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Xie RG, Xu GY, Wu SX, Luo C. Presynaptic glutamate receptors in nociception. Pharmacol Ther 2023; 251:108539. [PMID: 37783347 DOI: 10.1016/j.pharmthera.2023.108539] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Revised: 08/19/2023] [Accepted: 09/25/2023] [Indexed: 10/04/2023]
Abstract
Chronic pain is a frequent, distressing and poorly understood health problem. Plasticity of synaptic transmission in the nociceptive pathways after inflammation or injury is assumed to be an important cellular basis for chronic, pathological pain. Glutamate serves as the main excitatory neurotransmitter at key synapses in the somatosensory nociceptive pathways, in which it acts on both ionotropic and metabotropic glutamate receptors. Although conventionally postsynaptic, compelling anatomical and physiological evidence demonstrates the presence of presynaptic glutamate receptors in the nociceptive pathways. Presynaptic glutamate receptors play crucial roles in nociceptive synaptic transmission and plasticity. They modulate presynaptic neurotransmitter release and synaptic plasticity, which in turn regulates pain sensitization. In this review, we summarize the latest understanding of the expression of presynaptic glutamate receptors in the nociceptive pathways, and how they contribute to nociceptive information processing and pain hypersensitivity associated with inflammation / injury. We uncover the cellular and molecular mechanisms of presynaptic glutamate receptors in shaping synaptic transmission and plasticity to mediate pain chronicity, which may provide therapeutic approaches for treatment of chronic pain.
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Affiliation(s)
- Rou-Gang Xie
- Department of Neurobiology, Fourth Military Medical University, Xi'an 710032, China.
| | - Guang-Yin Xu
- Jiangsu Key Laboratory of Neuropsychiatric Diseases, Institute of Neuroscience, Soochow University, Suzhou 215123, China
| | - Sheng-Xi Wu
- Department of Neurobiology, Fourth Military Medical University, Xi'an 710032, China.
| | - Ceng Luo
- Department of Neurobiology, Fourth Military Medical University, Xi'an 710032, China.
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Tian W, He D, Liu J, Chen F, Zhang W, Hu J, Wang S. Topical borneol relieves nonhistaminergic pruritus via targeting TRPA1 and TRPM8 channels in peripheral nerve terminals of mice. Eur J Pharmacol 2023:175833. [PMID: 37290679 DOI: 10.1016/j.ejphar.2023.175833] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2023] [Revised: 04/26/2023] [Accepted: 06/06/2023] [Indexed: 06/10/2023]
Abstract
Borneol has been used successfully for the treatment of itchy skin in traditional Chinese medicine. However, the antipruritic effect of borneol has rarely been studied, and the mechanism is unclear. Here, we showed that topical application of borneol on skin substantially suppressed pruritogen chloroquine- and compound 48/80-induced itching in mice. The potential targets of borneol, including transient receptor potential cation channel subfamily V member 3 (TRPV3), transient receptor potential cation channel subfamily A member 1 (TRPA1), transient receptor potential cation channel subfamily M member 8 (TRPM8), and gamma-aminobutyric acid type A (GABAA) receptor were pharmacologically inhibited or genetically knocked out one by one in mouse. Itching behavior studies demonstrated that the antipruritic effect of borneol is largely independent of TRPV3 and GABAA receptor, and TRPA1 and TRPM8 channels are responsible for a major portion of the effect of borneol on chloroquine-induced nonhistaminergic itching. Borneol activates TRPM8 and inhibits TRPA1 in sensory neurons of mice. Topical co-application of TRPA1 antagonist and TRPM8 agonist mimicked the effect of borneol on chloroquine-induced itching. Intrathecal injection of a group II metabotropic glutamate receptor antagonist partially attenuated the effect of borneol and completely abolished the effect of TRPM8 agonist on chloroquine-induced itching, suggesting that a spinal glutamatergic mechanism is involved. In contrast, the effect of borneol on compound 48/80-induced histaminergic itching occurs through TRPA1-and TRPM8-independent mechanisms. Our work demonstrates that borneol is an effective topical itch reliever, and TRPA1 inhibition and TRPM8 activation in peripheral nerve terminals account for its antipruritic effect.
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Affiliation(s)
- Weifeng Tian
- Department of Neurology, Institute of Neuroscience, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, The Second Affiliated Hospital, School of Basic Medical Sciences, Guangzhou Medical University, Guangzhou, China; State Key Laboratory of Primate Biomedical Research, Institute of Primate Translational Medicine, Kunming University of Science and Technology, Kunming, China; Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences & Yunnan Province, and Ion Channel Research and Drug Development Center, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, China
| | - Dongmei He
- Department of Neurology, Institute of Neuroscience, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, The Second Affiliated Hospital, School of Basic Medical Sciences, Guangzhou Medical University, Guangzhou, China
| | - Jingjing Liu
- Department of Neurology, Institute of Neuroscience, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, The Second Affiliated Hospital, School of Basic Medical Sciences, Guangzhou Medical University, Guangzhou, China
| | - Feiyu Chen
- Department of Neurology, Institute of Neuroscience, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, The Second Affiliated Hospital, School of Basic Medical Sciences, Guangzhou Medical University, Guangzhou, China
| | - Wenjie Zhang
- Department of Neurology, Institute of Neuroscience, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, The Second Affiliated Hospital, School of Basic Medical Sciences, Guangzhou Medical University, Guangzhou, China
| | - Jinsheng Hu
- State Key Laboratory of Primate Biomedical Research, Institute of Primate Translational Medicine, Kunming University of Science and Technology, Kunming, China.
| | - Shu Wang
- Department of Neurology, Institute of Neuroscience, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, The Second Affiliated Hospital, School of Basic Medical Sciences, Guangzhou Medical University, Guangzhou, China.
