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Mazzitelli M, Presto P, Antenucci N, Meltan S, Neugebauer V. Recent Advances in the Modulation of Pain by the Metabotropic Glutamate Receptors. Cells 2022; 11:2608. [PMID: 36010684 PMCID: PMC9406805 DOI: 10.3390/cells11162608] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 08/16/2022] [Accepted: 08/18/2022] [Indexed: 01/22/2023] Open
Abstract
Metabotropic glutamate receptors (mGluR or mGlu) are G-protein coupled receptors activated by the binding of glutamate, the main classical neurotransmitter of the nervous system. Eight different mGluR subtypes (mGluR1-8) have been cloned and are classified in three groups based on their molecular, pharmacological and signaling properties. mGluRs mediate several physiological functions such as neuronal excitability and synaptic plasticity, but they have also been implicated in numerous pathological conditions including pain. The availability of new and more selective allosteric modulators together with the canonical orthosteric ligands and transgenic technologies has led to significant advances in our knowledge about the role of the specific mGluR subtypes in the pathophysiological mechanisms of various diseases. Although development of successful compounds acting on mGluRs for clinical use has been scarce, the subtype-specific-pharmacological manipulation might be a compelling approach for the treatment of several disorders in humans, including pain; this review aims to summarize and update on preclinical evidence for the roles of different mGluRs in the pain system and discusses knowledge gaps regarding mGluR-related sex differences and neuroimmune signaling in pain.
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Affiliation(s)
- Mariacristina Mazzitelli
- Department of Pharmacology and Neuroscience, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Peyton Presto
- Department of Pharmacology and Neuroscience, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Nico Antenucci
- Department of Pharmacology and Neuroscience, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Shakira Meltan
- Department of Pharmacology and Neuroscience, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Volker Neugebauer
- Department of Pharmacology and Neuroscience, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
- Center of Excellence for Translational Neuroscience and Therapeutics, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
- Garrison Institute on Aging, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
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Chen S, Kadakia F, Davidson S. Group II metabotropic glutamate receptor expressing neurons in anterior cingulate cortex become sensitized after inflammatory and neuropathic pain. Mol Pain 2021; 16:1744806920915339. [PMID: 32326814 PMCID: PMC7227149 DOI: 10.1177/1744806920915339] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The anterior cingulate cortex is a limbic region associated with the emotional processing of pain. How neuropathic and inflammatory pain models alter the neurophysiology of specific subsets of neurons in the anterior cingulate cortex remains incompletely understood. Here, we used a GRM2Cre:tdtomato reporter mouse line to identify a population of pyramidal neurons selectively localized to layer II/III of the murine anterior cingulate cortex. GRM2encodes the group II metabotropic glutamate receptor subtype 2 which possesses analgesic properties in mouse and human models, although its function in the anterior cingulate cortex is not known. The majority of GRM2-tdtomato anterior cingulate cortex neurons expressed GRM2gene product in situ but did not overlap with cortical markers of local inhibitory interneurons, parvalbumin or somatostatin. Physiological properties of GRM2-tdtomato anterior cingulate cortex neurons were investigated using whole-cell patch clamp techniques in slice from animals with neuropathic or inflammatory pain, and controls. After hind-paw injection of Complete Freund’s Adjuvant or chronic constriction injury, GRM2-tdtomato anterior cingulate cortex neurons exhibited enhanced excitability as measured by an increase in the number of evoked action potentials and a decreased rheobase. This hyperexcitability was reversed pharmacologically by bath application of the metabotropic glutamate receptor subtype 2 agonist (2R, 4R)-4-Aminopyrrolidine-2,4-dicarboxylate APDC (1 µM) in both inflammatory and neuropathic models. We conclude that layer II/III pyramidal GRM2-tdtomato anterior cingulate cortex neurons express functional group II metabotropic glutamate receptors and undergo changes to membrane biophysical properties under conditions of inflammatory and neuropathic pain.
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Affiliation(s)
- Sisi Chen
- Department of Anesthesiology, Pain Research Center, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Feni Kadakia
- Neuroscience Graduate Program, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Steve Davidson
- Department of Anesthesiology, Pain Research Center, University of Cincinnati College of Medicine, Cincinnati, OH, USA.,Neuroscience Graduate Program, University of Cincinnati College of Medicine, Cincinnati, OH, USA
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Mazzitelli M, Neugebauer V. Amygdala group II mGluRs mediate the inhibitory effects of systemic group II mGluR activation on behavior and spinal neurons in a rat model of arthritis pain. Neuropharmacology 2019; 158:107706. [PMID: 31306647 DOI: 10.1016/j.neuropharm.2019.107706] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Revised: 07/03/2019] [Accepted: 07/10/2019] [Indexed: 12/16/2022]
Abstract
The amygdala plays a critical role in emotional-affective aspects of behaviors and pain modulation. The central nucleus of amygdala (CeA) serves major output functions, and neuroplasticity in the CeA is linked to pain-related behaviors in different models. Activation of Gi/o-coupled group II metabotropic glutamate receptors (mGluRs), which consist of mGluR2 and mGluR3, can decrease neurotransmitter release and regulate synaptic plasticity. Group II mGluRs have emerged as targets for neuropsychiatric disorders and can inhibit pain-related processing and behaviors. Surprisingly, site and mechanism of antinociceptive actions of systemically applied group II mGluR agonists are not clear. Our previous work showed that group II mGluR activation in the amygdala inhibits pain-related CeA activity, but behavioral and spinal consequences remain to be determined. Here we studied the contribution of group II mGluRs in the amygdala to the antinociceptive effects of a systemically applied group II mGluR agonist (LY379268) on behavior and spinal dorsal horn neuronal activity, using the kaolin/carrageenan-induced knee joint arthritis pain model. Audible and ultrasonic vocalizations (emotional responses) and mechanical reflex thresholds were measured in adult rats with and without arthritis (5-6 h postinduction). Extracellular single-unit recordings were made from spinal dorsal horn wide dynamic range neurons of anesthetized (isoflurane) rats with and without arthritis (5-6 h postinduction). Systemic (intraperitoneal) application of a group II mGluR agonist (LY379268) decreased behaviors and activity of spinal neurons in the arthritis pain model but not under normal conditions. Stereotaxic administration of LY379268 into the CeA mimicked the effects of systemic application. Conversely, stereotaxic administration of a group II mGluR antagonist (LY341495) into the CeA reversed the effects of systemic application of LY379268 on behaviors and dorsal horn neuronal activity in arthritic rats. The data show for the first time that the amygdala is the critical site of action for the antinociceptive behavioral and spinal neuronal effects of systemically applied group II mGluR agonists.
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Affiliation(s)
- Mariacristina Mazzitelli
- Department of Pharmacology and Neuroscience, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX, 79430-6592, USA
| | - Volker Neugebauer
- Department of Pharmacology and Neuroscience, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX, 79430-6592, USA; Center of Excellence for Translational Neuroscience and Therapeutics, Texas Tech University Health Sciences Center, Lubbock, TX, 79430-6592, USA; Garrison Institute on Aging, Texas Tech University Health Sciences Center, Lubbock, TX, 79430-6592, USA.
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Mazzitelli M, Palazzo E, Maione S, Neugebauer V. Group II Metabotropic Glutamate Receptors: Role in Pain Mechanisms and Pain Modulation. Front Mol Neurosci 2018; 11:383. [PMID: 30356691 PMCID: PMC6189308 DOI: 10.3389/fnmol.2018.00383] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2018] [Accepted: 09/24/2018] [Indexed: 12/12/2022] Open
Abstract
Glutamate is the main excitatory neurotransmitter in the nervous system and plays a critical role in nociceptive processing and pain modulation. G-protein coupled metabotropic glutamate receptors (mGluRs) are widely expressed in the central and peripheral nervous system, and they mediate neuronal excitability and synaptic transmission. Eight different mGluR subtypes have been identified so far, and are classified into Groups I-III. Group II mGluR2 and mGluR3 couple negatively to adenylyl cyclase through Gi/Go proteins, are mainly expressed presynaptically, and typically inhibit the release of neurotransmitters, including glutamate and GABA. Group II mGluRs have consistently been linked to pain modulation; they are expressed in peripheral, spinal and supraspinal elements of pain-related neural processing. Pharmacological studies have shown anti-nociceptive/analgesic effects of group II mGluR agonists in preclinical models of acute and chronic pain, although much less is known about mechanisms and sites of action for mGluR2 and mGluR3 compared to other mGluRs. The availability of orthosteric and new selective allosteric modulators acting on mGluR2 and mGluR3 has provided valuable tools for elucidating (subtype) specific contributions of these receptors to the pathophysiological mechanisms of pain and other disorders and their potential as therapeutic targets. This review focuses on the important role of group II mGluRs in the neurobiology of pain mechanisms and behavioral modulation, and discusses evidence for their therapeutic potential in pain.
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Affiliation(s)
- Mariacristina Mazzitelli
- Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center, Lubbock, TX, United States
| | - Enza Palazzo
- Section of Pharmacology L. Donatelli, Department of Experimental Medicine, University of Campania Luigi Vanvitelli, Naples, Italy
| | - Sabatino Maione
- Section of Pharmacology L. Donatelli, Department of Experimental Medicine, University of Campania Luigi Vanvitelli, Naples, Italy
| | - Volker Neugebauer
- Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center, Lubbock, TX, United States
- Center of Excellence for Translational Neuroscience and Therapeutics, Texas Tech University Health Sciences Center, Lubbock, TX, United States
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Notartomaso S, Mascio G, Bernabucci M, Zappulla C, Scarselli P, Cannella M, Imbriglio T, Gradini R, Battaglia G, Bruno V, Nicoletti F. Analgesia induced by the epigenetic drug, L-acetylcarnitine, outlasts the end of treatment in mouse models of chronic inflammatory and neuropathic pain. Mol Pain 2017; 13:1744806917697009. [PMID: 28326943 PMCID: PMC5407675 DOI: 10.1177/1744806917697009] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Background L-acetylcarnitine, a drug marketed for the treatment of chronic pain, causes analgesia by epigenetically up-regulating type-2 metabotropic glutamate (mGlu2) receptors in the spinal cord. Because the epigenetic mechanisms are typically long-lasting, we hypothesized that analgesia could outlast the duration of L-acetylcarnitine treatment in models of inflammatory and neuropathic pain. Results A seven-day treatment with L-acetylcarnitine (100 mg/kg, once a day, i.p.) produced an antiallodynic effect in the complete Freund adjuvant mouse model of chronic inflammatory pain. L-Acetylcarnitine-induced analgesia persisted for at least 14 days after drug withdrawal. In contrast, the analgesic effect of pregabalin, amitryptiline, ceftriaxone, and N-acetylcysteine disappeared seven days after drug withdrawal. L-acetylcarnitine treatment enhanced mGlu2/3 receptor protein levels in the dorsal region of the spinal cord. This effect also persisted for two weeks after drug withdrawal and was associated with increased levels of acetylated histone H3 bound to the Grm2 gene promoter in the dorsal root ganglia. A long-lasting analgesic effect of L-acetylcarnitine was also observed in mice subjected to chronic constriction injury of the sciatic nerve. In these animals, a 14-day treatment with pregabalin, amitryptiline, tramadol, or L-acetylcarnitine produced a significant antiallodynic effect, with pregabalin displaying the greatest efficacy. In mice treated with pregabalin, tramadol or L-acetylcarnitine the analgesic effect was still visible 15 days after the end of drug treatment. However, only in mice treated with L-acetylcarnitine analgesia persisted 37 days after drug withdrawal. This effect was associated with an increase in mGlu2/3 receptor protein levels in the dorsal horns of the spinal cord. Conclusions Our findings suggest that L-acetylcarnitine has the unique property to cause a long-lasting analgesic effect that might reduce relapses in patients suffering from chronic pain.
