paul; Loh, Horace H.; Law, Ping-Yee; Liao, Dezhi

    2009-01-01

    Fentanyl is a frequently used and abused opioid analgesic and can cause internalization of mu opioid receptors (MORs). Receptor internalization modulates the signaling pathways of opioid receptors. Because changes in dendritic spines and synaptic AMPA receptors play important roles in addiction and memory loss, we investigated how fentanyl affects dendritic spines and synaptic AMPA receptors in cultured hippocampal neurons. Fentanyl at low concentrations (0.01 and 0.1 µM) caused collapse of d...

  7. Micro-opioid receptor activation in the basolateral amygdala mediates the learning of increases but not decreases in the incentive value of a food reward.

    Wassum, Kate M; Cely, Ingrid C; Balleine, Bernard W; Maidment, Nigel T

    2011-02-01

    The decision to perform, or not perform, actions known to lead to a rewarding outcome is strongly influenced by the current incentive value of the reward. Incentive value is largely determined by the affective experience derived during previous consumption of the reward-the process of incentive learning. We trained rats on a two-lever, seeking-taking chain paradigm for sucrose reward, in which responding on the initial seeking lever of the chain was demonstrably controlled by the incentive value of the reward. We found that infusion of the μ-opioid receptor antagonist, CTOP (d-Phe-Cys-Tyr-d-Trp-Orn-Thr-Pen-Thr-NH(2)), into the basolateral amygdala (BLA) during posttraining, noncontingent consumption of sucrose in a novel elevated-hunger state (a positive incentive learning opportunity) blocked the encoding of incentive value information normally used to increase subsequent sucrose-seeking responses. Similar treatment with δ [N, N-diallyl-Tyr-Aib-Aib-Phe-Leu-OH (ICI 174,864)] or κ [5'-guanidinonaltrindole (GNTI)] antagonists was without effect. Interestingly, none of these drugs affected the ability of the rats to encode a decrease in incentive value resulting from experiencing the sucrose in a novel reduced-hunger state. However, the μ agonist, DAMGO ([d-Ala2, NMe-Phe4, Gly5-ol]-enkephalin), appeared to attenuate this negative incentive learning. These data suggest that upshifts and downshifts in endogenous opioid transmission in the BLA mediate the encoding of positive and negative shifts in incentive value, respectively, through actions at μ-opioid receptors, and provide insight into a mechanism through which opiates may elicit inappropriate desire resulting in their continued intake in the face of diminishing affective experience. PMID:21289167

  8. Interaction and regulatory functions of μ- and δ-opioid receptors in nociceptive afferent neurons

    Xu Zhang; Lan Bao

    2012-01-01

    μ-opioid receptor (MOR) agonists such as morphine are powerful analgesics used for pain therapy.However,the use of these drugs is limited by their side-effects,which include antinociceptive tolerance and dependence.Earlier studies reported that MOR analgesic tolerance is reduced by blockade of δ-opioid receptors (DORs) that interact with MORs.Recent studies show that the MOR/DOR interaction in nociceptive afferent neurons in the dorsal root ganglion may contribute to morphine analgesic tolerance.Further analysis of the mechanisms for regulating the trafficking of receptors,ion channels and signaling molecules in nociceptive afferent neurons would help to understand the nociceptive mechanisms and improve pain therapy.

  9. Delta opioid receptors presynaptically regulate cutaneous mechanosensory neuron input to the spinal cord dorsal horn.

    Bardoni, Rita; Tawfik, Vivianne L; Wang, Dong; François, Amaury; Solorzano, Carlos; Shuster, Scott A; Choudhury, Papiya; Betelli, Chiara; Cassidy, Colleen; Smith, Kristen; de Nooij, Joriene C; Mennicken, Françoise; O'Donnell, Dajan; Kieffer, Brigitte L; Woodbury, C Jeffrey; Basbaum, Allan I; MacDermott, Amy B; Scherrer, Grégory

    2014-03-19

    Cutaneous mechanosensory neurons detect mechanical stimuli that generate touch and pain sensation. Although opioids are generally associated only with the control of pain, here we report that the opioid system in fact broadly regulates cutaneous mechanosensation, including touch. This function is predominantly subserved by the delta opioid receptor (DOR), which is expressed by myelinated mechanoreceptors that form Meissner corpuscles, Merkel cell-neurite complexes, and circumferential hair follicle endings. These afferents also include a small population of CGRP-expressing myelinated nociceptors that we now identify as the somatosensory neurons that coexpress mu and delta opioid receptors. We further demonstrate that DOR activation at the central terminals of myelinated mechanoreceptors depresses synaptic input to the spinal dorsal horn, via the inhibition of voltage-gated calcium channels. Collectively our results uncover a molecular mechanism by which opioids modulate cutaneous mechanosensation and provide a rationale for targeting DOR to alleviate injury-induced mechanical hypersensitivity. PMID:24583022

  10. Dual Labeled Peptides as Tools to Study Receptors: Nanomolar Affinity Derivatives of TIPP (Tyr-Tic-Phe-Phe) Containing an Affinity Label and Biotin as Probes of δ Opioid Receptors

    Aldrich, Jane V.; Kumar, Vivek; Murray, Thomas F.; Guang, Wei; Wang, Jia Bei

    2009-01-01

    A general strategy for the design of dual labeled peptides was developed and derivatives of the δ opioid receptor (DOR) selective antagonist TIPP (Tyr-Tic-Phe-PheOH) containing both an affinity label and biotin were prepared by solid phase synthesis. Tyr-Tic-Phe-Phe(p-X)-Asp-NH(CH2CH2O)2-CH2CH2NH-biotin (where X = N=C=S or NHCOCH2Br) exhibit nanomolar DOR affinity. The ability to detect receptors labeled with these peptides following solubilization and SDS-PAGE demonstrate the applicability o...

  11. Early role of the κ opioid receptor in ethanol-induced reinforcement

    Pautassi, Ricardo Marcos; Nizhnikov, Michael E.; Acevedo, Ma. Belén; Norman E. Spear

    2012-01-01

    Effects of early ethanol exposure on later ethanol intake emphasize the importance of understanding the neurobiology of ethanol-induced reinforcement early in life. Infant rats exhibit ethanol-induced appetitive conditioning and ethanol-induced locomotor activation, which have been linked in theory and may have mechanisms in common. The appetitive effects of ethanol are significantly modulated by μ and δ opioid receptors, whereas μ but not δ receptors are involved in the motor stimulant effec...

  12. On the Role of Cannabinoid CB1- and μ-Opioid Receptors in Motor Impulsivity

    Wiskerke, Joost; van Mourik, Yvar; Schetters, Dustin; Schoffelmeer, Anton N. M.; Pattij, Tommy

    2012-01-01

    Previous studies using a rat 5-choice serial reaction time task have established a critical role for dopamine D2 receptors in regulating increments in motor impulsivity induced by acute administration of the psychostimulant drugs amphetamine and nicotine. Here we investigated whether cannabinoid CB1 and/or μ-opioid receptors are involved in nicotine-induced impulsivity, given recent findings indicating that both receptor systems mediate amphetamine-induced motor impulsivity. Results showed th...

  13. Expression of the Mu Opioid Receptor in the Human Immunodeficiency Virus Type 1 Transgenic Rat Model▿

    Chang, Sulie L.; Beltran, Jose A.; SWARUP, SHILPA

    2007-01-01

    Opioids, via the mu opioid receptor (MOR), can exacerbate bacterial infections and the immunopathogenesis of human immunodeficiency virus type 1 (HIV-1) infection. Recently, an HIV-1 transgenic (HIV-1Tg) rat model containing circulating HIV-1 gp120 was created. Using real-time reverse transcription-PCR, we found that MOR mRNA levels were significantly higher in the peritoneal macrophages of the HIV-1Tg rat than those in control animals. Lipopolysaccharide, a bacterial endotoxin, induced secre...

  14. Kappa and delta opioid receptor signaling is augmented in the failing heart

    Bolte, Craig; Newman, Gilbert; Schultz, Jo El J.

    2009-01-01

    The opioidergic system, an endogenous stress pathway, modulates cardiac function. Furthermore, opioid peptide and receptor expression is altered in a number of cardiac pathologies. However, whether the response of myocardial opioid receptor signaling is altered in heart failure progression is currently unknown. Elucidating possible alterations in and effects of opioidergic signaling in the failing myocardium is of critical importance as opioids are commonly used for pain management, including...

  15. NMR structure and dynamics of the agonist dynorphin peptide bound to the human kappa opioid receptor

    O’Connor, Casey; White, Kate L.; Doncescu, Nathalie; Didenko, Tatiana; Roth, Bryan L.; Czaplicki, Georges; Stevens, Raymond C.; Wüthrich, Kurt; Milon, Alain

    2015-01-01

    The human kappa opioid receptor (KOR) is implicated in addiction, pain, reward, mood, cognition, and perception. Activation of KOR by the neuropeptide dynorphin is critical in mediating analgesia and tolerance. Our solution NMR study of dynorphin (1–13) provided quantitative data on a KOR-bound conformation. Analysis of the peptide structure and dynamics revealed a central helical turn bounded on both sides by flexibly disordered peptide segments. Future drug development will benefit from kno...

  16. The role of kappa opioid receptors in stress-induced reinstatement of alcohol seeking in rats

    Funk, Douglas; Coen, Kathleen; Lê, A.D.

    2014-01-01

    Introduction Stress is related to heavy alcohol use and relapse in alcoholics. Using the reinstatement model, we have shown that corticotropin-releasing factor (CRF) underlies stress-induced relapse to alcohol seeking in laboratory rodents. Little is known about how other neurotransmitters interact with CRF in these effects. Dynorphin and its receptor (kappa opioid receptor, KOR) are involved in stress responses and in alcohol seeking. KOR and CRF receptors (CRF R) may interact in the product...

  17. Targeting Endogenous Mu- and Delta-Opioid Receptor Systems for the Treatment of Drug Addiction

    Shippenberg, T S; LeFevour, A.; Chefer, V.I.

    2008-01-01

    Drug addiction is a chronic, relapsing disorder that is characterized by a compulsion to take drug regardless of the adverse consequences that may ensue. Although the involvement of mesoaccumbal dopamine neurons in the initiation of drug abuse is well-established, neuroadaptations within the limbic cortical- striatopallidal circuit that occur as a consequence of repeated drug use are thought to lead to the behavioral dysregulation that characterizes addiction. Opioid receptors and their endog...

  18. Delta Opioid Receptors Presynaptically Regulate Cutaneous Mechanosensory Neuron Input to the Spinal Cord Dorsal Horn

    Bardoni, Rita; Tawfik, Vivianne L.; Wang, Dong; François, Amaury; Solorzano, Carlos; Shuster, Scott A.; Choudhury, Papiya; Betelli, Chiara; Cassidy, Colleen; Smith, Kristen; de Nooij, Joriene C.; Mennicken, Françoise; O’Donnell, Dajan; Kieffer, Brigitte L.; Woodbury, C. Jeffrey

    2014-01-01

    Cutaneous mechanosensory neurons detect mechanical stimuli that generate touch and pain sensation. Although opioids are generally associated only with the control of pain, here we report that the opioid system in fact broadly regulates cutaneous mechanosensation, including touch. This function is predominantly subserved by the delta opioid receptor (DOR), which is expressed by myelinated mechanoreceptors that form Meissner corpuscles, Merkel cell-neurite complexes, and circumferential hair fo...

  19. Decreased response to social defeat stress in μ-opioid-receptor knockout mice

    Komatsu, Hiroshi; Ohara, Arihisa; Sasaki, Kazumasu; Abe, Hiromi; Hattori, Hisaki; Hall, F Scott; Uhl, George R.; Sora, Ichiro

    2011-01-01

    Substantial evidence exists that opioid systems are involved in stress response and that changes in opioid systems in response to stressors affect both reward and analgesia. Reportedly, mice suffering chronic social defeat stress subsequently show aversion to social contact with unfamiliar mice. To further examine the role of opioid systems in stress response, the behavioral and neurochemical effects of chronic social defeat stress (psychosocial stress) were evaluated in μ-opioid-receptor kno...

  20. Sex differences in kappa opioid receptor function and their potential impact on addiction

    Elena eChartoff; Maria eMavrikaki

    2015-01-01

    Behavioral, biological and social sequelae that lead to drug addiction differ between men and women. Our efforts to understand addiction on a mechanistic level must include studies in both males and females. Stress, anxiety, and depression are tightly linked to addiction, and whether they precede or result from compulsive drug use depends on many factors, including biological sex. The neuropeptide dynorphin (DYN), an endogenous ligand at kappa opioid receptors (KORs), is necessary for stress...

  1. Sex Differences in Kappa Opioid Receptor Function and Their Potential Impact on Addiction

    Chartoff, Elena H.; Mavrikaki, Maria

    2015-01-01

    Behavioral, biological, and social sequelae that lead to drug addiction differ between men and women. Our efforts to understand addiction on a mechanistic level must include studies in both males and females. Stress, anxiety, and depression are tightly linked to addiction, and whether they precede or result from compulsive drug use depends on many factors, including biological sex. The neuropeptide dynorphin (DYN), an endogenous ligand at kappa opioid receptors (KORs), is necessary for stress...

  2. Functional characteristics of the naked mole rat μ-opioid receptor.

    Melanie Busch-Dienstfertig

    Full Text Available While humans and most animals respond to µ-opioid receptor (MOR agonists with analgesia and decreased aggression, in the naked mole rat (NMR opioids induce hyperalgesia and severe aggression. Single nucleotide polymorphisms in the human mu-opioid receptor gene (OPRM1 can underlie altered behavioral responses to opioids. Therefore, we hypothesized that the primary structure of the NMR MOR may differ from other species. Sequencing of the NMR oprm1 revealed strong homology to other mammals, but exposed three unique amino acids that might affect receptor-ligand interactions. The NMR and rat oprm1 sequences were cloned into mammalian expression vectors and transfected into HEK293 cells. Radioligand binding and 3'-5'-cyclic adenosine monophosphate (cAMP enzyme immunoassays were used to compare opioid binding and opioid-mediated cAMP inhibition. At normalized opioid receptor protein levels we detected significantly lower [3H]DAMGO binding to NMR compared to rat MOR, but no significant difference in DAMGO-induced cAMP inhibition. Strong DAMGO-induced MOR internalization was detectable using radioligand binding and confocal imaging in HEK293 cells expressing rat or NMR receptor, while morphine showed weak or no effects. In summary, we found minor functional differences between rat and NMR MOR suggesting that other differences e.g. in anatomical distribution of MOR underlie the NMR's extreme reaction to opioids.

  3. [3H]Ethylketocyclazocine binding to mouse brain membranes: evidence for a kappa opioid receptor type

    The binding of the putative kappa agonist ethylketocyclazocine (EKC) to synaptosomal membranes of mouse brain was studied. This benzomorphan was able to bind to different opioid receptors. A portion of this binding was not inhibited by the agonist naloxone, even at high concentrations (10 microM). This population of receptors, to which opioate alkaloids and opiod peptides display very low affinity, is probably the sigma receptor. Another class of binding sites was identified by the simultaneous addition of the selective agonists Sandoz FK-33824 and D-Ala2-D-Leu5-enkephalin, which blocked the access of EKC to mu and delta opioid receptors, respectively, leaving a portion of naloxone-displaceable benzomorphan binding still detectable. Analysis of this remaining binding revealed a small population of receptors of high affinity, the kappa receptor. Therefore, EKC binds to the mu, delta, kappa and sigma receptors in the mouse brain, with similar affinities for the mu and kappa (0.22 and 0.15 nM). These results confirm the existence of a kappa opioid receptor type in the mouse brain

  4. Kappa opioid receptors stimulate phosphoinositide turnover in rat brain

    The effects of various subtype-selective opioid agonists and antagonists on the phosphoinositide (PI) turnover response were investigated in the rat brain. The κ-agonists U-50,488H and ketocyclazocine produced a concentration-dependent increase in the accumulation of IP's in hippocampal slices. The other κ-agonists Dynorphin-A (1-13) amide, and its protected analog D[Ala]2-dynorphin-A (1-13) amide also produced a significant increase in the formation of [3H]-IP's, whereas the μ-selective agonists [D-Ala2-N-Me-Phe4-Gly5-ol]-enkephalin and morphine and the δ-selective agonist [D-Pen2,5]-enkephalin were ineffective. The increase in IP's formation elicited by U-50,488H was partially antagonized by naloxone and more completely antagonized by the κ-selective antagonists nor-binaltorphimine and MR 2266. The formation of IP's induced by U-50,488H varies with the regions of the brain used, being highest in hippocampus and amygdala, and lowest in striatum and pons-medullar. The results indicate that brain κ- but neither μ- nor δ- receptors are coupled to the PI turnover response

  5. Kappa opioid receptors stimulate phosphoinositide turnover in rat brain

    Periyasamy, S.; Hoss, W. (Univ. of Toledo, OH (USA))

    1990-01-01

    The effects of various subtype-selective opioid agonists and antagonists on the phosphoinositide (PI) turnover response were investigated in the rat brain. The {kappa}-agonists U-50,488H and ketocyclazocine produced a concentration-dependent increase in the accumulation of IP's in hippocampal slices. The other {kappa}-agonists Dynorphin-A (1-13) amide, and its protected analog D(Ala){sup 2}-dynorphin-A (1-13) amide also produced a significant increase in the formation of ({sup 3}H)-IP's, whereas the {mu}-selective agonists (D-Ala{sup 2}-N-Me-Phe{sup 4}-Gly{sup 5}-ol)-enkephalin and morphine and the {delta}-selective agonist (D-Pen{sup 2,5})-enkephalin were ineffective. The increase in IP's formation elicited by U-50,488H was partially antagonized by naloxone and more completely antagonized by the {kappa}-selective antagonists nor-binaltorphimine and MR 2266. The formation of IP's induced by U-50,488H varies with the regions of the brain used, being highest in hippocampus and amygdala, and lowest in striatum and pons-medullar. The results indicate that brain {kappa}- but neither {mu}- nor {delta}- receptors are coupled to the PI turnover response.