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3
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Group II metabotropic glutamate receptor activation suppresses ATP currents in rat dorsal root ganglion neurons. Neuropharmacology 2023; 227:109443. [PMID: 36709909 DOI: 10.1016/j.neuropharm.2023.109443] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2022] [Revised: 01/23/2023] [Accepted: 01/25/2023] [Indexed: 01/28/2023]
Abstract
P2X3 receptors and group II metabotropic glutamate receptors (mGluRs) have been found to be expressed in primary sensory neurons. P2X3 receptors participate in a variety of pain processes, while the activation of mGluRs has an analgesic effect. However, it's still unclear whether there is a link between them in pain. Herein, we reported that the group II mGluR activation inhibited the electrophysiological activity of P2X3 receptors in rat dorsal root ganglia (DRG) neurons. Group II mGluR agonist LY354740 concentration-dependently decreased P2X3 receptor-mediated and α,β-methylene-ATP (α,β-meATP)-evoked inward currents in DRG neurons. LY354740 significantly suppressed the maximum response of P2X3 receptor to α,β-meATP, but did not change their affinity. Inhibition of ATP currents by LY354740 was blocked by the group II mGluR antagonist LY341495, also prevented by the intracellular dialysis of either the Gi/o protein inhibitor pertussis toxin, the cAMP analog 8-Br-cAMP, or the protein kinase A (PKA) inhibitor H-89. Moreover, LY354740 decreased α,β-meATP-induced membrane potential depolarization and action potential bursts in DRG neurons. Finally, intraplantar injection of LY354740 also relieved α,β-meATP-induced spontaneous nociceptive behaviors and mechanical allodynia in rats by activating peripheral group Ⅱ mGluRs. These results indicated that peripheral group II mGluR activation inhibited the functional activity of P2X3 receptors via a Gi/o protein and cAMP/PKA signaling pathway in rat DRG neurons, which revealed a novel mechanism underlying analgesic effects of peripheral group II mGluRs. This article is part of the Special Issue on "Purinergic Signaling: 50 years".
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Lukacs IP, Francavilla R, Field M, Hunter E, Howarth M, Horie S, Plaha P, Stacey R, Livermore L, Ansorge O, Tamas G, Somogyi P. Differential effects of group III metabotropic glutamate receptors on spontaneous inhibitory synaptic currents in spine-innervating double bouquet and parvalbumin-expressing dendrite-targeting GABAergic interneurons in human neocortex. Cereb Cortex 2023; 33:2101-2142. [PMID: 35667019 PMCID: PMC9977385 DOI: 10.1093/cercor/bhac195] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2022] [Revised: 04/27/2022] [Accepted: 04/28/2022] [Indexed: 11/12/2022] Open
Abstract
Diverse neocortical GABAergic neurons specialize in synaptic targeting and their effects are modulated by presynaptic metabotropic glutamate receptors (mGluRs) suppressing neurotransmitter release in rodents, but their effects in human neocortex are unknown. We tested whether activation of group III mGluRs by L-AP4 changes GABAA receptor-mediated spontaneous inhibitory postsynaptic currents (sIPSCs) in 2 distinct dendritic spine-innervating GABAergic interneurons recorded in vitro in human neocortex. Calbindin-positive double bouquet cells (DBCs) had columnar "horsetail" axons descending through layers II-V innervating dendritic spines (48%) and shafts, but not somata of pyramidal and nonpyramidal neurons. Parvalbumin-expressing dendrite-targeting cell (PV-DTC) axons extended in all directions innervating dendritic spines (22%), shafts (65%), and somata (13%). As measured, 20% of GABAergic neuropil synapses innervate spines, hence DBCs, but not PV-DTCs, preferentially select spine targets. Group III mGluR activation paradoxically increased the frequency of sIPSCs in DBCs (to median 137% of baseline) but suppressed it in PV-DTCs (median 92%), leaving the amplitude unchanged. The facilitation of sIPSCs in DBCs may result from their unique GABAergic input being disinhibited via network effect. We conclude that dendritic spines receive specialized, diverse GABAergic inputs, and group III mGluRs differentially regulate GABAergic synaptic transmission to distinct GABAergic cell types in human cortex.