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Affiliation(s)
| | | | | | | | | | | | | | - Roberto Gradini
- 1 I.R.C.C.S. Neuromed, Pozzilli, Italy.,2 Department of Experimental Medicine, Sapienza University, Rome, Italy
| | | | - Valeria Bruno
- 1 I.R.C.C.S. Neuromed, Pozzilli, Italy.,3 Department of Physiology and Pharmacology, Sapienza University, Rome, Italy
| | - Ferdinando Nicoletti
- 1 I.R.C.C.S. Neuromed, Pozzilli, Italy.,3 Department of Physiology and Pharmacology, Sapienza University, Rome, Italy
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Johnson MP, Muhlhauser MA, Nisenbaum ES, Simmons RMA, Forster BM, Knopp KL, Yang L, Morrow D, Li DL, Kennedy JD, Swanson S, Monn JA. Broad spectrum efficacy with LY2969822, an oral prodrug of metabotropic glutamate 2/3 receptor agonist LY2934747, in rodent pain models. Br J Pharmacol 2017; 174:822-835. [PMID: 28177520 DOI: 10.1111/bph.13740] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Revised: 01/27/2017] [Accepted: 01/31/2017] [Indexed: 01/12/2023] Open
Abstract
BACKGROUND AND PURPOSE A body of evidence suggests activation of metabotropic glutamate 2/3 (mGlu2/3 ) receptors would be an effective analgesic in chronic pain conditions. Thus, the analgesic properties of a novel mGlu2/3 receptor agonist prodrug were investigated. EXPERIMENTAL APPROACH After oral absorption, the prodrug LY2969822 rapidly converts to the brain penetrant, potent and subtype-selective mGlu2/3 receptor agonist LY2934747. Behavioural assessments of allodynia, hyperalgesia and nocifensive behaviours were determined in preclinical pain models after administration of LY2969822 0.3-10 mg·kg-1 . In addition, the ability of i.v. LY2934747 to modulate dorsal horn spinal cord wide dynamic range (WDR) neurons in spinal nerve ligated (SNL) rats was assessed. KEY RESULTS Following treatment with LY2934747, the spontaneous activity and electrically-evoked wind-up of WDR neurons in rats that had undergone spinal nerve ligation and developed mechanical allodynia were suppressed. In a model of sensitization, orally administered LY2969822 prevented the nociceptive behaviours induced by an intraplantar injection of formalin. The on-target nature of this effect was confirmed by blockade with an mGlu2/3 receptor antagonist. LY2969822 prevented capsaicin-induced tactile hypersensitivity, reversed the SNL-induced tactile hypersensitivity and reversed complete Freund's adjuvant - induced mechanical hyperalgesia. The mGlu2/3 receptor agonist prodrug demonstrated efficacy in visceral pain models, including a colorectal distension model and partially prevented the nocifensive behaviours in the mouse acetic acid writhing model. CONCLUSIONS AND IMPLICATIONS Following oral administration of the prodrug LY2969822, the mGlu2/3 receptor agonist LY2934747 was formed and this attenuated pain behaviours across a broad range of preclinical pain models.
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Affiliation(s)
- Michael P Johnson
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN, USA
| | - Mark A Muhlhauser
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN, USA
| | - Eric S Nisenbaum
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN, USA
| | - Rosa M A Simmons
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN, USA
| | - Beth M Forster
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN, USA
| | - Kelly L Knopp
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN, USA
| | - Lijuan Yang
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN, USA
| | - Denise Morrow
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN, USA
| | - Dominic L Li
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN, USA
| | - Jeffrey D Kennedy
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN, USA
| | - Steven Swanson
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN, USA
| | - James A Monn
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN, USA
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7
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Palazzo E, Marabese I, Luongo L, Guida F, de Novellis V, Maione S. Nociception modulation by supraspinal group III metabotropic glutamate receptors. J Neurochem 2017; 141:507-519. [DOI: 10.1111/jnc.13725] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Revised: 06/15/2016] [Accepted: 06/20/2016] [Indexed: 02/02/2023]
Affiliation(s)
- Enza Palazzo
- Department of Experimental Medicine; The Second University of Naples; Naples Italy
| | - Ida Marabese
- Department of Experimental Medicine; The Second University of Naples; Naples Italy
| | - Livio Luongo
- Department of Experimental Medicine; The Second University of Naples; Naples Italy
| | - Francesca Guida
- Department of Experimental Medicine; The Second University of Naples; Naples Italy
| | - Vito de Novellis
- Department of Experimental Medicine; The Second University of Naples; Naples Italy
| | - Sabatino Maione
- Department of Experimental Medicine; The Second University of Naples; Naples Italy
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Witkin JM, Mitchell SN, Wafford KA, Carter G, Gilmour G, Li J, Eastwood BJ, Overshiner C, Li X, Rorick-Kehn L, Rasmussen K, Anderson WH, Nikolayev A, Tolstikov VV, Kuo MS, Catlow JT, Li R, Smith SC, Mitch CH, Ornstein PL, Swanson S, Monn JA. Comparative Effects of LY3020371, a Potent and Selective Metabotropic Glutamate (mGlu) 2/3 Receptor Antagonist, and Ketamine, a Noncompetitive N-Methyl-d-Aspartate Receptor Antagonist in Rodents: Evidence Supporting the Use of mGlu2/3 Antagonists, for the Treatment of Depression. J Pharmacol Exp Ther 2017; 361:68-86. [PMID: 28138040 DOI: 10.1124/jpet.116.238121] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2016] [Accepted: 01/05/2017] [Indexed: 12/17/2022] Open
Abstract
The ability of the N-methyl-d-aspartate receptor antagonist ketamine to alleviate symptoms in patients suffering from treatment-resistant depression (TRD) is well documented. In this paper, we directly compare in vivo biologic responses in rodents elicited by a recently discovered metabotropic glutamate (mGlu) 2/3 receptor antagonist 2-amino-3-[(3,4-difluorophenyl)sulfanylmethyl]-4-hydroxy-bicyclo[3.1.0]hexane-2,6-dicarboxylic acid (LY3020371) with those produced by ketamine. Both LY3020371 and ketamine increased the number of spontaneously active dopamine cells in the ventral tegmental area of anesthetized rats, increased O2 in the anterior cingulate cortex, promoted wakefulness, enhanced the efflux of biogenic amines in the prefrontal cortex, and produced antidepressant-related behavioral effects in rodent models. The ability of LY3020371 to produce antidepressant-like effects in the forced-swim assay in rats was associated with cerebrospinal fluid (CSF) drug levels that matched concentrations required for functional antagonist activity in native rat brain tissue preparations. Metabolomic pathway analyses from analytes recovered from rat CSF and hippocampus demonstrated that both LY3020371 and ketamine activated common pathways involving GRIA2 and ADORA1. A diester analog of LY3020371 [bis(((isopropoxycarbonyl)oxy)-methyl) (1S,2R,3S,4S,5R,6R)-2-amino-3-(((3,4-difluorophenyl)thio)methyl)-4-hydroxy-bicyclo[3.1.0]hexane-2,6-dicarboxylate (LY3027788)] was an effective oral prodrug; when given orally, it recapitulated effects of intravenous doses of LY3020371 in the forced-swim and wake-promotion assays, and augmented the antidepressant-like effects of fluoxetine or citalopram without altering plasma or brain levels of these compounds. The broad overlap of biologic responses produced by LY3020371 and ketamine supports the hypothesis that mGlu2/3 receptor blockade might be a novel therapeutic approach for the treatment of TRD patients. LY3020371 and LY3027788 represent molecules that are ready for clinical tests of this hypothesis.
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Affiliation(s)
- J M Witkin
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN (J.M.W., C.O., X.L., L.R.-K., K.R., W.H.A., A.N., V.V.T., M.-S.K., J.T.C., R.L., S.C.S., C.H.M., P.L.O., S.S., J.A.M.); and Lilly Research Laboratories, Eli Lilly and Company, Windlesham, Surrey, United Kingdom (S.N.M., K.A.W., G.C., G.G., J.L., B.J.E.)
| | - S N Mitchell
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN (J.M.W., C.O., X.L., L.R.-K., K.R., W.H.A., A.N., V.V.T., M.-S.K., J.T.C., R.L., S.C.S., C.H.M., P.L.O., S.S., J.A.M.); and Lilly Research Laboratories, Eli Lilly and Company, Windlesham, Surrey, United Kingdom (S.N.M., K.A.W., G.C., G.G., J.L., B.J.E.)
| | - K A Wafford
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN (J.M.W., C.O., X.L., L.R.-K., K.R., W.H.A., A.N., V.V.T., M.-S.K., J.T.C., R.L., S.C.S., C.H.M., P.L.O., S.S., J.A.M.); and Lilly Research Laboratories, Eli Lilly and Company, Windlesham, Surrey, United Kingdom (S.N.M., K.A.W., G.C., G.G., J.L., B.J.E.)
| | - G Carter
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN (J.M.W., C.O., X.L., L.R.-K., K.R., W.H.A., A.N., V.V.T., M.-S.K., J.T.C., R.L., S.C.S., C.H.M., P.L.O., S.S., J.A.M.); and Lilly Research Laboratories, Eli Lilly and Company, Windlesham, Surrey, United Kingdom (S.N.M., K.A.W., G.C., G.G., J.L., B.J.E.)
| | - G Gilmour
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN (J.M.W., C.O., X.L., L.R.-K., K.R., W.H.A., A.N., V.V.T., M.-S.K., J.T.C., R.L., S.C.S., C.H.M., P.L.O., S.S., J.A.M.); and Lilly Research Laboratories, Eli Lilly and Company, Windlesham, Surrey, United Kingdom (S.N.M., K.A.W., G.C., G.G., J.L., B.J.E.)
| | - J Li
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN (J.M.W., C.O., X.L., L.R.-K., K.R., W.H.A., A.N., V.V.T., M.-S.K., J.T.C., R.L., S.C.S., C.H.M., P.L.O., S.S., J.A.M.); and Lilly Research Laboratories, Eli Lilly and Company, Windlesham, Surrey, United Kingdom (S.N.M., K.A.W., G.C., G.G., J.L., B.J.E.)
| | - B J Eastwood
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN (J.M.W., C.O., X.L., L.R.-K., K.R., W.H.A., A.N., V.V.T., M.-S.K., J.T.C., R.L., S.C.S., C.H.M., P.L.O., S.S., J.A.M.); and Lilly Research Laboratories, Eli Lilly and Company, Windlesham, Surrey, United Kingdom (S.N.M., K.A.W., G.C., G.G., J.L., B.J.E.)
| | - C Overshiner
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN (J.M.W., C.O., X.L., L.R.-K., K.R., W.H.A., A.N., V.V.T., M.-S.K., J.T.C., R.L., S.C.S., C.H.M., P.L.O., S.S., J.A.M.); and Lilly Research Laboratories, Eli Lilly and Company, Windlesham, Surrey, United Kingdom (S.N.M., K.A.W., G.C., G.G., J.L., B.J.E.)
| | - X Li
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN (J.M.W., C.O., X.L., L.R.-K., K.R., W.H.A., A.N., V.V.T., M.-S.K., J.T.C., R.L., S.C.S., C.H.M., P.L.O., S.S., J.A.M.); and Lilly Research Laboratories, Eli Lilly and Company, Windlesham, Surrey, United Kingdom (S.N.M., K.A.W., G.C., G.G., J.L., B.J.E.)
| | - L Rorick-Kehn
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN (J.M.W., C.O., X.L., L.R.-K., K.R., W.H.A., A.N., V.V.T., M.-S.K., J.T.C., R.L., S.C.S., C.H.M., P.L.O., S.S., J.A.M.); and Lilly Research Laboratories, Eli Lilly and Company, Windlesham, Surrey, United Kingdom (S.N.M., K.A.W., G.C., G.G., J.L., B.J.E.)
| | - K Rasmussen
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN (J.M.W., C.O., X.L., L.R.-K., K.R., W.H.A., A.N., V.V.T., M.-S.K., J.T.C., R.L., S.C.S., C.H.M., P.L.O., S.S., J.A.M.); and Lilly Research Laboratories, Eli Lilly and Company, Windlesham, Surrey, United Kingdom (S.N.M., K.A.W., G.C., G.G., J.L., B.J.E.)
| | - W H Anderson
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN (J.M.W., C.O., X.L., L.R.-K., K.R., W.H.A., A.N., V.V.T., M.-S.K., J.T.C., R.L., S.C.S., C.H.M., P.L.O., S.S., J.A.M.); and Lilly Research Laboratories, Eli Lilly and Company, Windlesham, Surrey, United Kingdom (S.N.M., K.A.W., G.C., G.G., J.L., B.J.E.)
| | - A Nikolayev
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN (J.M.W., C.O., X.L., L.R.-K., K.R., W.H.A., A.N., V.V.T., M.-S.K., J.T.C., R.L., S.C.S., C.H.M., P.L.O., S.S., J.A.M.); and Lilly Research Laboratories, Eli Lilly and Company, Windlesham, Surrey, United Kingdom (S.N.M., K.A.W., G.C., G.G., J.L., B.J.E.)
| | - V V Tolstikov
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN (J.M.W., C.O., X.L., L.R.-K., K.R., W.H.A., A.N., V.V.T., M.-S.K., J.T.C., R.L., S.C.S., C.H.M., P.L.O., S.S., J.A.M.); and Lilly Research Laboratories, Eli Lilly and Company, Windlesham, Surrey, United Kingdom (S.N.M., K.A.W., G.C., G.G., J.L., B.J.E.)
| | - M-S Kuo
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN (J.M.W., C.O., X.L., L.R.-K., K.R., W.H.A., A.N., V.V.T., M.-S.K., J.T.C., R.L., S.C.S., C.H.M., P.L.O., S.S., J.A.M.); and Lilly Research Laboratories, Eli Lilly and Company, Windlesham, Surrey, United Kingdom (S.N.M., K.A.W., G.C., G.G., J.L., B.J.E.)
| | - J T Catlow
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN (J.M.W., C.O., X.L., L.R.-K., K.R., W.H.A., A.N., V.V.T., M.-S.K., J.T.C., R.L., S.C.S., C.H.M., P.L.O., S.S., J.A.M.); and Lilly Research Laboratories, Eli Lilly and Company, Windlesham, Surrey, United Kingdom (S.N.M., K.A.W., G.C., G.G., J.L., B.J.E.)