  6. Activity profiles of dalargin and its analogues in mu-, delta- and kappa-opioid receptor selective bioassays.

    Pencheva, N; Pospisek, J; Hauzerova, L; Barth, T; Milanov, P

    1999-10-01

    1. To elucidate the structural features ensuring action of [D-Ala2, Leu5]-enkephalyl-Arg (dalargin), a series of dalargin analogues were tested for their effectiveness in depressing electrically-evoked contractions of the guinea-pig myenteric plexus-longitudinal muscle preparations (mu- and kappa-opioid receptors) and the vasa deferentia of the hamster (delta-opioid receptors), mouse (mu-, delta- and kappa-opioid receptors), rat (similar to mu-opioid receptors) and rabbit (kappa-opioid receptors). The naloxone KB values in the myenteric plexus were also obtained. 2. [L-Ala2]-dalargin was 19 times less potent than dalargin, and its pharmacological activity was peptidase-sensitive. The ratio of delta-activity to mu-activity for [L-Ala2]-dalargin was 6.78, and KB was 7.9 nM. This emphasizes the role that D-configuration of Ala2 plays in determining the active folding of dalargin molecule as well as in conferring resistance to peptidases. 3. [Met5]-dalargin was equipotent to dalargin in the myenteric plexus, but was more potent in the vasa deferentia of hamster and mouse (KB=5.5 nM). Leu5 and the interdependence of Leu5 and D-Ala2 are of importance for the selectivity of dalargin for mu-opioid receptors. 4. Dalarginamide was more potent and selective for mu-opioid receptors than dalargin, whilst dalarginethylamide, though equipotent to dalarginamide in the myenteric plexus, was more potent at delta-opioid receptors (KB=5.0 nM). [D-Phe4]-dalarginamide and N-Me-[D-Phe4]-dalarginamide were inactive indicating the contribution of L-configuration of Phe4 to the pharmacological potency of dalargin. 5. N-Me-[L-Phe4]-dalarginamide possessed the highest potency and selectivity for mu-opioid receptors (the ratio of delta-activity to mu-activity was 0.00053; KB=2.6 nM). The CONH2 terminus combined with the N-methylation of L-Phe4 increased the potency and selectivity of dalargin for mu-opioid receptors. PMID:10516634

  7. Activity profiles of dalargin and its analogues in μ-, δ- and κ-opioid receptor selective bioassays

    Pencheva, Nevena; Pospišek, Jan; Hauzerova, Linda; Barth, Tomislav; Milanov, Peter

    1999-01-01

    To elucidate the structural features ensuring action of [D-Ala2, Leu5]-enkephalyl-Arg (dalargin), a series of dalargin analogues were tested for their effectiveness in depressing electrically-evoked contractions of the guinea-pig myenteric plexus-longitudinal muscle preparations (μ- and κ-opioid receptors) and the vasa deferentia of the hamster (δ-opioid receptors), mouse (μ-, δ- and κ-opioid receptors), rat (similar to μ-opioid receptors) and rabbit (κ-opioid receptors). The naloxone KB values in the myenteric plexus were also obtained.[L-Ala2]-dalargin was 19 times less potent than dalargin, and its pharmacological activity was peptidase-sensitive. The ratio of δ-activity to μ-activity for [L-Ala2]-dalargin was 6.78, and KB was 7.9 nM. This emphasizes the role that D-configuration of Ala2 plays in determining the active folding of dalargin molecule as well as in conferring resistance to peptidases.[Met5]-dalargin was equipotent to dalargin in the myenteric plexus, but was more potent in the vasa deferentia of hamster and mouse (KB=5.5 nM). Leu5 and the interdependence of Leu5 and D-Ala2 are of importance for the selectivity of dalargin for μ-opioid receptors.Dalarginamide was more potent and selective for μ-opioid receptors than dalargin, whilst dalarginethylamide, though equipotent to dalarginamide in the myenteric plexus, was more potent at δ-opioid receptors (KB=5.0 nM). [D-Phe4]-dalarginamide and N-Me-[D-Phe4]-dalarginamide were inactive indicating the contribution of L-configuration of Phe4 to the pharmacological potency of dalargin.N-Me-[L-Phe4]-dalarginamide possessed the highest potency and selectivity for μ-opioid receptors (the ratio of δ-activity to μ-activity was 0.00053; KB=2.6 nM). The CONH2 terminus combined with the N-methylation of L-Phe4 increased the potency and selectivity of dalargin for μ-opioid receptors. PMID:10516634

  8. Interaction of co-expressed mu- and delta-opioid receptors in transfected rat pituitary GH(3) cells.

    Martin, N A; Prather, P L

    2001-04-01

    mu- and delta-Opioid agonists interact in a synergistic manner to produce analgesia in several animal models. Additionally, receptor binding studies using membranes derived from brain tissue indicate that interactions between mu- and delta-opioid receptors might be responsible for the observation of multiple opioid receptor subtypes. To examine potential interactions between mu- and delta-opioid receptors, we examined receptor binding and functional characteristics of mu-, delta-, or both mu- and delta-opioid receptors stably transfected in rat pituitary GH(3) cells (GH(3)MOR, GH(3)DOR, and GH(3)MORDOR, respectively). Saturation and competition binding experiments revealed that coexpression of mu- and delta-opioid receptors resulted in the appearance of multiple affinity states for mu- but not delta-opioid receptors. Additionally, coadministration of selective mu- and delta-opioid agonists in GH(3)MORDOR cells resulted in a synergistic competition with [(3)H][D-Pen(2,5)]enkephalin (DPDPE) for delta-opioid receptors. Finally, when equally effective concentrations of [D-Ala(2),N-MePhe(4),Gly-ol(5)]enkephalin (DAMGO) and two different delta-opioid agonists (DPDPE or 2-methyl-4a alpha-(3-hydroxyphenyl)-1,2,3,4,4a,5,12,12a alpha-octahydroquinolino-[2,3,3-g]-isoquinoline; TAN67) were coadministered in GH(3)MORDOR cells, a synergistic inhibition of adenylyl cyclase activity was observed. These results strongly suggest that cotransfection of mu- and delta-opioid receptors alters the binding and functional characteristics of the receptors. Therefore, we propose that the simultaneous exposure of GH(3)MORDOR cells to selective mu- and delta-opioid agonists produces an interaction between receptors resulting in enhanced receptor binding. This effect is translated into an augmented ability of these agonists to inhibit adenylyl cyclase activity. Similar interactions occurring in neurons that express both mu- and delta-opioid receptors could explain observations of multiple

  9. A Commonly Carried Genetic Variant in the Delta Opioid Receptor Gene, OPRD1, is Associated with Smaller Regional Brain Volumes: Replication in Elderly and Young Populations

    Roussotte, Florence F.; Jahanshad, Neda; Hibar, Derrek P.; Sowell, Elizabeth R.; Kohannim, Omid; Barysheva, Marina; Hansell, Narelle K.; McMahon, Katie L.; de Zubicaray, Greig I.; Montgomery, Grant W.; Martin, Nicholas G.; Wright, Margaret J.; Toga, Arthur W.; Jack, Clifford R.; Weiner, Michael W

    2013-01-01

    Delta opioid receptors are implicated in a variety of psychiatric and neurological disorders. These receptors play a key role in the reinforcing properties of drugs of abuse, and polymorphisms in OPRD1 (the gene encoding delta opioid receptors) are associated with drug addiction. Delta opioid receptors are also involved in protecting neurons against hypoxic and ischemic stress. Here, we first examined a large sample of 738 elderly participants with neuroimaging and genetic data from the Alzhe...

  10. δ-阿片受体抑制阿片诱发痛觉过敏的研究进展%The role of δ- opioid receptor in the inhibition of opioid induced hyperalgesia

    李依泽; 王海云; 王国林

    2012-01-01

    Background Opioids are the most powerful analgesics for the treatment of moderate to severe pain.Although opioids have analgesic effect,they have many side effects at the same time.Long term opioids exposure can induce hyperalgesia and tolerance.Moreover,increasing the dose of opioids,paradoxically,aggravates the hyperalgesia and tolerance,causing a vicious cycle.The use of opioids,therefore,is largely limited in the clinical setting. Objective The relevant literatures involved in the role of δ-opioid receptors in the attenuation of opioid induced hyperalgesia (OIH) in recent years were summarized,which helps readership to update the latest information about this topic. Content The structure,distribution,physiological function and the progress of antihyperalgesic effect of δ-opioid receptors were reviewed in this article.Those researches suggest that OIH and tolerance can be attenuated by the inhibition of δ-opioid receptor phosphorylation,knocking out δ-opioid receptor coding genes and the application of δ-opioid receptor antagonists. Trend Since the antihyperalgesia effect of δ-opioid receptor is widely acknowledged,δ- opioid receptor may become a new target to relieve pain in the clinical setting.%背景 阿片类药物是治疗中、重度疼痛的主要药物,长时间应用可出现阿片诱发的痛觉过敏和耐受,而增加药物剂量可造成更严重的痛觉过敏和耐受,从而形成恶性循环,很大程度上限制了阿片类药物在临床工作中的应用.目的 通过对近年δ-阿片受体在痛觉过敏中所起作用的研究进行总结,帮助读者了解国外相关研究的最新趋势和进展.内容 就δ-阿片受体的结构、分布、生理功能和δ-阿片受体的抗痛觉过敏作用的研究进展进行综述.得出如下结论,通过抑制δ-阿片受体磷酸化、敲除δ-阿片受体编码基因和应用δ-阿片受体拮抗剂等方法,可抑制痛觉过敏和耐受的形成.趋向 随着越来越多的学者对

  11. Opioid mediated activity and expression of mu and delta opioid receptors in isolated human term non-labouring myometrium.

    Fanning, Rebecca A

    2013-01-05

    The existence of opioid receptors in mammalian myometrial tissue is now widely accepted. Previously enkephalin degrading enzymes have been shown to be elevated in pregnant rat uterus and a met-enkephalin analogue has been shown to alter spontaneous contractility of rat myometrium. Here we have undertaken studies to determine the effects of met-enkephalin on in vitro human myometrial contractility and investigate the expression of opioid receptors in pregnant myometrium. Myometrial biopsies were taken from women undergoing elective caesarean delivery at term. Organ bath experiments were used to investigate the effect of the met-enkephalin analogue [d-Ala 2, d-met 5] enkephalin (DAMEA) on spontaneous contractility. A confocal immunofluorescent technique and real time PCR were used to determine the expression of protein and mRNA, respectively for two opioid receptor subtypes, mu and delta. DAMEA had a concentration dependent inhibitory effect on contractile activity (1 × 10(-7)M-1 × 10(-4)M; 54% reduction in contractile activity, P<0.001 at 1 × 10(-4)M concentration). Mu and delta opioid receptor protein sub-types and their respective mRNA were identified in all tissues sampled. This is the first report of opioid receptor expression and of an opioid mediated uterorelaxant action in term human non-labouring myometrium in vitro.

  12. Effects of defeat stress on behavioral flexibility in males and females: modulation by the mu-opioid receptor

    Laredo, Sarah A.; Steinman, Michael Q.; Robles, Cindee F.; Ferrer, Emilio; Ragen, Benjamin J.; Trainor, Brian C.

    2014-01-01

    Behavioral flexibility is a component of executive functioning that allows individuals to adapt to changing environmental conditions. Independent lines of research indicate that the mu opioid receptor (MOR) is an important mediator of behavioral flexibility and responses to psychosocial stress. The current study bridges these two lines of research and tests the extent to which social defeat and MOR affect behavioral flexibility and whether sex moderates these effects in California mice (Peromyscus californicus). Males and females assigned to social defeat or control conditions were tested in a Barnes maze. In males, defeat impaired behavioral flexibility but not acquisition. Female performance was unaffected by defeat. MOR binding in defeated and control mice in the orbitofrontal cortex (OFC), striatum, and hippocampus was examined via autoradiography. Stressed males had reduced MOR binding in the OFC whereas females were unaffected. The MOR antagonist beta-funaltrexamine (1 mg/kg) impaired performance in males naïve to defeat during the reversal phase but had no effect on females. Finally, we examined the effects of the MOR agonist morphine (2.5, 5 mg/kg) on stressed mice. As expected, morphine improved behavioral flexibility in stressed males. The stress-induced deficits in behavioral flexibility in males are consistent with a proactive coping strategy, including previous observations that stressed male California mice exhibit strong social approach and aggression. Our pharmacological data suggest that a down-regulation of MOR signaling in males may contribute to sex differences in behavioral flexibility following stress. This is discussed in the framework of coping strategies for individuals with mood disorders. PMID:25615538

  13. Fourteenβ-(bromoacetamido)morphine irreversibly labels μ opioid receptors in rat brain membranes

    The binding properties of 14β-(bromoacetamido)morphine (BAM) and the ability of BAM to irreversibly inhibit opioid binding to rat brain membranes were examined to characterize the affinity and selectivity of BAM as an irreversible affinity ligand for opioid receptors. BAM had the same receptor selectivity as morphine, with a 3-5-fold decrease in affinity for the different types of opioid receptors. When brain membranes were incubated with BAM, followed by extensive washing, opioid binding was restored to control levels. However, when membranes were incubated with dithiothreitol (DTT), followed by BAM, and subsequently washed, 90% of the 0.25 nM [3H][D-Ala2,(Me)Phe4,Gly(ol)5]enkephalin (DAGO) binding was irreversibly inhibited as a result of the specific alkylation of a sulfhydryl group at the μ binding site. This inhibition was dependent on the concentrations of both DTT and BAM. The μ receptor specificity of BAM alkylation was demonstrated by the ability of BAM alkylated membranes to still bind the δ-selective peptide [3H][D-penicillamine2,D-penicillamine5]enkephalin (DPDPE) and (-)-[3H]bremazocine in the presence of μ and δ blockers, selective for κ binding sites. Morphine and naloxone partially protected the binding site from alkylation with BAM, while ligands that did not bind to the μs site did not afford protection. These studies have demonstrated that when a disulfide bond at or near μ opioid binding sites was reduced, BAM could then alkylate this site, resulting in the specific irreversible labeling of μ opioid receptors

  14. Fourteen. beta. -(bromoacetamido)morphine irreversibly labels. mu. opioid receptors in rat brain membranes

    Bidlack, J.M.; Frey, D.K.; Seyed-Mozaffari, A.; Archer, S. (Univ. of Rochester School of Medicine and Dentistry, NY (USA))

    1989-05-16

    The binding properties of 14{beta}-(bromoacetamido)morphine (BAM) and the ability of BAM to irreversibly inhibit opioid binding to rat brain membranes were examined to characterize the affinity and selectivity of BAM as an irreversible affinity ligand for opioid receptors. BAM had the same receptor selectivity as morphine, with a 3-5-fold decrease in affinity for the different types of opioid receptors. When brain membranes were incubated with BAM, followed by extensive washing, opioid binding was restored to control levels. However, when membranes were incubated with dithiothreitol (DTT), followed by BAM, and subsequently washed, 90% of the 0.25 nM ({sup 3}H)(D-Ala{sup 2},(Me)Phe{sup 4},Gly(ol){sup 5})enkephalin (DAGO) binding was irreversibly inhibited as a result of the specific alkylation of a sulfhydryl group at the {mu} binding site. This inhibition was dependent on the concentrations of both DTT and BAM. The {mu} receptor specificity of BAM alkylation was demonstrated by the ability of BAM alkylated membranes to still bind the {delta}-selective peptide ({sup 3}H)(D-penicillamine{sup 2},D-penicillamine{sup 5})enkephalin (DPDPE) and (-)-({sup 3}H)bremazocine in the presence of {mu} and {delta} blockers, selective for {kappa} binding sites. Morphine and naloxone partially protected the binding site from alkylation with BAM, while ligands that did not bind to the {mu}s site did not afford protection. These studies have demonstrated that when a disulfide bond at or near {mu} opioid binding sites was reduced, BAM could then alkylate this site, resulting in the specific irreversible labeling of {mu} opioid receptors.

