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Gass JT, Olive MF. Transcriptional profiling of the rat frontal cortex following administration of the mGlu5 receptor antagonists MPEP and MTEP. Eur J Pharmacol 2008; 584:253-62. [PMID: 18346726 DOI: 10.1016/j.ejphar.2008.02.032] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2007] [Revised: 01/16/2008] [Accepted: 02/12/2008] [Indexed: 10/22/2022]
Abstract
The development of selective type 5 metabotropic glutamate receptor (mGlu5) antagonists, such as 2-methyl-6-(phenylethynyl)-pyridine (MPEP) and 3-[(2-methyl-1,3-thiazol-4-yl)ethynyl]-pyridine (MTEP), has revealed an important role for these receptors in various disorders of the nervous system including depression, anxiety, epilepsy, Parkinson's disease, drug addiction, and alcoholism. In this study, we used microarray technology to examine changes in gene expression induced by repeated administration of the mGlu5 antagonists MPEP and MTEP. Male Wistar rats (n=5 per treatment group) were administered MPEP (10 mg/kg), MTEP (10 mg/kg) or vehicle intraperitoneally twice daily for 5 days. Approximately 30 min following the final drug administration, rats were sacrificed and frontal cortices were then dissected and examined for changes in gene expression by cDNA microarray analysis. Changes in gene expression with p-values less than 0.01 were considered to be statistically significant. The expression of 63 genes was changed by both MPEP and MTEP, with 58 genes down-regulated and 5 genes up-regulated. Quantitative PCR verified the magnitude and direction of change in expression of 9 of these genes (r2=0.556, p=0.017). Pathway analysis revealed that many of the biological processes altered by repeated MPEP and MTEP treatment were related to ATP synthesis, hydrolase activity, and signaling pathways associated with mitogen-activated protein kinase (MAPK). Our results demonstrate diverse effects of MPEP and MTEP gene expression in the frontal cortex, and these results may help elucidate the mechanisms by which these compounds produce beneficial effects in animal models of various disorders of the central nervous system.
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Affiliation(s)
- Justin T Gass
- Center for Drug and Alcohol Programs, Department of Psychiatry and Behavioral Sciences, Medical University of South Carolina, Charleston, SC, 29425, USA
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102
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Sukhotina IA, Dravolina OA, Novitskaya Y, Zvartau EE, Danysz W, Bespalov AY. Effects of mGlu1 receptor blockade on working memory, time estimation, and impulsivity in rats. Psychopharmacology (Berl) 2008; 196:211-20. [PMID: 17909752 DOI: 10.1007/s00213-007-0953-2] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2007] [Accepted: 09/17/2007] [Indexed: 12/27/2022]
Abstract
RATIONALE Metabotropic glutamate 1 (mGlu1) receptor antagonists were reported to induce cognitive deficits in several animal models using aversive learning procedures. OBJECTIVE The present study aimed to further characterize behavioral effects of mGlu1 receptor antagonists using appetitively motivated tasks that evaluate working memory, timing, and impulsivity functions. MATERIALS AND METHODS Separate groups of adult male Wistar rats were trained to perform four food-reinforced operant tasks: delayed non-matching to position (DNMTP), differential reinforcement of low rates of responding 18 s (DRL 18-s), signal duration discrimination (2-s vs 8-s bisection), and tolerance to delay of reward. Before the tests, rats were pretreated with (3-ethyl-2-methyl-quinolin-6-yl)-(4-methoxy-cyclohexyl)-methanone methanesulfonate (EMQMCM; 2.5-10 mg/kg, i.p.; JNJ16567083). RESULTS In DNMTP task, EMQMCM produced delay-dependent increases in performance accuracy so that, at 10 mg/kg dose level, percentage of correct lever choices was enhanced at 8- and 16-s delays. In DRL task, at all three tested doses, response rates were higher, and reinforcement rates were lower than under control conditions. In signal duration discrimination tasks, EMQMCM did not have any specific effects on temporal control. In tolerance to delay of reward, EMQMCM (5 and 10 mg/kg) facilitated choice of the lever associated with large reward at longer delay levels. CONCLUSIONS Blockade of mGlu1 receptors improves working memory and reduces impulsive choice at the doses that have no effects on time perception but appear to facilitate impulsive action.
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Affiliation(s)
- Irina A Sukhotina
- Laboratory of Behavioral Pharmacology, Institute of Pharmacology, Pavlov Medical University, 6/8 Leo Tolstoy Str., St. Petersburg, 197089, Russia
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103
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Lima VCF, Molchanov ML, Aguiar DC, Campos AC, Guimarães FS. Modulation of defensive responses and anxiety-like behaviors by group I metabotropic glutamate receptors located in the dorsolateral periaqueductal gray. Prog Neuropsychopharmacol Biol Psychiatry 2008; 32:178-85. [PMID: 17804134 DOI: 10.1016/j.pnpbp.2007.08.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/12/2007] [Revised: 08/01/2007] [Accepted: 08/08/2007] [Indexed: 10/22/2022]
Abstract
Glutamatergic neurotransmission in the dorsolateral periaqueductal gray (dlPAG) is related to defensive responses. However, the role of group I glutamate metabotropic receptors (mGluR) in these responses has been poorly investigated. The objective of the present study, therefore, was to test the hypothesis that interference with group I mGluR-mediated neurotransmission in dlPAG could modulate defensive responses. Male Wistar rats with cannulae aimed at the dlPAG were submitted to the following experiments: 1. intra dlPAG injections of vehicle (veh, 0.2 microL) or (RS)1-aminoindan-1,5-dicarboxylic acid (AIDA, 30-100 nmol, an mGluR1 receptor competitive antagonist) followed, 5 min later, by veh or trans-(+)-1-amino-1,3-ciclopentanedicarboxylic acid (tACPD, a group I and II mGluR agonist, 30 nmol); 2. intra-dlPAG injections of veh, AIDA (30 nmol) or 2-methyl-6-(phenylethynyl)-pyridine (MPEP, an mGluR5 receptor non-competitive antagonist, 50 nmol) followed by trans-azetidine-2,4-dicarboxylic acid (tADA, a group I mGluR agonist, 10 nmol); 3. and 4. intra-dlPAG injections of vehicle, AIDA (10-30 nmol) or MPEP (10-50 nmol) before the elevated plus maze (EPM) test; 5. intra-dlPAG injections of vehicle, AIDA (30 nmol) or MPEP (50 nmol) before the Vogel punished licking test. tACPD induced defensive responses characterized by jumps and an increased number of crossings in the observation box. These responses were attenuated by AIDA (30 nmol). tADA produced similar responses, although of lower intensity. tADA effects were prevented by AIDA and MPEP. Both drugs also produced anxiolytic-like effects in the EPM and Vogel tests when injected alone. The results suggest that group I metabotropic glutamate receptors in the dlPAG facilitate defensive responses and may also be involved in regulating anxiety-like behavior.
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Affiliation(s)
- Vivian C F Lima
- Department of Pharmacology, School of Medicine of Ribeirão Preto Campus, USP, 14049-900, Ribeirão Preto, SP, Brazil
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104
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Dong XW, Jia Y, Lu SX, Zhou X, Cohen-Williams M, Hodgson R, Li H, Priestley T. The antipsychotic drug, fluphenazine, effectively reverses mechanical allodynia in rat models of neuropathic pain. Psychopharmacology (Berl) 2008; 195:559-68. [PMID: 17891479 DOI: 10.1007/s00213-007-0942-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2006] [Accepted: 09/05/2007] [Indexed: 11/28/2022]
Abstract
RATIONALE Fluphenazine is a potent antipsychotic drug used to treat schizophrenia and other psychotic symptoms. Its clinical benefit is mainly mediated by the antagonism of dopamine D2 receptors. We have recently discovered, however, that fluphenazine is also a potent sodium channel blocker, a property that may offer additional therapeutical indications, including analgesia. OBJECTIVES The present study sought to determine the analgesic effect of fluphenazine on neuropathic pain in animal models. METHODS The effect of fluphenazine on mechanical allodynia was assessed in three animal neuropathic pain models, including spinal nerve ligation, chronic constriction nerve injury (CCI), and sural-spared sciatic nerve injury models. RESULTS Systemic fluphenazine effectively attenuated mechanical allodynia in all three rat neuropathic pain models at doses (0.03-0.3 mg/kg) that approximate those used in rodent models of psychosis. In parallel with its in vivo antiallodynic effect, fluphenazine (3-30 microM) effectively suppressed the ectopic discharges in injured afferent fibers without affecting the propagation of action potentials evoked by electrical nerve stimulation in an ex vivo dorsal root ganglia (DRG)-nerve preparation excised from CCI rats. Furthermore, similar concentrations of fluphenazine significantly blocked sodium channels in DRG neurons. CONCLUSIONS The inhibitory action of fluphenazine on ectopic afferent discharges may be due to its ability to block voltage-gated sodium channels, and this may also provide a mechanistic basis for the drug's antiallodynic effect in animal models of neuropathic pain. In summary, our study demonstrates that the classic antipsychotic drug fluphenazine has antiallodynic properties in multiple rodent models of nerve injury-induced neuropathic pain.