| | - R Li
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN (J.M.W., C.O., X.L., L.R.-K., K.R., W.H.A., A.N., V.V.T., M.-S.K., J.T.C., R.L., S.C.S., C.H.M., P.L.O., S.S., J.A.M.); and Lilly Research Laboratories, Eli Lilly and Company, Windlesham, Surrey, United Kingdom (S.N.M., K.A.W., G.C., G.G., J.L., B.J.E.)
| | - S C Smith
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN (J.M.W., C.O., X.L., L.R.-K., K.R., W.H.A., A.N., V.V.T., M.-S.K., J.T.C., R.L., S.C.S., C.H.M., P.L.O., S.S., J.A.M.); and Lilly Research Laboratories, Eli Lilly and Company, Windlesham, Surrey, United Kingdom (S.N.M., K.A.W., G.C., G.G., J.L., B.J.E.)
| | - C H Mitch
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN (J.M.W., C.O., X.L., L.R.-K., K.R., W.H.A., A.N., V.V.T., M.-S.K., J.T.C., R.L., S.C.S., C.H.M., P.L.O., S.S., J.A.M.); and Lilly Research Laboratories, Eli Lilly and Company, Windlesham, Surrey, United Kingdom (S.N.M., K.A.W., G.C., G.G., J.L., B.J.E.)
| | - P L Ornstein
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN (J.M.W., C.O., X.L., L.R.-K., K.R., W.H.A., A.N., V.V.T., M.-S.K., J.T.C., R.L., S.C.S., C.H.M., P.L.O., S.S., J.A.M.); and Lilly Research Laboratories, Eli Lilly and Company, Windlesham, Surrey, United Kingdom (S.N.M., K.A.W., G.C., G.G., J.L., B.J.E.)
| | - S Swanson
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN (J.M.W., C.O., X.L., L.R.-K., K.R., W.H.A., A.N., V.V.T., M.-S.K., J.T.C., R.L., S.C.S., C.H.M., P.L.O., S.S., J.A.M.); and Lilly Research Laboratories, Eli Lilly and Company, Windlesham, Surrey, United Kingdom (S.N.M., K.A.W., G.C., G.G., J.L., B.J.E.)
| | - J A Monn
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN (J.M.W., C.O., X.L., L.R.-K., K.R., W.H.A., A.N., V.V.T., M.-S.K., J.T.C., R.L., S.C.S., C.H.M., P.L.O., S.S., J.A.M.); and Lilly Research Laboratories, Eli Lilly and Company, Windlesham, Surrey, United Kingdom (S.N.M., K.A.W., G.C., G.G., J.L., B.J.E.)
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9
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Witkin JM, Ornstein PL, Mitch CH, Li R, Smith SC, Heinz BA, Wang XS, Xiang C, Carter JH, Anderson WH, Li X, Broad LM, Pasqui F, Fitzjohn SM, Sanger HE, Smith JL, Catlow J, Swanson S, Monn JA. In vitro pharmacological and rat pharmacokinetic characterization of LY3020371, a potent and selective mGlu 2/3 receptor antagonist. Neuropharmacology 2015; 115:100-114. [PMID: 26748052 DOI: 10.1016/j.neuropharm.2015.12.021] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Revised: 12/09/2015] [Accepted: 12/22/2015] [Indexed: 12/27/2022]
Abstract
Metabotropic glutamate 2/3 (mGlu2/3) receptors are of considerable interest owing to their role in modulating glutamate transmission via presynaptic, postsynaptic and glial mechanisms. As part of our ongoing efforts to identify novel ligands for these receptors, we have discovered (1S,2R,3S,4S,5R,6R)-2-amino-3-[(3,4-difluorophenyl)sulfanylmethyl]-4-hydroxy-bicyclo[3.1.0]hexane-2,6-dicarboxylic acid; (LY3020371), a potent and selective orthosteric mGlu2/3 receptor antagonist. In this account, we characterize the effects of LY3020371 in membranes and cells expressing human recombinant mGlu receptor subtypes as well as in native rodent and human brain tissue preparations, providing important translational information for this molecule. In membranes from cells expressing recombinant human mGlu2 and mGlu3 receptor subtypes, LY3020371.HCl competitively displaced binding of the mGlu2/3 agonist ligand [3H]-459477 with high affinity (hmGlu2 Ki = 5.26 nM; hmGlu3 Ki = 2.50 nM). In cells expressing hmGlu2 receptors, LY3020371.HCl potently blocked mGlu2/3 agonist (DCG-IV)-inhibited, forskolin-stimulated cAMP formation (IC50 = 16.2 nM), an effect that was similarly observed in hmGlu3-expressing cells (IC50 = 6.21 nM). Evaluation of LY3020371 in cells expressing the other human mGlu receptor subtypes revealed high mGlu2/3 receptor selectivity. In rat native tissue assays, LY3020371 demonstrated effective displacement of [3H]-459477 from frontal cortical membranes (Ki = 33 nM), and functional antagonist activity in cortical synaptosomes measuring both the reversal of agonist-suppressed second messenger production (IC50 = 29 nM) and agonist-inhibited, K+-evoked glutamate release (IC50 = 86 nM). Antagonism was fully recapitulated in both primary cultured cortical neurons where LY3020371 blocked agonist-suppressed spontaneous Ca2+ oscillations (IC50 = 34 nM) and in an intact hippocampal slice preparation (IC50 = 46 nM). Functional antagonist activity was similarly demonstrated in synaptosomes prepared from epileptic human cortical or hippocampal tissues, suggesting a translation of the mGlu2/3 antagonist pharmacology from rat to human. Intravenous dosing of LY3020371 in rats led to cerebrospinal fluid drug levels that are expected to effectively block mGlu2/3 receptors in vivo. Taken together, these results establish LY3020371 as an important new pharmacological tool for studying mGlu2/3 receptors in vitro and in vivo. This article is part of the Special Issue entitled 'Metabotropic Glutamate Receptors, 5 years on'.
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Affiliation(s)
- Jeffrey M Witkin
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN 46285, USA
| | - Paul L Ornstein
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN 46285, USA
| | - Charles H Mitch
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN 46285, USA
| | - Renhua Li
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN 46285, USA
| | - Stephon C Smith
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN 46285, USA
| | - Beverly A Heinz
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN 46285, USA
| | - Xu-Shan Wang
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN 46285, USA
| | - Chuanxi Xiang
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN 46285, USA
| | - Joan H Carter
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN 46285, USA
| | - Wesley H Anderson
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN 46285, USA
| | - Xia Li
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN 46285, USA
| | | | | | | | | | | | - John Catlow
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN 46285, USA
| | - Steven Swanson
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN 46285, USA
| | - James A Monn
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN 46285, USA.
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10
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Kiritoshi T, Neugebauer V. Group II mGluRs modulate baseline and arthritis pain-related synaptic transmission in the rat medial prefrontal cortex. Neuropharmacology 2015; 95:388-94. [PMID: 25912637 DOI: 10.1016/j.neuropharm.2015.04.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Revised: 03/26/2015] [Accepted: 04/02/2015] [Indexed: 01/02/2023]
Abstract
The medial prefrontal cortex (mPFC) serves executive control functions that are impaired in neuropsychiatric disorders and pain. Therefore, restoring normal synaptic transmission and output is a desirable goal. Group II metabotropic glutamate receptors mGluR2 and mGluR3 are highly expressed in the mPFC, modulate synaptic transmission, and have been targeted for neuropsychiatric disorders. Their pain-related modulatory effects in the mPFC remain to be determined. Here we evaluated their ability to restore pyramidal output in an arthritis pain model. Whole-cell patch-clamp recordings of layer V mPFC pyramidal cells show that a selective group II mGluR agonist (LY379268) decreased synaptically evoked spiking in brain slices from normal and arthritic rats. Effects were concentration-dependent and reversed by a selective antagonist (LY341495). LY379268 decreased monosynaptic excitatory postsynaptic currents (EPSCs) and glutamate-driven inhibitory postsynaptic currents (IPSCs) in the pain model. Effects on EPSCs preceded those on IPSCs and could explain the overall inhibitory effect on pyramidal output. LY379268 decreased frequency, but not amplitude, of miniature EPSCs without affecting miniature IPSCs. LY341495 alone increased synaptically evoked spiking under normal conditions and in the pain model. In conclusion, group II mGluRs act on glutamatergic synapses to inhibit direct excitatory transmission and feedforward inhibition onto pyramidal cells. Their net effect is decreased pyramidal cell output. Facilitatory effects of a group II antagonist suggest the system may be tonically active to control pyramidal output. Failure to release the inhibitory tone and enhance mPFC output could be a mechanism for the development or persistence of a disease state such as pain.
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Affiliation(s)
- Takaki Kiritoshi
- Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center (TTUHSC), School of Medicine, 3601 4th Street, Mail Stop 6592, Lubbock, TX 79430-6592, USA
| | - Volker Neugebauer
- Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center (TTUHSC), School of Medicine, 3601 4th Street, Mail Stop 6592, Lubbock, TX 79430-6592, USA; Center of Excellence for Translational Neuroscience and Therapeutics, Texas Tech University Health Sciences Center (TTUHSC), School of Medicine, 3601 4th Street, Mail Stop 6592, Lubbock, TX 79430-6592, USA.
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11
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Kolber BJ. mGluRs Head to Toe in Pain. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2015; 131:281-324. [DOI: 10.1016/bs.pmbts.2014.12.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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12
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Zammataro M, Sortino MA, Parenti C, Gereau RW, Chiechio S. HDAC and HAT inhibitors differently affect analgesia mediated by group II metabotropic glutamate receptors. Mol Pain 2014; 10:68. [PMID: 25406541 PMCID: PMC4247606 DOI: 10.1186/1744-8069-10-68] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2014] [Accepted: 11/04/2014] [Indexed: 12/24/2022] Open
Abstract
Background Histone deacetylases (HDACs) and histone acetyltransferases (HATs) are key players in epigenetic regulation of gene expression. Analgesic activity by HDAC inhibitors has been reported in different pain models including inflammatory and neuropathic pain. These drugs interfere with gene expression through different mechanisms including chromatin remodeling and/or activation of transcription factors. Among other targets, HDAC inhibitors regulate metabotropic glutamate receptors type 2 (mGlu2) expression in central and peripheral central nervous system. However whether inhibition of HAT activity also regulates mGlu2 expression has not been reported. Findings Here we report that curcumin (CUR), a naturally occurring compound endowed with p300/CREB-binding protein HAT inhibitory activity, is able to induce a drastic down-regulation of the mGlu2 receptor in the mouse spinal cord after systemic administration together with a marked hypoacetylation of histones H3 and H4 in dorsal root ganglia (DRG). Furthermore, the analgesic activity of the mGlu2/3 agonist, LY379268 is lost after a 3-day treatment with CUR. Conversely the analgesic activity of LY379268 is potentiated in mice pretreated for 5 consecutive days with the HDAC inhibitor, Suberoylanilide Hydroxamic Acid (SAHA), known to induce mGlu2-upregulation. Conclusions Our results demonstrate that systemically injected CUR is able to inhibit H3 and H4 acetylation in the DRG and to down-regulate mGlu2 receptors in the spinal cord. We also demonstrate that long term modification of the mGlu2 expression affects the analgesic properties of the orthosteric mGlu2/3 agonist, LY379268. These data open up the possibility that epigenetic modulators might be given in combination with “traditional” drugs in a context of a multi target approach for a better analgesic efficacy.
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Affiliation(s)
| | | | | | | | - Santina Chiechio
- Department of Drug Sciences, Section of Pharmacology and Toxicology, University of Catania, 95125 Catania, Italy.
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13
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Pharmacology of metabotropic glutamate receptor allosteric modulators: structural basis and therapeutic potential for CNS disorders. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2013; 115:61-121. [PMID: 23415092 DOI: 10.1016/b978-0-12-394587-7.00002-6] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The metabotropic glutamate receptors (mGlus) mediate a neuromodulatory role throughout the brain for the major excitatory neurotransmitter, glutamate. Seven of the eight mGlu subtypes are expressed within the CNS and are attractive targets for a variety of psychiatric and neurological disorders including anxiety, depression, schizophrenia, Parkinson's disease, and Fragile X syndrome. Allosteric modulation of these class C 7-transmembrane spanning receptors represents a novel approach to facilitate development of mGlu subtype-selective probes and therapeutics. Allosteric modulators that interact with sites topographically distinct from the endogenous ligand-binding site offer a number of advantages over their competitive counterparts. In particular for CNS therapeutics, allosteric modulators have the potential to maintain the spatial and temporal aspects of endogenous neurotransmission. The past 15 years have seen the discovery of numerous subtype-selective allosteric modulators for the majority of the mGlu family members, including positive, negative, and neutral allosteric modulators, with a number of mGlu allosteric modulators now in clinical trials.