  15. In vivo and in vitro evaluation of novel μ-opioid receptor agonist compounds.

    Nikaido, Yoshiaki; Kurosawa, Aya; Saikawa, Hitomi; Kuroiwa, Satoshi; Suzuki, Chiharu; Kuwabara, Nobuo; Hoshino, Hazime; Obata, Hideaki; Saito, Shigeru; Saito, Tamio; Osada, Hiroyuki; Kobayashi, Isao; Sezutsu, Hideki; Takeda, Shigeki

    2015-11-15

    Opioids are the most effective and widely used drugs for pain treatment. Morphine is an archetypal opioid and is an opioid receptor agonist. Unfortunately, the clinical usefulness of morphine is limited by adverse effects such as analgesic tolerance and addiction. Therefore, it is important to study the development of novel opioid agonists as part of pain control. The analgesic effects of opioids are mediated by three opioid receptors, namely opioid μ-, δ-, and κ-receptors. They belong to the G protein-coupled receptor superfamily and are coupled to Gi proteins. In the present study, we developed a ligand screening system to identify novel opioid μ-receptor agonists that measures [(35)S]GTPγS binding to cell membrane fractions prepared from the fat body of transgenic silkworms expressing μ-receptor-Gi1α fusion protein. We screened the RIKEN Natural Products Depository (NPDepo) chemical library, which contains 5848 compounds, and analogs of hit compounds. We successfully identified a novel, structurally unique compound, that we named GUM1, with agonist activity for the opioid μ-receptor (EC50 of 1.2 µM). The Plantar Test (Hargreaves' Method) demonstrated that subcutaneous injection of 3mg/kg of GUM1 into wild-type rats significantly extended latency time. This extension was also observed in a rat model of morphine tolerance and was inhibited by pre-treatment of naloxone. The unique molecular skeleton of GUM1 makes it an attractive molecule for further ligand-opioid receptor binding studies. PMID:26476280

  16. Antidepressant-like effect of venlafaxine is abolished in µ-opioid receptor knockout mice

    Ide, Soichiro; Fujiwara, Shunsuke; Fujiwara, Masayuki; Sora, Ichiro; Ikeda, Kazutaka; Minami, Masabumi; Uhl, George R; Ishihara, Kumatoshi

    2010-01-01

    Although the opioid system is known to modulate depression-like behaviors, its role in the effects of antidepressants is not yet clear. We investigated the role of µ-opioid receptors (MOPs) in the effects of venlafaxine, a serotonin and norepinephrine reuptake inhibitor, in the forced swim test using MOP-knockout (KO) mice. Venlafaxine reduced immobility time in wildtype mice (C57BL/6J), but not in MOP-KO mice, although no significant effects were observed on locomotor activity. These results...

  17. Chronic morphine treatment up-regulates mu opioid receptor binding in cells lacking Filamin A

    Onoprishvili, Irma; Simon, Eric J.

    2007-01-01

    We investigated the effects of morphine and other agonists on the human mu opioid receptor (MOP) expressed in M2 melanoma cells, lacking the actin cytoskeleton protein filamin A and in A7, a sub clone of the M2 melanoma cells, stably transfected with filamin A cDNA. The results of binding experiments showed, that after chronic morphine treatment (24 hr) of A7 cells, MOP binding sites were down-regulated to 63% of control, whereas, unexpectedly, in M2 cells, MOP binding was up-regulated to 188...

  18. Specific binding of a ligand of σ-opioid receptors - N-allylnormetazocine (SKF 10047) - with liver membranes

    A ligand of the σ-opioid receptors - N-allylnormetazocine (SKF 10047) -binds specifically and reversible with rat liver membranes. In relation to a number of properties, the sites binding SKF 10047 in the liver are similar to the σ-opioid receptors of the central nervous system. They do not interact with classical opiates (morphine, naloxone) and with opioid peptides, but bind well benzomorphans (bremazocine, SKF 10047) and a number of compounds of different chemical structures with a pronounced psychtropic action (haloperidol, imipramine, phencyclidine, etc.)

  19. Specific binding of a ligand of sigma-opioid receptors - N-allylnormetazocine (SKF 10047) - with liver membranes

    Samovilova, N.N.; Yarygin, K.N.; Vinogradov, V.A.

    1986-08-01

    A ligand of the sigma-opioid receptors - N-allylnormetazocine (SKF 10047) -binds specifically and reversible with rat liver membranes. In relation to a number of properties, the sites binding SKF 10047 in the liver are similar to the sigma-opioid receptors of the central nervous system. They do not interact with classical opiates (morphine, naloxone) and with opioid peptides, but bind well benzomorphans (bremazocine, SKF 10047) and a number of compounds of different chemical structures with a pronounced psychtropic action (haloperidol, imipramine, phencyclidine, etc.).

  20. Delay discounting of the μ-opioid receptor agonist remifentanil in rhesus monkeys.

    Maguire, David R; Gerak, Lisa R; France, Charles P

    2016-04-01

    Although increased impulsivity (delay discounting) is an important risk factor for drug abuse, the impact of delay on drug taking has received relatively little attention. This study examined delay discounting of the μ-opioid receptor agonist remifentanil in rhesus monkeys (n=4) responding for intravenous infusions under a concurrent choice procedure. Dose-effect curves for remifentanil were determined by varying the dose available on one lever (0.001-0.32 μg/kg/infusion) while keeping the dose available on the other lever (0.1 μg/kg/infusion) the same. Dose-effect curves were determined when both infusions were delivered immediately and when delivery of the fixed dose was delayed (15-180 s). When both doses of remifentanil were delivered immediately, monkeys chose the large dose. Delaying delivery of the fixed dose reduced choice of that dose and increased choice of small immediately available doses. Extending previous studies, these results show that the effects of delay on choice between two doses of a μ-opioid receptor agonist are consistent with hyperbolic discounting. Delaying delivery of a preferred reinforcer (e.g. large dose of drug) reduces its effectiveness and increases the effectiveness of small immediately available doses. This effect of delay, particularly on drug self-administration, might contribute to drug abuse. PMID:26397761

  1. Multiple opioid receptor binding in dissociated intact guinea pig brain cells

    Tam, S.W.; James, D.W.

    1986-03-05

    Dissociated intact guinea pig brain cells were prepared by the method of Rogers and El-Fakahany. Over 95% of these cells are viable as demonstrated by their exclusion of the dye trypan blue. Opioid receptor binding assays were performed in a modified Kreb-Ringers physiological buffer. The following radiolabeled ligands and conditions were used to selectively labeled multiple opioid receptors: mu binding, 1 nM (/sup 3/H)naloxone + 20 nM DADLE + 300 nM U50,488H; kappa binding, 4 nM (-)-(/sup 3/H)-EKC + 100 nM DAGO + 500 nM DADLE; delta binding, 2 nM (/sup 3/H)-DADLE + 100 nM DAGO + 300 nM U50,488H; sigma binding, 4 nM (+)-(/sup 3/H)SKF 10,047. The intact brain cells in physiological buffer demonstrated specific binding for mu, kappa, delta, and sigma receptors. The relative binding potency of naloxone for each of the receptor types is arbitrarily set at 1.

  2. Inhibition of Activity of GABA Transporter GAT1 by δ-Opioid Receptor

    Lu Pu

    2012-01-01

    Full Text Available Analgesia is a well-documented effect of acupuncture. A critical role in pain sensation plays the nervous system, including the GABAergic system and opioid receptor (OR activation. Here we investigated regulation of GABA transporter GAT1 by δOR in rats and in Xenopus oocytes. Synaptosomes of brain from rats chronically exposed to opiates exhibited reduced GABA uptake, indicating that GABA transport might be regulated by opioid receptors. For further investigation we have expressed GAT1 of mouse brain together with mouse δOR and μOR in Xenopus oocytes. The function of GAT1 was analyzed in terms of Na+-dependent [3H]GABA uptake as well as GAT1-mediated currents. Coexpression of δOR led to reduced number of fully functional GAT1 transporters, reduced substrate translocation, and GAT1-mediated current. Activation of δOR further reduced the rate of GABA uptake as well as GAT1-mediated current. Coexpression of μOR, as well as μOR activation, affected neither the number of transporters, nor rate of GABA uptake, nor GAT1-mediated current. Inhibition of GAT1-mediated current by activation of δOR was confirmed in whole-cell patch-clamp experiments on rat brain slices of periaqueductal gray. We conclude that inhibition of GAT1 function will strengthen the inhibitory action of the GABAergic system and hence may contribute to acupuncture-induced analgesia.

  3. Multiple opioid receptor binding in dissociated intact guinea pig brain cells

    Dissociated intact guinea pig brain cells were prepared by the method of Rogers and El-Fakahany. Over 95% of these cells are viable as demonstrated by their exclusion of the dye trypan blue. Opioid receptor binding assays were performed in a modified Kreb-Ringers physiological buffer. The following radiolabeled ligands and conditions were used to selectively labeled multiple opioid receptors: mu binding, 1 nM [3H]naloxone + 20 nM DADLE + 300 nM U50,488H; kappa binding, 4 nM (-)-[3H]-EKC + 100 nM DAGO + 500 nM DADLE; delta binding, 2 nM [3H]-DADLE + 100 nM DAGO + 300 nM U50,488H; sigma binding, 4 nM (+)-[3H]SKF 10,047. The intact brain cells in physiological buffer demonstrated specific binding for mu, kappa, delta, and sigma receptors. The relative binding potency of naloxone for each of the receptor types is arbitrarily set at 1

  4. Partial purification of the mu opioid receptor irreversibly labeled with [3H]b-funaltrexamine

    The mu opioid receptor in bovine striatal membranes was specifically and irreversibly labeled by incubation with 5 nM [3H]β-funaltrexamine (approx.-FNA) at 370C for 90 min in the presence of 100 mM NaCl. The specific and irreversible binding of [3H]β-FNA as defined by that blocked by 1 +M naloxone was about 60% of total irreversible binding. The specific irreversible binding was saturable, stereospecific, time-, temperature, and tissue-dependent. Mu opioid ligands were much more potent than delta or kappa ligands in inhibiting the specific irreversible labeling. SDS polyacrylamide gel electrophoresis of solubilized membranes in the presence of 2-mercaptoethanol yielded a major radiolabeled broad band of MW 68-97K daltons, characteristic of a glycoprotein band. This band was not observed in membranes labeled in the presence of excess unlabeled naloxone. The glycoprotein nature of the [3H]β-FNA-labeled opioid receptor was confirmed by its binding to a wheat germ agglutinin-Sepharose column and its elution with N-acetylglucosamine

  5. Human Mu Opioid Receptor (OPRM1A118G) polymorphism is associated with brain mu- opioid receptor binding potential in smokers

    Ray, R.; Logan, J.; Ray, R.; Ruparel, K.; Newberg, A.; Wileyto, E.P.; Loughead, J.W.; Divgi, C.; Blendy, J.A.; Logan, J.; Zubieta, J.-K.; Lerman, C.

    2011-04-15

    Evidence points to the endogenous opioid system, and the mu-opioid receptor (MOR) in particular, in mediating the rewarding effects of drugs of abuse, including nicotine. A single nucleotide polymorphism (SNP) in the human MOR gene (OPRM1 A118G) has been shown to alter receptor protein level in preclinical models and smoking behavior in humans. To clarify the underlying mechanisms for these associations, we conducted an in vivo investigation of the effects of OPRM1 A118G genotype on MOR binding potential (BP{sub ND} or receptor availability). Twenty-two smokers prescreened for genotype (12 A/A, 10 */G) completed two [{sup 11}C] carfentanil positron emission tomography (PET) imaging sessions following overnight abstinence and exposure to a nicotine-containing cigarette and a denicotinized cigarette. Independent of session, smokers homozygous for the wild-type OPRM1 A allele exhibited significantly higher levels of MOR BP{sub ND} than smokers carrying the G allele in bilateral amygdala, left thalamus, and left anterior cingulate cortex. Among G allele carriers, the extent of subjective reward difference (denicotinized versus nicotine cigarette) was associated significantly with MOR BP{sub ND} difference in right amygdala, caudate, anterior cingulate cortex, and thalamus. Future translational investigations can elucidate the role of MORs in nicotine addiction, which may lead to development of novel therapeutics.

  6. Human Mu Opioid Receptor (OPRM1A118G) polymorphism is associated with brain mu- opioid receptor binding potential in smokers

    Evidence points to the endogenous opioid system, and the mu-opioid receptor (MOR) in particular, in mediating the rewarding effects of drugs of abuse, including nicotine. A single nucleotide polymorphism (SNP) in the human MOR gene (OPRM1 A118G) has been shown to alter receptor protein level in preclinical models and smoking behavior in humans. To clarify the underlying mechanisms for these associations, we conducted an in vivo investigation of the effects of OPRM1 A118G genotype on MOR binding potential (BPND or receptor availability). Twenty-two smokers prescreened for genotype (12 A/A, 10 */G) completed two [11C] carfentanil positron emission tomography (PET) imaging sessions following overnight abstinence and exposure to a nicotine-containing cigarette and a denicotinized cigarette. Independent of session, smokers homozygous for the wild-type OPRM1 A allele exhibited significantly higher levels of MOR BPND than smokers carrying the G allele in bilateral amygdala, left thalamus, and left anterior cingulate cortex. Among G allele carriers, the extent of subjective reward difference (denicotinized versus nicotine cigarette) was associated significantly with MOR BPND difference in right amygdala, caudate, anterior cingulate cortex, and thalamus. Future translational investigations can elucidate the role of MORs in nicotine addiction, which may lead to development of novel therapeutics.

  7. Interleukin-1 beta-induced up-regulation of opioid receptors in the untreated and morphine-desensitized U87 MG human astrocytoma cells

    Byrne Linda

    2012-11-01

    Full Text Available Abstract Background Interleukin-1beta (IL-1β is a pro-inflammatory cytokine that can be produced in the central nervous system during inflammatory conditions. We have previously shown that IL-1β expression is altered in the rat brain during a morphine tolerant state, indicating that this cytokine may serve as a convergent point between the immune challenge and opiate mediated biological pathways. We hypothesized that IL-1β up-regulates opioid receptors in human astrocytes in both untreated and morphine-desensitized states. Methods To test this hypothesis, we compared the basal expression of the mu (MOR, delta (DOR, and kappa (KOR opioid receptors in the human U87 MG astrocytic cell line to SH-SY5Y neuronal and HL-60 immune cells using absolute quantitative real time RT-PCR (AQ-rt-RT-PCR. To demonstrate that IL-1β induced up-regulation of the MOR, DOR and KOR, U87 MG cells (2 x 105 cells/well were treated with IL-1β (20 ng/mL or 40 ng/mL, followed by co-treatment with interleukin-1 receptor antagonist protein (IL-1RAP (400 ng/mL or 400 ng/mL. The above experiment was repeated in the cells desensitized with morphine, where U87 MG cells were pre-treated with 100 nM morphine. The functionality of the MOR in U87 MG cells was then demonstrated using morphine inhibition of forksolin-induced intracellular cAMP, as determined by radioimmunoassay. Results U87 MG cells treated with IL-1β for 12 h showed a significant up-regulation of MOR and KOR. DOR expression was also elevated, although not significantly. Treatment with IL-1β also showed a significant up-regulation of the MOR in U87 MG cells desensitized with morphine. Co-treatment with IL-1β and interleukin-1 receptor antagonist protein (IL-1RAP resulted in a significant decrease in IL-1β-mediated MOR up-regulation. Conclusion Our results indicate that the pro-inflammatory cytokine, IL-1β, affects opiate-dependent pathways by up-regulating the expression of the MOR in both untreated and

  8. Cutaneous nociceptors lack sensitisation, but reveal μ-opioid receptor-mediated reduction in excitability to mechanical stimulation in neuropathy

    Schmidt Yvonne; Labuz Dominika; Heppenstall Paul A; Machelska Halina

    2012-01-01

    Abstract Background Peripheral nerve injuries often trigger a hypersensitivity to tactile stimulation. Behavioural studies demonstrated efficient and side effect-free analgesia mediated by opioid receptors on peripheral sensory neurons. However, mechanistic approaches addressing such opioid properties in painful neuropathies are lacking. Here we investigated whether opioids can directly inhibit primary afferent neuron transmission of mechanical stimuli in neuropathy. We analysed the mechanica...

  9. Deltorphin II enhances extracellular levels of dopamine in the nucleus accumbens via opioid receptor-independent mechanisms.

    Murakawa, K.; Hirose, N.; Takada, K.; Suzuki, T.; Nagase, H.; Cools, A.R.; Koshikawa, N.