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Affiliation(s)
- Istvan P Lukacs
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, UK
| | | | - Martin Field
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, UK
| | - Emily Hunter
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, UK
| | - Michael Howarth
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, UK
| | - Sawa Horie
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, UK
| | - Puneet Plaha
- Department of Neurosurgery, John Radcliffe Hospital, OUH NHS Foundation Trust, Oxford OX3 9DU, UK
| | - Richard Stacey
- Department of Neurosurgery, John Radcliffe Hospital, OUH NHS Foundation Trust, Oxford OX3 9DU, UK
| | - Laurent Livermore
- Department of Neurosurgery, John Radcliffe Hospital, OUH NHS Foundation Trust, Oxford OX3 9DU, UK
| | - Olaf Ansorge
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DU, UK
| | - Gabor Tamas
- Department of Physiology, Anatomy and Neuroscience, University of Szeged, 6726 Szeged, Hungary
| | - Peter Somogyi
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, UK
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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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Park SK, Cho YS, Kim JH, Kim YS, Bae YC. Ultrastructure of Rat Rostral Nucleus of the Solitary Tract Terminals in the Parabrachial Nucleus and Medullary Reticular Formation. Front Cell Neurosci 2022; 16:858617. [PMID: 35370562 PMCID: PMC8968100 DOI: 10.3389/fncel.2022.858617] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Accepted: 02/18/2022] [Indexed: 11/13/2022] Open
Abstract
Neurons in the rostral nucleus of the solitary tract (rNST) receive taste information from the tongue and relay it mainly to the parabrachial nucleus (PBN) and the medullary reticular formation (RF) through two functionally different neural circuits. To help understand how the information from the rNST neurons is transmitted within these brainstem relay nuclei in the taste pathway, we examined the terminals of the rNST neurons in the PBN and RF by use of anterograde horseradish peroxidase (HRP) labeling, postembedding immunogold staining for glutamate, serial section electron microscopy, and quantitative analysis. Most of the anterogradely labeled, glutamate-immunopositive axon terminals made a synaptic contact with only a single postsynaptic element in PBN and RF, suggesting that the sensory information from rNST neurons, at the individual terminal level, is not passed to multiple target cells. Labeled terminals were usually presynaptic to distal dendritic shafts in both target nuclei. However, the frequency of labeled terminals that contacted dendritic spines was significantly higher in the PBN than in the RF, and the frequency of labeled terminals that contacted somata or proximal dendrites was significantly higher in the RF than in the PBN. Labeled terminals receiving axoaxonic synapses, which are a morphological substrate for presynaptic modulation frequently found in primary sensory afferents, were not observed. These findings suggest that the sensory information from rNST neurons is processed in a relatively simple manner in both PBN and RF, but in a distinctly different manner in the PBN as opposed to the RF.
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Wistrom E, Chase R, Smith PR, Campbell ZT. A compendium of validated pain genes. WIREs Mech Dis 2022; 14:e1570. [PMID: 35760453 PMCID: PMC9787016 DOI: 10.1002/wsbm.1570] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Revised: 05/28/2022] [Accepted: 06/06/2022] [Indexed: 12/30/2022]
Abstract
The development of novel pain therapeutics hinges on the identification and rigorous validation of potential targets. Model organisms provide a means to test the involvement of specific genes and regulatory elements in pain. Here we provide a list of genes linked to pain-associated behaviors. We capitalize on results spanning over three decades to identify a set of 242 genes. They support a remarkable diversity of functions spanning action potential propagation, immune response, GPCR signaling, enzymatic catalysis, nucleic acid regulation, and intercellular signaling. Making use of existing tissue and single-cell high-throughput RNA sequencing datasets, we examine their patterns of expression. For each gene class, we discuss archetypal members, with an emphasis on opportunities for additional experimentation. Finally, we discuss how powerful and increasingly ubiquitous forward genetic screening approaches could be used to improve our ability to identify pain genes. This article is categorized under: Neurological Diseases > Genetics/Genomics/Epigenetics Neurological Diseases > Molecular and Cellular Physiology.
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Affiliation(s)
- Eric Wistrom
- Department of Biological SciencesUniversity of Texas at DallasRichardsonTexasUSA
| | - Rebecca Chase
- Department of Biological SciencesUniversity of Texas at DallasRichardsonTexasUSA
| | - Patrick R. Smith
- Department of Biological SciencesUniversity of Texas at DallasRichardsonTexasUSA
| | - Zachary T. Campbell
- Department of Biological SciencesUniversity of Texas at DallasRichardsonTexasUSA,Center for Advanced Pain StudiesUniversity of Texas at DallasRichardsonTexasUSA
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Li YL, Chang XR, Ma JT, Zhao X, Yin LT, Yan LJ, Guo JH, Zhang C, Yang XR. Activation of peripheral group III metabotropic glutamate receptors suppressed formalin-induced nociception. Clin Exp Pharmacol Physiol 2021; 49:319-326. [PMID: 34657305 DOI: 10.1111/1440-1681.13602] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Revised: 09/20/2021] [Accepted: 10/14/2021] [Indexed: 11/28/2022]
Abstract
Intraplantar injection of formalin produces persistent spontaneous nociception and hyperalgesia. The underlying mechanism, however, remains unclear. The present study was, therefore, designed to determine the roles of peripheral group III metabotropic glutamate receptors (mGluRs) in formalin-evoked spontaneous nociception. Pre-treatment with intraplantar injections of L-serine-O-phosphate (L-SOP), a group III mGluRs agonist, significantly inhibited formalin-induced nociceptive behaviours and decreased Fos production in the spinal dorsal horn. The inhibitory effects of L-SOP were abolished completely by pre-treatment with the group III mGluR antagonist (RS)-a-methylserine-O-phosphate (M-SOP). These data suggest that the activation of group III mGluRs in the periphery may play a differential role in formalin-induced nociception. In addition, L-SOP decreased the formalin-induced upregulation of tumour necrosis factor-α (TNF-α) as well as interleukine-1β (IL-1β) expression in the spinal cord, suggesting that activation of peripheral group III mGluRs reduces formalin-induced nociception through inhibition of the pro-inflammatory cytokines in the spinal cord. Therefore, the agonists acting peripheral group III mGluRs possess therapeutic effectiveness in chronic pain.