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14
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Julio-Pieper M, O'Connor RM, Dinan TG, Cryan JF. Regulation of the brain-gut axis by group III metabotropic glutamate receptors. Eur J Pharmacol 2012; 698:19-30. [PMID: 23123053 DOI: 10.1016/j.ejphar.2012.10.027] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2012] [Revised: 10/11/2012] [Accepted: 10/22/2012] [Indexed: 01/14/2023]
Abstract
L-glutamate is produced by a great variety of peripheral tissues in both health and disease. Like other components of the glutamatergic system, metabotropic glutamate (mGlu) receptors also have a widespread distribution outside the central nervous system (CNS). In particular, group III mGlu receptors have been recently found in human stomach and colon revealing an extraordinary potential for these receptors in the treatment of peripheral disorders, including gastrointestinal dysfunction. The significance of these findings is that pharmacological tools originally designed for mGlu receptors in the CNS may also be directed towards new disease targets in the periphery. Targeting mGlu receptors can also be beneficial in the treatment of disorders involving central components together with gastrointestinal dysfunction, such as irritable bowel syndrome, which can be co-morbid with anxiety and depression. Conversely, the development of more specific therapeutic approaches for mGlu ligands both centrally as in the gut will depend on the elucidation of tissue-specific elements in mGlu receptor signalling.
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Affiliation(s)
- Marcela Julio-Pieper
- Instituto de Química, Facultad de Ciencias, Pontificia Universidad Católica de Valparaíso, Av Universidad 330, Curauma, Valparaíso, Chile.
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15
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Hovelsø N, Sotty F, Montezinho LP, Pinheiro PS, Herrik KF, Mørk A. Therapeutic potential of metabotropic glutamate receptor modulators. Curr Neuropharmacol 2012; 10:12-48. [PMID: 22942876 PMCID: PMC3286844 DOI: 10.2174/157015912799362805] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2010] [Revised: 01/10/2011] [Accepted: 03/04/2011] [Indexed: 12/21/2022] Open
Abstract
Glutamate is the main excitatory neurotransmitter in the central nervous system (CNS) and is a major player in complex brain functions. Glutamatergic transmission is primarily mediated by ionotropic glutamate receptors, which include NMDA, AMPA and kainate receptors. However, glutamate exerts modulatory actions through a family of metabotropic G-protein-coupled glutamate receptors (mGluRs). Dysfunctions of glutamatergic neurotransmission have been implicated in the etiology of several diseases. Therefore, pharmacological modulation of ionotropic glutamate receptors has been widely investigated as a potential therapeutic strategy for the treatment of several disorders associated with glutamatergic dysfunction. However, blockade of ionotropic glutamate receptors might be accompanied by severe side effects due to their vital role in many important physiological functions. A different strategy aimed at pharmacologically interfering with mGluR function has recently gained interest. Many subtype selective agonists and antagonists have been identified and widely used in preclinical studies as an attempt to elucidate the role of specific mGluRs subtypes in glutamatergic transmission. These studies have allowed linkage between specific subtypes and various physiological functions and more importantly to pathological states. This article reviews the currently available knowledge regarding the therapeutic potential of targeting mGluRs in the treatment of several CNS disorders, including schizophrenia, addiction, major depressive disorder and anxiety, Fragile X Syndrome, Parkinson’s disease, Alzheimer’s disease and pain.
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Affiliation(s)
- N Hovelsø
- Department of Neurophysiology, H. Lundbeck A/S, Ottiliavej 9, 2500 Copenhagen-Valby, Denmark
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16
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Montana MC, Gereau RW. Metabotropic glutamate receptors as targets for analgesia: antagonism, activation, and allosteric modulation. Curr Pharm Biotechnol 2012; 12:1681-8. [PMID: 21466446 DOI: 10.2174/138920111798357438] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2010] [Accepted: 08/20/2010] [Indexed: 12/20/2022]
Abstract
The metabotropic glutamate receptors (mGluRs) are expressed pre- and post-synaptically throughout the nervous system where they serve as modulators of synaptic transmission and neuronal excitability. Activation of mGluRs can be pro- or anti-nociceptive, depending on their anatomic location and the signaling cascades to which they couple. Antagonists of Group I mGluRs and agonists of Group II and III mGluRs have shown therapeutic promise in animal pain models. This article reviews the potential therapeutic utility of several agents that act predominantly via mGluRs, specifically focusing on their analgesic efficacy and discussing possible off-target effects. Glutamate, the primary excitatory neurotransmitter in the vertebrate nervous system, mediates its effects via activation of two main classes of receptors: ligand-gated ion channels known as ionotropic receptors and G-protein coupled metabotropic receptors. Antagonists of ionotropic glutamate receptors, such as ketamine, have robust analgesic properties; however, their analgesic utility is limited to monitored clinical settings due to the potential for psychomimetic effects.
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Affiliation(s)
- Michael C Montana
- Washington University Pain Center, Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110, USA
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17
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Liu XH, Han M, Zhu JX, Sun N, Tang JS, Huo FQ, Li J, Xu FY, Du JQ. Metabotropic glutamate subtype 7 and 8 receptors oppositely modulate cardiac nociception in the rat nucleus tractus solitarius. Neuroscience 2012; 220:322-9. [PMID: 22617702 DOI: 10.1016/j.neuroscience.2012.05.024] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2012] [Revised: 04/27/2012] [Accepted: 05/09/2012] [Indexed: 01/08/2023]
Abstract
Recent study from our laboratory has indicated that microinjection of glutamate into the nucleus tractus solitarius (NTS) facilitates the cardiac-somatic reflex induced by pericardial capsaicin. Further, N-methyl-d-aspartate (NMDA) receptors and metabotropic glutamate receptors (mGluRs) mediate this function. However, the roles of the individual receptor subtypes or subunits in modulating cardiac nociception are unknown. Among the three groups of mGluRs, group III mGluRs are the primary mGluR subtype expressed in visceral afferent neurons in the NTS. The present study examined the roles of group III mGluRs and their subtype 7 and 8 receptors (mGluR7 and mGluR8) in modulating the cardiac-somatic reflex induced by pericardial capsaicin, which was monitored by recording electromyogram (EMG) activity from the spinotrapezius muscle in anesthetized rats. Intra-NTS microinjection of a group III mGluR agonist, l-(+)-2-Amino-4-phosphonobutyric acid (l-AP4, at 1, 10, and 20 nmol) or a selective mGluR7 agonist, N,N'-diphenylmethyl-1,2-ethanediamine dihydrochloride (AMN082, at 1, 2, and 4 nmol) both decreased the EMG response in a dose-dependent manner. This decrease was inhibited by the group III mGluR antagonist (RS)-α-Methylserine-O-phosphate (MSOP, at 20 nmol). In contrast, intra-NTS microinjection of a selective mGluR8 agonist, (S)-3, 4-dicarboxyphenylglycine (DCPG, at 6 and 8 nmol), significantly increased the EMG response above control levels. This effect was eliminated by intra-NTS MSOP and by vagal deafferentation. These data suggest that group III mGluRs and mGluR7 in the NTS display an inhibitory effect, while mGluR8 displays a facilitatory effect in modulating cardiac nociception, and this facilitatory effect is dependent on vagal afferents.
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Affiliation(s)
- X H Liu
- Department of Physiology and Pathophysiology, Xi'an Jiaotong University College of Medicine, Yanta Road W. 76#, Xi'an, Shaanxi 710061, China
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18
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Govea RM, Zhou S, Carlton SM. Group III metabotropic glutamate receptors and transient receptor potential vanilloid 1 co-localize and interact on nociceptors. Neuroscience 2012; 217:130-9. [PMID: 22609935 DOI: 10.1016/j.neuroscience.2012.05.014] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2012] [Revised: 05/03/2012] [Accepted: 05/07/2012] [Indexed: 11/26/2022]
Abstract
Several lines of evidence indicate group III metabotropic glutamate receptors (mGluRs) have systemic anti-hyperalgesic effects. We hypothesized this could occur through modulation of transient receptor potential vanilloid 1 (TRPV1) receptors on nociceptors. To address this question we performed anatomical studies to determine if group III mGluRs were expressed on cutaneous axons and if they co-localized with TRPV1. Immunostaining at the electron microscopic level demonstrated that 22% of unmyelinated axons labeled for mGluR8. Immunostaining at the light microscopic level in lumbar dorsal root ganglia (DRG) demonstrated that 80% and 28% of neurons labeled for mGluR8 or TRPV1, respectively. Of those neurons labeled for mGluR8, 25% labeled for TRPV1; of those labeled for TRPV1, 71% labeled for mGluR8. In behavior studies intraplantar injection of the group III mGluR agonist, L-(+)-2-amino-4-phosphonobutyric acid (L-AP-4: 0.1, 1.0, and 10.0 μM) had no effect on paw withdrawal latency (PWL) to heat in naïve rats but administration of 10 μM L-AP-4 prior to 0.05% capsaicin (CAP), significantly attenuated CAP-induced lifting/licking and reduced flinching behavior. The L-AP-4 effect was specific since administration of a group III antagonist α-methyl-3-methyl-4-phosphonophenylglycine (UBP1112) (100μM) blocked the L-AP-4 effect on CAP, resulting in behaviors similar to CAP alone. Intraplantar injection of UBP1112 alone did not result in nociceptive behaviors, indicating group III mGluRs are not tonically active. Finally, the anti-hyperalgesic effect of group III in this paradigm was local and not systemic since intraplantar administration of L-AP-4 in one hind paw did not attenuate nociceptive behaviors following CAP injection in the contralateral hind paw. Adenyl cyclase/cyclic AMP/PKA may be the second messenger pathway linking these two receptor families because intraplantar injection of forskolin (FSK, 10 μM) reduced PWL to heat and L-AP-4 reversed this FSK effect. Taken together, these results suggest group III mGluRs can negatively modulate TRPV1 through inhibition of adenyl cyclase and downstream intracellular activity, blocking TRPV1-induced activation of nociceptors.
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Affiliation(s)
- R M Govea
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, TX 77555-1069, USA
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19
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Dmitrieva N, Rodríguez-Malaver AJ, Pérez J, Hernández L. Differential release of neurotransmitters from superficial and deep layers of the dorsal horn in response to acute noxious stimulation and inflammation of the rat paw. Eur J Pain 2012; 8:245-52. [PMID: 15109975 DOI: 10.1016/j.ejpain.2003.09.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2003] [Accepted: 09/01/2003] [Indexed: 11/29/2022]
Abstract
Experimental evidence suggests that release of neurotransmitters in response to acute noxious stimulation and inflammation can differ in superficial and deeper dorsal horn (DH) laminae. Using two different microdialysis probes, we studied changes in levels of glutamate, aspartate, arginine and GABA in dialysates collected from the surface of the spinal cord and within the DH induced by pinching the paw or paw inflammation. In penthotal anaesthetized rats, a flexible microdialysis probe was placed on the dorsal surface of the L4-L5 or L6-S2 spinal segments. In other rats, a rigid microdialysis probe was implanted within the DH of the same segments. Samples were collected every minute before, during and after pinching the hind paw (acute pain), and every half an hour after injecting either carrageenan or saline into the same paw (inflammation-induced pain). Amino acids were measured by capillary zone electrophoresis with laser-induced fluorescence detection (CZE-LIFD). Pinching the paw induced a significant but short lasting increase in extracellular glutamate and aspartate in dialysates from the surface of the DH. Carrageenan, but not saline, injected into the paw significantly increased concentrations of glutamate, aspartate and arginine both on the surface and within the DH of L4-L5 and also within the DH of the L6-S2 segments. The GABA level was significantly increased following carrageenan only within the DH. The maximum increase on the surface was detected 60-120 min after the onset of inflammation whereas the response within the DH reached a maximum between 150 and 180 min after carrageenan. These results indicate that unlike acute mechanical noxious stimulation which enhances amino acid neurotransmitters in surface dialysate, inflammation induced neurotransmitter release in all layers of the DH suggesting sensitization of the DH.
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Affiliation(s)
- Natalia Dmitrieva
- Program in Neuroscience, Florida State University, Tallahassee, FL 32306-1270, USA.
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Liu CC, Shi CQ, Franaszczuk PJ, Crone NE, Schretlen D, Ohara S, Lenz FA. Painful laser stimuli induce directed functional interactions within and between the human amygdala and hippocampus. Neuroscience 2011; 178:208-17. [PMID: 21256929 DOI: 10.1016/j.neuroscience.2011.01.029] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2010] [Revised: 01/12/2011] [Accepted: 01/13/2011] [Indexed: 01/15/2023]
Abstract
The pathways by which painful stimuli are signaled within the human medial temporal lobe are unknown. Rodent studies have shown that nociceptive inputs are transmitted from the brainstem or thalamus through one of two pathways to the central nucleus of the amygdala. The indirect pathway projects from the basal and lateral nuclei of the amygdala to the central nucleus, while the direct pathway projects directly to the central nucleus. We now test the hypothesis that the human ventral amygdala (putative basal and lateral nuclei) exerts a causal influence upon the dorsal amygdala (putative central nucleus), during the application of a painful laser stimulus. Local field potentials (LFPs) were recorded from depth electrode contacts implanted in the medial temporal lobe for the treatment of epilepsy, and causal influences were analyzed by Granger causality (GRC). This analysis indicates that the dorsal amygdala exerts a pre-stimulus causal influence upon the hippocampus, consistent with an attention-related response to the painful laser. Within the amygdala, the analysis indicates that the ventral contacts exert a causal influence upon dorsal contacts, consistent with the human (putative) indirect pathway. Potentials evoked by the laser (LEPs) were not recorded in the ventral nuclei, but were recorded at dorsal amygdala contacts which were not preferentially those receiving causal influences from the ventral contacts. Therefore, it seems likely that the putative indirect pathway is associated with causal influences from the ventral to the dorsal amygdala, and is distinct from the human (putative) indirect pathway which mediates LEPs in the dorsal amygdala.