    2004-01-01

    The effects of the delta2-opioid receptor agonist, deltorphin II, on extracellular levels of dopamine in the rat nucleus accumbens were investigated in awake animals by in vivo brain microdialysis. In agreement with previous studies, perfusion of deltorphin II (50.0 nmol) into the nucleus accumbens

  10. Preserved cardiac mitochondrial function and reduced ischaemia/reperfusion injury afforded by chronic continuous hypoxia: Role of opioid receptors

    Maslov, L. N.; Naryzhnaya, N. V.; Prokudina, E. S.; Kolář, František; Gorbunov, A. S.; Zhang, Y.; Wang, H.; Tsibulnikov, S.Yu.; Portnichenko, A. G.; Lasukova, T. V.; Lishmanov, Yu. B.

    2015-01-01

    Roč. 42, č. 5 (2015), s. 496-501. ISSN 1440-1681 R&D Projects: GA ČR(CZ) GAP303/12/1162 Institutional support: RVO:67985823 Keywords : cardioprotection * chronic hypoxia * ischaemia/reperfusion * mitochondrial function * opioid receptors Subject RIV: ED - Physiology Impact factor: 2.372, year: 2014

  11. κ-Opioid Receptor Is Colocalized in GnRH and KNDy Cells in the Female Ovine and Rat Brain.

    Weems, Peyton W; Witty, Christine F; Amstalden, Marcel; Coolen, Lique M; Goodman, Robert L; Lehman, Michael N

    2016-06-01

    Kisspeptin-neurokinin B-dynorphin (KNDy) cells of the hypothalamus are a key component in the neuroendocrine regulation of GnRH secretion. Evidence in sheep and other species suggests that dynorphin released by KNDy cells inhibits pulsatile GnRH secretion by acting upon κ-opioid receptors (KOR). However, the precise anatomical location and neurochemical phenotype of KOR-expressing cells in sheep remain unknown. To this end, we determined the distribution of KOR mRNA and protein in the brains of luteal phase ewes, using an ovine specific KOR mRNA probe for in situ hybridization and an antibody whose specificity we confirmed by Western blot analyses and blocking peptide controls. KOR cells were observed in a number of regions, including the preoptic area (POA); anterior hypothalamic area; supraoptic and paraventricular nuclei; ventromedial, dorsomedial, and lateral hypothalamus; and arcuate nucleus. Next, we determined whether KOR is colocalized in KNDy and/or GnRH cells. Dual-label immunofluorescence and confocal analysis of the KNDy population showed a high degree of colocalization, with greater than 90% of these neurons containing KOR. Surprisingly, GnRH cells also showed high levels of colocalization in sheep, ranging from 74.4% to 95.4% for GnRH cells in the POA and medial basal hypothalamus, respectively. Similarly, 97.4% of GnRH neurons in the POA of ovariectomized, steroid-primed female rats also contained immunoreactive KOR protein. These findings suggest that the inhibitory effects of dynorphin on pulsatile GnRH secretion may occur either indirectly by actions upon KOR within the KNDy population and/or directly via the activation of KOR on GnRH cells. PMID:27064940

  12. The Peptide Oxytocin Antagonist F-792, When Given Systemically, Does Not Act Centrally in Lactating Rats.

    Leng, G; Russell, J A

    2016-04-01

    Oxytocin secreted by nerve terminals in the posterior pituitary has important actions for ensuring a successful outcome of pregnancy: it stimulates uterine contractions that lead to birth and it is essential in the milk-ejection reflex, enabling milk to be expelled from the mammary glands into the mouths of suckling young. Oxytocin also has important actions in the brain: released from dendrites of neurones that innervate the posterior pituitary, oxytocin auto-excites the neurones to fire action potentials in co-ordinated bursts, causing secretion of pulses of oxytocin. Central oxytocin actions are blocked by an oxytocin antagonist given into the brain and, consequently, milk transfer stops. Systemic peptide oxytocin antagonist (atosiban) treatment is used clinically in management of pre-term labour, a major obstetric problem. Hence, it is important to know whether an oxytocin antagonist given peripherally can enter the brain and interfere with central oxytocin actions. In the present study, we tested F792, a peptide oxytocin antagonist. In urethane-anaesthetised suckled rats, we show that the mammary gland responsiveness to oxytocin is blocked by i.v. injections of 7 μg/kg of F792, and the milk-ejection reflex is blocked when F792 is given directly into the brain at a dose of 0.2 μg. To critically test whether F792 given systemically can enter the brain, we recorded the suckling- and oxytocin-induced burst-firing of individual antidromically identified oxytocin neurones in the paraventricular nucleus. Given systemically at 100 μg/kg i.v., F792 acted only peripherally, blocking the milk-ejecting actions of oxytocin, but not the burst-firing of oxytocin neurones during suckling (n = 5 neurones in five rats). Hence, this peptide oxytocin antagonist does not enter the brain from the circulation to interfere with an essential oxytocin function in the brain. Furthermore, the functions of oxytocin in the brain evidently cannot be explored with a systemic peptide

  13. Modulation of the behavioral and neurochemical effects of psychostimulants by kappa-opioid receptor systems.

    Shippenberg, T S; Chefer, V I; Zapata, A; Heidbreder, C A

    2001-06-01

    The repeated, intermittent use of cocaine and other drugs of abuse produces profound and often long-lasting alterations in behavior and brain chemistry. It has been suggested that these consequences of drug use play a critical role in drug craving and relapse to addiction. This article reviews the effects of psychostimulant administration on dopaminergic and excitatory amino acid neurotransmission in brain regions comprising the brain's motive circuit and provides evidence that the activation of endogenous kappa-opioid receptor systems in these regions opposes the behavioral and neurochemical consequences of repeated drug use. The role of this opioid system in mediating alterations in mood and affect that occur during abstinence from repeated psychostimulant use are also discussed. PMID:11458540

  14. Photoaffinity labeling of opioid receptor with morphine-7,8-oxide (morphine epoxide)

    Takayanagi, I.; Shibata, R.; Miyata, N.; Hirobe, M.

    1982-05-01

    The opioid receptor mediating inhibitory action of morphine in the electrically stimulated guinea pig ileum was irreversibly photoinactivated by morphine epoxide (3 X 10(-6) M). Morphine epoxide (up to 3 X 10(-5) M) did not influence the responses of rat vas deferens (epsilon-receptor) or rabbit vas deferens (kappa-receptor) to electrical stimulation. Effective concentrations of morphine epoxide were much lower in the guinea pig ileum (mu-receptor) than in the mouse vas deference (delta-receptor). The inhibitory action of (Met)-enkephalin on the twitch responses of the rat vas deferens and mouse vas deferens to electrical stimulation were not influenced after irradiation in the presence of morphine epoxide (3 X 10(-6) M). Therefore, morphine epoxide is probably a useful probe for photoaffinity labeling of the mu-receptor in vitro.

  15. Photoaffinity labeling of opioid receptor with morphine-7,8-oxide (morphine epoxide)

    The opioid receptor mediating inhibitory action of morphine in the electrically stimulated guinea pig ileum was irreversibly photoinactivated by morphine epoxide (3 X 10(-6) M). Morphine epoxide (up to 3 X 10(-5) M) did not influence the responses of rat vas deferens (epsilon-receptor) or rabbit vas deferens (kappa-receptor) to electrical stimulation. Effective concentrations of morphine epoxide were much lower in the guinea pig ileum (mu-receptor) than in the mouse vas deference (delta-receptor). The inhibitory action of [Met]-enkephalin on the twitch responses of the rat vas deferens and mouse vas deferens to electrical stimulation were not influenced after irradiation in the presence of morphine epoxide (3 X 10(-6) M). Therefore, morphine epoxide is probably a useful probe for photoaffinity labeling of the mu-receptor in vitro

  16. Expression of mu-opioid receptors in human chronic inflamed knee joint synovium tissue

    YUAN Hong-bin; HE Xing-ying; XU Hai-tao; ZHU Qiu-feng; WANG Ya-hua; SHI Xue-yin

    2006-01-01

    Objective:To examine the changes of mu-opioid receptors (MORs) expression in human chronic inflamed knee joint synovium tissue. Methods:Knee joint synovium tissues were taken from 21 patients with chronic arthritis(inflamed group) and 6 fresh bodies with normal knee joints(control group). And the expression of MORs was detected by using immunohistochemistry, flow cytometry (FCM) and reverse-transcription polymerase chain reaction(RT-PCR). Results: The expression of MORs in the inflamed group was significantly higher than that in the normal group by using the 3 techniques(P<0.05).Conclusion: Chronic inflammation enhances the up-regulation of MORs in human knee joint synovium tissue.

  17. Effect of sodium ion on the affinity of naloxone for the kappa opioid receptor

    Several investigators have observed that sodium ion enhances the binding of naloxone to opioid receptors. This effect has generally been attributed to allosteric modulation of the state of the mu receptor. However, a recent claim has been made that the enhancement does not involve a change in the mu receptor, but instead occurs because naloxone becomes a more kappa-specific drug when sodium ion is present in high concentration. Since the claim was not based on experimental evidence from binding studies involving known high-affinity kappa ligands, the authors have investigated the competition of naloxone for the kappa site using [3H]U-69593 as the marker for receptor binding. Assays were carried out in the presence and absence of 100 mM NaCl. The results of the study indicate that sodium ion does not increase the affinity of naloxone or U-69593 for the kappa receptor. 9 references, 1 figure

  18. Effect of sodium ion on the affinity of naloxone for the kappa opioid receptor

    Cheney, B.V.; Lahti, R.A.

    1987-03-16

    Several investigators have observed that sodium ion enhances the binding of naloxone to opioid receptors. This effect has generally been attributed to allosteric modulation of the state of the mu receptor. However, a recent claim has been made that the enhancement does not involve a change in the mu receptor, but instead occurs because naloxone becomes a more kappa-specific drug when sodium ion is present in high concentration. Since the claim was not based on experimental evidence from binding studies involving known high-affinity kappa ligands, the authors have investigated the competition of naloxone for the kappa site using (/sup 3/H)U-69593 as the marker for receptor binding. Assays were carried out in the presence and absence of 100 mM NaCl. The results of the study indicate that sodium ion does not increase the affinity of naloxone or U-69593 for the kappa receptor. 9 references, 1 figure.

  19. delta-Opioid receptors are more efficiently coupled to adenylyl cyclase than to L-type Ca(2+) channels in transfected rat pituitary cells.

    Prather, P L; Song, L; Piros, E T; Law, P Y; Hales, T G

    2000-11-01

    Opioid receptors often couple to multiple effectors within the same cell. To examine potential mechanisms that contribute to the specificity by which delta-receptors couple to distinct intracellular effectors, we stably transfected rat pituitary GH(3) cells with cDNAs encoding for delta-opioid receptors. In cells transfected with a relatively low delta-receptor density of 0.55 pmol/mg of protein (GH(3)DOR), activation of delta-receptors produced inhibition of adenylyl cyclase activity but was unable to alter L-type Ca(2+) current. In contrast, activation of delta-receptors in a clone that contained a higher density of delta-receptors (2.45 pmol/mg of protein) and was also coexpressed with mu-opioid receptors (GH(3)MORDOR), resulted in not only the expected inhibition of adenylyl cyclase activity but also produced inhibition of L-type Ca(2+) current. The purpose of the present study was to determine whether these observations resulted from differences in delta-opioid receptor density between clones or interaction between delta- and mu-opioid receptors to allow the activation of different G proteins and signaling to Ca(2+) channels. Using the delta-opioid receptor alkylating agent SUPERFIT, reduction of available delta-opioid receptors in GH(3)MORDOR cells to a density similar to that of delta-opioid receptors in the GH(3)DOR clone resulted in abolishment of coupling to Ca(2+) channels, but not to adenylyl cyclase. Furthermore, although significantly greater amounts of all G proteins were activated by delta-opioid receptors in GH(3)MORDOR cells, delta-opioid receptor activation in GH(3)DOR cells resulted in coupling to the identical pattern of G proteins seen in GH(3)MORDOR cells. These findings suggest that different threshold densities of delta-opioid receptors are required to activate critical amounts of G proteins needed to produce coupling to specific effectors and that delta-opioid receptors couple more efficiently to adenylyl cyclase than to L-type Ca(2

  20. Pharmacological properties of novel cyclic pentapeptides with µ-opioid receptor agonist activity.

    Perlikowska, Renata; Piekielna, Justyna; Fichna, Jakub; do-Rego, Jean Claude; Toth, Geza; Janecki, Tomasz; Janecka, Anna

    2014-03-01

    In our previous paper we have reported the synthesis and biological activity of a cyclic analog, Tyr-c(D-Lys- Phe-Phe-Asp)-NH2, based on endomorphin-2 (EM-2) structure. This analog displayed high affinity for the µ-opioid receptor, was much more stable than EM-2 in rat brain homogenate and showed remarkable antinociceptive activity after intracerebroventricular (i.c.v.) injection. Even more importantly, the cyclic analog elicited weak analgesia also after peripheral administration, giving evidence that it was able to cross, at least to some extent, the blood-brain barrier (BBB). Here we describe further modifications of this analog aimed at enhancing brain delivery by increasing lipophilicity. Two new cyclic pentapeptides, Tyr-c(D-Lys-D-1-Nal-Phe-Asp)-NH2 and Tyr-c(D-Lys-D-2-Nal-Phe-Asp)-NH2 (where 1-Nal=1- naphthyl-3-alanine, 2-Nal=2-naphthyl-3-alanine) were synthesized and evaluated in biological assays. Both analogs showed high µ-opioid receptor affinity and agonist activity and were stable in the rat brain homogenates. Unfortunately, the increase of lipophilicity was achieved at the expense of water solubility. The analog with D-2-Nal residue showed strong analgesic effect when given i.c.v. but could not be tested after intravenous (i.v.) administration where higher concentrations of the compound are required. However, this analog showed inhibitory effect on gastrointestinal (GI) motility in vivo, providing an interesting approach to the development of peripherally restricted agents that could be useful for studying gastrointestinal disorders in animal models. PMID:23628088

  1. Comparative modeling and molecular dynamics studies of the delta, kappa and mu opioid receptors.

    Strahs, D; Weinstein, H

    1997-09-01

    Molecular models of the trans-membrane domains of delta, kappa and mu opioid receptors, members of the G-protein coupled receptor (GPCR) superfamily, were developed using techniques of homology modeling and molecular dynamics simulations. Structural elements were predicted from sequence alignments of opioid and related receptors based on (i) the consensus, periodicities and biophysical interpretations of alignment-derived properties, and (ii) tertiary structure homology to rhodopsin. Initial model structures of the three receptors were refined computationally with energy minimization and the result of the first 210 ps of a 2 ns molecular dynamics trajectory at 300K. Average structures from the trajectory obtained for each receptor subtype after release of the initial backbone constraints show small backbone deviations, indicating stability. During the molecular dynamics phase, subtype-differentiated residues of the receptors developed divergent structures within the models, including changes in regions common to the three subtypes and presumed to belong to ligand binding regions. The divergent features developed by the model structures appear to be consistent with the observed ligand binding selectivities of the opioid receptors. The results thus implicate identifiable receptor microenvironments as primary determinants of some of the observed subtype specificities in opiate ligand binding and in functional effects of mutagenesis. Networks of interacting residues observed in the models are common to the opiate receptors and other GPCRs, indicating core interfaces that are potentially responsible for structural integrity and signal transduction. Analysis of extended molecular dynamics trajectories reveals concerted motions of distant parts of ligand-binding regions, suggesting motion-sensitive components of ligand binding. The comparative modeling results from this study help clarify experimental observations of subtype differences and suggest both structural and

  2. Multiscale design of coarse-grained elastic network-based potentials for the μ opioid receptor.

    Fossépré, Mathieu; Leherte, Laurence; Laaksonen, Aatto; Vercauteren, Daniel P

    2016-09-01

    Despite progress in computer modeling, most biological processes are still out of reach when using all-atom (AA) models. Coarse-grained (CG) models allow classical molecular dynamics (MD) simulations to be accelerated. Although simplification of spatial resolution at different levels is often investigated, simplification of the CG potential in itself has been less common. CG potentials are often similar to AA potentials. In this work, we consider the design and reliability of purely mechanical CG models of the μ opioid receptor (μOR), a G protein-coupled receptor (GPCR). In this sense, CG force fields (FF) consist of a set of holonomic constraints guided by an elastic network model (ENM). Even though ENMs are used widely to perform normal mode analysis (NMA), they are not often implemented as a single FF in the context of MD simulations. In this work, various ENM-like potentials were investigated by varying their force constant schemes and connectivity patterns. A method was established to systematically parameterize ENM-like potentials at different spatial resolutions by using AA data. To do so, new descriptors were introduced. The choice of conformation descriptors that also include flexibility information is important for a reliable parameterization of ENMs with different degrees of sensitivity. Hence, ENM-like potentials, with specific parameters, can be sufficient to accurately reproduce AA MD simulations of μOR at highly coarse-grained resolutions. Therefore, the essence of the flexibility properties of μOR can be captured with simple models at different CG spatial resolutions, opening the way to mechanical approaches to understanding GPCR functions. Graphical Abstract All atom structure, residue interaction network and coarse-grained elastic network models of the μ opioid receptor (μOR). PMID:27566318

  3. Nucleoside-Derived Antagonists to A3 Adenosine Receptors Lower Mouse Intraocular Pressure and Act across Species

    Wang, Zhao; Do, Chi Wai; Avila, Marcel Y.; Peterson-Yantorno, Kim; Stone, Richard A.; Gao, Zhan-Guo; Joshi, Bhalchandra; Besada, Pedro; Jeong, Lak Shin; Jacobson, Kenneth A.; Civan, Mortimer M.