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Affiliation(s)
- Yan-Li Li
- Department of Neurology, First Hospital, Shanxi Medical University, Taiyuan, Shanxi, P.R.China
| | - Xin-Rui Chang
- Key Laboratory of Cellular Physiology at Shanxi Medical University, Ministry of Education, Key Laboratory of Cellular Physiology in Shanxi Province, The Department of Physiology, Shanxi Medical University, Taiyuan, Shanxi, P.R.China
| | - Jin-Teng Ma
- Key Laboratory of Cellular Physiology at Shanxi Medical University, Ministry of Education, Key Laboratory of Cellular Physiology in Shanxi Province, The Department of Physiology, Shanxi Medical University, Taiyuan, Shanxi, P.R.China
| | - Xin Zhao
- Key Laboratory of Cellular Physiology at Shanxi Medical University, Ministry of Education, Key Laboratory of Cellular Physiology in Shanxi Province, The Department of Physiology, Shanxi Medical University, Taiyuan, Shanxi, P.R.China
| | - Li-Tian Yin
- Key Laboratory of Cellular Physiology at Shanxi Medical University, Ministry of Education, Key Laboratory of Cellular Physiology in Shanxi Province, The Department of Physiology, Shanxi Medical University, Taiyuan, Shanxi, P.R.China
| | - Liang-Jun Yan
- Department of Pharmaceutical Sciences, College of Pharmacy, University of North Texas Health Science Center, Fort Worth, Texas, USA
| | - Jun-Hong Guo
- Department of Neurology, First Hospital, Shanxi Medical University, Taiyuan, Shanxi, P.R.China
| | - Ce Zhang
- Key Laboratory of Cellular Physiology at Shanxi Medical University, Ministry of Education, Key Laboratory of Cellular Physiology in Shanxi Province, The Department of Physiology, Shanxi Medical University, Taiyuan, Shanxi, P.R.China
| | - Xiao-Rong Yang
- Key Laboratory of Cellular Physiology at Shanxi Medical University, Ministry of Education, Key Laboratory of Cellular Physiology in Shanxi Province, The Department of Physiology, Shanxi Medical University, Taiyuan, Shanxi, P.R.China
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Cisani F, Roggeri A, Olivero G, Garrone B, Tongiani S, Di Giorgio FP, Pittaluga A. Acute Low Dose of Trazodone Recovers Glutamate Release Efficiency and mGlu2/3 Autoreceptor Impairments in the Spinal Cord of Rats Suffering From Chronic Sciatic Ligation. Front Pharmacol 2020; 11:1108. [PMID: 32765286 PMCID: PMC7379891 DOI: 10.3389/fphar.2020.01108] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Accepted: 07/08/2020] [Indexed: 11/16/2022] Open
Abstract
We investigated whether chronic sciatic ligation modifies the glutamate release in spinal cord nerve endings (synaptosomes) as well as the expression and the function of presynaptic release-regulating mGlu2/3 autoreceptors and 5-HT2A heteroreceptors in these particles. Synaptosomes were from the spinal cord of animals suffering from the sciatic ligation that developed on day 6 post-surgery a significant decrease of the force inducing paw-withdrawal in the lesioned paw. The exocytosis of glutamate (quantified as release of preloaded [3H]D-aspartate, [3H]D-Asp) elicited by a mild depolarizing stimulus (15 mM KCl) was significantly increased in synaptosomes from injured rats when compared to controls (uninjured rats). The mGlu2/3 agonist LY379268 (1000 pM) significantly inhibited the 15 mM KCl-evoked [3H]D-Asp overflow from control synaptosomes, but not in terminals isolated from injured animals. Differently, a low concentration (10 nM) of (±) DOI, unable to modify the 15 mM KCl-evoked [3H]D-Asp overflow in control spinal cord synaptosomes, significantly reduced the glutamate exocytosis in nerve endings isolated from the injured rats. Acute oral trazodone (TZD, 0.3 mg/kg on day 7 post-surgery) efficiently recovered glutamate exocytosis as well as the efficiency of LY379268 in inhibiting this event in spinal cord synaptosomes from injured animals. The sciatic ligation significantly reduced the expression of mGlu2/3, but not of 5-HT2A, receptor proteins in spinal cord synaptosomal lysates. Acute TZD recovered this parameter. Our results support the use of 5-HT2A antagonists for restoring altered spinal cord glutamate plasticity in rats suffering from sciatic ligation.