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Affiliation(s)
- C C Liu
- Department of Neurosurgery, Johns Hopkins University, 600 North Wolfe Street, Baltimore, MD 2105, USA
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Spinal cord mechanisms mediating behavioral hyperalgesia induced by neurokinin-1 tachykinin receptor activation in the rostral ventromedial medulla. Neuroscience 2010; 171:1341-56. [PMID: 20888891 DOI: 10.1016/j.neuroscience.2010.09.040] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2010] [Revised: 08/24/2010] [Accepted: 09/22/2010] [Indexed: 11/23/2022]
Abstract
Hyperalgesia in animal injury models is linked to activation of descending raphespinal modulatory circuits originating in the rostral ventromedial medulla (RVM). A neurokinin-1 (NK-1) receptor antagonist microinjected into the RVM before or after inflammation produced by complete Freund's adjuvant (CFA) resulted in an attenuation of thermal hyperalgesia. A transient (acute) or a continuous infusion of Substance P (SP) microinjected into the RVM of non-inflamed animals led to similar pain hypersensitivity. Intrathecal pretreatment or post-treatment of a 5-HT3 receptor antagonist (Y-25130 or ondansetron) blocked the SP-induced hyperalgesia. The SP-induced hyperalgesia was both GABA(A) and NMDA receptor-dependent after pre- and post-treatment with selective antagonists at the spinal level. A microinjection of SP into the RVM also led to increased NMDA NR1 receptor subunit phosphorylation in spinal cord tissue. The GABA(A) receptor-mediated hyperalgesia involved a shift in the anionic gradient in dorsal horn nociceptive neurons and an increase in phosphorylated NKCC1 protein (isoform of the Na-K-Cl cotransporter). Following a low dose of SP infused into the RVM, intrathecal muscimol (GABA(A) agonist) increased SP-induced thermal hyperalgesia, phosphorylated NKCC1 protein expression, and NMDA NR1 subunit phosphorylation in the spinal cord. The thermal hyperalgesia was blocked by intrathecal gabazine, the GABA(A) receptor antagonist, and MK-801, the NMDA receptor channel blocker. These findings indicate that NK-1 receptors in the RVM are involved in SP-induced thermal hyperalgesia, this hyperalgesia is 5-HT3-receptor dependent at the spinal level, and involves the functional interaction of spinal GABA(A) and NMDA receptors.
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Palazzos E, de Novellis V, Marabese I, Rossi F, Maione S. Metabotropic glutamate and cannabinoid receptor crosstalk in periaqueductal grey pain processing. Curr Neuropharmacol 2010; 4:225-31. [PMID: 18615148 DOI: 10.2174/157015906778019545] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2006] [Revised: 06/09/2006] [Accepted: 06/29/2006] [Indexed: 11/22/2022] Open
Abstract
Metabotropic glutamate (mGlu) and cannabinoid receptors are G-protein coupled receptors which have shown synaptic co-operation through small lipid messengers in the central nervous system (CNS). A functional interaction between these two receptor families could have a relevant potential in the treatment of CNS disorders, including chronic pain. Indeed, both mGlu and cannabinoid receptors play a crucial role in the neurobiology of pain and their simultaneous manipulation could lead to novel strategies in pain management. In particular, as both mGlu and cannabinoid receptors have been found in the periaqueductal gray (PAG), a crucial station in the pain modulatory system, these receptors could be a substrate for producing analgesia at this level. In this review we aim to briefly illustrate the role of mGlu and can-nabinoid receptors in controlling nociceptive processes, some points of convergence, and their functional interaction in pain processing. Further insights into this functional linkage between the mGlu and cannabinoid receptors could pave the way to a new strategy for pain relief, such as a drug cocktail acting on cannabinoid/metabotropic glutamate receptors.
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Affiliation(s)
- E Palazzos
- Department of Experimental Medicine- Section of Pharmacology "L. Donatelli", Faculty of Medicine and Surgery, Second University of Naples, Via Costantinopoli 16, 80138 Naples, Italy.
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Chen HS, Qu F, He X, Kang SM, Liao D, Lu SJ. Differential Roles of Peripheral Metabotropic Glutamate Receptors in Bee Venom-Induced Nociception and Inflammation in Conscious Rats. THE JOURNAL OF PAIN 2010; 11:321-9. [DOI: 10.1016/j.jpain.2009.07.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2008] [Revised: 06/03/2009] [Accepted: 07/30/2009] [Indexed: 11/27/2022]
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Chiechio S, Copani A, Zammataro M, Battaglia G, Gereau RW, Nicoletti F. Transcriptional regulation of type-2 metabotropic glutamate receptors: an epigenetic path to novel treatments for chronic pain. Trends Pharmacol Sci 2010; 31:153-60. [PMID: 20064669 DOI: 10.1016/j.tips.2009.12.003] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2009] [Revised: 12/10/2009] [Accepted: 12/11/2009] [Indexed: 11/24/2022]
Abstract
Activation of metabotropic glutamate 2 (mGlu2) receptors inhibits pain transmission at the synapses between primary afferent fibers and neurons in the dorsal horn of the spinal cord. In addition, mGlu2 receptors are found in peripheral nociceptors, and in pain-regulatory centers of the brain stem and forebrain. mGlu2 receptor agonists produce analgesia in models of inflammatory and neuropathic pain, but their use is limited by the development of tolerance. A new therapeutic strategy could be based on the transcriptional regulation of mGlu2 receptors via the acetylation-promoted activation of the p65/RelA transcription factor. "Epigenetic" drugs that increase mGlu2 receptor expression, including l-acetylcarnitine and inhibitors of histone deacetylases, have a different analgesic profile with no tolerance to the therapeutic effect after repeated dosing.
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Affiliation(s)
- Santina Chiechio
- Department of Pharmaceutical Sciences, University of Catania, Catania, Italy
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Zhou F, Hongmin B, Xiang Z, Enyu L. Changes of mGluR4 and the effects of its specific agonist L-AP4 in a rodent model of diffuse brain injury. J Clin Neurosci 2009; 10:684-8. [PMID: 14592619 DOI: 10.1016/j.jocn.2003.04.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
OBJECTIVE Excessive release of glutamate from nerve terminals following diffuse brain injury (DBI) is thought to contribute to neuronal calcium overload leading to calcium-mediated cell damage. Metabotropic glutamate receptor subtype 4 (mGluR4) is regarded as one of the neuroprotective receptors in mammalian brains. Therefore, the mGluR4 specific agonists might exert neuroprotective effects after DBI. The focus of this study is to examine the changes of expression of mGluR4 after DBI and the role of its specific agonist L-AP4 in vivo. METHODS One hundred and sixty-one male SD rats were randomized into two groups. Group A included normal control, sham-operated control and DBI group. DBI was produced by Marmarou's diffuse head injury model. The mRNA expression of mGluR4 was detected by hybridization in situ. Group B included DBI alone, DBI treated with normal saline and DBI treated with L-AP4. All DBI rats were trained in a series of performance tests, following which they were subjected to DBI. At 1 and 12 h, animals were injected intracerebroventricularly with L-AP4 (100 mM, 10 microl) or normal saline, respectively. The rats were tested for motor and cognitive performance at 1, 3, 7, 14 days post-injury and the damaged neurons were detected. RESULTS There was no significant difference between the normal control group and sham-operated group in the expression of mGluR4 (P>0.05). The animals exposed to DBI showed a significant increased expression of mRNA of mGluR4 compared with that of the sham-operated animals 1 h after injuries (P<0.05). At 6 h, the evolution of neuronal expression of mGluR4 in the trauma alone group was relatively static. Compared with saline-treated control animals, rats treated with L-AP4 showed decreased number of damaged neurons and a better motor and cognitive performance. CONCLUSIONS The increased expression of mGluR4 is an important process in the pathophysiological of DBI and its specific agonist L-AP4 can provide a remarkable neuroprotection against DBI not only at the histopathological level but also in the motor and cognitive performance.
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Affiliation(s)
- Fei Zhou
- Department of Neurosurgery, Xijing Hospital, Fourth Military Medical University, Xi'an, PR China.
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Central sensitization: a generator of pain hypersensitivity by central neural plasticity. THE JOURNAL OF PAIN 2009; 10:895-926. [PMID: 19712899 DOI: 10.1016/j.jpain.2009.06.012] [Citation(s) in RCA: 2238] [Impact Index Per Article: 149.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2009] [Revised: 06/08/2009] [Accepted: 06/08/2009] [Indexed: 02/08/2023]
Abstract
UNLABELLED Central sensitization represents an enhancement in the function of neurons and circuits in nociceptive pathways caused by increases in membrane excitability and synaptic efficacy as well as to reduced inhibition and is a manifestation of the remarkable plasticity of the somatosensory nervous system in response to activity, inflammation, and neural injury. The net effect of central sensitization is to recruit previously subthreshold synaptic inputs to nociceptive neurons, generating an increased or augmented action potential output: a state of facilitation, potentiation, augmentation, or amplification. Central sensitization is responsible for many of the temporal, spatial, and threshold changes in pain sensibility in acute and chronic clinical pain settings and exemplifies the fundamental contribution of the central nervous system to the generation of pain hypersensitivity. Because central sensitization results from changes in the properties of neurons in the central nervous system, the pain is no longer coupled, as acute nociceptive pain is, to the presence, intensity, or duration of noxious peripheral stimuli. Instead, central sensitization produces pain hypersensitivity by changing the sensory response elicited by normal inputs, including those that usually evoke innocuous sensations. PERSPECTIVE In this article, we review the major triggers that initiate and maintain central sensitization in healthy individuals in response to nociceptor input and in patients with inflammatory and neuropathic pain, emphasizing the fundamental contribution and multiple mechanisms of synaptic plasticity caused by changes in the density, nature, and properties of ionotropic and metabotropic glutamate receptors.
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Liu CC, Ohara S, Franaszczuk P, Zagzoog N, Gallagher M, Lenz FA. Painful stimuli evoke potentials recorded from the medial temporal lobe in humans. Neuroscience 2009; 165:1402-11. [PMID: 19925853 DOI: 10.1016/j.neuroscience.2009.11.026] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2009] [Revised: 11/09/2009] [Accepted: 11/10/2009] [Indexed: 10/20/2022]
Abstract
The role of human medial temporal structures in fear conditioning has led to the suggestion that neurons in these structures might respond to painful stimuli. We have now tested the hypothesis that recordings from these structures will demonstrate potentials related to the selective activation of cutaneous nociceptors by a painful laser stimulus (laser evoked potential, LEP) (Kenton B, Coger R, Crue B, Pinsky J, Friedman Y, Carmon A (1980) Neurosci Lett 17:301-306). Recordings were carried out through electrodes implanted bilaterally in these structures for the investigation of intractable epilepsy. Reproducible LEPs were commonly recorded both bilaterally and unilaterally, while LEPs were recorded at contacts on the left (9/14, P=0.257) as commonly as on the right (5/14), independent of the hand stimulated. Along electrodes traversing the amygdala the majority of LEPs were recorded from dorsal contacts near the central nucleus of the amygdala and the nucleus basalis. Stimulus evoked changes in theta activity were observed at contacts on the right at which isolated early negative LEPs (N2*) responses could be recorded. Contacts at which LEPs could be recorded were as commonly located in medial temporal structures with evidence of seizure activity as on those without. These results demonstrate the presence of pain-related inputs to the medial temporal lobe where they may be involved in associative learning to produce anxiety and disability related to painful stimuli.
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Affiliation(s)
- C C Liu
- Department of Neurosurgery, Meyer 5-181, Johns Hopkins University, Baltimore, MD 21287-7713, USA
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28
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Nakamichi N, Takarada T, Yoneda Y. Neurogenesis mediated by gamma-aminobutyric acid and glutamate signaling. J Pharmacol Sci 2009; 110:133-49. [PMID: 19483378 DOI: 10.1254/jphs.08r03cr] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Abstract
In this review, we will summarize our ongoing studies on the functionality of both gamma-aminobutyric acid (GABA) and glutamate receptors expressed by undifferentiated neural progenitor cells isolated from embryonic rodent brains. Cells were cultured with growth factors for the formation of round spheres by clustered cells under floating conditions, whereas a reverse transcription polymerase chain reaction analysis revealed expression of mRNA for particular subtypes of different ionotropic and metabotropic GABA and glutamate receptors in undifferentiated progenitors and neurospheres. Moreover, sustained exposure to either GABAergic or glutamatergic agonists not only modulated the size of neurospheres formed, but also affected spontaneous and induced differentiation of neural progenitor cells into particular progeny cell lineages such as neurons and astroglia. Both GABA and glutamate could play a pivotal role in the mechanisms underlying proliferation for self-replication along with the determination of subsequent differentiation fate toward particular progeny lineages through activation of their receptor subtypes functionally expressed by undifferentiated neural progenitor cells. Accordingly, neurogenesis seems to be also under control by GABAergic and glutamatergic signaling in developing brains as seen with neurotransmission in adult brains.