    2009-01-01

    The purpose of the study was to determine whether novel, selective antagonists of human A3 adenosine receptors (ARs) derived from the A3-selective agonist Cl-IB-MECA lower intraocular pressure (IOP) and act across species. IOP was measured invasively with a micropipette by the Servo-Null Micropipette System (SNMS) and by non-invasive pneumotonometry during topical drug application. Antagonist efficacy was also assayed by measuring inhibition of adenosine-triggered shrinkage of native bovine n...

  4. Possible Involvement of µ Opioid Receptor in the Antidepressant-Like Effect of Shuyu Formula in Restraint Stress-Induced Depression-Like Rats

    Fu-rong Wang

    2015-01-01

    Full Text Available Recently μ opioid receptor (MOR has been shown to be closely associated with depression. Here we investigated the action of Shuyu, a Chinese herbal prescription, on repeated restraint stress induced depression-like rats, with specific attention to the role of MOR and the related signal cascade. Our results showed that repeated restraint stress caused significant depressive-like behaviors, as evidenced by reduced body weight gain, prolonged duration of immobility in forced swimming test, and decreased number of square-crossings and rearings in open field test. The stress-induced depression-like behaviors were relieved by Shuyu, which was accompanied by decreased expression of MOR in hippocampus. Furthermore, Shuyu upregulated BDNF protein expression, restored the activity of CREB, and stimulated MEK and ERK phosphorylation in hippocampus of stressed rats. More importantly, MOR is involved in the effects of Shuyu on these depression-related signals, as they can be strengthened by MOR antagonist CTAP. Collectively, these data indicated that the antidepressant-like properties of Shuyu are associated with MOR and the corresponding CREB, BDNF, MEK, and ERK signal pathway. Our study supports clinical use of Shuyu as an effective treatment of depression and also suggests that MOR might be a target for treatment of depression and developing novel antidepressants.

  5. Downregulation of δ opioid receptor by RNA interference enhances the sensitivity of BEL/FU drug-resistant human hepatocellular carcinoma cells to 5-FU

    Tang, Bo; Hu, Zhigao; Li, Yang; YUAN, SHENGGUANG; Wang, Zhenran; Yu, Shuiping; He, Songqing

    2015-01-01

    δ opioid receptor (DOR) was the first opioid receptor of the G protein-coupled receptor family to be cloned. Our previous studies demonstrated that DOR is involved in regulating the development and progression of human hepatocellular carcinoma (HCC), and is involved in the regulation of the processes of invasion and metastasis of HCC cells. However, whether DOR is involved in the development and progression of drug resistance in HCC has not been reported and requires further elucidation. The ...

  6. Safety of long acting muscarinic antagonists: are all these drugs always and equally safe?

    Melani, Andrea S; Sestini, Piersante

    2016-05-01

    Inhaled bronchodilators - such as long-acting muscarinic receptor antagonists (LAMAs) - are central to the pharmacological management of symptomatic chronic obstructive pulmonary disease. LAMAs are considered to be safe drugs at recommended dosages. In the present issue of the Journal safety of umeclidinium, a recently marketed LAMA, at twice the recommended dosage, has been evaluated with good results in a Japanese, COPD population. However, because muscarinic receptors are expressed not only in the lungs but also at the level of heart, digestive and urinary apparatus, the potential exists for LAMAs to cause adverse events related to stimulation of receptors in these organs. Head-to-head and post-marketing vigilance studies are required to determine the profile risk of these drugs, ultimately, and whether differences exist between currently available LAMAs. PMID:26789695

  7. The interaction between histamine H1 receptor and μ- opioid receptor in scratching behavior in ICR mice.

    Nakasone, Tasuku; Sugimoto, Yumi; Kamei, Chiaki

    2016-04-15

    In this study, we examined the interaction between histamine H1 receptor and μ-opioid receptor in scratching behavior in ICR mice. Both histamine and morphine caused scratching and simultaneous injection of histamine and morphine had an additive effect. Chlorpheniramine and naloxone inhibited histamine-induced scratching behavior. These two drugs also inhibited morphine-induced scratching behavior. Simultaneous injection of chlorpheniramine and naloxone caused a significant inhibition of histamine-induced scratching compared with separate injections. The same findings were also noted for morphine-induced scratching. These results strongly indicate a close relationship between histamine H1 receptor and μ-opioid receptor in scratching behavior in ICR mice. PMID:26948312

  8. Role of Opioid Receptors Signaling in Remote Electrostimulation - Induced Protection against Ischemia/Reperfusion Injury in Rat Hearts

    Tsai, Hsin-Ju; Huang, Shiang-Suo; Tsou, Meng-Ting; Wang, Hsiao-Ting; Chiu, Jen-Hwey

    2015-01-01

    Aims Our previous studies demonstrated that remote electro-stimulation (RES) increased myocardial GSK3 phosphorylation and attenuated ischemia/ reperfusion (I/R) injury in rat hearts. However, the role of various opioid receptors (OR) subtypes in preconditioned RES-induced myocardial protection remains unknown. We investigated the role of OR subtype signaling in RES-induced cardioprotection against I/R injury of the rat heart. Methods & Results Male Spraque-Dawley rats were used. RES was perf...

  9. It’s MORe exciting than mu: crosstalk between mu opioid receptors and glutamatergic transmission in the mesolimbic dopamine system

    Chartoff, Elena H.; Connery, Hilary S.

    2014-01-01

    Opioids selective for the G protein-coupled mu opioid receptor (MOR) produce potent analgesia and euphoria. Heroin, a synthetic opioid, is considered one of the most addictive substances, and the recent exponential rise in opioid addiction and overdose deaths has made treatment development a national public health priority. Existing medications (methadone, buprenorphine, and naltrexone), when combined with psychosocial therapies, have proven efficacy in reducing aspects of opioid addiction. U...

  10. On the role of cannabinoid CB1- and µ-opioid receptors in nicotine-induced motor impulsivity

    TommyPattij

    2012-01-01

    Previous studies using a rat 5-choice serial reaction time task (5-CSRTT) have established a critical role for dopamine D2 receptors in regulating increments in motor impulsivity induced by acute administration of the psychostimulant drugs amphetamine and nicotine. Here we investigated whether cannabinoid CB1 and/or µ-opioid receptors are involved in nicotine-induced impulsivity, given recent findings indicating that both receptor systems mediate amphetamine-induced motor impulsivity. Re...

  11. Effects of defeat stress on behavioral flexibility in males and females: modulation by the mu-opioid receptor

    Laredo, Sarah A.; Steinman, Michael Q.; Robles, Cindee F.; Ferrer, Emilio; Ragen, Benjamin J.; Trainor, Brian C.

    2015-01-01

    Behavioral flexibility is a component of executive functioning that allows individuals to adapt to changing environmental conditions. Independent lines of research indicate that the mu opioid receptor (MOR) is an important mediator of behavioral flexibility and responses to psychosocial stress. The current study bridges these two lines of research and tests the extent to which social defeat and MOR affect behavioral flexibility and whether sex moderates these effects in California mice (Perom...

  12. Functional role of peripheral opioid receptors in the regulation of cardiac spinal afferent nerve activity during myocardial ischemia

    Fu, Liang-Wu; Longhurst, John C.

    2013-01-01

    Thinly myelinated Aδ-fiber and unmyelinated C-fiber cardiac sympathetic (spinal) sensory nerve fibers are activated during myocardial ischemia to transmit the sensation of angina pectoris. Although recent observations showed that myocardial ischemia increases the concentrations of opioid peptides and that the stimulation of peripheral opioid receptors inhibits chemically induced visceral and somatic nociception, the role of opioids in cardiac spinal afferent signaling during myocardial ischem...

  13. Autistic-Like Syndrome in Mu Opioid Receptor Null Mice is Relieved by Facilitated mGluR4 Activity

    Becker, Jérôme AJ; Clesse, Daniel; Spiegelhalter, Coralie; Schwab, Yannick; Le Merrer, Julie; Kieffer, Brigitte L.

    2014-01-01

    The etiology of Autism Spectrum Disorders (ASDs) remains largely unknown. Identifying vulnerability genes for autism represents a major challenge in the field and allows the development of animal models for translational research. Mice lacking the mu opioid receptor gene (Oprm1−/−) were recently proposed as a monogenic mouse model of autism, based on severe deficits in social behavior and communication skills. We confirm this hypothesis by showing that adult Oprm1−/− animals recapitulate core...

  14. Effect of forced treadmill exercise and blocking of opioid receptors with naloxone on memory in male rats

    Atefeh Asadi Rizi; Parham Reisi; Nooshin Naghsh

    2016-01-01

    Background: The forced treadmill running can influence the opioid contents of the brain, through both effects of exercise and the effects of stress caused by coercion. Since opioids can cause negative effects on brain functions, this study aimed to evaluate the effect of forced treadmill exercise and blocking of opioid receptors with naloxone on memory in male rats. Materials and Methods: Experimental groups were the control, the exercise, the naloxone, and the naloxone exercise. The exerc...

  15. Abolished thermal and mechanical antinociception but retained visceral chemical antinociception induced by butorphanol in μ-opioid receptor knockout mice

    Ide, Soichiro; Minami, Masabumi; Ishihara, Kumatoshi; Uhl, George R; Satoh, Masamichi; Sora, Ichiro; Ikeda, Kazutaka

    2008-01-01

    Butorphanol is hypothesized to induce analgesia via opioid pathways, although the precise mechanisms for its effects remain unknown. In this study, we investigated the role of the μ-opioid receptor (MOP) in thermal, mechanical, and visceral chemical antinociception induced by butorphanol using MOP knockout (KO) mice. Butorphanol-induced thermal antinociception, assessed by the hot-plate and tail-flick tests, was significantly reduced in heterozygous and abolished in homozygous MOP-KO mice com...

  16. Sex differences in kappa opioid receptor function and their potential impact on addiction

    Elena eChartoff

    2015-12-01

    Full Text Available Behavioral, biological and social sequelae that lead to drug addiction differ between men and women. Our efforts to understand addiction on a mechanistic level must include studies in both males and females. Stress, anxiety, and depression are tightly linked to addiction, and whether they precede or result from compulsive drug use depends on many factors, including biological sex. The neuropeptide dynorphin (DYN, an endogenous ligand at kappa opioid receptors (KORs, is necessary for stress-induced aversive states and is upregulated in the brain after chronic exposure to drugs of abuse. KOR agonists produce signs of anxiety, fear, and depression in laboratory animals and humans, findings that have led to the hypothesis that drug withdrawal-induced DYN release is instrumental in negative reinforcement processes that drive addiction. However, these studies were almost exclusively conducted in males. Only recently is evidence available that there are sex differences in the effects of KOR activation on affective state. This review focuses on sex differences in DYN and KOR systems and how these might contribute to sex differences in addictive behavior. Much of what is known about how biological sex influences KOR systems is from research on pain systems. The basic molecular and genetic mechanisms that have been discovered to underlie sex differences in KOR function in pain systems may apply to sex differences in KOR function in reward systems. Our goals are to discuss the current state of knowledge on how biological sex contributes to KOR function in the context of pain,mood and addiction and to explore potential mechanisms for sex differences in KOR function. We will highlight evidence that the function of DYN-KOR systems is influenced in a sex-dependent manner by: polymorphisms in the prodynorphin (pDYN gene, genetic linkage with the melanocortin-1 receptor (MC1R, heterodimerization of KORs and mu opioid receptors (MORs, and gonadal hormones

  17. Functional and structural characterization of axonal opioid receptors as targets for analgesia

    Mambretti, Egle M; Kistner, Katrin; Mayer, Stefanie; Massotte, Dominique; Kieffer, Brigitte L; Hoffmann, Carsten; Reeh, Peter W; Brack, Alexander; Asan, Esther

    2016-01-01

    Background Opioids are the gold standard for the treatment of acute pain despite serious side effects in the central and enteric nervous system. µ-opioid receptors (MOPs) are expressed and functional at the terminals of sensory axons, when activated by exogenous or endogenous ligands. However, the presence and function of MOP along nociceptive axons remains controversial particularly in naïve animals. Here, we characterized axonal MOPs by immunofluorescence, ultrastructural, and functional analyses. Furthermore, we evaluated hypertonic saline as a possible enhancer of opioid receptor function. Results Comparative immunolabeling showed that, among several tested antibodies, which all provided specific MOP detection in the rat central nervous system (CNS), only one monoclonal MOP-antibody yielded specificity and reproducibility for MOP detection in the rat peripheral nervous system including the sciatic nerve. Double immunolabeling documented that MOP immunoreactivity was confined to calcitonin gene-related peptide (CGRP) positive fibers and fiber bundles. Almost identical labeling and double labeling patterns were found using mcherry-immunolabeling on sciatic nerves of mice producing a MOP-mcherry fusion protein (MOP-mcherry knock-in mice). Preembedding immunogold electron microscopy on MOP-mcherry knock-in sciatic nerves indicated presence of MOP in cytoplasm and at membranes of unmyelinated axons. Application of [D-Ala2, N-MePhe4, Gly-ol]-enkephalin (DAMGO) or fentanyl dose-dependently inhibited depolarization-induced CGRP release from rat sciatic nerve axons ex vivo, which was blocked by naloxone. When the lipophilic opioid fentanyl was applied perisciatically in naïve Wistar rats, mechanical nociceptive thresholds increased. Subthreshold doses of fentanyl or the hydrophilic opioid DAMGO were only effective if injected together with hypertonic saline. In vitro, using β-arrestin-2/MOP double-transfected human embryonic kidney cells, DAMGO as well as fentanyl

  18. Somatostatin and opioid receptors do not regulate proliferation or apoptosis of the human multiple myeloma U266 cells

    Allouche Stéphane

    2009-06-01

    Full Text Available Abstract Background opioid and somatostatin receptors (SSTRs that can assemble as heterodimer were individually reported to modulate malignant cell proliferation and to favour apoptosis. Materials and methods: SSTRs and opioid receptors expression were examined by RT-PCR, western-blot and binding assays, cell proliferation was studied by XTT assay and propidium iodide (PI staining and apoptosis by annexin V-PI labelling. Results almost all human malignant haematological cell lines studied here expressed the five SSTRs. Further experiments were conducted on the human U266 multiple myeloma cells, which express also μ-opioid receptors (MOP-R. XTT assays and cell cycle studies provide no evidence for a significant effect upon opioid or somatostatin receptors stimulation. Furthermore, neither direct effect nor potentiation of the Fas-receptor pathway was detected on apoptosis after these treatments. Conclusion these data suggest that SSTRs or opioid receptors expression is not a guaranty for an anti-tumoral action in U266 cell line.

  19. Reconstitution of rate brain μ opioid receptors with purified guanine nucleotide-binding regulatory proteins, Gi and Go

    Reconstitution of purified μ opioid receptors with purified guanine nucleotide-binding regulatory proteins (G proteins) was investigated. The purified μ opioid receptor (pI 5.6) migrated as a single Mr 58,000 polypeptide by NaDodSO4/PAGE, a value identical to that obtained by affinity cross-linking purified μ receptors. When purified μ receptors were reconstituted with purified Gi, the G protein that mediates the inhibition of adenylate cyclase, the displacement of [3H]naloxone binding by [D-Ala2,MePhe4,Gly-ol5]enkephalin was increased 215-fold; this increase was abolished by adding 100 μM guanosine 5'-[γ-thio]triphosphate. Similar increases in agonist displacement of [3H]naloxone binding (33-fold) and its abolition by guanosine 5'-[γ-thio]triphosphate were observed with Go, the G protein of unknown function, but not with the v-Ki-ras protein p.21. The stoichiometry was such that the stimulation of 1 mol of μ receptor led to the binding of [3H]guanosine 5'-[β,γ-imido]triphosphate to 2.5 mol of Gi or to 1.37 mol of Go. These results suggest that the purified μ opioid receptor is functionally coupled to Gi and Go in the reconstituted phospholipid vesicles

  20. Synthesis and evaluation of aryl-naloxamide opiate analgesics targeting truncated exon 11-associated mu opioid receptor (MOR-1) splice variants

    Majumdar, Susruta; Subrath, Joan; Le Rouzic, Valerie; Polikar, Lisa; Burgman, Maxim; Nagakura, Kuni; Ocampo, Julie; Haselton, Nathan; Pasternak, Anna R.; Grinnell, Steven; Pan, Ying-Xian; Pasternak, Gavril W.