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Affiliation(s)
- Francesca Cisani
- Department of Pharmacy, DIFAR, Pharmacology and Toxicology Section and Center of Excellence for Biomedical Research, University of Genoa, Genoa, Italy
| | - Alessandra Roggeri
- Department of Pharmacy, DIFAR, Pharmacology and Toxicology Section and Center of Excellence for Biomedical Research, University of Genoa, Genoa, Italy
| | - Guendalina Olivero
- Department of Pharmacy, DIFAR, Pharmacology and Toxicology Section and Center of Excellence for Biomedical Research, University of Genoa, Genoa, Italy
| | - Beatrice Garrone
- Angelini RR&D (Research, Regulatory & Development), Angelini Pharma S.p.A., Rome, Italy
| | - Serena Tongiani
- Angelini RR&D (Research, Regulatory & Development), Angelini Pharma S.p.A., Rome, Italy
| | | | - Anna Pittaluga
- Department of Pharmacy, DIFAR, Pharmacology and Toxicology Section and Center of Excellence for Biomedical Research, University of Genoa, Genoa, Italy.,IRCCS Ospedale Policlinico San Martino, Genova, Italy
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Activation of peripheral group III metabotropic glutamate receptors inhibits pain transmission by decreasing neuronal excitability in the CFA-inflamed knee joint. Neurosci Lett 2019; 694:111-115. [DOI: 10.1016/j.neulet.2018.11.033] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Revised: 11/20/2018] [Accepted: 11/21/2018] [Indexed: 11/20/2022]
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11
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Tripathi GM, Kalita J, Misra UK. Role of glutamate and its receptors in migraine with reference to amitriptyline and transcranial magnetic stimulation therapy. Brain Res 2018; 1696:31-37. [DOI: 10.1016/j.brainres.2018.05.046] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2018] [Revised: 05/14/2018] [Accepted: 05/30/2018] [Indexed: 01/03/2023]
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12
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Opposing Roles of Estradiol and Testosterone on Stress-Induced Visceral Hypersensitivity in Rats. THE JOURNAL OF PAIN 2018; 19:764-776. [PMID: 29496640 DOI: 10.1016/j.jpain.2018.02.007] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Revised: 01/30/2018] [Accepted: 02/14/2018] [Indexed: 12/19/2022]
Abstract
Chronic stress produces maladaptive pain responses, manifested as alterations in pain processing and exacerbation of chronic pain conditions including irritable bowel syndrome. Female predominance, especially during reproductive years, strongly suggests a role of gonadal hormones. However, gonadal hormone modulation of stress-induced pain hypersensitivity is not well understood. In the present study, we tested the hypothesis that estradiol is pronociceptive and testosterone is antinociceptive in a model of stress-induced visceral hypersensitivity (SIVH) in rats by recording the visceromotor response to colorectal distention after a 3-day forced swim (FS) stress paradigm. FS induced visceral hypersensitivity that persisted at least 2 weeks in female, but only 2 days in male rats. Ovariectomy blocked and orchiectomy facilitated SIVH. Furthermore, estradiol injection in intact male rats increased SIVH and testosterone in intact female rats attenuated SIVH. Western blot analyses indicated estradiol increased excitatory glutamate ionotropic receptor NMDA type subunit 1 expression and decreased inhibitory metabotropic glutamate receptor 2 expression after FS in male thoracolumbar spinal cord. In addition, the presence of estradiol during stress increased spinal brain-derived neurotrophic factor (BDNF) expression independent of sex. In contrast, testosterone blocked the stress-induced increase in BDNF expression in female rats. These data suggest that estradiol facilitates and testosterone attenuates SIVH by modulating spinal excitatory and inhibitory glutamatergic receptor expression. PERSPECTIVE SIVH is more robust in female rats. Estradiol facilitates whereas testosterone dampens the development of SIVH. This could partially explain the greater prevalence of certain chronic visceral pain conditions in women. An increase in spinal BDNF is concomitant with increased stress-induced pain. Pharmaceutical interventions targeting this molecule could provide promising alleviation of SIVH in women.
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Wang S, Zhang D, Hu J, Jia Q, Xu W, Su D, Song H, Xu Z, Cui J, Zhou M, Yang J, Xiao J. A clinical and mechanistic study of topical borneol-induced analgesia. EMBO Mol Med 2018; 9:802-815. [PMID: 28396565 PMCID: PMC5452010 DOI: 10.15252/emmm.201607300] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Bingpian is a time‐honored herb in traditional Chinese medicine (TCM). It is an almost pure chemical with a chemical composition of (+)‐borneol and has been historically used as a topical analgesic for millennia. However, the clinical efficacy of topical borneol lacks stringent evidence‐based clinical studies and verifiable scientific mechanism. We examined the analgesic efficacy of topical borneol in a randomized, double‐blind, placebo‐controlled clinical study involving 122 patients with postoperative pain. Topical application of borneol led to significantly greater pain relief than placebo did. Using mouse models of pain, we identified the TRPM8 channel as a molecular target of borneol and showed that topical borneol‐induced analgesia was almost exclusively mediated by TRPM8, and involved a downstream glutamatergic mechanism in the spinal cord. Investigation of the actions of topical borneol and menthol revealed mechanistic differences between borneol‐ and menthol‐induced analgesia and indicated that borneol exhibits advantages over menthol as a topical analgesic. Our work demonstrates that borneol, which is currently approved by the US FDA to be used only as a flavoring substance or adjuvant in food, is an effective topical pain reliever in humans and reveals a key part of the molecular mechanism underlying its analgesic effect.