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Affiliation(s)
- Xiao-Wei Dong
- Department of Neurobiology, Schering-Plough Research Institute, K-15-2-2600, 2015 Galloping Hill Road, Kenilworth, NJ 07033, USA.
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105
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Chapter 4.4 The glutamatergic system as a potential therapeutic target for the treatment of anxiety disorders. HANDBOOK OF ANXIETY AND FEAR 2008. [DOI: 10.1016/s1569-7339(07)00013-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
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106
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Sharko AC, Hodge CW. Differential modulation of ethanol-induced sedation and hypnosis by metabotropic glutamate receptor antagonists in C57BL/6J mice. Alcohol Clin Exp Res 2007; 32:67-76. [PMID: 18070246 DOI: 10.1111/j.1530-0277.2007.00554.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Emerging evidence implicates metabotropic glutamate receptor (mGluR) function in the neurobiological effects of ethanol. The recent development of subtype specific mGluR antagonists has made it possible to examine the roles of specific mGluRs in biochemical and behavioral responses to ethanol. The purpose of the present study was to determine if mGluRs modulate the acute sedative-hypnotic properties of ethanol in mice. METHODS C57BL/6J mice were tested for locomotor activity (sedation) and duration of loss of the righting reflex (hypnosis) following acute systemic administration of ethanol alone or in combination with the mGluR5-selective antagonist, 2-methyl-6-(phenylethynyl)pyridine (MPEP), the mGluR1-selective antagonist, 7-(hydroxyimino)cyclopropa[b]chromen-1a-carboxylate ethyl ester (CPCCOEt), or the mGluR2/3-selective antagonist (2S)-2-Amino-2-[(1S,2S)-2-carboxycycloprop-1-yl]-3-(xanth-9-yl) propanoic acid (LY341495)). RESULTS MPEP (10 and 30 mg/kg) significantly enhanced both the sedative and hypnotic effects of ethanol, while LY341495 (10 and 30 mg/kg) significantly reduced the sedative-hypnotic effects of ethanol. CPCCOEt had no effect at any concentration tested. Further loss of righting reflex experiments revealed that LY341495 (30 mg/kg) significantly reduced hypnosis induced by the gamma-aminobutyric acid type A (GABAA) positive modulators, pentobarbital (50 mg/kg) and midazolam (60 mg/kg), and the N-methyl-d-aspartate (NMDA) receptor antagonist, ketamine (150 mg/kg), while MPEP (30 mg/kg) only significantly enhanced the hypnotic properties of ketamine (150 mg/kg). CONCLUSIONS These findings suggest that specific subtypes of the metabotropic glutamate receptor differentially modulate the sedative-hypnotic properties of ethanol through separate mechanisms of action, potentially involving GABA(A) and NMDA receptors.
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Affiliation(s)
- Amanda C Sharko
- Department of Pharmacology, Bowles Center for Alcohol Studies, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7178, USA
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107
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Effect of 2-methyl-6-(phenylethynyl) pyridine on intravenous self-administration of ketamine and heroin in the rat. Behav Pharmacol 2007; 18:717-24. [DOI: 10.1097/fbp.0b013e3282f18d58] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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108
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Analgesic activity of metabotropic glutamate receptor 1 antagonists on spontaneous post-operative pain in rats. Eur J Pharmacol 2007; 580:314-21. [PMID: 18054908 DOI: 10.1016/j.ejphar.2007.09.047] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2007] [Revised: 09/11/2007] [Accepted: 09/23/2007] [Indexed: 11/21/2022]
Abstract
Activation of metabotropic glutamate (mGlu) receptors has previously been shown to play a role in inflammatory or neuropathic pain states. However, the role of mGlu type 1 receptors in post-operative pain remains to be investigated. In the present study, effects of potent and selective mGlu1 receptor antagonists A-841720, A-794282, A-794278, and A-850002 were evaluated in a skin incision-induced post-operative pain model in rats. Post-operative pain was examined 2 h following surgery using weight-bearing difference between injured and uninjured paws as a measure of spontaneous pain. In this model, A-841720, A-794282, A-794278, and A-850002 induced significant attenuation of spontaneous post-operative pain behavior, with ED50s of 10, 50, 50, and 65 micromol/kg i.p., respectively. Depending on the compound, significant motor side effects were also observed at 3 to 10 fold higher doses. These results support the notion that mGlu1 receptor activation plays a significant role in nociceptive transmission in post-operative pain, though motor impairment may be a limiting factor in developing mGlu1 receptor antagonists as novel analgesics.
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109
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Fischer BD, Zimmerman EI, Picker MJ, Dykstra LA. Morphine in combination with metabotropic glutamate receptor antagonists on schedule-controlled responding and thermal nociception. J Pharmacol Exp Ther 2007; 324:732-9. [PMID: 17982001 DOI: 10.1124/jpet.107.131417] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The present study examined the interactive effects of morphine in combination with metabotropic glutamate (mGlu) receptor antagonists on schedule-controlled responding and thermal nociception. Drug interaction data were examined with isobolographic and dose-addition analysis. Morphine, the mGlu1 receptor antagonist JNJ16259685 [(3,4-dihydro-2H-pyrano-[2,3-b]quinolin-7-yl)-(cis-4-methoxycyclohexyl)-methanone], the mGlu5 receptor antagonist MPEP [2-methyl-6-(phenylethynyl)pyridine hydrochloride], and the mGlu2/3 receptor antagonist LY341495 [(2S)-2-amino-2-[(1S,2S-2-carboxycycloprop-1-yl]-3-(xanth-9-yl) propanoic acid] all decreased rates of schedule-controlled responding. JNJ16259685/morphine, MPEP/morphine, and LY341495/morphine mixtures produced additive effects on this endpoint. Morphine also produced dose-dependent antinociception in the assay of thermal nociception, whereas JNJ16259685, MPEP, and LY341495 failed to produce an effect. In this assay, JNJ16259685 and LY341495 potentiated the antinociceptive effects of morphine, whereas MPEP/morphine mixtures produced additive effects. These results suggest that an mGlu1 and an mGlu2/3 receptor antagonist, but not an mGlu5 receptor antagonist, selectively enhance the antinociceptive effects of morphine. In addition, these data confirm that the behavioral effects of drug mixtures depend on the endpoint under study.
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Affiliation(s)
- Bradford D Fischer
- Department of Psychology, CB# 3270, Davie Hall, University of North Carolina, Chapel Hill, NC 27599-3270, USA.
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110
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Lindström E, Brusberg M, Hughes PA, Martin CM, Brierley SM, Phillis BD, Martinsson R, Abrahamsson C, Larsson H, Martinez V, Blackshaw AL. Involvement of metabotropic glutamate 5 receptor in visceral pain. Pain 2007; 137:295-305. [PMID: 17937975 DOI: 10.1016/j.pain.2007.09.008] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2007] [Revised: 08/30/2007] [Accepted: 09/10/2007] [Indexed: 12/11/2022]
Abstract
Metabotropic glutamate 5 receptor (mGluR5) antagonists are effective in animal models of inflammatory and neuropathic pain. The involvement of mGluR5 in visceral pain pathways from the gastrointestinal tract is as yet unknown. We evaluated effects of mGluR5 antagonists on the colorectal distension (CRD)-evoked visceromotor (VMR) and cardiovascular responses in conscious rats, and on mechanosensory responses of mouse colorectal afferents in vitro. Sprague-Dawley rats were subjected to repeated, isobaric CRD (12 x 80 mmHg, for 30s with 5 min intervals). The VMR and cardiovascular responses to CRD were monitored. The mGluR5 antagonists MPEP (1-10 micromol/kg, i.v.) and MTEP (1-3 micromol/kg, i.v.) reduced the VMR to CRD dose-dependently with maximal inhibition of 52+/-8% (p<0.01) and 25+/-11% (p<0.05), respectively, without affecting colonic compliance. MPEP (10 micromol/kg, i.v.) reduced CRD-evoked increases in blood pressure and heart rate by 33+/-9% (p<0.01) and 35+/-8% (p<0.05), respectively. Single afferent recordings were made from mouse pelvic and splanchnic nerves of colorectal mechanoreceptors. Circumferential stretch (0-5 g force) elicited slowly-adapting excitation of action potentials in pelvic distension-sensitive afferents. This response was reduced 55-78% by 10 microM MTEP (p<0.05). Colonic probing (2g von Frey hair) activated serosal splanchnic afferents; their responses were reduced 50% by 10 microM MTEP (p<0.01). We conclude that mGluR5 antagonists inhibit CRD-evoked VMR and cardiovascular changes in conscious rats, through an effect, at least in part, at peripheral afferent endings. Thus, mGluR5 participates in mediating mechanically evoked visceral nociception in the gastrointestinal tract.