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Affiliation(s)
- Noritaka Nakamichi
- Laboratory of Molecular Pharmacology, Division of Pharmaceutical Sciences, Kanazawa University Graduate School of Natural Science and Technology, Ishikawa, Japan
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29
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Hallock RM, Martyniuk CJ, Finger TE. Group III metabotropic glutamate receptors (mGluRs) modulate transmission of gustatory inputs in the brain stem. J Neurophysiol 2009; 102:192-202. [PMID: 19369363 DOI: 10.1152/jn.00135.2009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Glutamate is the principal neurotransmitter at the primary sensory afferent synapse in the medulla for the taste system. At this synapse, glutamate activates N-methyl-D-aspartate (NMDA) and non-NMDA (alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid [AMPA] and kainate) ionotropic receptors to effect a response in the second-order neurons. The current experiment is the first to examine the role of metabotropic glutamate receptors (mGluRs) in the transmission of taste information. In an in vitro slice preparation of the primary vagal gustatory nucleus in goldfish, primary gustatory afferent fibers were stimulated electrically, whereas evoked dendritic field potentials were recorded in the sensory layers. Recordings were made before, during, and after bath application of mGluR agonists for various mGluR groups and subtypes. Whereas L-AP4, a group III agonist, reduced the field potential, group I and group II agonists had no effect. Furthermore, the selective mGluR4 agonist ACPT-III and mGluR8 agonist PPG were effective at reducing the field potential, whereas agonists selective for mGluR6 and 7 were not. MAP4, a group III mGluR antagonist, attenuated frequency-dependent depression, indicating that endogenous glutamate binds to presynaptic mGluRs under normal conditions. Furthermore, polymerase chain reaction showed that mRNA for mGluR4 and 8 is expressed in the vagal ganglia, a prerequisite if those receptors are expressed presynaptically in the vagal lobe. Collectively, these experiments indicate that mGluR4 and 8 are presynaptic at the primary gustatory afferent synapse and that their activation inhibits glutamatergic release.
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Affiliation(s)
- Robert M Hallock
- Rocky Mountain Taste and Smell Center, Department of Cell and Developmental Biology, Room L18-11403-G, RC-1, 12801 E. 17th Ave., MS 8108, P.O. Box 6511, Aurora, CO 80045-6511, USA.
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Abstract
Glutamate and gamma-amino butyric acid (GABA) are respectively two major excitatory and inhibitory neurotransmitters of the adult mammalian central nervous system. These neurotransmitters exert their action through two types of receptors: ionotropic and metabotropic receptors. While ionotropic receptors are ligand gated ion channels involved in fast synaptic transmission, metabotropic receptors belong to the superfamily of G-protein coupled receptors (GPCRs) and are responsible for the neuromodulatory effect of glutamate and GABA. Metabotropic glutamate receptors (mGluRs) and metabotropic GABA receptors (GABA-B) are present at different levels of the pain neuraxis where they regulate nociceptive transmission and pain. The present review will focus on the role of these receptors in the modulation of pain perception.
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Carlton SM, Du J, Zhou S. Group II metabotropic glutamate receptor activation on peripheral nociceptors modulates TRPV1 function. Brain Res 2008; 1248:86-95. [PMID: 19026992 DOI: 10.1016/j.brainres.2008.10.066] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2008] [Revised: 10/22/2008] [Accepted: 10/23/2008] [Indexed: 11/25/2022]
Abstract
Transient receptor potential vanilloid 1 (TRPV1) receptors are critical to nociceptive processing. Understanding how these receptors are modulated gives insight to potential therapies for pain. We demonstrate using double labeling immunohistochemistry that Group II metabotropic glutamate receptors (mGluRs) are co-expressed with TRPV1 on rat dorsal root ganglion (DRG) cells. In behavioral studies, intraplantar 0.1 microM APDC, a group II agonist, significantly attenuates capsaicin-induced nociceptive behaviors through a local effect. The APDC-induced inhibition of capsaicin responses is blocked by 1 microM LY341495, a group II antagonist. At the single fiber level, nociceptor responses to capsaicin are significantly decreased following exposure to APDC and this effect is blocked by LY341495. Finally, activation of peripheral group II mGluRs inhibits forskolin-induced thermal hyperalgesia and nociceptor heat sensitization, suggesting group II receptors are negatively coupled to the cAMP/PKA pathway. The data indicate that group II mGluRs and TRPV1 receptors are co-expressed on peripheral nociceptors and activation of mGluRs can inhibit painful sensory transmission following TRPV1 activation. The data are consistent with group II and TRPV1 receptors being linked intracellularly by the cAMP/PKA pathway. Peripheral group II mGluRs are important targets for drug discovery in controlling TRPV1-induced nociception.
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Affiliation(s)
- Susan M Carlton
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch, 301 University Blvd., Galveston, TX 77555-1069, USA.
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Cho CH, Shin HK. Spinal Metabotropic Glutamate Receptors (mGluRs) are Involved in the Melittin-induced Nociception in Rats. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2008; 12:237-43. [PMID: 19967062 DOI: 10.4196/kjpp.2008.12.5.237] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Intraplantar injection of melittin has been known to induce sustained decrease of mechanical threshold and increase of spontaneous flinchings. The present study was undertaken to investigate how the melittin-induced nociceptive responses were modulated by changes of metabotropic glutamate receptor (mGluR) activity. Changes in paw withdrawal threshold (PWT), number of flinchings and paw thickness were measured at a given time point after injection of melittin (10 microg/paw) into the mid-plantar area of rat hindpaw. To observe the effects of mGluRs on the melittin-induced nociceptions, group I mGluR (AIDA, 100 microg and 200 microg), mGluR(1) (LY367385, 50 microg and 100 microg) and mGluR(5) (MPEP, 200 microg and 300 microg) antagonists, group II (APDC, 100 microg and 200 microg) and III (L-SOP, 100 microg and 200 microg) agonists were intrathecally administered 20 min before melittin injection. Intraplantar injection of melittin induced a sustained decrease of mechanical threshold, spontaneous flinchings and edema. The effects of melittin to reduce mechanical threshold and to induce spontaneous flinchings were significantly suppressed following intrathecal pre-administration of group I mGluR, mGluR(1) and mGluR(5) antagonists, group II and III mGluR agonists. Group I mGluR antagonists and group II and III mGluR agonists had no significant effect on melittin-induced edema. These experimental findings indicate that multiple spinal mGluRs are involved in the modulation of melittin-induced nociceptive responses.
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Affiliation(s)
- Chul Hyun Cho
- Department of Orthopedic Surgery, School of Medicine, Keimyung University, Daegu 700-712, Korea
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Du J, Zhou S, Carlton SM. Group II metabotropic glutamate receptor activation attenuates peripheral sensitization in inflammatory states. Neuroscience 2008; 154:754-66. [PMID: 18487022 DOI: 10.1016/j.neuroscience.2008.03.084] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2007] [Revised: 03/21/2008] [Accepted: 03/22/2008] [Indexed: 01/13/2023]
Abstract
Several lines of evidence indicate that Group II metabotropic glutamate receptor (mGluR) activation can depress sensory transmission. We have reported the expression of Group II mGluRs on unmyelinated axons, many of which were presumed to be nociceptors, in the rat digital nerve [Carlton SM, Hargett GL, Coggeshall RE (2001b) Localization of metabotropic glutamate receptors 2/3 on primary afferent axons in the rat. Neuroscience 105:957-969]. The goals of the present study are to further our understanding of Group II modulation of nociceptor processing in the periphery, documenting behavioral changes using inflammatory models and documenting, for the first time, cutaneous single fiber activity following exposure to a Group II agonist (2R,4R)-4-aminopyrrolidine-2,4-dicarboxylate (APDC) and antagonist (2S)-2-amino-2-[(1S,2S)-2-carboxycycloprop-1-yl]-3-(xanth-9-yl) propanoic acid (LY341495, LY). The data indicate that peripheral Group II mGluR activation does not depress nociceptive behaviors or nociceptor fiber responses in the non-sensitized state (i.e. following brief nociceptive mechanical or thermal stimulation) but can depress these responses when nociceptors are sensitized by exposure to formalin or inflammatory soup. Group II mGluR agonist-induced inhibition can be blocked by a selective Group II antagonist. Peripheral Group II mGluR-induced inhibition evoked in these studies occurs through activation of local receptors and not through spinal or supraspinal mechanisms. The data indicate that administration of selective Group II agonists may be potent therapeutic agents for prevention of peripheral sensitization and for treatment of inflammatory pain.
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Affiliation(s)
- J Du
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Marine Biomedical Institute, Galveston, TX 77555-1069, USA
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Imre G. The preclinical properties of a novel group II metabotropic glutamate receptor agonist LY379268. CNS DRUG REVIEWS 2008; 13:444-64. [PMID: 18078428 DOI: 10.1111/j.1527-3458.2007.00024.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Activation of group II metabotropic glutamate (mGlu2/3) receptors reduces excessive glutamate release that is often associated with neurodegenerative and psychiatric disorders. This finding encouraged the search for potent and selective agonists as potential therapeutic agents. The search led to the discovery of LY379268 {(-)-2-oxa-4-aminobicyclo[3.1.0]hexane-4,6-dicarboxylic acid}, which is a highly potent and systemically available mGlu2/3 receptor agonist. LY379268 was effective in several animal models of stroke, epilepsy, drug abuse, schizophrenia, and pain. Suppression of motor activity is the major side effect of LY379268. Upon repeated administration tolerance develops to this side effect, while the therapeutic effects of LY379268 remain. To date, no clinical data with LY379268 are available. This review article summarizes the preclinical pharmacology of LY379268.
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Affiliation(s)
- Gabor Imre
- Department of Behavioral Pharmacology, Gedeon Richter Ltd., Budapest, Hungary.
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Nakamichi N, Yoshida K, Ishioka Y, Makanga JO, Fukui M, Yoneyama M, Kitayama T, Nakamura N, Taniura H, Yoneda Y. Group III metabotropic glutamate receptor activation suppresses self-replication of undifferentiated neocortical progenitor cells. J Neurochem 2008; 105:1996-2012. [PMID: 18266930 DOI: 10.1111/j.1471-4159.2008.05289.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
We evaluated the possible functional expression of metabotropic glutamate receptors (mGluRs) by neural progenitors from embryonic mouse neocortex. Constitutive expression was seen with group I, II, and III mGluRs in undifferentiated cells and neurospheres formed by clustered cells during culture with epidermal growth factor. The group III mGluR agonist, L-2-amino-4-phosphonobutyrate, drastically reduced proliferation activity at 1-100 microM without inducing cell death, with group I and group II mGluR agonists being ineffective, in these neurospheres. Both forskolin and a group III mGluR antagonist significantly increased the proliferation alone, but significantly prevented the suppression by L-2-amino-4-phosphonobutyrate. Activation of group III mGluR significantly decreased mRNA expression of the cell cycle regulator cyclinD1, in addition to inhibiting the transactivation mediated by cAMP of cyclinD1 gene in the pluripotent P19 progenitor cells. Prior activation of group III mGluR led to a significant decrease in the number of cells immunoreactive for a neuronal marker, with an increase in that for an astroglial marker irrespective of differentiation inducers. These results suggest that group III mGluR may be functionally expressed to suppress self-renewal capacity through a mechanism related to cAMP formation with promotion of subsequent differentiation into astroglial lineage in neural progenitors.
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Affiliation(s)
- Noritaka Nakamichi
- Laboratory of Molecular Pharmacology, Division of Pharmaceutical Sciences, Kanazawa University Graduate School of Natural Science and Technology, Kanazawa, Ishikawa, Japan
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Abstract
Peripheral capsaicin treatment induces molecular changes that sensitize the responses of nociceptive neurons in the spinal dorsal horn. The current studies demonstrate that capsaicin also undermines the adaptive plasticity of the spinal cord, rendering the system incapable of learning a simple instrumental task. In these studies, male rats are transected at the second thoracic vertebra and are tested 24 to 48 hours later. During testing, subjects receive shock to one hindleg when it is extended (controllable stimulation). Rats quickly learn to maintain the leg in a flexed position. Rats that have been injected with capsaicin (1% or 3%) in the hindpaw fail to learn, even when tested on the leg contralateral to the injection. This learning deficit lasts at least 24 hours. Interestingly, training with controllable electrical stimulation prior to capsaicin administration protects the spinal cord against the maladaptive effects. Rats pretrained with controllable stimulation do not display a learning deficit or tactile allodynia. Moreover, controllable stimulation, combined with naltrexone, reverses the capsaicin-induced deficit. These data suggest that peripheral inflammation, accompanying spinal cord injuries, might have an adverse effect on recovery.