    2012-01-01

    3-Iodobenzoylnaltrexamide 1 (IBNtxA) is a potent analgesic acting through a novel receptor target that lack many side-effects of traditional opiates composed, in part, of exon 11-associated truncated six transmembrane domain MOR-1 (6TM/E11) splice variants. To better understand the SAR of this drug target, a number of 4,5-epoxymorphinan analogs were synthesized. Results show the importance of a free 3-phenolic group, a phenyl ring at the 6 position, an iodine at the 3′ or 4′ position of the phenyl ring and an N-allyl or c-propylmethyl group to maintain high 6TM/E11 affinity and activity. 3-Iodobenzoylnaloxamide 15 (IBNalA) with a N-allyl group displayed lower delta opioid receptor affinity than its naltrexamine analog, was 10-fold more potent an analgesic than morphine, elicited no respiratory depression or physical dependence and only limited inhibition of gastrointestinal transit. Thus, the aryl-naloxamide scaffold can generate a potent analgesic acting through the 6TM/E11 sites with advantageous side-effect profile and greater selectivity. PMID:22734622

  1. Synthesis and evaluation of aryl-naloxamide opiate analgesics targeting truncated exon 11-associated μ opioid receptor (MOR-1) splice variants.

    Majumdar, Susruta; Subrath, Joan; Le Rouzic, Valerie; Polikar, Lisa; Burgman, Maxim; Nagakura, Kuni; Ocampo, Julie; Haselton, Nathan; Pasternak, Anna R; Grinnell, Steven; Pan, Ying-Xian; Pasternak, Gavril W

    2012-07-26

    3-Iodobenzoylnaltrexamide 1 (IBNtxA) is a potent analgesic acting through a novel receptor target that lack many side-effects of traditional opiates composed, in part, of exon 11-associated truncated six transmembrane domain MOR-1 (6TM/E11) splice variants. To better understand the SAR of this drug target, a number of 4,5-epoxymorphinan analogues were synthesized. Results show the importance of a free 3-phenolic group, a phenyl ring at the 6 position, an iodine at the 3'or 4' position of the phenyl ring, and an N-allyl or c-propylmethyl group to maintain high 6TM/E11 affinity and activity. 3-Iodobenzoylnaloxamide 15 (IBNalA) with a N-allyl group displayed lower δ opioid receptor affinity than its naltrexamine analogue, was 10-fold more potent an analgesic than morphine, elicited no respiratory depression or physical dependence, and only limited inhibition of gastrointestinal transit. Thus, the aryl-naloxamide scaffold can generate a potent analgesic acting through the 6TM/E11 sites with advantageous side-effect profile and greater selectivity. PMID:22734622

  2. Evaluation of radioiodinated C6-O- and N-iodoallyl analogues of diprenorphine as ligands for cerebral opioid receptors

    Lever, J.R.; Scheffel, U.; Stathis, M. [The Johns Hopkins Medical Institutions, Baltimore, MD (United States)] [and others

    1994-05-01

    Analogues of diprenorphine (DPN) having C6-O-iodoallyl (O-IA-DPN) and N-iodoallyl (N-IA-DPN) substituents can be I-125 labeled in good yield with high specific activity by radioiododestannylation. When tested in vitro against [H-3]-DPN in rat brain membranes, the apparent affinity (Ki) of O-IA-DPN (1.35 nM) proved 17-fold stronger than that of N-IA-DPN (23.4 nM). Against selective [H-3]-ligands, O-IA-DPN showed high apparent affinities for {mu}(1.9 nM), {gamma}(1.1 nM) and {kappa}(0.9 nM) sites. Consistent with the low apparent affinity in vitro, [I-125]-N-IA- DPN did not allow localization of cerebral opioid receptors after i.v. administration to mice. By contrast, [I-125]-O-IA-DPN exhibited a regional brain distribution which reflects binding to multiple opioid receptors. The highest radioactivity concentrations were in superior colliculi, hypothalamus, olfactory tubercles, thalamus and striatum. Peak levels (2.5-3.5 %ID/g) were maintained over the first 60 min. At all times, the lowest levels of radioactivity were in the cerebellum. Binding in vivo was saturable by O-IA-DPN, was blocked by (-)- but not by (+)-naloxone, and was inhibited by naltrexone in dose-dependent fashion. Specific binding was 83-93% for all tissues except cerebellum, where 50% blockade was noted with naltrexone (5.0 mg/kg). Using naltrexone blockade to define non-specific binding, the highest ratio of specific to non-specific binding (> 14 to 1) was noted for superior colliculi at 60 min. Inhibition studies with drugs selective for {mu}, {gamma} or {kappa} sites established that multiple opioid receptors are labeled. [123I]-O-IA-DPN has been prepared (84%, >2400 mCi/{mu}mol), and allows visualization of opioid receptors in mouse brain by ex vivo autoradiography. Together, these results suggest that [123I]-O-IA-DPN is suitable for SPECT studies of multiple opioid receptors.

  3. Chronic Morphine Reduces Surface Expression of δ-Opioid Receptors in Subregions of Rostral Striatum.

    Leah, Paul M; Heath, Emily M L; Balleine, Bernard W; Christie, Macdonald J

    2016-03-01

    The delta opioid receptor (DOPr), whilst not the primary target of clinically used opioids, is involved in development of opioid tolerance and addiction. There is growing evidence that DOPr trafficking is involved in drug addiction, e.g., a range of studies have shown increased plasma membrane DOPr insertion during chronic treatment with opioids. The present study used a transgenic mouse model in which the C-terminal of the DOPr is tagged with enhanced-green fluorescence protein to examine the effects of chronic morphine treatment on surface membrane expression in striatal cholinergic interneurons that are implicated in motivated learning following both chronic morphine and morphine sensitization treatment schedules in male mice. A sex difference was noted throughout the anterior striatum, which was most prominent in the nucleus accumbens core region. Incontrast with previous studies in other neurons, chronic exposure to a high dose of morphine for 6 days had no effect, or slightly decreased (anterior dorsolateral striatum) surface DOPr expression. A morphine sensitization schedule produced similar results with a significant decrease in surface DOPr expression in nucleus accumbens shell. These results suggest that chronic morphine and morphine sensitisation treatment may have effects on instrumental reward-seeking behaviours and learning processes related to drug addiction, via effects on striatal DOPr function. PMID:26093651

  4. Behavioural activation system sensitivity is associated with cerebral μ-opioid receptor availability.

    Karjalainen, Tomi; Tuominen, Lauri; Manninen, Sandra; Kalliokoski, Kari K; Nuutila, Pirjo; Jääskeläinen, Iiro P; Hari, Riitta; Sams, Mikko; Nummenmaa, Lauri

    2016-08-01

    The reinforcement-sensitivity theory proposes that behavioural activation and inhibition systems (BAS and BIS, respectively) guide approach and avoidance behaviour in potentially rewarding and punishing situations. Their baseline activity presumably explains individual differences in behavioural dispositions when a person encounters signals of reward and harm. Yet, neurochemical bases of BAS and BIS have remained poorly understood. Here we used in vivo positron emission tomography with a µ-opioid receptor (MOR) specific ligand [(11)C]carfentanil to test whether individual differences in MOR availability would be associated with BAS or BIS. We scanned 49 healthy subjects and measured their BAS and BIS sensitivities using the BIS/BAS scales. BAS but not BIS sensitivity was positively associated with MOR availability in frontal cortex, amygdala, ventral striatum, brainstem, cingulate cortex and insula. Strongest associations were observed for the BAS subscale 'Fun Seeking'. Our results suggest that endogenous opioid system underlies BAS, and that differences in MOR availability could explain inter-individual differences in reward seeking behaviour. PMID:27053768

  5. Weight loss after bariatric surgery normalizes brain opioid receptors in morbid obesity.

    Karlsson, H K; Tuulari, J J; Tuominen, L; Hirvonen, J; Honka, H; Parkkola, R; Helin, S; Salminen, P; Nuutila, P; Nummenmaa, L

    2016-08-01

    Positron emission tomography (PET) studies suggest opioidergic system dysfunction in morbid obesity, while evidence for the role of the dopaminergic system is less consistent. Whether opioid dysfunction represents a state or trait in obesity remains unresolved, but could be assessed in obese subjects undergoing weight loss. Here we measured brain μ-opioid receptor (MOR) and dopamine D2 receptor (D2R) availability in 16 morbidly obese women twice-before and 6 months after bariatric surgery-using PET with [(11)C]carfentanil and [(11)C]raclopride. Data were compared with those from 14 lean control subjects. Receptor-binding potentials (BPND) were compared between the groups and between the pre- and postoperative scans among the obese subjects. Brain MOR availability was initially lower among obese subjects, but weight loss (mean=26.1 kg, s.d.=7.6 kg) reversed this and resulted in ~23% higher MOR availability in the postoperative versus preoperative scan. Changes were observed in areas implicated in reward processing, including ventral striatum, insula, amygdala and thalamus (P'ssystem plays an important role in the pathophysiology of human obesity. Because bariatric surgery and concomitant weight loss recover downregulated MOR availability, lowered MOR availability is associated with an obese phenotype and may mediate excessive energy uptake. Our results highlight that understanding the opioidergic contribution to overeating is critical for developing new treatments for obesity. PMID:26460230

  6. Cannabinoid, melanocortin and opioid receptor expression on DRD1 and DRD2 subpopulations in rat striatum

    Ralph J Oude-Ophuis

    2014-03-01

    Full Text Available The striatum harbors two neuronal populations that enable action selection. One population represents the striatonigral pathway, expresses the dopamine receptor D1 (DRD1 and promotes the execution of motor programs, while the other population represents the striatopallidal pathway, expresses the dopamine receptor D2 (DRD2 and suppresses voluntary activity. The two populations integrate distinct sensorimotor, cognitive and emotional information streams and their combined activity enables the selection of adaptive behaviors. Characterization of these populations is critical to the understanding of their role in action selection, because it aids the identification of the molecular mechanisms that separate them. To that end, we used fluorescent in-situ hybridization to quantify the percentage of striatal cells that (coexpress dopaminergic receptors and receptors of the cannabinoid, melanocortin or opioid neurotransmitters systems. Our main findings are that the cannabinoid 1 receptor is equally expressed on both populations with a gradient from dorsal to ventral striatum, that the opioid receptors have a preference for expression with either the DRD1 or DRD2 and that the melanocortin 4 receptor (MC4R is predominantly expressed in ventral parts of the striatum. In addition, we find that the level of MC4R expression determines its localization to either the DRD1 or the DRD2 population. Thereby, we provide insight into the sensitivity of the two dopaminoceptive populations to these neurotransmitters and progress the understanding of the mechanisms that enable action selection.

  7. IRAS Modulates Opioid Tolerance and Dependence by Regulating μ Opioid Receptor Trafficking.

    Li, Fei; Ma, Hao; Wu, Ning; Li, Jin

    2016-09-01

    Imidazoline receptor antisera-selected (IRAS) protein, the mouse homologue named Nischarin, was found to target to early endosomes with properties of sorting nexins in vitro. Recently, we generated IRAS knockout mice and found IRAS deficiency exacerbated the analgesic tolerance and physical dependence caused by opioids, suggesting that IRAS plays a role in regulating μ opioid receptor (MOR) functions. In the present study, we found that IRAS interacts with MOR and regulates MOR trafficking in vitro. In the CHO or HEK293 cells co-expressing MOR and IRAS, IRAS, through its PX domain, interacted with MOR. The interaction facilitated the recycling of internalized MOR and prevented MOR downregulation induced by DAMGO, the MOR agonist. Functionally, IRAS accelerated MOR resensitization and attenuated DAMGO-induced MOR desensitization, which is believed as one of mechanisms mediating opioid tolerance and dependence. Taken together, we propose that IRAS is a new MOR interacting protein and regulates agonist-induced trafficking of MOR via sorting internalized MOR to the recycling pathway, which may be a molecular mechanism underlying IRAS modulating opioid tolerance and dependence. PMID:26363797

  8. Stable expression of human opioid receptor-like 1 in chinese hamster ovary cells

    Objective: To stably transfect human opioid receptor-like 1 (hORL1) in Chinese hamster ovary (CHO) cells. Methods: pcDNA3.1 (+) -hORL1 was stably transfected into CHO cells by a lipofectamine based method. Transfected CHO cells were selected in culture medium containing G418. Radioligand receptor binding assay and [35S] GTPSγ binding assay were used to determine densities and functions of the expressed receptors. Results and Conclusion: hORL1 was expressed in the CHO cells. The Kd and Bmax were (0.44 ± 0.21) nmol/L and (0.35 ± 0.06) pmol/mg protein, respectively, for hORL1 in [3H] nociceptin binding assay. The EC50 of nociceptin was 3.45 nmol/L in stimulation of [35S] GTPγS binding by nociceptin.A model system of CHO cells with stable expression of hORL1 is established. (authors)

  9. Effect of delta opioid receptor activation on spatial cognition and neurogenesis in cerebral ischemic rats.

    Wang, Shu-Yan; Duan, Ya-Le; Zhao, Bing; Wang, Xiang-Rui; Zhao, Zheng; Zhang, Guang-Ming

    2016-05-01

    This study aimed to investigate whether a selective delta opioid receptor agonist, [D-Ala2, D-Leu5]-Enkephalin (DADLE), regulates neurogenesis in the hippocampus of ischemic rats. Using an intracerebral cannula, rats were subjected to cerebral ischemia using the standard four-vessel occlusion. DADLE (2.5nmol), DADLE (2.5nmol) with naltrindole (NAL) (2.5nmol), or vehicle was administered at the onset of reperfusion. Bromodeoxyuridine (BrdU, 100mg/kg, intraperitoneal) was used to label newly formed cells from days 1 to 7 after ischemia. Immunohistochemistry was used to evaluate cell proliferation and apoptosis and differentiation 7days 28 days, respectively, after ischemia. Morris water maze test was conducted to test spatial learning and memory 23-27 days after ischemia. We found that DADLE treatment improved performance in the Morris water maze test, promoted proliferation and differentiation of newly formed neurons, and inhibited differentiation into astrocytes in a rat model of cerebral ischemia. Furthermore, the protective effects of DADLE were significantly reversed by co-administration of NAL (Pstrategy for cerebral ischemia. PMID:27016387

  10. Up-regulation of -opioid receptors in the spinal cord of morphine-tolerant rats

    Subrata Basu Ray; Himanshu Gupta; Yogendra Kumar Gupta

    2004-03-01

    Though morphine remains the most powerful drug for treating pain, its effectiveness is limited by the development of tolerance and dependence. The mechanism underlying development of tolerance to morphine is still poorly understood. One of the factors could be an alteration in the number of m-receptors within specific parts of the nervous system. However, reports on changes in the -opioid receptor density in the spinal cord after chronic morphine administration are conflicting. Most of the studies have used subcutaneously implanted morphine pellets to produce tolerance. However, it does not simulate clinical conditions, where it is more common to administer morphine at intervals, either by injections or orally. In the present study, rats were made tolerant to morphine by injecting increasing doses of morphine (10–50 mg/kg, subcutaneously) for five days. In vitro tissue autoradiography for localization of -receptor in the spinal cord was done using [3H]-DAMGO. As compared to the spinal cord of control rats, the spinal cord of tolerant rats showed an 18.8% increase or up-regulation in the density of -receptors in the superficial layers of the dorsal horn. This up-regulation of -receptors after morphine tolerance suggests that a fraction of the receptors have been rendered desensitized, which in turn could lead to tolerance.

  11. Combined autoradiographic-immunocytochemical analysis of opioid receptors and opioid peptide neuronal systems in brain

    Using adjacent section autoradiography-immunocytochemistry, the distribution of [3H]naloxone binding sites was studied in relation to neuronal systems containing [Leu]enkephalin, dynorphin A, or beta-endorphin immunoreactivity in rat brain. Brain sections from formaldehyde-perfused rats show robust specific binding of [3H]naloxone, the pharmacological (mu-like) properties of which appear unaltered. In contrast, specific binding of the delta ligand [3H]D-Ala2,D-Leu5-enkephalin was virtually totally eliminated as a result of formaldehyde perfusion. Using adjacent section analysis, the authors have noted associations between [3H]naloxone binding sites and one, two, or all three opioid systems in different brain regions; however, in some areas, no apparent relationship could be observed. Within regions, the relationship was complex. The complexity of the association between [3H]naloxone binding sites and the multiple opioid systems, and previous reports of co-localization of mu and kappa receptors in rat brain, are inconsistent with a simple-one-to-one relationship between a given opioid precursor and opioid receptor subtype. Instead, since differential processing of the three precursors gives rise to peptides of varying receptor subtype potencies and selectivities, the multiple peptide-receptor relationships may point to a key role of post-translational processing in determining the physiological consequences of opioid neurotransmission

  12. Corelation Between Single Nucleotide Polymorphisms in Mu Opioid Receptor Exon 2 and Stereotypic Behaviour in Sows

    LI Jianhong; BAO Jun; CUI Weiguo

    2008-01-01

    Three breeds of sows were observed to investigate the relationship between Single Nucleotide Polymorphisms (SNPs) in Mu Opioid Receptor (MOR) and stereotypic behaviour, such as, sham-chewing, bar biting and standing still in order to better understand the mechanism of stereotypic development of the animals in restrained conditions. MOR exon 2 partial sequences were amplified to analyze single nucleotide polymorphisms by PCR-SSCE One SNP, a silence mutant was found. A significant difference (P<0.01) was found in the frequency of genotypes in these 3 breeds where only the BB genotype, which was identical to that published in GenBank, was found in the Duroc breed, while no AA genotype was found in Landrace, 3 genotypes AA, BB and AB were found in Yorkshire. The result also indicated that the individuals with AA and AB genotypes tended to be more active in sham-chewing than those with the BB genotype (P<0.05). The overall results of this study suggested that sham-chewing of sows may be subjected to both genetic control and environmental conditions, but activity level was more likely to be affected by their environment. We can putatively draw the conclusion that MOR gene has effect on the sham-chewing behavioral traits of sow.