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Affiliation(s)
- Erik Lindström
- AstraZeneca R&D, Mölndal, Sweden Nerve Gut Research Laboratory, Hanson Institute, Royal Adelaide Hospital, University of Adelaide, Australia Discipline of Medicine, School of Molecular and Biomedical Sciences, University of Adelaide, Australia Discipline of Physiology, School of Molecular and Biomedical Sciences, University of Adelaide, Australia
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111
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Wu WL, Burnett DA, Domalski M, Greenlee WJ, Li C, Bertorelli R, Fredduzzi S, Lozza G, Veltri A, Reggiani A. Discovery of Orally Efficacious Tetracyclic Metabotropic Glutamate Receptor 1 (mGluR1) Antagonists for the Treatment of Chronic Pain. J Med Chem 2007; 50:5550-3. [DOI: 10.1021/jm070590c] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Wen-Lian Wu
- Schering-Plough Research Institute, 2015 Galloping Hill Road, Kenilworth, New Jersey 07033, and Schering-Plough Research Institute, San Raffaele Science Park, Via Olgettina, 58, 20132 Milan, Italy
| | - Duane A. Burnett
- Schering-Plough Research Institute, 2015 Galloping Hill Road, Kenilworth, New Jersey 07033, and Schering-Plough Research Institute, San Raffaele Science Park, Via Olgettina, 58, 20132 Milan, Italy
| | - Martin Domalski
- Schering-Plough Research Institute, 2015 Galloping Hill Road, Kenilworth, New Jersey 07033, and Schering-Plough Research Institute, San Raffaele Science Park, Via Olgettina, 58, 20132 Milan, Italy
| | - William J. Greenlee
- Schering-Plough Research Institute, 2015 Galloping Hill Road, Kenilworth, New Jersey 07033, and Schering-Plough Research Institute, San Raffaele Science Park, Via Olgettina, 58, 20132 Milan, Italy
| | - Cheng Li
- Schering-Plough Research Institute, 2015 Galloping Hill Road, Kenilworth, New Jersey 07033, and Schering-Plough Research Institute, San Raffaele Science Park, Via Olgettina, 58, 20132 Milan, Italy
| | - Rosalia Bertorelli
- Schering-Plough Research Institute, 2015 Galloping Hill Road, Kenilworth, New Jersey 07033, and Schering-Plough Research Institute, San Raffaele Science Park, Via Olgettina, 58, 20132 Milan, Italy
| | - Silva Fredduzzi
- Schering-Plough Research Institute, 2015 Galloping Hill Road, Kenilworth, New Jersey 07033, and Schering-Plough Research Institute, San Raffaele Science Park, Via Olgettina, 58, 20132 Milan, Italy
| | - Gianluca Lozza
- Schering-Plough Research Institute, 2015 Galloping Hill Road, Kenilworth, New Jersey 07033, and Schering-Plough Research Institute, San Raffaele Science Park, Via Olgettina, 58, 20132 Milan, Italy
| | - Alessio Veltri
- Schering-Plough Research Institute, 2015 Galloping Hill Road, Kenilworth, New Jersey 07033, and Schering-Plough Research Institute, San Raffaele Science Park, Via Olgettina, 58, 20132 Milan, Italy
| | - Angelo Reggiani
- Schering-Plough Research Institute, 2015 Galloping Hill Road, Kenilworth, New Jersey 07033, and Schering-Plough Research Institute, San Raffaele Science Park, Via Olgettina, 58, 20132 Milan, Italy
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112
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Stachowicz K, Gołembiowska K, Sowa M, Nowak G, Chojnacka-Wójcik E, Pilc A. Anxiolytic-like action of MTEP expressed in the conflict drinking Vogel test in rats is serotonin dependent. Neuropharmacology 2007; 53:741-8. [PMID: 17870136 DOI: 10.1016/j.neuropharm.2007.08.002] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2007] [Revised: 08/04/2007] [Accepted: 08/06/2007] [Indexed: 11/30/2022]
Abstract
The purpose of the present study was to investigate whether the anxiolytic-like action of a selective and brain penetrable group I metabotropic glutamate (mGlu5) receptor antagonist 3-[(2-methyl-1,3-tiazol-4-yl)ethynyl]-pyridine (MTEP) is dependent upon the serotonergic system. Experiments were performed on male Wistar rats. The Vogel conflict drinking test was used to detect anxiolytic-like activity. MTEP administered intraperitoneally at doses of 1, 3 and 6 mg/kg induced anxiolytic-like effect. The potential anxiolytic effect of MTEP (1 mg/kg) was inhibited by a nonselective 5-HT receptor antagonist metergoline (2 mg/kg i.p.) and 5-HT2A/2C receptor antagonist ritanserin (0.5 mg/kg i.p.), but not by a 5-HT1A receptor antagonist N-{2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl}-N-(2-pyridynyl)cyclohexane-carboxamide (WAY 100635) (0.1 mg/kg i.p). The anxiolytic effect of MTEP (6 mg/kg) was attenuated by ritanserin (1 mg/kg i.p.). Moreover, MTEP-induced a dose-dependent release of serotonin in the frontal cortex. The obtained results suggest that the potential anxiolytic effect of the mGlu5 receptor antagonist MTEP is due to the increased serotonin release with subsequent activation of 5-HT2A/2C receptors, most probably located postsynaptically, but not by the 5-HT1A receptors.
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Affiliation(s)
- K Stachowicz
- Institute of Pharmacology, Polish Academy of Sciences, Smetna 12, 31-343 Kraków, Poland.
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113
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Scotland PE, Coderre TJ. Enhanced 3,5-dihydroxyphenylglycine-induced sustained nociceptive behaviors in rats with neuropathy or chronic inflammation. Behav Brain Res 2007; 184:150-6. [PMID: 17681386 DOI: 10.1016/j.bbr.2007.07.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2007] [Revised: 06/22/2007] [Accepted: 07/04/2007] [Indexed: 11/18/2022]
Abstract
Sustained nociceptive behaviors (SNBs) are an important but under-studied component of chronic pain conditions. The group I metabotropic glutamate receptor (mGluR) agonist (R,S)-3,5-dihydroxyphenylglycine (DHPG) produces SNBs when injected intrathecally, and group I mGluR antagonists are effective at reducing symptoms of neuropathic and inflammatory pain. The present experiments examined whether rats with sciatic nerve injury or persistent inflammation exhibit greater SNBs following intrathecal DHPG compared with control animals. SNBs were observed following intrathecal injection of DHPG (25 nmol) between the L4 and L5 vertebrae. We used a behavioral observation scoring system that allowed for assessment of specific behaviors in the hind paws. When DHPG was injected intrathecally in rats with chronic constriction injury (CCI) of the sciatic nerve, they showed increased paw stamping behavior compared to DHPG-injected sham controls. Rats treated with complete Freund's adjuvant (CFA)-induced inflammation failed to demonstrate a significant increase in paw stamping behavior. However, both CCI and CFA rats showed increased paw licking and biting of the neuropathic/inflamed hind paw after intrathecal DHPG injection. These results provide evidence for behaviorally relevant contributions of group I mGluRs to SNBs in models of neuropathic and inflammatory pain.