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Affiliation(s)
- Michelle A Hook
- Department of Psychology, Texas A&M University, College Station 77843-4235, USA.
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Goudet C, Chapuy E, Alloui A, Acher F, Pin JP, Eschalier A. Group III metabotropic glutamate receptors inhibit hyperalgesia in animal models of inflammation and neuropathic pain. Pain 2007; 137:112-124. [PMID: 17900808 DOI: 10.1016/j.pain.2007.08.020] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2006] [Revised: 07/20/2007] [Accepted: 08/20/2007] [Indexed: 11/24/2022]
Abstract
Glutamate plays a key role in modulation of nociceptive processing. This excitatory amino acid exerts its action through two distinct types of receptors, ionotropic and metabotropic glutamate receptors (mGluRs). Eight mGluRs have been identified and divided in three groups based on their sequence similarity, pharmacology and G-protein coupling. While the role of group I and II mGluRs is now well established, little is known about the part played by group III mGluRs in pain. In this work, we studied comparatively the involvement of spinal group III mGluR in modulation of acute, inflammatory and neuropathic pain. While intrathecal injection of ACPT-I, a selective group III mGluR agonist, failed to induce any change in vocalization thresholds of healthy animals submitted to mechanical or thermal stimuli, it dose-dependently inhibited the nociceptive behavior of rats submitted to the formalin test and the mechanical hyperalgesia associated with different animal models of inflammatory (carrageenan-treated and monoarthritic rats) or neuropathic pain (mononeuropathic and vincristine-treated rats). Similar effects were also observed following intrathecal injection of PHCCC, a positive allosteric modulator of mGlu4. Antihyperalgesia induced by ACPT-I was blocked either by LY341495, a nonselective antagonist of mGluR, by MAP4, a selective group III antagonist. This study provide new evidences supporting the role of spinal group III mGluRs in the modulation of pain perception in different pathological pain states of various etiologies but not in normal conditions. It more particularly highlights the specific involvement of mGlu4 in this process and may be a useful therapeutic approach to chronic pain treatment.
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Affiliation(s)
- Cyril Goudet
- Univ Montpellier I& II, CNRS UMR5203, Institut de Génomique Fonctionnelle, 141 Rue de la Cardonille, F-34094 Montpellier Cedex 5, France INSERM, U661, Montpellier, F-34094, France INSERM, UMR766, Pharmacologie Fondamentale et Clinique de la Douleur, Clermont-Ferrand, F-63001, France Univ Clermont 1, Faculté de Médecine, Laboratoire de Pharmacologie Médicale, Clermont-Ferrand, F-63001, France CHU Clermont-Ferrand, Service de Pharmacologie, Clermont-Ferrand, F-63003, France UMR8601-CNRS, Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques, Université Paris V, 45 rue des Saints-Pères, 75270 Paris 06, France
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Pan HL, Wu ZZ, Zhou HY, Chen SR, Zhang HM, Li DP. Modulation of pain transmission by G-protein-coupled receptors. Pharmacol Ther 2007; 117:141-61. [PMID: 17959251 DOI: 10.1016/j.pharmthera.2007.09.003] [Citation(s) in RCA: 137] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2007] [Accepted: 09/07/2007] [Indexed: 01/17/2023]
Abstract
The heterotrimeric G-protein-coupled receptors (GPCR) represent the largest and most diverse family of cell surface receptors and proteins. GPCR are widely distributed in the peripheral and central nervous systems and are one of the most important therapeutic targets in pain medicine. GPCR are present on the plasma membrane of neurons and their terminals along the nociceptive pathways and are closely associated with the modulation of pain transmission. GPCR that can produce analgesia upon activation include opioid, cannabinoid, alpha2-adrenergic, muscarinic acetylcholine, gamma-aminobutyric acidB (GABAB), groups II and III metabotropic glutamate, and somatostatin receptors. Recent studies have led to a better understanding of the role of these GPCR in the regulation of pain transmission. Here, we review the current knowledge about the cellular and molecular mechanisms that underlie the analgesic actions of GPCR agonists, with a focus on their effects on ion channels expressed on nociceptive sensory neurons and on synaptic transmission at the spinal cord level.
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Affiliation(s)
- Hui-Lin Pan
- Department of Anesthesiology and Pain Medicine, The University of Texas M.D. Anderson Cancer Center, Program in Neuroscience, The University of Texas Graduate School of Biomedical Sciences, Houston, TX 77225, United States.
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LaCroix-Fralish ML, Tawfik VL, Spratt KF, DeLeo JA. Sex differences in lumbar spinal cord gene expression following experimental lumbar radiculopathy. J Mol Neurosci 2007; 30:283-95. [PMID: 17401154 DOI: 10.1385/jmn:30:3:283] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/1999] [Revised: 11/30/1999] [Accepted: 11/30/1999] [Indexed: 01/07/2023]
Abstract
Considerable evidence indicates that there are sex-related differences in clinical and experimental pain sensitivity. In the present study, we sought to determine what genes were expressed in the spinal cord in a sexually dimorphic manner. We first analyzed global gene expression in the lumbar spinal cord of uninjured male and female rats using the Affymetrix RAE230A GeneChip platform in order to identify genes that are selectively expressed in male and female rats at a basal level. We subsequently analyzed global gene expression in the lumbar spinal cord of male and female rats at two time points (7 days and 14 d) following a rodent model of lumbar radiculopathy (L5 nerve root ligation) in order to determine what genes were regulated in a sexually dimorphic manner following nerve root injury. We utilized a linear regression analysis method to identify genes that were significantly different from the corresponding sham surgical controls. The expression patterns of several genes of interest were subsequently confirmed using RT-PCR. Our findings demonstrate significant differences in lumbar spinal cord gene expression in both uninjured and injured (L5 nerve root ligation) male and female rats. Further confirmation of a subset of the genes identified Neuregulin 1 and its high affinity receptor, ErbB4, Tachykinin 1, and Metabotropic glutamate receptor 6 as female specific genes upregulated following L5 nerve root injury. These findings provide several target genes for further study that may elucidate the neurochemical mechanisms underlying sex differences in pain sensitivity and lead to improved treatments for chronic pain syndromes.
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Marabese I, Rossi F, Palazzo E, de Novellis V, Starowicz K, Cristino L, Vita D, Gatta L, Guida F, Di Marzo V, Rossi F, Maione S. Periaqueductal gray metabotropic glutamate receptor subtype 7 and 8 mediate opposite effects on amino acid release, rostral ventromedial medulla cell activities, and thermal nociception. J Neurophysiol 2007; 98:43-53. [PMID: 17507496 DOI: 10.1152/jn.00356.2007] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The current study has investigated the involvement of periaqueductal gray (PAG) metabotropic glutamate subtype 7 and 8 receptors (mGluR(7) and mGluR(8)) in modulating rostral ventromedial medulla (RVM) ongoing and tail flick-related on and off cell activities. Our study has also investigated the role of PAG mGluR(7) on thermoceptive threshold and PAG glutamate and GABA release. Intra-ventrolateral PAG (S)-3,4-dicarboxyphenylglycine [(S)-3,4-DCPG (2 and 4 nmol/rat)] or N,N(I)-dibenzhydrylethane-1,2-diamin dihydrochloride (AMN082, (1 and 2 nmol/rat), selective mGluR(8) and mGluR(7) agonists, respectively, caused opposite effects on the ongoing RVM on and off cell activities. Tail flick latency was increased or decreased by (S)-3,4-DCPG or AMN082 (2 nmol/rat), respectively. (S)-3,4-DCPG reduced the pause and delayed the onset of the off cell pause. Conversely, AMN082 increased the pause and shortened the onset of off cell pause. (S)-3,4-DCPG or AMN082 did not change the tail flick-induced onset of on-cell peak firing. The tail flick latency and its related electrophysiological effects induced by (S)-3,4-DCPG or AMN082 were prevented by (RS)-alpha-methylserine-o-phosphate (100 nmol/rat), a group III mGluR antagonist. Intra-ventrolateral PAG perfusion with AMN082 (10 and 25 microM), decreased thermoceptive thresholds and glutamate extracellular levels. A decrease in GABA release was also observed. These results show that stimulation of PAG mGluR(8) or mGluR(7) could either relieve or worsen pain perception. The opposite effects on pain behavior correlate with the opposite roles played by mGluR(7) and mGluR(8) on glutamate and GABA release and the ongoing and tail flick-related activities of the RVM on and off cells.
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Affiliation(s)
- Ida Marabese
- Dept of Experimental Medicine, Sect of Pharmacology L Donatelli, Faculty of Medicine and Surgery, Second University of Naples, Via Constantinopoli, Naples, Italy
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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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Yamamoto T, Saito O, Aoe T, Bartolozzi A, Sarva J, Zhou J, Kozikowski A, Wroblewska B, Bzdega T, Neale JH. Local administration of N-acetylaspartylglutamate (NAAG) peptidase inhibitors is analgesic in peripheral pain in rats. Eur J Neurosci 2007; 25:147-58. [PMID: 17241276 DOI: 10.1111/j.1460-9568.2006.05272.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The peptide neurotransmitter N-acetylaspartylglutamate (NAAG) selectively activates group II metabotropic glutamate receptors (mGluRs). Systemic administration of inhibitors of the enzymes that inactivate NAAG results in decreased pain responses in rat models of inflammatory and neuropathic pain. These effects are blocked by a group II mGluR antagonist. This research tested the hypothesis that some analgesic effects of NAAG peptidase inhibition are mediated by NAAG acting on sensory neurite mGluRs at the site of inflammation. Group II mGluR agonists, SLx-3095-1, NAAG and APDC, or NAAG peptidase inhibitors, ZJ-43 and 2-PMPA, injected into the rat footpad reduced pain responses in carrageenan or formalin models. The analgesic effects of SLx-3095-1, APDC, ZJ-43, 2-PMPA and NAAG were blocked by co-injection of LY341495, a selective group II mGluR antagonist. Injection of group II mGluR agonists, NAAG or the peptidase inhibitors into the contralateral rat footpad had no effect on pain perception in the injected paw. At 10-100 microm ZJ-43 and 2-PMPA demonstrated no consistent agonist activity at mGluR2 or mGluR3. Consistent with the conclusion that peripherally administered NAAG peptidase inhibitors increase the activation of mGluR3 by NAAG that is released from peripheral sensory neurites, we found that the tissue average concentration of NAAG in the unstimulated rat hind paw was about 6 microm. These data extend our understanding of the role of this peptide in sensory neurons and reveal the potential for treatment of inflammatory pain via local application of NAAG peptidase inhibitors at doses that may have little or no central nervous system effects.
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Affiliation(s)
- Tatsuo Yamamoto
- Department of Anaesthesiology, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba-shi, Chiba 260-8670, Japan
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Proudfoot CJ, Garry EM, Cottrell DF, Rosie R, Anderson H, Robertson DC, Fleetwood-Walker SM, Mitchell R. Analgesia mediated by the TRPM8 cold receptor in chronic neuropathic pain. Curr Biol 2006; 16:1591-605. [PMID: 16920620 DOI: 10.1016/j.cub.2006.07.061] [Citation(s) in RCA: 300] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2006] [Revised: 07/11/2006] [Accepted: 07/21/2006] [Indexed: 01/27/2023]
Abstract
BACKGROUND Chronic established pain, especially that following nerve injury, is difficult to treat and represents a largely unmet therapeutic need. New insights are urgently required, and we reasoned that endogenous processes such as cooling-induced analgesia may point the way to novel strategies for intervention. Molecular receptors for cooling have been identified in sensory nerves, and we demonstrate here how activation of one of these, TRPM8, produces profound, mechanistically novel analgesia in chronic pain states. RESULTS We show that activation of TRPM8 in a subpopulation of sensory afferents (by either cutaneous or intrathecal application of specific pharmacological agents or by modest cooling) elicits analgesia in neuropathic and other chronic pain models in rats, thereby inhibiting the characteristic sensitization of dorsal-horn neurons and behavioral-reflex facilitation. TRPM8 expression was increased in a subset of sensory neurons after nerve injury. The essential role of TRPM8 in suppression of sensitized pain responses was corroborated by specific knockdown of its expression after intrathecal application of an antisense oligonucleotide. We further show that the analgesic effect of TRPM8 activation is centrally mediated and relies on Group II/III metabotropic glutamate receptors (mGluRs), but not opioid receptors. We propose a scheme in which Group II/III mGluRs would respond to glutamate released from TRPM8-containing afferents to exert an inhibitory gate control over nociceptive inputs. CONCLUSIONS TRPM8 and its central downstream mediators, as elements of endogenous-cooling-induced analgesia, represent a novel analgesic axis that can be exploited in chronic sensitized pain states.