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Affiliation(s)
- Shu Wang
- Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences/Key Laboratory of Bioactive Peptides of Yunnan Province, Ion Channel Research and Drug Development Center, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, China .,Kunming College of Life Science, University of Chinese Academy of Sciences, Kunming, China
| | - Dan Zhang
- Department of Orthopedic Oncology, Shanghai Changzheng Hospital, The Second Military Medical University, Shanghai, China
| | - Jinsheng Hu
- Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences/Key Laboratory of Bioactive Peptides of Yunnan Province, Ion Channel Research and Drug Development Center, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, China.,Kunming College of Life Science, University of Chinese Academy of Sciences, Kunming, China
| | - Qi Jia
- Department of Orthopedic Oncology, Shanghai Changzheng Hospital, The Second Military Medical University, Shanghai, China
| | - Wei Xu
- Department of Orthopedic Oncology, Shanghai Changzheng Hospital, The Second Military Medical University, Shanghai, China
| | - Deyuan Su
- Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences/Key Laboratory of Bioactive Peptides of Yunnan Province, Ion Channel Research and Drug Development Center, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, China.,Kunming College of Life Science, University of Chinese Academy of Sciences, Kunming, China
| | - Hualing Song
- Department of Preventive Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Zhichun Xu
- Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences/Key Laboratory of Bioactive Peptides of Yunnan Province, Ion Channel Research and Drug Development Center, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, China.,Kunming College of Life Science, University of Chinese Academy of Sciences, Kunming, China
| | - Jianmin Cui
- Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences/Key Laboratory of Bioactive Peptides of Yunnan Province, Ion Channel Research and Drug Development Center, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, China.,Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, Cardiac Bioelectricity and Arrhythmia Center, Washington University, St. Louis, MO, USA
| | - Ming Zhou
- Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences/Key Laboratory of Bioactive Peptides of Yunnan Province, Ion Channel Research and Drug Development Center, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, China.,Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX, USA
| | - Jian Yang
- Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences/Key Laboratory of Bioactive Peptides of Yunnan Province, Ion Channel Research and Drug Development Center, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, China .,Department of Biological Sciences, Columbia University, New York, NY, USA
| | - Jianru Xiao
- Department of Orthopedic Oncology, Shanghai Changzheng Hospital, The Second Military Medical University, Shanghai, China
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14
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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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15
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Khangura RK, Bali A, Jaggi AS, Singh N. Histone acetylation and histone deacetylation in neuropathic pain: An unresolved puzzle? Eur J Pharmacol 2017; 795:36-42. [DOI: 10.1016/j.ejphar.2016.12.001] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Revised: 11/25/2016] [Accepted: 12/01/2016] [Indexed: 12/18/2022]
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16
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Davidson S, Golden JP, Copits BA, Ray PR, Vogt SK, Valtcheva MV, Schmidt RE, Ghetti A, Price T, Gereau RW. Group II mGluRs suppress hyperexcitability in mouse and human nociceptors. Pain 2016; 157:2081-2088. [PMID: 27218869 PMCID: PMC4988887 DOI: 10.1097/j.pain.0000000000000621] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
We introduce a strategy for preclinical research wherein promising targets for analgesia are tested in rodent and subsequently validated in human sensory neurons. We evaluate group II metabotropic glutamate receptors, the activation of which is efficacious in rodent models of pain. Immunohistochemical analysis showed positive immunoreactivity for mGlu2 in rodent dorsal root ganglia (DRG), peripheral fibers in skin, and central labeling in the spinal dorsal horn. We also found mGlu2-positive immunoreactivity in human neonatal and adult DRG. RNA-seq analysis of mouse and human DRG revealed a comparative expression profile between species for group II mGluRs and for opioid receptors. In rodent sensory neurons under basal conditions, activation of group II mGluRs with a selective group II agonist produced no changes to membrane excitability. However, membrane hyperexcitability in sensory neurons exposed to the inflammatory mediator prostaglandin E2 (PGE2) was prevented by (2R,4R)-4-aminopyrrolidine-2,4-dicarboxylate (APDC). In human sensory neurons from donors without a history of chronic pain, we show that PGE2 produced hyperexcitability that was similarly blocked by group II mGluR activation. These results reveal a mechanism for peripheral analgesia likely shared by mice and humans and demonstrate a translational research strategy to improve preclinical validation of novel analgesics using cultured human sensory neurons.