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Affiliation(s)
- Phoebe E Scotland
- Department of Psychology, McGill University, Montreal, Quebec, Canada
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114
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Conley RK, Hutson PH. Effects of acute and chronic treatment with fluoxetine on stress-induced hyperthermia in telemetered rats and mice. Eur J Pharmacol 2007; 564:138-45. [PMID: 17462624 DOI: 10.1016/j.ejphar.2007.02.063] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2007] [Revised: 02/16/2007] [Accepted: 02/20/2007] [Indexed: 10/23/2022]
Abstract
Preclinical and clinical evidence suggests that anxiolytic effects are observed after chronic administration of the selective serotonin reuptake inhibitor fluoxetine. In contrast, acute treatment may increase signs of anxiety. The present study examined the effects of acute and chronic administration of fluoxetine on a physiological measure of anxiety, stress-induced hyperthermia, in rats and mice using radiotelemetry to record core temperature and locomotor activity and ethologically relevant stressors to evoke the hyperthermic response. In both species, the benzodiazepine agonist chlordiazepoxide reduced stress-induced hyperthermia at doses (5 mg/kg i.p. rat, 10 mg/kg p.o. mouse) that had no significant effect on locomotor activity. Similarly, in both species, chronic (21 days) treatment with fluoxetine attenuated the hyperthermic response without significantly affecting locomotor activity. However, acute fluoxetine elicited species-specific effects. Thus in mice, stress-induced hyperthermia and activity were unaffected by fluoxetine (20 mg/kg p.o.) consistent with a lack of anxiolytic or anxiogenic activity. In contrast, in rats, fluoxetine (10 mg/kg i.p.) caused a significant baseline hypothermia in the absence of stress, confounding further interpretation. In conclusion, stress-induced hyperthermia in mice was unaffected by acute treatment and significantly reduced by chronic treatment with fluoxetine. However, in rats chronic administration of fluoxetine significantly reduced stress-induced hyperthermia while the effects of acute treatment were confounded by a decrease in body temperature in the absence of stress. Together, these observations support the view that chronic administration of fluoxetine is anxiolytic; however, the stress-induced hyperthermia assay does not reveal anxiogenic effects of acute administration of fluoxetine in rats or mice.
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Affiliation(s)
- Rachel K Conley
- Merck Sharp & Dohme, Neuroscience Research Centre, Harlow, Essex, UK.
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115
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Palucha A, Pilc A. Metabotropic glutamate receptor ligands as possible anxiolytic and antidepressant drugs. Pharmacol Ther 2007; 115:116-47. [PMID: 17582504 DOI: 10.1016/j.pharmthera.2007.04.007] [Citation(s) in RCA: 175] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2007] [Accepted: 04/25/2007] [Indexed: 11/18/2022]
Abstract
Depression and anxiety represent a major problem. However, the current treatment of both groups of diseases is not satisfactory. As the glutamatergic system may play an important role in pathophysiology of both depression and anxiety, we decided to discuss the recent data on possible anxiolytic and/or antidepressant effects of metabotropic glutamate (mGlu) receptor ligands. Preclinical data indicated that antagonists of group I mGlu receptors, particularly antagonists of mGlu5 receptors, produced both anxiolytic-like and antidepressant-like effects. Clinical data also demonstrated that mGlu5 receptor antagonist, fenobam, was an active anxiolytic drug. The anxiolytic effects exerted by mGlu5 receptor antagonists are profound, comparable with or stronger than those of benzodiazepines. However, the problem with the psychotomimetic activity of mGlu5 receptor antagonists and their possible influence on memory has to be further investigated. Among all mGlu receptor ligands, group II mGlu receptor agonists seem to be the drugs with the most promising therapeutic potential and a good safety profile. Animal studies showed anxiolytic-like effects of group II mGlu receptor agonists. Currently, group II mGlu receptor agonists are in phase III clinical trials for potential treatment of anxiety disorders. On the other hand, data has been accumulated, indicating that antagonists of group II mGlu receptors have an antidepressant potential. Group III mGlu receptor ligands represent the least investigated group of mGlu receptors. However, preclinical data also indicates that ligands of these receptors, both agonists and antagonists, may have an anxiolytic-like and antidepressant-like potential.
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Affiliation(s)
- Agnieszka Palucha
- Institute of Pharmacology, Polish Academy of Sciences, Smetna 12, 31-343 Kraków, Poland
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116
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Nordquist RE, Durkin S, Jaeschke G, Spooren W. Stress-induced hyperthermia: effects of acute and repeated dosing of MPEP. Eur J Pharmacol 2007; 568:199-202. [PMID: 17537432 DOI: 10.1016/j.ejphar.2007.04.034] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2006] [Revised: 04/12/2007] [Accepted: 04/19/2007] [Indexed: 10/23/2022]
Abstract
The mGlu5 receptor antagonist 2-methyl-6-(phenylethylnyl)-pyridine (MPEP) is highly anxiolytic in rodent models of anxiety. Recent studies showed that MPEP remains effective in some models of anxiety after repeated treatment, but tolerance may develop in other models. To further evaluate anxiolytic properties of repeated MPEP, a single administration of 3, 10, or 30 mg/kg p.o. and repeated administration of 30 mg/kg p.o. was tested in the stress-induced hyperthermia model in mice. MPEP dose-dependently inhibited stress-induced hyperthermia when given acutely. MPEP remained equally active in reducing stress-induced hyperthermia after five daily treatments with 30 mg/kg, further validating MPEP as a potential anxiolytic for chronic use.
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Affiliation(s)
- Rebecca E Nordquist
- F. Hoffmann-La Roche Ltd., PRBD-N, Psychiatry Disease Area, CH-4070 Basel, Switzerland
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117
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Koros E, Rosenbrock H, Birk G, Weiss C, Sams-Dodd F. The selective mGlu5 receptor antagonist MTEP, similar to NMDA receptor antagonists, induces social isolation in rats. Neuropsychopharmacology 2007; 32:562-76. [PMID: 16794564 DOI: 10.1038/sj.npp.1301133] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
It has repeatedly been shown that uncompetitive N-methyl-D-aspartate (NMDA) receptor antagonists can mimic certain aspects of positive and negative symptoms of schizophrenia in human volunteers and laboratory animals. The purpose of the present study was to expand these findings and to determine whether the selective metabotropic glutamate receptor subtype 5 (mGluR5) antagonist, MTEP (3-[(2-methyl-1,3-thiazol-4-yl)ethynyl]pyridine), could induce similar effects in Wistar rats. First, MTEP (1.0-10.0 mg/kg; intraperitoneally) after acute and subchronic (daily for 5 days) administration as well as the uncompetitive antagonists of the NMDA receptor of either high affinity, phencyclidine (0.5-4.0 mg/kg; subcutaneously (s.c.)) and (+)-MK-801 (0.03-0.25 mg/kg; s.c.), or low-moderate affinity, ketamine (2.0-16.0 mg/kg; s.c.) and memantine (0.15-20.0 mg/kg; s.c.), following daily administration for 3 days were tested in the social interaction test to determine their ability to reproduce the negative and positive symptoms measured by social isolation and stereotyped behavior, respectively. Second, the compounds were tested in the motility test following acute administration to determine their ability to induce locomotor hyperactivity reflecting the positive symptoms. In line with previous findings, all examined NMDA receptor antagonists produced social interaction deficits, locomotor hyperactivity, and stereotypy except memantine. Notably, this study found that MTEP following both acute and subchronic administration dose-dependently induced social isolation, but did not cause either locomotor hyperactivity or stereotypy. These data demonstrate that social behavior deficits in rats can be caused by both the blockade of the NMDA receptor and the inhibition of mGluR5, whereas mGluR5 antagonists may not independently be able to mimic the positive symptoms.
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Affiliation(s)
- Eliza Koros
- Department of CNS Research, Boehringer-Ingelheim Pharma GmbH & Co. KG, Biberach, Germany.
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118
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Abstract
Glutamate acts through a variety of receptors to modulate neurotransmission and neuronal excitability. Glutamate plays a critical role in neuroplasticity as well as in nervous system dysfunctions and disorders. Hyperfunction or dysfunction of glutamatergic neurotransmission also represents a key mechanism of pain-related plastic changes in the central and peripheral nervous system. This chapter will review the classification of glutamate receptors and their role in peripheral and central nociceptive processing. Evidence from preclinical pain models and clinical studies for the therapeutic value of certain glutamate receptor ligands will be discussed.
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Affiliation(s)
- V Neugebauer
- Department of Neuroscience and Cell Biology, The University of Texas Medical Branch, 301 University Blvd., Galveston, TX 77555-1069, USA.