  13. Mu Opioid Receptor Binding Correlates with Nicotine Dependence and Reward in Smokers.

    Hiroto Kuwabara

    Full Text Available The rewarding effects of nicotine are associated with activation of nicotine receptors. However, there is increasing evidence that the endogenous opioid system is involved in nicotine's rewarding effects. We employed PET imaging with [11C]carfentanil to test the hypotheses that acute cigarette smoking increases release of endogenous opioids in the human brain and that smokers have an upregulation of mu opioid receptors (MORs when compared to nonsmokers. We found no significant changes in binding potential (BPND of [11C]carfentanil between the placebo and the active cigarette sessions, nor did we observe differences in MOR binding between smokers and nonsmokers. Interestingly, we showed that in smokers MOR availability in bilateral superior temporal cortices during the placebo condition was negatively correlated with scores on the Fagerström Test for Nicotine Dependence (FTND. Also in smokers, smoking-induced decreases in [11C]carfentanil binding in frontal cortical regions were associated with self-reports of cigarette liking and wanting. Although we did not show differences between smokers and nonsmokers, the negative correlation with FTND corroborates the role of MORs in superior temporal cortices in nicotine addiction and provides preliminary evidence of a role of endogenous opioid signaling in frontal cortex in nicotine reward.

  14. Ethanol Disinhibits Dorsolateral Striatal Medium Spiny Neurons Through Activation of A Presynaptic Delta Opioid Receptor.

    Patton, Mary H; Roberts, Bradley M; Lovinger, David M; Mathur, Brian N

    2016-06-01

    The dorsolateral striatum mediates habit formation, which is expedited by exposure to alcohol. Across species, alcohol exposure disinhibits the DLS by dampening GABAergic transmission onto this structure's principal medium spiny projection neurons (MSNs), providing a potential mechanistic basis for habitual alcohol drinking. However, the molecular and circuit components underlying this disinhibition remain unknown. To examine this, we used a combination of whole-cell patch-clamp recordings and optogenetics to demonstrate that ethanol potently depresses both MSN- and fast-spiking interneuron (FSI)-MSN GABAergic synaptic transmission in the DLS. Concentrating on the powerfully inhibitory FSI-MSN synapse, we further show that acute exposure of ethanol (50 mM) to striatal slices activates delta opioid receptors that reside on FSI axon terminals and negatively couple to adenylyl cyclase to induce a long-term depression of GABA release onto both direct and indirect pathway MSNs. These findings elucidate a mechanism through which ethanol may globally disinhibit the DLS. PMID:26758662

  15. Nucleoside-derived antagonists to A3 adenosine receptors lower mouse intraocular pressure and act across species.

    Wang, Zhao; Do, Chi Wai; Avila, Marcel Y; Peterson-Yantorno, Kim; Stone, Richard A; Gao, Zhan-Guo; Joshi, Bhalchandra; Besada, Pedro; Jeong, Lak Shin; Jacobson, Kenneth A; Civan, Mortimer M

    2010-01-01

    The purpose of the study was to determine whether novel, selective antagonists of human A3 adenosine receptors (ARs) derived from the A3-selective agonist Cl-IB-MECA lower intraocular pressure (IOP) and act across species. IOP was measured invasively with a micropipette by the Servo-Null Micropipette System (SNMS) and by non-invasive pneumotonometry during topical drug application. Antagonist efficacy was also assayed by measuring inhibition of adenosine-triggered shrinkage of native bovine nonpigmented ciliary epithelial (NPE) cells. Five agonist-based A3AR antagonists lowered mouse IOP measured with SNMS tonometry by 3-5 mm Hg within minutes of topical application. Of the five agonist derivatives, LJ 1251 was the only antagonist to lower IOP measured by pneumotonometry. No effect was detected pneumotonometrically over 30 min following application of the other four compounds, consonant with slower, smaller responses previously measured non-invasively following topical application of A3AR agonists and the dihydropyridine A3AR antagonist MRS 1191. Latanoprost similarly lowered SNMS-measured IOP, but not IOP measured non-invasively over 30 min. Like MRS 1191, agonist-based A3AR antagonists applied to native bovine NPE cells inhibited adenosine-triggered shrinkage. In summary, the results indicate that antagonists of human A3ARs derived from the potent, selective A3 agonist Cl-IB-MECA display efficacy in mouse and bovine cells, as well. When intraocular delivery was enhanced by measuring mouse IOP invasively, five derivatives of the A3AR agonist Cl-IB-MECA lowered IOP but only one rapidly reduced IOP measured non-invasively after topical application. We conclude that derivatives of the highly-selective A3AR agonist Cl-IB-MECA can reduce IOP upon reaching their intraocular target, and that nucleoside-based derivatives are promising A3 antagonists for study in multiple animal models. PMID:19878673

  16. MGM-9 [(E)-methyl 2-(3-ethyl-7a,12a-(epoxyethanoxy)-9-fluoro-1,2,3,4,6,7,12,12b-octahydro-8-methoxyindolo[2,3-a]quinolizin-2-yl)-3-methoxyacrylate], a derivative of the indole alkaloid mitragynine: a novel dual-acting mu- and kappa-opioid agonist with potent antinociceptive and weak rewarding effects in mice.

    Matsumoto, Kenjiro; Takayama, Hiromitsu; Narita, Minoru; Nakamura, Atsushi; Suzuki, Masami; Suzuki, Tsutomu; Murayama, Toshihiko; Wongseripipatana, Sumphan; Misawa, Kaori; Kitajima, Mariko; Tashima, Kimihito; Horie, Syunji

    2008-08-01

    Mitragynine is a major indole alkaloid isolated from the Thai medicinal plant Mitragyna speciosa that has opium-like properties, although its chemical structure is quite different from that of morphine. We attempted to develop novel analgesics derived from mitragynine, and thus synthesized the ethylene glycol-bridged and C10-fluorinated derivative of mitragynine, MGM-9 [(E)-methyl 2-(3-ethyl-7a,12a-(epoxyethanoxy)-9-fluoro-1,2,3,4,6,7,12,12b-octahydro-8-methoxyindolo[2,3-a]quinolizin-2-yl)-3-methoxyacrylate]. We hypothesized that a dual-acting mu- and kappa-opioid agonist could produce potent antinociceptive effects with fewer rewarding effects compared with mu agonists. In this study, MGM-9 exhibited high affinity for mu- and kappa-opioid receptors with Ki values of 7.3 and 18 nM, respectively. MGM-9 showed a potent opioid agonistic effect, and its effects were meditated by mu- and kappa-opioid receptor mechanisms in in vitro assays. Subcutaneous and oral administration of MGM-9 produced potent antinociceptive effects in mouse tail-flick, hot-plate, and writhing tests. When administered orally, the antinociceptive effect of MGM-9 was seven to 22 times more potent than that of morphine. The antinociceptive effects of MGM-9 were mediated by both mu- and kappa-opioid receptors. Subcutaneous administration of MGM-9 twice daily for 5 days led to antinociceptive tolerance. In the gastrointestinal transit study, MGM-9 inhibited gastrointestinal transit, but its effect was weaker than that of morphine at equi-antinociceptive doses. Furthermore, MGM-9 induced less hyperlocomotion and fewer rewarding effects than morphine. The rewarding effect of MGM-9 was blocked by a mu antagonist and enhanced by a kappa antagonist. Taken together, the results suggest that MGM-9 is a promising novel analgesic that has a stronger antinociceptive effect and weaker adverse effects than morphine. PMID:18550129

  17. Truncated G protein-coupled mu opioid receptor MOR-1 splice variants are targets for highly potent opioid analgesics lacking side effects.

    Majumdar, Susruta; Grinnell, Steven; Le Rouzic, Valerie; Burgman, Maxim; Polikar, Lisa; Ansonoff, Michael; Pintar, John; Pan, Ying-Xian; Pasternak, Gavril W

    2011-12-01

    Pain remains a pervasive problem throughout medicine, transcending all specialty boundaries. Despite the extraordinary insights into pain and its mechanisms over the past few decades, few advances have been made with analgesics. Most pain remains treated by opiates, which have significant side effects that limit their utility. We now describe a potent opiate analgesic lacking the traditional side effects associated with classical opiates, including respiratory depression, significant constipation, physical dependence, and, perhaps most important, reinforcing behavior, demonstrating that it is possible to dissociate side effects from analgesia. Evidence indicates that this agent acts through a truncated, six-transmembrane variant of the G protein-coupled mu opioid receptor MOR-1. Although truncated splice variants have been reported for a number of G protein-coupled receptors, their functional relevance has been unclear. Our evidence now suggests that truncated variants can be physiologically important through heterodimerization, even when inactive alone, and can comprise new therapeutic targets, as illustrated by our unique opioid analgesics with a vastly improved pharmacological profile. PMID:22106286

  18. Long-acting muscarinic antagonists for the prevention of exacerbations of chronic obstructive pulmonary disease.

    Jones, Paul W

    2015-06-01

    Exacerbations of chronic obstructive pulmonary disease (COPD) have important consequences for lung function, health status and mortality. Furthermore, they are associated with high economic costs, predominantly related to hospitalization. They are managed acutely with short-acting bronchodilators, systemic corticosteroids or antibiotics; however, a large proportion of COPD exacerbations are unreported and therefore untreated or self-managed. There is evidence to suggest that these unreported exacerbations also have important consequences for health status; therefore, reducing exacerbation risk is an important goal in the management of COPD. Current guidelines recommend long-acting muscarinic antagonists (LAMAs) as first-line bronchodilator therapy in patients with stable COPD who have a high risk of exacerbation or increased symptoms. To date, three LAMAs, tiotropium bromide, aclidinium bromide and glycopyrronium bromide, have been approved as maintenance bronchodilator treatments for stable COPD. These all provide clinically significant improvements in lung function, reduce symptoms and improve health status compared with placebo in patients with COPD. This paper reviews evidence from randomized, controlled clinical trials demonstrating that tiotropium, aclidinium and glycopyrronium reduce exacerbation risk in patients with COPD. Reductions were seen irrespective of the exacerbation measure used, whether time to first event or annualized exacerbation rate. Furthermore, studies with aclidinium suggest LAMAs can reduce exacerbation risk irrespective of whether exacerbation events are assessed, using an event-based approach or a symptom-based method which includes unreported events. Together these results demonstrate that LAMAs have the potential to provide clinical benefit in the management of exacerbations in patients with stable COPD. PMID:25801643

  19. Kappa Opioid Receptor-Mediated Dysregulation of GABAergic Transmission in the Central Amygdala in Cocaine Addiction

    Kallupi, Marsida; Wee, Sunmee; Edwards, Scott; Whitfield, Tim W.; Oleata, Christopher S.; Luu, George; Schmeichel, Brooke E.; Koob, George F.; Roberto, Marisa

    2013-01-01

    Background Studies have demonstrated an enhanced dynorphin/kappa-opioid receptor (KOR) system following repeated cocaine exposure, but few reports have focused on neuroadaptations within the central amygdala (CeA). Methods We identified KOR-related physiological changes in the CeA following escalation of cocaine self-administration in rats. We used in vitro slice electrophysiological (intracellular and whole-cell recordings) methods to assess whether differential cocaine access in either 1h (short access, ShA) or 6h (long access, LgA) sessions induced plasticity at CeA GABAergic synapses, or altered the sensitivity of these synapses to KOR agonism (U50488) or antagonism (nor-BNI). We then determined the functional effects of CeA KOR blockade in cocaine-related behaviors. Results Baseline evoked GABAergic transmission was enhanced in the CeA from ShA and LgA rats compared to cocaine-naïve rats. Acute cocaine (1 uM) application significantly decreased GABA release in all groups (naïve, ShA, and LgA rats). Application of U50488 (1 uM) significantly decreased GABAergic transmission in the CeA from naïve rats, but increased it in LgA rats. Conversely, nor-BNI (200 nM) significantly increased GABAergic transmission in the CeA from naïve rats, but decreased it in LgA rats. Nor-BNI did not alter the acute cocaine-induced inhibition of GABAergic responses. Finally, CeA microinfusion of nor-BNI blocked cocaine-induced locomotor sensitization and attenuated the heightened anxiety-like behavior observed during withdrawal from chronic cocaine exposure in the defensive burying paradigm. Conclusion Together these data demonstrate that CeA dynorphin/KOR systems are dysregulated following excessive cocaine exposure and suggest KOR antagonism as a viable therapeutic strategy for cocaine addiction. PMID:23751206

  20. Delta opioid receptors expressed in forebrain GABAergic neurons are responsible for SNC80-induced seizures

    CHUNG, Paul CHU SIN; BOEHRER, Annie; STEPHAN, Aline; MATIFAS, Audrey; SCHERRER, Gregory; DARCQ, Emmanuel; BEFORT, Katia; KIEFFER, Brigitte L.

    2014-01-01

    The delta opioid receptor (DOR) has raised much interest for the development of new therapeutic drugs, particularly to treat patients suffering from mood disorders and chronic pain. Unfortunately, the prototypal DOR agonist SNC80 induces mild epileptic seizures in rodents. Although recently developed agonists do not seem to show convulsant properties, mechanisms and neuronal circuits that support DOR-mediated epileptic seizures remain to be clarified. DORs are expressed throughout the nervous system. In this study we tested the hypothesis that SNC80-evoked seizures stem from DOR activity at the level of forebrain GABAergic transmission, whose inhibition is known to facilitate the development of epileptic seizures. We generated a conditional DOR knockout mouse line, targeting the receptor gene specifically in GABAergic neurons of the forebrain (Dlx-DOR). We measured effects of SNC80 (4.5, 9, 13.5 and 32 mg/kg), ARM390 (10, 30 and 60 mg/kg) or ADL5859 (30, 100 and 300 mg/kg) administration on electroencephalograms (EEGs) recorded in Dlx-DOR mice and their control littermates (Ctrl mice). SNC80 produced dose-dependent seizure events in Ctrl mice, but these effects were not detected in Dlx-DOR mice. As expected, ARM390 and ADL5859 did not trigger any detectable change in mice from both genotypes. These results demonstrate for the first time that SNC80-induced DOR activation induces epileptic seizures via direct inhibition of GABAergic forebrain neurons, and supports the notion of differential activities between first and second-generation DOR agonists. PMID:25447299

  1. Galpha-subunits differentially alter the conformation and agonist affinity of kappa-opioid receptors.

    Yan, Feng; Mosier, Philip D; Westkaemper, Richard B; Roth, Bryan L

    2008-02-12

    Although ligand-induced conformational changes in G protein-coupled receptors (GPCRs) are well-documented, there is little direct evidence for G protein-induced changes in GPCR conformation. To investigate this possibility, the effects of overexpressing Galpha-subunits (Galpha16 or Galphai2) with the kappa-opioid receptor (KOR) were examined. The changes in KOR conformation were subequently examined via the substituted cysteine accessibility method (SCAM) in transmembrane domains 6 (TM6) and 7 (TM7) and extracellular loop 2 (EL2). Significant conformational changes were observed on TM7, the extracellular portion of TM6, and EL2. Seven SCAM-sensitive residues (S3107.33, F3147.37, and I3167.39 to Y3207.43) on TM7 presented a cluster pattern when the KOR was exposed to baseline amounts of G protein, and additional residues became sensitive upon overexpression of various G proteins. In TM7, S3117.34 and N3267.49 were found to be sensitive in Galpha16-overexpressed cells and Y3137.36, N3227.45, S3237.46, and L3297.52 in Galphai2-overexpressed cells. In addition, the degree of sensitivity for various TM7 residues was augmented, especially in Galphai2-overexpressed cells. A similar phenomenon was also observed for residues in TM6 and EL2. In addition to an enhanced sensitivity of certain residues, our findings also indicated that a slight rotation was predicted to occur in the upper part of TM7 upon G protein overexpression. These relatively modest conformational changes engendered by G protein overexpression had both profound and differential effects on the abilities of agonists to bind to KOR. These data are significant because they demonstrate that Galpha-subunits differentially modulate the conformation and agonist affinity of a prototypical GPCR. PMID:18205395

  2. A novel alternatively spliced isoform of the mu-opioid receptor: functional antagonism

    Wentworth Sean

    2010-06-01

    Full Text Available Abstract Background Opioids are the most widely used analgesics for the treatment of clinical pain. They produce their therapeutic effects by binding to μ-opioid receptors (MORs, which are 7 transmembrane domain (7TM G-protein-coupled receptors (GPCRs, and inhibiting cellular activity. However, the analgesic efficacy of opioids is compromised by side-effects such as analgesic tolerance, dependence and opioid-induced hyperalgesia (OIH. In contrast to opioid analgesia these side effects are associated with cellular excitation. Several hypotheses have been advanced to explain these phenomena, yet the molecular mechanisms underlying tolerance and OIH remain poorly understood. Results We recently discovered a new human alternatively spliced isoform of MOR (MOR1K that is missing the N-terminal extracellular and first transmembrane domains, resulting in a 6TM GPCR variant. To characterize the pattern of cellular transduction pathways activated by this human MOR1K isoform, we conducted a series of pharmacological and molecular experiments. Results show that stimulation of MOR1K with morphine leads to excitatory cellular effects. In contrast to stimulation of MOR1, stimulation of MOR1K leads to increased Ca2+ levels as well as increased nitric oxide (NO release. Immunoprecipitation experiments further reveal that unlike MOR1, which couples to the inhibitory Gαi/o complex, MOR1K couples to the stimulatory Gαs complex. Conclusion The major MOR1 and the alternative MOR1K isoforms mediate opposite cellular effects in response to morphine, with MOR1K driving excitatory processes. These findings warrant further investigations that examine animal and human MORK1 expression and function following chronic exposure to opioids, which may identify MOR1K as a novel target for the development of new clinically effective classes of opioids that have high analgesic efficacy with diminished ability to produce tolerance, OIH, and other unwanted side-effects.