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Affiliation(s)
- Steve Davidson
- Washington University in St. Louis, School of Medicine, Pain Center and Department of Anesthesiology. St. Louis, MO. 63110
| | - Judith P. Golden
- Washington University in St. Louis, School of Medicine, Pain Center and Department of Anesthesiology. St. Louis, MO. 63110
| | - Bryan A. Copits
- Washington University in St. Louis, School of Medicine, Pain Center and Department of Anesthesiology. St. Louis, MO. 63110
| | - Pradipta R. Ray
- School of Brain and Behavioral Sciences, University of Texas at Dallas. 75080
| | - Sherri K. Vogt
- Washington University in St. Louis, School of Medicine, Pain Center and Department of Anesthesiology. St. Louis, MO. 63110
| | - Manouela V. Valtcheva
- Washington University in St. Louis, School of Medicine, Pain Center and Department of Anesthesiology. St. Louis, MO. 63110
| | - Robert E. Schmidt
- Washington University in St. Louis, School of Medicine Department of Neuropathology, St. Louis, MO. 63110
| | | | - Theodore Price
- School of Brain and Behavioral Sciences, University of Texas at Dallas. 75080
| | - Robert W. Gereau
- Washington University in St. Louis, School of Medicine, Pain Center and Department of Anesthesiology. St. Louis, MO. 63110
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17
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Eliava M, Melchior M, Knobloch-Bollmann HS, Wahis J, da Silva Gouveia M, Tang Y, Ciobanu AC, Triana Del Rio R, Roth LC, Althammer F, Chavant V, Goumon Y, Gruber T, Petit-Demoulière N, Busnelli M, Chini B, Tan LL, Mitre M, Froemke RC, Chao MV, Giese G, Sprengel R, Kuner R, Poisbeau P, Seeburg PH, Stoop R, Charlet A, Grinevich V. A New Population of Parvocellular Oxytocin Neurons Controlling Magnocellular Neuron Activity and Inflammatory Pain Processing. Neuron 2016; 89:1291-1304. [PMID: 26948889 DOI: 10.1016/j.neuron.2016.01.041] [Citation(s) in RCA: 277] [Impact Index Per Article: 34.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Revised: 08/02/2015] [Accepted: 01/21/2016] [Indexed: 11/18/2022]
Abstract
Oxytocin (OT) is a neuropeptide elaborated by the hypothalamic paraventricular (PVN) and supraoptic (SON) nuclei. Magnocellular OT neurons of these nuclei innervate numerous forebrain regions and release OT into the blood from the posterior pituitary. The PVN also harbors parvocellular OT cells that project to the brainstem and spinal cord, but their function has not been directly assessed. Here, we identified a subset of approximately 30 parvocellular OT neurons, with collateral projections onto magnocellular OT neurons and neurons of deep layers of the spinal cord. Evoked OT release from these OT neurons suppresses nociception and promotes analgesia in an animal model of inflammatory pain. Our findings identify a new population of OT neurons that modulates nociception in a two tier process: (1) directly by release of OT from axons onto sensory spinal cord neurons and inhibiting their activity and (2) indirectly by stimulating OT release from SON neurons into the periphery.
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Affiliation(s)
- Marina Eliava
- Schaller Research Group on Neuropeptides at German Cancer Research Center (DKFZ) and Cell Network Cluster of Excellence at the University of Heidelberg, Heidelberg 69120, Germany
| | - Meggane Melchior
- Institut of Cellular and Integrative Neurosciences (INCI) UPR3212, Centre National de la Recherche Scientifique (CNRS), University of Strasbourg, Strasbourg 67084, France
| | - H Sophie Knobloch-Bollmann
- Schaller Research Group on Neuropeptides at German Cancer Research Center (DKFZ) and Cell Network Cluster of Excellence at the University of Heidelberg, Heidelberg 69120, Germany; Max Planck Institute for Medical Research, Heidelberg 69120, Germany
| | - Jérôme Wahis
- Institut of Cellular and Integrative Neurosciences (INCI) UPR3212, Centre National de la Recherche Scientifique (CNRS), University of Strasbourg, Strasbourg 67084, France
| | - Miriam da Silva Gouveia
- Schaller Research Group on Neuropeptides at German Cancer Research Center (DKFZ) and Cell Network Cluster of Excellence at the University of Heidelberg, Heidelberg 69120, Germany
| | - Yan Tang
- Schaller Research Group on Neuropeptides at German Cancer Research Center (DKFZ) and Cell Network Cluster of Excellence at the University of Heidelberg, Heidelberg 69120, Germany; Institute of Brain Functional Genomics, East China Normal University, Shanghai 200062, China
| | - Alexandru Cristian Ciobanu
- Center for Psychiatric Neurosciences, Hôpital de Cery, Lausanne University Hospital (CHUV), Lausanne 1008, Switzerland
| | - Rodrigo Triana Del Rio
- Center for Psychiatric Neurosciences, Hôpital de Cery, Lausanne University Hospital (CHUV), Lausanne 1008, Switzerland
| | - Lena C Roth
- Schaller Research Group on Neuropeptides at German Cancer Research Center (DKFZ) and Cell Network Cluster of Excellence at the University of Heidelberg, Heidelberg 69120, Germany; Max Planck Institute for Medical Research, Heidelberg 69120, Germany
| | - Ferdinand Althammer