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119
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Heinke B, Sandkühler J. Group I metabotropic glutamate receptor-induced Ca(2+)-gradients in rat superficial spinal dorsal horn neurons. Neuropharmacology 2006; 52:1015-23. [PMID: 17174986 DOI: 10.1016/j.neuropharm.2006.10.020] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2006] [Revised: 07/28/2006] [Accepted: 10/30/2006] [Indexed: 01/26/2023]
Abstract
Here, we investigated changes in the free cytosolic Ca(2+) concentration ([Ca(2+)](i)), induced by the pharmacological activation of metabotropic glutamate receptors (mGluRs), in nociceptive neurons of the superficial spinal dorsal horn. Microfluorometric Ca(2+) measurements with fura-2 in a lumbar spinal cord slice preparation from young rats were used. Bath application of the specific group I mGluR agonist (S)-3,5-dihydroxyphenylglycine ((S)-3,5-DHPG) resulted in a distinct increase of [Ca(2+)](i) in most of the neurons in superficial dorsal horn. In contrast, activation of groups II or III mGluRs by DCG-IV or l-AP4, respectively, failed to evoke any significant change in [Ca(2+)](i). The effect of (S)-3,5-DHPG was mediated by both group I subtypes mGluR1 and mGluR5, since combined pre-treatment with the subtype antagonists (S)-4-CPG and MPEP was necessary to abolish the [Ca(2+)](i) increase. Depleting intracellular Ca(2+) stores with CPA or inhibiting IP(3)-receptors with 2-APB, respectively, reduced the (S)-3,5-DHPG-evoked [Ca(2+)](i) increase significantly. Inhibition of voltage-dependent L-type Ca(2+) channels (VDCCs) by verapamil or nicardipine reduced the (S)-3,5-DHPG-induced [Ca(2+)](i) rise likewise. Thus, in rat spinal cord, (S)-3,5-DHPG enhances Ca(2+) signalling in superficial dorsal horn neurons, mediated by the release of Ca(2+) from IP(3)-sensitive intracellular stores and by an influx through L-type VDCCs. This may be relevant to the processing of nociceptive information in the spinal cord.
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Affiliation(s)
- Bernhard Heinke
- Department of Neurophysiology, Center for Brain Research, Medical University of Vienna, Spitalgasse 4, A-1090 Vienna, Austria
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120
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Lominac KD, Kapasova Z, Hannun RA, Patterson C, Middaugh LD, Szumlinski KK. Behavioral and neurochemical interactions between Group 1 mGluR antagonists and ethanol: potential insight into their anti-addictive properties. Drug Alcohol Depend 2006; 85:142-56. [PMID: 16697125 DOI: 10.1016/j.drugalcdep.2006.04.003] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2005] [Revised: 04/08/2006] [Accepted: 04/12/2006] [Indexed: 10/24/2022]
Abstract
Blockade of the mGluR5 subtype of Group 1 metabotropic glutamate receptor (mGluRs) reduces the rewarding effects of ethanol (EtOH), while the effects of mGluR1a blockade remain under-investigated. The present study compared the effects of pretreatment with the mGluR5 antagonist MPEP and the mGluR1a antagonist CPCCPOEt upon behavioral and neurochemical variables associated with EtOH reward in alcohol-preferring C57BL/6J mice. Pretreatment with either antagonist (0-10 mg/kg, IP) dose-dependently reduced measures of EtOH reward in an operant self-administration paradigm and the maximally effective antagonist dose (10 mg/kg) also blocked the expression of EtOH-induced place conditioning, as well as EtOH consumption under 24-h free-access conditions. MPEP pretreatment did not significantly alter the EtOH dose-locomotor response function; however, it prevented EtOH-induced changes in extracellular dopamine, glutamate and GABA in the nucleus accumbens (NAC). In contrast, CPCCOEt shifted the EtOH dose-response function downwards, enhanced the capacity of higher EtOH doses to elevate NAC levels of GABA and lowered extracellular dopamine and glutamate below baseline following EtOH injection. It is suggested that the "anti-alcohol" effects of MPEP may involve an attenuation of the neurochemical signals mediating EtOH reward, whereas those of CPCCOEt may involve an increased sensitivity to the inhibitory effects of EtOH upon brain and behavior.
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Affiliation(s)
- Kevin D Lominac
- Department of Psychology, University of California Santa Barbara, Santa Barbara, CA 93106-9660, USA
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121
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Abstract
Pain is an important survival and protection mechanism for animals. However, chronic/persistent pain may be differentiated from normal physiological pain in that it confers no obvious advantage. An accumulating body of pharmacological, electrophysiological, and behavioral evidence is emerging in support of the notion that glutamate receptors play a crucial role in pain pathways and that modulation of glutamate receptors may have potential for therapeutic utility in several categories of persistent pain, including neuropathic pain resulting from injury and/or disease of central (e.g., spinal cord injury) or peripheral nerves (e.g., diabetic neuropathy, radiculopathy) and inflammatory or joint-related pain (e.g., rheumatoid arthritis, osteoarthritis). This review focuses on the role of glutamate receptors, including both ionotropic (AMPA, NMDA and kainate) and metabotropic (mGlu1-8) receptors in persistent pain states with particular emphasis on their expression patterns in nociceptive pathways and their potential as targets for pharmacological intervention strategies.
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Affiliation(s)
- David Bleakman
- Neuroscience Division, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN 46285, USA.
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122
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El-Kouhen O, Lehto SG, Pan JB, Chang R, Baker SJ, Zhong C, Hollingsworth PR, Mikusa JP, Cronin EA, Chu KL, McGaraughty SP, Uchic ME, Miller LN, Rodell NM, Patel M, Bhatia P, Mezler M, Kolasa T, Zheng GZ, Fox GB, Stewart AO, Decker MW, Moreland RB, Brioni JD, Honore P. Blockade of mGluR1 receptor results in analgesia and disruption of motor and cognitive performances: effects of A-841720, a novel non-competitive mGluR1 receptor antagonist. Br J Pharmacol 2006; 149:761-74. [PMID: 17016515 PMCID: PMC2014656 DOI: 10.1038/sj.bjp.0706877] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND AND PURPOSE To further assess the clinical potential of the blockade of metabotropic glutamate receptors (mGluR1) for the treatment of pain. EXPERIMENTAL APPROACH We characterized the effects of A-841720, a novel, potent and non-competitive mGluR1 antagonist in models of pain and of motor and cognitive function. KEY RESULTS At recombinant human and native rat mGluR1 receptors, A-841720 inhibited agonist-induced calcium mobilization, with IC50 values of 10.7+/-3.9 and 1.0 +/- 0.2 nM, respectively, while showing selectivity over other mGluR receptors, in addition to other neurotransmitter receptors, ion channels, and transporters. Intraperitoneal injection of A-841720 potently reduced complete Freund's adjuvant-induced inflammatory pain (ED50 = 23 micromol kg(-1)) and monoiodoacetate-induced joint pain (ED50 = 43 micromol kg(-1)). A-841720 also decreased mechanical allodynia observed in both the sciatic nerve chronic constriction injury and L5-L6 spinal nerve ligation (SNL) models of neuropathic pain (ED50 = 28 and 27 micromol kg(-1), respectively). Electrophysiological studies demonstrated that systemic administration of A-841720 in SNL animals significantly reduced evoked firing in spinal wide dynamic range neurons. Significant motor side effects were observed at analgesic doses and A-841720 also impaired cognitive function in the Y-maze and the Water Maze tests. CONCLUSIONS AND IMPLICATIONS The analgesic effects of a selective mGluR1 receptor antagonist are associated with motor and cognitive side effects. The lack of separation between efficacy and side effects in pre-clinical models indicates that mGluR1 antagonism may not provide an adequate therapeutic window for the development of such antagonists as novel analgesic agents in humans.