  3. In vivo antinociception of potent mu opioid agonist tetrapeptide analogues and comparison with a compact opioid agonist - neurokinin 1 receptor antagonist chimera

    Guillemyn Karel

    2012-01-01

    Full Text Available Abstract Background An important limiting factor in the development of centrally acting pharmaceuticals is the blood-brain barrier (BBB. Transport of therapeutic peptides through this highly protective physiological barrier remains a challenge for peptide drug delivery into the central nervous system (CNS. Because the most common strategy to treat moderate to severe pain consists of the activation of opioid receptors in the brain, the development of active opioid peptide analogues as potential analgesics requires compounds with a high resistance to enzymatic degradation and an ability to cross the BBB. Results Herein we report that tetrapeptide analogues of the type H-Dmt1-Xxx2-Yyy3-Gly4-NH2 are transported into the brain after intravenous and subcutaneous administration and are able to activate the μ- and δ opioid receptors more efficiently and over longer periods of time than morphine. Using the hot water tail flick test as the animal model for antinociception, a comparison in potency is presented between a side chain conformationally constrained analogue containing the benzazepine ring (BVD03, Yyy3: Aba, and a "ring opened" analogue (BVD02, Yyy3: Phe. The results show that in addition to the increased lipophilicity through amide bond N-methylation, the conformational constraint introduced at the level of the Phe3 side chain causes a prolonged antinociception. Further replacement of NMe-D-Ala2 by D-Arg2 in the tetrapeptide sequence led to an improved potency as demonstrated by a higher and maintained antinociception for AN81 (Xxx2: D-Arg vs. BVD03 (Xxx2: NMe-D-Ala. A daily injection of the studied opioid ligands over a time period of 5 days did however result in a substantial decrease in antinociception on the fifth day of the experiment. The compact opioid agonist - NK1 antagonist hybrid SBCHM01 could not circumvent opioid induced tolerance. Conclusions We demonstrated that the introduction of a conformational constraint has an important

  4. Renal responses produced by microinjection of the kappa opioid receptor agonist, U50-488H, into sites within the rat lamina terminalis.

    Franklin, Cynthia; Fortepiani, Lourdes; Nguyen, Tin; Rangel, Yolanda; Strong, Randy; Gottlieb, Helmut B

    2015-03-01

    Activation of central kappa opioid receptors (KOR) has been demonstrated to produce marked free water diuresis with a concurrent increase in renal sympathetic nerve activity (RSNA). This study investigated the cardiovascular (CV) and renal effects evoked by central activation of KOR in two lamina terminalis sites, the median preoptic area (MPA) and anterolateral division of the bed nuclei of the stria terminalis (BST). Rats anesthetized with urethane alpha-chloralose were instrumented to record mean arterial pressure, heart rate, RSNA, and urine output (V). Rats were infused with isotonic saline (25 μL/min) and urine samples were collected during two 10-min control periods and six consecutive 10-min experimental periods following microinjection of vehicle, U50-448H (U50, KOR agonist) alone or norbinaltorphimine (nor-BNI, KOR antagonist) plus U50. Microinjection of U50 into the BST increased V (peak at 30 min, 84.8 ± 12.9 μL/min) as compared to its respective control, vehicle, or nor-BNI plus U50. This diuretic effect occurred without any significant changes in CV parameters, RSNA, or urinary sodium excretion. In contrast, U50 injection into the MPA significantly increased RSNA (peak at 20 mins: 129 ± 9.9) without increasing the other parameters. This study demonstrated novel sites through which activation of KOR selectively increases V and RSNA. The ability of U50 to increase V without affecting sodium excretion and RSNA raises the possibility that LT neurons could be an important substrate through which drugs targeting KOR could selectively facilitate water excretion in sodium-retaining diseases such as congestive heart failure. PMID:26038693

  5. δ-Opioid receptor-stimulated Akt signaling in neuroblastoma x glioma (NG108-15) hybrid cells involves receptor tyrosine kinase-mediated PI3K activation

    δ-Opioid receptor (DOR) agonists possess cytoprotective properties, an effect associated with activation of the 'pro-survival' kinase Akt. Here we delineate the signal transduction pathway by which opioids induce Akt activation in neuroblastoma x glioma (NG108-15) hybrid cells. Exposure of the cells to both [D-Pen2,5]enkephalin and etorphine resulted in a time- and dose-dependent increase in Akt activity, as measured by means of an activation-specific antibody recognizing phosphoserine-473. DOR-mediated Akt signaling is blocked by the opioid antagonist naloxone and involves inhibitory Gi/o proteins, because pre-treatment with pertussis toxin, but not over-expression of the Gq/11 scavengers EBP50 and GRK2-K220R, prevented this effect. Further studies with Wortmannin and LY294002 revealed that phophoinositol-3-kinase (PI3K) plays a central role in opioid-induced Akt activation. Opioids stimulate Akt activity through transactivation of receptor tyrosine kinases (RTK), because pre-treatment of the cells with inhibitors for neurotrophin receptor tyrosine kinases (AG879) and the insulin-like growth factor receptor IGF-1 (AG1024), but not over-expression of the Gβγ scavenger phosducin, abolished this effect. Activated Akt translocates to the nuclear membrane, where it promotes GSK3 phosphorylation and prevents caspase-3 cleavage, two key events mediating inhibition of cell apoptosis and enhancement of cell survival. Taken together, these results demonstrate that in NG108-15 hybrid cells DOR agonists possess cytoprotective properties mediated by activation of the RTK/PI3K/Akt signaling pathway.

  6. Delta-Opioid Receptor (δOR) Targeted Near-Infrared Fluorescent Agent for Imaging of Lung Cancer: Synthesis and Evaluation In Vitro and In Vivo.

    Cohen, Allison S; Patek, Renata; Enkemann, Steven A; Johnson, Joseph O; Chen, Tingan; Toloza, Eric; Vagner, Josef; Morse, David L

    2016-02-17

    In the United States, lung cancer is the leading cause of cancer death and ranks second in the number of new cases annually among all types of cancers. Better methods or tools for diagnosing and treating this disease are needed to improve patient outcomes. The delta-opioid receptor (δOR) is reported to be overexpressed in lung cancers and not expressed in normal lung. Thus, we decided to develop a lung cancer-specific imaging agent targeting this receptor. We have previously developed a δOR-targeted fluorescent imaging agent based on a synthetic peptide antagonist (Dmt-Tic) conjugated to a Cy5 fluorescent dye. In this work, we describe the synthesis of Dmt-Tic conjugated to a longer wavelength near-infrared fluorescent (NIRF) dye, Li-cor IR800CW. Binding affinity of Dmt-Tic-IR800 for the δOR was studied using lanthanide time-resolved fluorescence (LTRF) competitive binding assays in cells engineered to overexpress the δOR. In addition, we identified lung cancer cell lines with high and low endogenous expression of the δOR. We confirmed protein expression in these cell lines using confocal fluorescence microscopy imaging and used this technique to estimate the cell-surface receptor number in the endogenously expressing lung cancer cell lines. The selectivity of Dmt-Tic-IR800 for imaging of the δOR in vivo was shown using both engineered cell lines and endogenously expressing lung cancer cells in subcutaneous xenograft models in mice. In conclusion, the δOR-specific fluorescent probe developed in this study displays excellent potential for imaging of lung cancer. PMID:26488422

  7. {delta}-Opioid receptor-stimulated Akt signaling in neuroblastoma x glioma (NG108-15) hybrid cells involves receptor tyrosine kinase-mediated PI3K activation

    Heiss, Anika; Ammer, Hermann [Institute of Pharmacology, Toxicology and Pharmacy Ludwig-Maximilians-University of Munich Koeniginstrasse 16 80539 Muenchen Federal Republic of Germany (Germany); Eisinger, Daniela A., E-mail: eisinger@pharmtox.vetmed.uni-muenchen.de [Institute of Pharmacology, Toxicology and Pharmacy Ludwig-Maximilians-University of Munich Koeniginstrasse 16 80539 Muenchen Federal Republic of Germany (Germany)

    2009-07-15

    {delta}-Opioid receptor (DOR) agonists possess cytoprotective properties, an effect associated with activation of the 'pro-survival' kinase Akt. Here we delineate the signal transduction pathway by which opioids induce Akt activation in neuroblastoma x glioma (NG108-15) hybrid cells. Exposure of the cells to both [D-Pen{sup 2,5}]enkephalin and etorphine resulted in a time- and dose-dependent increase in Akt activity, as measured by means of an activation-specific antibody recognizing phosphoserine-473. DOR-mediated Akt signaling is blocked by the opioid antagonist naloxone and involves inhibitory G{sub i/o} proteins, because pre-treatment with pertussis toxin, but not over-expression of the G{sub q/11} scavengers EBP50 and GRK2-K220R, prevented this effect. Further studies with Wortmannin and LY294002 revealed that phophoinositol-3-kinase (PI3K) plays a central role in opioid-induced Akt activation. Opioids stimulate Akt activity through transactivation of receptor tyrosine kinases (RTK), because pre-treatment of the cells with inhibitors for neurotrophin receptor tyrosine kinases (AG879) and the insulin-like growth factor receptor IGF-1 (AG1024), but not over-expression of the G{beta}{gamma} scavenger phosducin, abolished this effect. Activated Akt translocates to the nuclear membrane, where it promotes GSK3 phosphorylation and prevents caspase-3 cleavage, two key events mediating inhibition of cell apoptosis and enhancement of cell survival. Taken together, these results demonstrate that in NG108-15 hybrid cells DOR agonists possess cytoprotective properties mediated by activation of the RTK/PI3K/Akt signaling pathway.

  8. [Cys(O2NH2)2]enkephalin analogues and dalargin: selectivity for delta-opioid receptors.

    Pencheva, N; Bocheva, A; Dimitrov, E; Ivancheva, C; Radomirov, R

    1996-05-23

    To investigate the structure-activity relationships for potent and selective action of enkephalins at the delta-opioid receptors, two newly synthesized analogues, [Cys(O2NH2)2,Leu5]enkephalin and [Cys(O2NH2)2, Met5] enkephalin and the hexapeptide [D-Ala2,Leu5]enkephalyl-Arg (dalargin) were tested and compared with [Leu5]enkephalin and [Met5]enkephalin, for their effectiveness to inhibit electrically evoked contractions of the mouse vas deferens (predominantly enkephalin-selective delta-opioid receptors) and the guinea pig ileum (mu- and kappa-opioid receptors). The mouse vas deferens assays included evaluation of the effects of opioid agonists on the first, purinergic, and the second, adrenergic, components of electrically evoked biphasic responses (10 Hz and 20 Hz) and on ATP- or noradrenaline-evoked, tetrodotoxin-resistant responses. The opioids tested inhibited in a similar manner: (i) the purinergic and the adrenergic components of the electrically evoked contractions; and (ii) the ATP- and noradrenaline-induced postjunctional responses of the mouse vas deferens. Extremely low IC50 values (of 2-5 orders) were found for [Cys(O2NH2)2,Leu5] enkephalin, whose relative potency was between 239 and 1316 times higher than that of [Leu5]enkephalin. The order of potency for the other peptides in this tissue was: [Cys(O2NH2)2,Met5]enkephalin > [Leu5]enkephalin > dalargin > [Met5]enkephalin. The highest IC50 values in the guinea pig ileum assays, indicating the lowest affinity for mu-/kappa-opioid receptors, were obtained for the cysteine sulfonamide analogues, while dalargin showed a potency four times higher than that of [Met5]enkephalin. The order of potency in this tissue was: dalargin > [Met5]enkephalin > [Leu5]enkephalin > [Cys(O2NH2)2,Met5]enkephalin > [Cys(O2NH2)2,Leu5]enkephalin. The ratio, IC50 in guinea pig ileum: IC50 in mouse vas deferens, indicating selectivity of the respective peptide for delta-opioid receptors, was extremely high for [Cys(O2NH2)2,Leu5

  9. Membrane glycoprotein M6A promotes μ-opioid receptor endocytosis and facilitates receptor sorting into the recycling pathway

    Ying-Jian Liang; Dai-Fei Wu; Ralf Stumm; Volker H(o)llt; Thomas Koch

    2008-01-01

    The interaction of μ-opioid receptor (MOPr) with the neuronal membrane glycoprotein M6a is known to facilitate MOPr endocytosis in human embryonic kidney 293 (HEK293) cells. To further study the role of M6a in the post-endocytotic sorting of MOPr, we investigated the agonist-induced co-internalization of MOPr and M6a and protein targeting after internalization in HEK293 cells that co-expressed HA-tagged MOPr and Myc-tagged M6a. We found that M6a, MOPr, and Rab 11, a marker for recycling endosomes, co-localized in endocytotic vesicles, indicating that MOPr and M6a are primarily targeted to recycling endosomes after endocytosis. Furthermore, co-expression of M6a augmented the post-endocytotic sorting of δ-opioid receptors into the recycling pathway, indicating that M6a might have a more general role in opioid receptor post-ndocytotic sorting. The enhanced post-endocytotic sorting of MOPr into the recycling pathway was accompanied by a decrease in agonist-induced receptor down-regulation of M6a in co-expressing cells. We tested the physiological relevance of these findings in primary cultures of cortical neurons and found that co-expression of M6a markedly increased the translocation of MOPrs from the plasma membrane to intracellular vesicles at steady state and significantly enhanced both constitutive and agonist-induced receptor endocytosis. In conclusion, our results strongly indicate that M6a modulates MOPr endocytosis and post-endocytotic sorting and has an important role in receptor regulation.

  10. Study of preparation of radioiodinated allyl diprenorphine as an single photon emission computed tomographic imaging agent for mapping opioid receptors

    Purpose: To prepare and evaluate radioiodinated allyl diprenorphine (DPN) as a new opioid receptor imaging agent for SPECT study. Methods: 7α-O-stannyl-DPN was obtained from DPN by acetylated it to protect the phenolic 3-OH group of DPN and then introduced the vinylstannane into the tertiary alcohol of the 7α-side chain. [125I]-7α-O-iodoallyl diprenorphine (7α-O-IA-DPN) was prepared by radioiododestannylation under acidic condition using iodobead as an oxidant reagent, and in vitro and in vivo opioid receptor binding assays, metabolism were performed with Kunming mouse brains. Study of distribution in the Wistar rat's brain and naloxone inhibition was carried out. The data were analyzed by statistical method. Results: The radiochemical yields of I-125-7α-O-IA-DPN were more than 90%. In TLC, Rf of 7α-O-IA-DPN and I-125-7α-O-IA-DPN was 0.83 and 0.93, respectively. In ambient temperature the radiochemical purity of I-125-7α-O-IA-DPN in rats showed higher in anterior and posterior colliculi, striatum and hippocampus. It was low in frontal lobe, temporal lobe and brain stem and was low in cerebellum and the other parts of the brain. Among the clearance from the structures in brain, it was fastest in cerebellum. At 20 min when the uptake reached to the peak, the ratio of anterior and posterior colliculi, striatum and hippocampus to the cerebellum was 4.36, 3.7 and 3.12, respectively. There were significant differences between the inhibition experimental group using the naloxone and control. Conclusions: I-125-7α-O-IA-DPN appears to be a potential opioid receptor imaging agent for SPECT study. (authors)