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Affiliation(s)
- Clare J Proudfoot
- Centre for Neuroscience Research, Division of Veterinary Biomedical Sciences, University of Edinburgh, Summerhall, Edinburgh EH9 1QH, United Kingdom
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Marabese I, de Novellis V, Palazzo E, Scafuro MA, Vita D, Rossi F, Maione S. Effects of (S)-3,4-DCPG, an mGlu8 receptor agonist, on inflammatory and neuropathic pain in mice. Neuropharmacology 2006; 52:253-62. [PMID: 17113112 DOI: 10.1016/j.neuropharm.2006.04.006] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2005] [Revised: 04/07/2006] [Accepted: 04/14/2006] [Indexed: 01/12/2023]
Abstract
In this study, the effect of (S)-3,4-dicarboxyphenylglycine (DCPG), a selective mGlu8 receptor agonist, has been investigated in inflammatory and neuropathic pain models in order to elucidate the role of mGlu8 receptor in modulating pain perception. Inflammatory pain was induced by the peripheral injection of formalin or carrageenan in awake mice. Systemic administration of (S)-3,4-DCPG, performed 15 min before formalin, decreased both early and delayed nociceptive responses of the formalin test. When this treatment was carried out 15 min after the peripheral injection of formalin it still reduced the late hyperalgesic phase. Similarly, systemic (S)-3,4-DCPG reduced carrageenan-induced thermal hyperalgesia and mechanical allodynia when administered 15 min before carrageenan, but no effect on pain behaviour was observed when (S)-3,4-DCPG was given after the development of carrageenan-induced inflammatory pain. When microinjected into the lateral PAG (RS)-alpha-methylserine-O-phoshate (MSOP), a group III receptor antagonist, antagonised the analgesic effect induced by systemic administration of (S)-3,4-DCPG in both of the inflammatory pain models. Intra-lateral PAG (S)-3,4-DCPG reduced pain behaviour when administered 10 min before formalin or carrageenan; both the effects were blocked by intra-lateral PAG MSOP. (S)-3,4-DCPG was ineffective in alleviating thermal hyperalgesia and mechanical allodynia 7 days after the chronic constriction injury of the sciatic nerve, whereas it proved effective 3 days after surgery. Taken together these results suggest that stimulation of mGlu8 receptors relieve formalin and carrageenan-induced hyperalgesia in inflammatory pain, whereas it would seem less effective in established inflammatory or neuropathic pain.
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Affiliation(s)
- I Marabese
- Department of Experimental Medicine, Section of Pharmacology L. Donatelli, Faculty of Medicine and Surgery-Second University of Naples, Via Costantinopoli 16, 80138 Naples, Italy
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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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46
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Li W, Neugebauer V. Differential changes of group II and group III mGluR function in central amygdala neurons in a model of arthritic pain. J Neurophysiol 2006; 96:1803-15. [PMID: 16760343 DOI: 10.1152/jn.00495.2006] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Metabotropic glutamate receptors (mGluRs) play important roles in neuroplasticity and disorders such as persistent pain. Group I mGluRs contribute to pain-related sensitization and synaptic plasticity of neurons in the laterocapsular division of the central nucleus of the amygdala (CeLC), although the roles of groups II and III mGluRs are not known. Extracellular single-unit recordings were made from 60 CeLC neurons in anesthetized adult rats. Background activity and evoked responses were measured before and during the development of the kaolin/carrageenan-induced knee-joint arthritis. Drugs were administered into the CeLC by microdialysis before and/or after arthritis induction. A selective group III mGluR agonist (LAP4) inhibited CeLC neurons' responses to stimulation of the knee and ankle in arthritis (n = 7) more potently than under normal conditions (n = 14). A selective group II agonist (LY354740) inhibited responses under normal conditions (n = 12) and became more potent in inhibiting responses to noxious stimulation of the knee in arthritis (n = 10). The effect of LY354740 on innocuous stimulation of the knee and stimulation of the ankle did not change in arthritis. Antagonists for groups II (EGLU, n = 9) and III (UBP1112, n = 8) had no effects under normal conditions. In arthritis, UPB1112 (n = 5) facilitated the responses to stimulation of knee and ankle, whereas EGLU (n = 5) selectively increased the responses to stimulation of the knee. These data suggest that mGluRs of groups II and III can inhibit nociceptive processing in CeLC neurons. The increased function and endogenous activation of group II mGluRs in the arthritis pain model appear more input-selective than the general changes of group III mGluRs.
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Affiliation(s)
- Weidong Li
- Department of Neuroscience and Cell Biology, The University of Texas Medical Branch, Galveston, TX 77555-1069, USA
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47
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Han JS, Fu Y, Bird GC, Neugebauer V. Enhanced group II mGluR-mediated inhibition of pain-related synaptic plasticity in the amygdala. Mol Pain 2006; 2:18. [PMID: 16681859 PMCID: PMC1471776 DOI: 10.1186/1744-8069-2-18] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2006] [Accepted: 05/08/2006] [Indexed: 11/10/2022] Open
Abstract
Background The latero-capsular part of the central nucleus of the amygdala (CeLC) is the target of the spino-parabrachio-amygdaloid pain pathway. Our previous studies showed that CeLC neurons develop synaptic plasticity and increased neuronal excitability in the kaolin/carrageenan model of arthritic pain. These pain-related changes involve presynaptic group I metabotropic glutamate receptors (mGluRs) and postsynaptic NMDA and calcitonin gene-related peptide (CGRP1) receptors. Here we address the role of group II mGluRs. Results Whole-cell current- and voltage-clamp recordings were made from CeLC neurons in brain slices from control rats and arthritic rats (>6 h postinjection of kaolin/carrageenan into the knee). Monosynaptic excitatory postsynaptic currents (EPSCs) were evoked by electrical stimulation of afferents from the pontine parabrachial (PB) area. A selective group II mGluR agonist (LY354740) decreased the amplitude of EPSCs more potently in CeLC neurons from arthritic rats (IC50 = 0.59 nM) than in control animals (IC50 = 15.0 nM). The inhibitory effect of LY354740 was reversed by a group II mGluR antagonist (EGLU) but not a GABAA receptor antagonist (bicuculline). LY354740 decreased frequency, but not amplitude, of miniature EPSCs in the presence of TTX. No significant changes of neuronal excitability measures (membrane slope conductance and action potential firing rate) were detected. Conclusion Our data suggest that group II mGluRs act presynaptically to modulate synaptic plasticity in the amygdala in a model of arthritic pain.
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Affiliation(s)
- Jeong S Han
- Department of Neuroscience and Cell Biology, The University of Texas Medical Branch, Galveston, Texas 77555-1069, USA
| | - Yu Fu
- Department of Neuroscience and Cell Biology, The University of Texas Medical Branch, Galveston, Texas 77555-1069, USA
| | - Gary C Bird
- Department of Neuroscience and Cell Biology, The University of Texas Medical Branch, Galveston, Texas 77555-1069, USA
| | - Volker Neugebauer
- Department of Neuroscience and Cell Biology, The University of Texas Medical Branch, Galveston, Texas 77555-1069, USA
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Höcht C, Opezzo JAW, Taira CA. Applicability of reverse microdialysis in pharmacological and toxicological studies. J Pharmacol Toxicol Methods 2006; 55:3-15. [PMID: 16567112 DOI: 10.1016/j.vascn.2006.02.007] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2006] [Accepted: 02/15/2006] [Indexed: 10/24/2022]
Abstract
A recent application of microdialysis is the introduction of a substance into the extracellular space via the microdialysis probe. The inclusion of a higher amount of a drug in the perfusate allows the drug to diffuse through the microdialysis membrane to the tissue. This technique, actually called as reverse microdialysis, not only allows the local administration of a substance but also permits the simultaneous sampling of the extracellular levels of endogenous compounds. Local effects of exogenous compounds have been studied in the central nervous system, hepatic tissue, dermis, heart and corpora luteae of experimental animals by means of reverse microdialysis. In central nervous studies, reverse microdialysis has been extensively used for the study of the effects on neurotransmission at different central nuclei of diverse pharmacological and toxicological agents, such as antidepressants, antipsychotics, antiparkinsonians, hallucinogens, drugs of abuse and experimental drugs. In the clinical setting, reverse microdialysis has been used for the study of local effects of drugs in the adipose tissue, skeletal muscle and dermis. The aim of this review is to describe the principles of the reverse microdialysis, to compare the technique with other available methods and finally to describe the applicability of reverse microdialysis in the study of drugs properties both in basic and clinical research.
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Affiliation(s)
- Christian Höcht
- Cátedra de Farmacología, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junín 956, (C1113AAD) Buenos Aires, Argentina.
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Buesa I, Ortiz V, Aguilera L, Torre F, Zimmermann M, Azkue JJ. Disinhibition of spinal responses to primary afferent input by antagonism at GABA receptors in urethane-anaesthetised rats is dependent on NMDA and metabotropic glutamate receptors. Neuropharmacology 2006; 50:585-94. [PMID: 16412481 DOI: 10.1016/j.neuropharm.2005.11.005] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2005] [Revised: 08/18/2005] [Accepted: 11/09/2005] [Indexed: 11/21/2022]
Abstract
Disruption of spinal GABAergic circuits, which regulate the conveyance of sensory information to spinal cord neurones from the primary afferent system, leads to miscoding of afferent input and often results in hyperresponsiveness states. In the present work, extracellular field potentials elicited by electrical peripheral nerve activation were recorded in the urethane-anaesthetised rat following spinal administration of GABA(A) or GABA(B) receptor-antagonists, and the involvement of glutamate receptors of the NMDA and metabotropic types in changes induced by altered GABAergic function was examined by pre-treating the spinal dorsal horn with appropriate antagonist drugs. Spinal administration of the GABA(A) receptor antagonist bicuculline (BIC) dose-dependently augmented poly- but not monosynaptic field potentials elicited by activation of A fibres or potentials elicited by activation of C fibres, whereas application of the GABA(B) receptor antagonist CGP35348 significantly increased the amplitudes of C- but not A fibre-evoked potentials. BIC-induced augmentation was blocked by pre-treatment with the NMDA receptor antagonist D-(-)-2-amino-5-phosphonopentanoic acid (D-AP5) or the group I or II metabotropic glutamate receptor (mGluR)-antagonists (RS)-1-aminoindan-1,5-dicarboxylic acid (AIDA) or (2S)-alpha-ethylglutamic acid (EGLU), respectively, but not by the group III mGluR-antagonist (RS)-alpha-methylserine-O-phosphate (MSOP). Augmentation of spinal field potentials induced by CGP35348 was prevented by pre-treatment with D-AP5 but not with mGluR-antagonists. The present findings provide novel evidence that disparate synaptic mechanisms subserved by metabotropic and NMDA glutamate receptors may be involved in spinal hyperresponsiveness states secondary to decreased GABA(A) or GABA(B) receptor activity.
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Affiliation(s)
- Itsaso Buesa
- Department of Neurosciences, School of Medicine and Dentistry, Basque Country University, Barrio Sarriena s/n, 48940 Leioa, Spain
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50
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Sun RQ, Tu YJ, Yan JY, Willis WD. Activation of protein kinase B/Akt signaling pathway contributes to mechanical hypersensitivity induced by capsaicin. Pain 2005; 120:86-96. [PMID: 16360265 DOI: 10.1016/j.pain.2005.10.017] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2005] [Revised: 09/09/2005] [Accepted: 10/19/2005] [Indexed: 11/20/2022]
Abstract
We investigated the involvement of the protein kinase B/Akt (PKB/Akt) signaling pathway in the mechanical hypersensitivity induced in rats by capsaicin. Intradermal injection of capsaicin results in activation of PKB/Akt in the lumbar spinal cord, most prominently in the dorsal horn, starting by 5 min after capsaicin injection and lasting at least 1h. The activated PKB/Akt in the spinal cord is in neurons, since phospho-PKB/Akt (p-PKB/Akt) colocalizes with the neuronal marker, neuronal-specific nuclear protein (NeuN). The mechanical hypersensitivity is shown by the enhanced paw withdrawal frequency to applications of von Frey filaments with different bending forces (30, 100, 200 mN) on the rat paw. Pre-treatment with several different PKB/Akt inhibitors, including SH-6, Akt inhibitor IV, and Akt inhibitor V, blocked the mechanical hypersensitivity induced by intradermal injection of capsaicin, a measure of spinal cord central sensitization. Two structurally unrelated phosphoinositide 3-Kinase (PI3K, upstream of PKB/Akt) inhibitors, Wortmannin and LY294002, also prevented the mechanical hypersensitivity induced by intradermal injection of capsaicin. Furthermore, post-treatment with the PI3K inhibitor, Wortmannin, or PKB/Akt inhibitors, such as NL-71-101, SH-6, Akt inhibitor IV, and inhibitor V significantly reduced the established mechanical hypersensitivity induced by capsaicin. The PKB/Akt signaling pathway in the spinal cord is therefore involved in pain hypersensitivity.
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Affiliation(s)
- Rui-Qing Sun
- Department of Neuroscience and Cell Biology, The University of Texas Medical Branch, 301 University Blvd, Galveston, TX 77555-1069, USA
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