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Affiliation(s)
- O El-Kouhen
- Neuroscience Research, Global Pharmaceutical Research Division, Abbott Laboratories Abbott Park, IL, USA
| | - S G Lehto
- Neuroscience Research, Global Pharmaceutical Research Division, Abbott Laboratories Abbott Park, IL, USA
| | - J B Pan
- Neuroscience Research, Global Pharmaceutical Research Division, Abbott Laboratories Abbott Park, IL, USA
| | - R Chang
- Neuroscience Research, Global Pharmaceutical Research Division, Abbott Laboratories Abbott Park, IL, USA
| | - S J Baker
- Neuroscience Research, Global Pharmaceutical Research Division, Abbott Laboratories Abbott Park, IL, USA
| | - C Zhong
- Neuroscience Research, Global Pharmaceutical Research Division, Abbott Laboratories Abbott Park, IL, USA
| | - P R Hollingsworth
- Neuroscience Research, Global Pharmaceutical Research Division, Abbott Laboratories Abbott Park, IL, USA
| | - J P Mikusa
- Neuroscience Research, Global Pharmaceutical Research Division, Abbott Laboratories Abbott Park, IL, USA
| | - E A Cronin
- Neuroscience Research, Global Pharmaceutical Research Division, Abbott Laboratories Abbott Park, IL, USA
| | - K L Chu
- Neuroscience Research, Global Pharmaceutical Research Division, Abbott Laboratories Abbott Park, IL, USA
| | - S P McGaraughty
- Neuroscience Research, Global Pharmaceutical Research Division, Abbott Laboratories Abbott Park, IL, USA
| | - M E Uchic
- Neuroscience Research, Global Pharmaceutical Research Division, Abbott Laboratories Abbott Park, IL, USA
| | - L N Miller
- Neuroscience Research, Global Pharmaceutical Research Division, Abbott Laboratories Abbott Park, IL, USA
| | - N M Rodell
- Neuroscience Research, Global Pharmaceutical Research Division, Abbott Laboratories Abbott Park, IL, USA
| | - M Patel
- Neuroscience Research, Global Pharmaceutical Research Division, Abbott Laboratories Abbott Park, IL, USA
| | - P Bhatia
- Neuroscience Research, Global Pharmaceutical Research Division, Abbott Laboratories Abbott Park, IL, USA
| | - M Mezler
- Neuroscience Research, Global Pharmaceutical Research Division, Abbott Laboratories Ludwigshafen, Germany
| | - T Kolasa
- Neuroscience Research, Global Pharmaceutical Research Division, Abbott Laboratories Abbott Park, IL, USA
| | - G Z Zheng
- Neuroscience Research, Global Pharmaceutical Research Division, Abbott Laboratories Abbott Park, IL, USA
| | - G B Fox
- Neuroscience Research, Global Pharmaceutical Research Division, Abbott Laboratories Abbott Park, IL, USA
| | - A O Stewart
- Neuroscience Research, Global Pharmaceutical Research Division, Abbott Laboratories Abbott Park, IL, USA
| | - M W Decker
- Neuroscience Research, Global Pharmaceutical Research Division, Abbott Laboratories Abbott Park, IL, USA
| | - R B Moreland
- Neuroscience Research, Global Pharmaceutical Research Division, Abbott Laboratories Abbott Park, IL, USA
| | - J D Brioni
- Neuroscience Research, Global Pharmaceutical Research Division, Abbott Laboratories Abbott Park, IL, USA
| | - P Honore
- Neuroscience Research, Global Pharmaceutical Research Division, Abbott Laboratories Abbott Park, IL, USA
- Author for correspondence:
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123
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Lea PM, Faden AI. Metabotropic glutamate receptor subtype 5 antagonists MPEP and MTEP. CNS DRUG REVIEWS 2006; 12:149-66. [PMID: 16958988 PMCID: PMC6494124 DOI: 10.1111/j.1527-3458.2006.00149.x] [Citation(s) in RCA: 128] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Glutamate regulates the function of central nervous system (CNS), in part, through the cAMP and/or IP3/DAG second messenger-associated metabotropic glutamate receptors (mGluRs). The mGluR5 antagonist 2-methyl-6-(phenylethynyl)-pyridine (MPEP) has been extensively used to elucidate potential physiological and pathophysiological functions of mGluR5. Unfortunately, recent evidence indicates significant non-specific actions of MPEP, including inhibition of NMDA receptors. In contrast, in vivo and in vitro characterization of the newer mGluR5 antagonist 3-[(2-methyl-1,3-thiazol-4-yl)ethynyl]pyridine (MTEP) indicates that it is more highly selective for mGluR5 over mGluR1, has no effect on other mGluR subtypes, and has fewer off-target effects than MPEP. This article reviews literature on both of these mGluR5 antagonists, which suggests their possible utility in neurodegeneration, addiction, anxiety and pain management.
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Affiliation(s)
| | - Alan I. Faden
- Department of Neuroscience, Georgetown University Medical Center, Washington, DC, USA
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124
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Dravolina OA, Zakharova ES, Shekunova EV, Zvartau EE, Danysz W, Bespalov AY. mGlu1 receptor blockade attenuates cue- and nicotine-induced reinstatement of extinguished nicotine self-administration behavior in rats. Neuropharmacology 2006; 52:263-9. [PMID: 16963088 DOI: 10.1016/j.neuropharm.2006.07.023] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2006] [Revised: 07/12/2006] [Accepted: 07/16/2006] [Indexed: 11/15/2022]
Abstract
Glutamatergic neurotransmission is believed to be critically involved in the acquisition and maintenance of drug addiction. The present study evaluated the role of metabotropic glutamate (mGlu) 1 receptors in the reinstatement of nicotine-seeking behavior. Rats were trained to nose-poke to receive response-contingent intravenous infusions of nicotine (0.01 mg/kg/infusion, free base). Following the subsequent extinction phase, reinstatement tests were conducted in animals that were exposed either to response-contingent presentations of the nicotine-associated discrete light cues or to non-contingent nicotine priming injection (0.3mg/kg, s.c., salt) just prior to the test session. In a separate experiment, rats were subjected to the nearly identical response-reinstatement procedure but operant responding was established using food pellets instead of nicotine infusions. Pretreatment with the mGlu1 receptor antagonist EMQMCM (JNJ16567083, (3-ethyl-2-methyl-quinolin-6-yl)-(4-methoxy-cyclohexyl)-methanone methanesulfonate) significantly inhibited cue-induced reinstatement of nicotine-seeking behavior (5 and 10, but not 2.5 mg/kg). EMQMCM (5 mg/kg) also prevented nicotine priming-induced reinstatement of nicotine-seeking behavior. At the highest tested dose only (10 mg/kg), EMQMCM attenuated cue-induced reinstatement of food-seeking behavior. Taken together with the previous reports, the present findings further suggest that blockade of mGlu1 receptors may be beneficial for preventing relapse to tobacco smoking in nicotine-dependent individuals.
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Affiliation(s)
- Olga A Dravolina
- Laboratory of Behavioral Pharmacology, Institute of Pharmacology, Pavlov Medical University, 6/8 Lev Tolstoy Street, St. Petersburg 197089, Russia.
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125
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Navarro JF, Postigo D, Martín M, Burón E. Antiaggressive effects of MPEP, a selective antagonist of mGlu5 receptors, in agonistic interactions between male mice. Eur J Pharmacol 2006; 551:67-70. [PMID: 17026995 DOI: 10.1016/j.ejphar.2006.08.055] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2006] [Revised: 08/26/2006] [Accepted: 08/28/2006] [Indexed: 10/24/2022]
Abstract
mGlu5 receptors are highly concentrated in limbic brain structures involved in motivational and emotional behaviours. This study describes the effects of 2-methyl-6-(phenylethylnyl)pyridine (MPEP; 5, 10, 15, 20 and 25 mg/kg, ip), a selective antagonist of the mGlu5 receptors, on agonistic behaviour elicited by isolation in male mice. Individually housed mice were exposed to anosmic opponents in a neutral area 30 min after drug administration. Besides other behaviours, the aggressive (threat and attack) and exploratory behaviours were evaluated during 10 min using an ethologically based analysis. MPEP produced a behavioural profile characterized by a notable decrement of offensive behaviours, accompanied by a significant increase of exploratory behaviours (nonsocial exploration and social investigation). These findings suggest a role for mGlu5 receptors in aggression modulation.
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Affiliation(s)
- José Francisco Navarro
- Department of Psychobiology, Faculty of Psychology, Campus de Teatinos s/n, University of Málaga, 29071 Málaga, Spain.
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126
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Li X, Need AB, Baez M, Witkin JM. Metabotropic glutamate 5 receptor antagonism is associated with antidepressant-like effects in mice. J Pharmacol Exp Ther 2006; 319:254-9. [PMID: 16803860 DOI: 10.1124/jpet.106.103143] [Citation(s) in RCA: 143] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Antidepressant-like effects of metabotropic glutamate (mGlu)5 receptor antagonists have been reported previously. We now provide definitive identification of mGlu5 receptors as a target for these effects through the combined use of selective antagonists and mice with targeted deletion of the mGlu5 protein. In these experiments, the mGlu5 receptor antagonists 2-methyl-6-(phenylethynyl)-pyridine (MPEP) and the more selective and metabolically stable analog 3-[(2-methyl-1,3-thiazol-4-yl)ethynyl]-pyridine (MTEP) decreased immobility in the mouse forced swim test, a test predictive of antidepressant efficacy in humans. mGlu5 receptor knockout mice had a phenotype in the forced swim test that was congruent with the effects of receptor blockade; mGlu5 receptor knockout mice were significantly less immobile than their wild-type counterparts. Consistent with mGlu5 receptor mediation of the antidepressant-like effects of MPEP, the effects of MPEP were not observed in mGlu5 receptor knockout mice, whereas comparable effects of the tricyclic antidepressant imiprimine remained active in the mutant mice. MPEP and imiprimine resulted in a synergistic antidepressant-like effect in the forced swim test. The drug interaction was not likely because of increased levels of drugs in the brain, suggesting a pharmacodynamic interaction of mGlu5 and monoaminergic systems in this effect. Thus, the present findings substantiate the hypothesis that mGlu5 receptor antagonism is associated with antidepressant-like effects. This mechanism may not only provide a novel approach to the therapeutic management of depressive disorders but also may be useful in the augmentation of effects of traditional antidepressant agents.
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Affiliation(s)
- Xia Li
- Neuroscience Discovery Research, Lilly Research Laboratories, Eli Lilly & Co, Indianapolis, IN 46285-0510, USA.
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127
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Pietraszek M, Nagel J, Gravius A, Schäfer D, Danysz W. The role of group I metabotropic glutamate receptors in schizophrenia. Amino Acids 2006; 32:173-8. [PMID: 16699816 DOI: 10.1007/s00726-006-0319-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2005] [Accepted: 01/12/2006] [Indexed: 12/22/2022]
Abstract
It has been proposed that glutamatergic transmission, in particular NMDA receptor function, might be altered in schizophrenia. This hypothesis is mainly based on the observation that uncompetitive NMDA receptor antagonists, e.g. phencyclidine, evoke psychotic symptoms in healthy subjects, whereas agonists interacting at the glycine site of the NMDA receptor complex, e.g. glycine or D-serine, administered jointly with typical neuroleptics, can alleviate schizophrenic symptoms. The function of NMDA receptors may be modulated by group I mGluRs (mGluR1 and mGluR5), which have also been shown to be altered in schizophrenia. In rodents, mGluR5 antagonists, but not mGluR1 ones, potentiate the locomotor activity and the deficit of prepulse inhibition (PPI) induced by uncompetitive NMDA receptor antagonists. These antagonists (of either type) administered alone are not active in the above tests. Hence, antagonists of mGluR1 and mGluR5 may evoke different effects on the NMDA receptor antagonists-induced behavior and, possibly, on schizophrenic symptoms.
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Affiliation(s)
- M Pietraszek
- Preclinical R&D, Merz Pharmaceuticals GmbH, Frankfurt am Main, Germany.
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128
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Millan MJ. Multi-target strategies for the improved treatment of depressive states: Conceptual foundations and neuronal substrates, drug discovery and therapeutic application. Pharmacol Ther 2006; 110:135-370. [PMID: 16522330 DOI: 10.1016/j.pharmthera.2005.11.006] [Citation(s) in RCA: 389] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2005] [Accepted: 11/28/2005] [Indexed: 12/20/2022]
Abstract
Major depression is a debilitating and recurrent disorder with a substantial lifetime risk and a high social cost. Depressed patients generally display co-morbid symptoms, and depression frequently accompanies other serious disorders. Currently available drugs display limited efficacy and a pronounced delay to onset of action, and all provoke distressing side effects. Cloning of the human genome has fuelled expectations that symptomatic treatment may soon become more rapid and effective, and that depressive states may ultimately be "prevented" or "cured". In pursuing these objectives, in particular for genome-derived, non-monoaminergic targets, "specificity" of drug actions is often emphasized. That is, priority is afforded to agents that interact exclusively with a single site hypothesized as critically involved in the pathogenesis and/or control of depression. Certain highly selective drugs may prove effective, and they remain indispensable in the experimental (and clinical) evaluation of the significance of novel mechanisms. However, by analogy to other multifactorial disorders, "multi-target" agents may be better adapted to the improved treatment of depressive states. Support for this contention is garnered from a broad palette of observations, ranging from mechanisms of action of adjunctive drug combinations and electroconvulsive therapy to "network theory" analysis of the etiology and management of depressive states. The review also outlines opportunities to be exploited, and challenges to be addressed, in the discovery and characterization of drugs recognizing multiple targets. Finally, a diversity of multi-target strategies is proposed for the more efficacious and rapid control of core and co-morbid symptoms of depression, together with improved tolerance relative to currently available agents.
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Affiliation(s)
- Mark J Millan
- Institut de Recherches Servier, Centre de Recherches de Croissy, Psychopharmacology Department, 125, Chemin de Ronde, 78290-Croissy/Seine, France.
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129
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Löscher W, Dekundy A, Nagel J, Danysz W, Parsons CG, Potschka H. mGlu1 and mGlu5 receptor antagonists lack anticonvulsant efficacy in rodent models of difficult-to-treat partial epilepsy. Neuropharmacology 2006; 50:1006-15. [PMID: 16563443 DOI: 10.1016/j.neuropharm.2006.02.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2005] [Revised: 01/26/2006] [Accepted: 02/01/2006] [Indexed: 10/24/2022]
Abstract
Modulation of metabotropic glutamate (mGlu) receptors represents an interesting new approach for the treatment of a range of neurological and psychiatric disorders. Several lines of evidence suggest that functional blockade of group I (mGlu1 and mGlu5) receptors may be beneficial for treatment of epileptic seizures. This study was conducted to investigate whether mGlu1 or mGlu5 receptor antagonists have the potential to block partial or secondarily generalized seizures as occurring in partial epilepsy, the most common and difficult-to-treat type of epilepsy in patients. For this purpose, we systemically administered novel highly selective and brain penetrable group I mGlu receptor antagonists, i.e., the mGlu1 receptor antagonist EMQMCM [3-ethyl-2-methyl-quinolin-6-yl-(4-methoxy-cyclohexyl)-methanone methanesulfonate] and the mGlu5 receptor antagonist MTEP ([(2-methyl-1,3-thiazol-4-yl) ethynyl] pyridine), at doses appropriate for mGlu1 or mGlu5 receptor-mediated effects in rodent models of partial seizures. Two models were used: the 6-Hz electroshock model of partial seizures in mice and the amygdala-kindling model in rats. Clinically established antiepileptic drugs were included in the experiments for comparison. Antiepileptic drugs exerted significant anticonvulsant effects in both models, while EMQMCM and MTEP were ineffective in this regard, although both compounds were administered up to doses associated with essentially full receptor occupancy and with typical mGlu receptor-mediated effects in rodent models of anxiety or pain. Brain microdialysis for determining extracellular levels of MTEP following i.p. administration in rats substantiated that effective brain concentrations were reached at times of our experiments in seizure models. The present results do not support a significant anticonvulsant potential of group I mGlu receptor antagonists in rodent models of difficult-to-treat partial epilepsy.
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Affiliation(s)
- Wolfgang Löscher
- Department of Pharmacology, Toxicology and Pharmacy, University of Veterinary Medicine, Bünteweg 17, D-30559 Hannover, Germany.
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130
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Iso Y, Grajkowska E, Wroblewski JT, Davis J, Goeders NE, Johnson KM, Sanker S, Roth BL, Tueckmantel W, Kozikowski AP. Synthesis and Structure−Activity Relationships of 3-[(2-Methyl-1,3-thiazol-4-yl)ethynyl]pyridine Analogues as Potent, Noncompetitive Metabotropic Glutamate Receptor Subtype 5 Antagonists; Search for Cocaine Medications. J Med Chem 2006; 49:1080-100. [PMID: 16451073 DOI: 10.1021/jm050570f] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Recent genetic and pharmacological studies have suggested that the metabotropic glutamate receptor subtype 5 (mGluR5) may represent a druggable target in identifying new therapeutics for the treatment of various central nervous system disorders including drug abuse. In particular, considerable attention in the mGluR5 field has been devoted to identifying ligands that bind to the allosteric modulatory site, distinct from the site for the primary agonist glutamate. Both 2-methyl-6-(phenylethynyl)pyridine (MPEP) and its analogue 3-[(2-methyl-4-thiazolyl)ethynyl]pyridine (MTEP) have been shown to be selective and potent noncompetitive antagonists of mGluR5. Because of results presented in this study showing that MTEP prevents the reinstatement of cocaine self-administration caused by the presentation of environmental cues previously associated with cocaine availability, we have prepared a series of analogues of MTEP with the aim of gaining a better understanding of the structural features relevant to its antagonist potency and with the ultimate aim of investigating the effects of such compounds in blunting the self-administration of cocaine. These efforts have led to the identification of compounds showing higher potency as mGluR5 antagonists than either MPEP or MTEP. Two compounds 19 and 59 exhibited functional activity as mGluR5 antagonists that are 490 and 230 times, respectively, better than that of MTEP.
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Affiliation(s)
- Yasuyoshi Iso
- Drug Discovery Program, Department of Medicinal Chemistry and Pharmacognosy, University of Illinois at Chicago, 833 South Wood Street, Chicago, IL 60612, USA
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Hodge CW, Miles MF, Sharko AC, Stevenson RA, Hillmann JR, Lepoutre V, Besheer J, Schroeder JP. The mGluR5 antagonist MPEP selectively inhibits the onset and maintenance of ethanol self-administration in C57BL/6J mice. Psychopharmacology (Berl) 2006; 183:429-38. [PMID: 16292590 PMCID: PMC2854492 DOI: 10.1007/s00213-005-0217-y] [Citation(s) in RCA: 124] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2005] [Accepted: 09/22/2005] [Indexed: 01/18/2023]
Abstract
RATIONALE Many of the biochemical, physiological, and behavioral effects of ethanol are known to be mediated by ionotropic glutamate receptors. Emerging evidence implicates metabotropic glutamate receptors (mGluRs) in the biobehavioral effects of ethanol and other drugs of abuse, but there is little information regarding the role of mGluRs in the reinforcing effects of ethanol. MATERIALS AND METHODS Male C57BL/6J mice were trained to lever-press on a concurrent fixed ratio 1 schedule of ethanol (10% v/v) vs water reinforcement during 16-h sessions. Effects of mGluR1, mGluR2/3, and mGluR5 antagonists were then tested on parameters of ethanol self-administration behavior. RESULTS The mGluR5 antagonist MPEP (1-10 mg/kg, i.p.) dose-dependently reduced ethanol-reinforced responding but had no effect on concurrent water-reinforced responding. Analysis of the temporal pattern of responding showed that MPEP reduced ethanol-reinforced responding during peak periods of behavior occurring during the early hours of the dark cycle. Further analysis showed that MPEP reduced the number of ethanol response bouts and bout-response rate. MPEP also produced a 13-fold delay in ethanol response onset (i.e., latency to the first response) with no corresponding effect on water response latency or locomotor activity. The mGluR1 antagonist CPCCOEt (1-10 mg/kg, i.p.) or the mGluR2/3 antagonist LY 341495 (1-30 mg/kg, i.p.) failed to alter ethanol- or water-reinforced responding. CONCLUSIONS These data indicate that mGlu5 receptors selectively regulate the onset and maintenance of ethanol self-administration in a manner that is consistent with reduction in ethanol's reinforcement function.
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Affiliation(s)
- Clyde W Hodge
- Department of Psychiatry, Bowles Center for Alcohol Studies School of Medicine, CB#7178, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7178, USA.
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Rorick-Kehn LM, Hart JC, McKinzie DL. Pharmacological characterization of stress-induced hyperthermia in DBA/2 mice using metabotropic and ionotropic glutamate receptor ligands. Psychopharmacology (Berl) 2005; 183:226-40. [PMID: 16175401 DOI: 10.1007/s00213-005-0169-2] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/11/2005] [Accepted: 08/11/2005] [Indexed: 11/26/2022]
Abstract
RATIONALE Accumulating evidence suggests that drugs acting on the glutamatergic system may represent promising novel therapeutic targets for the treatment of anxiety disorders. The stress-induced hyperthermia paradigm has been used widely to model some of the physiological symptoms associated with anxiety disorders and has produced results that are predictive of clinical efficacy. We have modified this paradigm to measure the autonomic consequences of stress induced by the fear of predation in mice. OBJECTIVE To evaluate the efficacy of several classes of metabotropic and ionotropic glutamate receptor ligands, as well as known anxiolytics and psychotropic comparators, in attenuating predatory-stress-induced hyperthermia. METHODS Male DBA/2 mice were implanted with radiotelemetric transmitters in the peritoneal cavity to measure stress-related increases in core body temperature, following placement in a novel cage containing soiled rat shavings. RESULTS Clinically active compounds such as chlordiazepoxide (5-10 mg/kg), alprazolam (0.3-3 mg/kg), and buspirone (10-30 mg/kg) exhibited an anxiolytic profile. Assessment of glutamatergic agents indicated that the mGlu1 receptor antagonist LY456236 (10-30 mg/kg), mGlu5 receptor antagonist MPEP (10-30 mg/kg), mGlu2/3 receptor agonist LY354740 (3-10 mg/kg), mGlu2 receptor potentiator LY566332 (30 and 100 mg/kg), mGlu8 receptor agonist (S)-3,4-dicarboxyphenylglycine (30-60 mg/kg), competitive NMDA receptor antagonist LY235959 (1 mg/kg), AMPA receptor antagonist GYKI-52466 (10-20 mg/kg), and glycine transporter-1 (GlyT-1) inhibitor ALX-5407 (3-10 mg/kg) dose-dependently attenuated stress-induced hyperthermia. The AMPA receptor potentiator LY451646, iGlu5 kainate receptor antagonist LY382884, glycine(B) receptor partial agonist D: -cycloserine, and GlyT-1 inhibitor ORG-24461 were ineffective in this model. CONCLUSION Select metabotropic and ionotropic glutamate receptor ligands exhibited an anxiolytic profile, as measured by the attenuation of stress-induced hyperthermia, and may represent viable targets for the development of pharmacological treatments for anxiety-related disorders.
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Affiliation(s)
- Linda M Rorick-Kehn
- Neuroscience Discovery Research, Eli Lilly & Company, Indianapolis, IN 46285, USA
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Cowen MS, Djouma E, Lawrence AJ. The Metabotropic Glutamate 5 Receptor Antagonist 3-[(2-Methyl-1,3-thiazol-4-yl)ethynyl]-pyridine Reduces Ethanol Self-Administration in Multiple Strains of Alcohol-Preferring Rats and Regulates Olfactory Glutamatergic Systems. J Pharmacol Exp Ther 2005; 315:590-600. [PMID: 16014750 DOI: 10.1124/jpet.105.090449] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The metabotropic glutamate 5 receptor (mGlu5) receptor has been implicated as having a role in pain modulation, anxiety, and depression, as well as drug-seeking behavior. In the present study, we examined the effect of the selective mGlu5 receptor antagonist 3-[(2-methyl-1,3-thiazol-4-yl)ethynyl]-pyridine (MTEP) on operant ethanol self-administration by two strains of rats, the Fawn-Hooded (FH) rat and the inbred alcohol-preferring (iP) rat. MTEP (2 mg/kg i.p.) caused a significant reduction in responding for ethanol by both strains of rats; however, in the iP rats, MTEP also induced apparent sedation at this dose, although still reduced alcohol responding at lower doses. Chronic MTEP (2 mg/kg/day) caused a significant reduction in ethanol consumption by FH rats in a two-bottle preference test; however, chronic treatment with this dose had no effect on anxiety-like behavior or depressive-like behavior in FH rats, suggesting the dose used was subthreshold for anxiolytic or antidepressive-like effects. Finally, repeated dosing with MTEP (2 mg/kg i.p.) caused significant reductions in expression of the mRNA encoding the NR1 subunit of the N-methyl-D-aspartate receptor and the GluR2 subunit of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptor in the cingulate cortex. A significant decrease in NR1 expression also occurred in the piriform cortex. Chronic MTEP also caused a significant decrease in mGlu5 gene expression and a significant increase in dopamine transporter and dopamine D(2)-like receptor binding within the olfactory tubercle. Collectively, these data suggest that MTEP can reduce alcohol-seeking behavior in different rodent models of alcoholism, and this effect is associated with regulation of cortical glutamate systems, particularly those in olfactory-related regions.
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Affiliation(s)
- Michael S Cowen
- Howard Florey Institute, Royal Parade, University of Melbourne, Victoria, Australia
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Shannon HE, Peters SC, Kingston AE. Anticonvulsant effects of LY456236, a selective mGlu1 receptor antagonist. Neuropharmacology 2005; 49 Suppl 1:188-95. [PMID: 16011839 DOI: 10.1016/j.neuropharm.2005.05.010] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2005] [Revised: 05/12/2005] [Accepted: 05/13/2005] [Indexed: 11/24/2022]
Abstract
Several lines of evidence suggest that mGlu1 metabotropic glutamate receptors may be involved in seizure disorders such as epilepsy. For example, the mGlu1 agonist DHPG produces limbic seizures and group I antagonists such as 4C3HPG and 4CPG are anticonvulsant when administered intracerebrally. The purpose of the present experiments was to characterize the anticonvulsant effects of the selective mGlu1 receptor antagonist LY456236 in mice and rats. In male and female DBA/2 mice, LY456236 produced a dose-related inhibition of sound-induced clonic-tonic seizures. In male CF1 mice, LY456236 produced a dose-related inhibition of tonic extensor seizures in the threshold electroshock model, and limbic seizures in the 6-Hz focal seizure model. However, this antagonist did not inhibit clonic seizures produced by pentylenetetrazol. In amygdala-kindled male Sprague-Dawley rats, LY456236 produced dose-related decreases in behavioral and electrographic seizures at threshold stimulus intensity. In addition, LY456236 produced a dose-related increase in the stimulus intensity required to produce generalized seizures. Taken together, the present results support the conclusion that mGlu1 receptor antagonists such as LY456236 may have clinical utility in the treatment of epilepsy and other seizure disorders.
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Affiliation(s)
- Harlan E Shannon
- Lilly Research Laboratories, Eli Lilly and Company, Lilly Corporate Center, Indianapolis, IN 46285, USA.
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