- Schaller Research Group on Neuropeptides at German Cancer Research Center (DKFZ) and Cell Network Cluster of Excellence at the University of Heidelberg, Heidelberg 69120, Germany
| | - Virginie Chavant
- Institut of Cellular and Integrative Neurosciences (INCI) UPR3212, Centre National de la Recherche Scientifique (CNRS), University of Strasbourg, Strasbourg 67084, France
| | - Yannick Goumon
- Institut of Cellular and Integrative Neurosciences (INCI) UPR3212, Centre National de la Recherche Scientifique (CNRS), University of Strasbourg, Strasbourg 67084, France
| | - Tim Gruber
- Schaller Research Group on Neuropeptides at German Cancer Research Center (DKFZ) and Cell Network Cluster of Excellence at the University of Heidelberg, Heidelberg 69120, Germany; Max Planck Institute for Medical Research, Heidelberg 69120, Germany
| | - Nathalie Petit-Demoulière
- Institut of Cellular and Integrative Neurosciences (INCI) UPR3212, Centre National de la Recherche Scientifique (CNRS), University of Strasbourg, Strasbourg 67084, France
| | - Marta Busnelli
- National Research Council, Institute of Neuroscience, Milan 20129, Italy
| | - Bice Chini
- National Research Council, Institute of Neuroscience, Milan 20129, Italy; Humanitas Clinical and Research Center, Rozzano 20089, Italy
| | - Linette L Tan
- Department for Molecular Pharmacology and Molecular Medicine Partnership Unit with European Molecular Biology Laboratories, Institute of Pharmacology, Heidelberg University, Heidelberg 69120, Germany
| | - Mariela Mitre
- Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, NY 10016, USA
| | - Robert C Froemke
- Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, NY 10016, USA
| | - Moses V Chao
- Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, NY 10016, USA
| | - Günter Giese
- Max Planck Institute for Medical Research, Heidelberg 69120, Germany
| | - Rolf Sprengel
- Max Planck Institute for Medical Research, Heidelberg 69120, Germany
| | - Rohini Kuner
- Department for Molecular Pharmacology and Molecular Medicine Partnership Unit with European Molecular Biology Laboratories, Institute of Pharmacology, Heidelberg University, Heidelberg 69120, Germany
| | - Pierrick Poisbeau
- Institut of Cellular and Integrative Neurosciences (INCI) UPR3212, Centre National de la Recherche Scientifique (CNRS), University of Strasbourg, Strasbourg 67084, France
| | - Peter H Seeburg
- Max Planck Institute for Medical Research, Heidelberg 69120, Germany
| | - Ron Stoop
- Center for Psychiatric Neurosciences, Hôpital de Cery, Lausanne University Hospital (CHUV), Lausanne 1008, Switzerland
| | - Alexandre Charlet
- Institut of Cellular and Integrative Neurosciences (INCI) UPR3212, Centre National de la Recherche Scientifique (CNRS), University of Strasbourg, Strasbourg 67084, France; University of Strasbourg Institute for Advanced Study (USIAS), Strasbourg 67000, France.
| | - Valery Grinevich
- Schaller Research Group on Neuropeptides at German Cancer Research Center (DKFZ) and Cell Network Cluster of Excellence at the University of Heidelberg, Heidelberg 69120, Germany; Max Planck Institute for Medical Research, Heidelberg 69120, Germany; Central Institute of Mental Health (ZI), Mannheim 68159, Germany.
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18
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Di Prisco S, Merega E, Bonfiglio T, Olivero G, Cervetto C, Grilli M, Usai C, Marchi M, Pittaluga A. Presynaptic, release-regulating mGlu2 -preferring and mGlu3 -preferring autoreceptors in CNS: pharmacological profiles and functional roles in demyelinating disease. Br J Pharmacol 2016; 173:1465-77. [PMID: 26791341 DOI: 10.1111/bph.13442] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Revised: 01/08/2016] [Accepted: 01/17/2016] [Indexed: 01/16/2023] Open
Abstract
BACKGROUND AND PURPOSE Presynaptic, release-regulating metabotropic glutamate 2 and 3 (mGlu2/3) autoreceptors exist in the CNS. They represent suitable targets for therapeutic approaches to central diseases that are typified by hyperglutamatergicity. The availability of specific ligands able to differentiate between mGlu2 and mGlu3 subunits allows us to further characterize these autoreceptors. In this study we investigated the pharmacological profile of mGlu2/3 receptors in selected CNS regions and evaluated their functions in mice with experimental autoimmune encephalomyelitis (EAE). EXPERIMENTAL APPROACH The comparative analysis of presynaptic mGlu2/3 autoreceptors was performed by determining the effect of selective mGlu2/3 receptor agonist(s) and antagonist(s) on the release of [(3)H]-D-aspartate from cortical and spinal cord synaptosomes in superfusion. In EAE mice, mGlu2/3 autoreceptor-mediated release functions were investigated and effects of in vivo LY379268 administration on impaired glutamate release examined ex vivo. KEY RESULTS Western blot analysis and confocal microscopy confirmed the presence of presynaptic mGlu2/3 receptor proteins. Cortical synaptosomes possessed LY541850-sensitive, NAAG-insensitive autoreceptors having low affinity for LY379268, while LY541850-insensitive, NAAG-sensitive autoreceptors with high affinity for LY379268 existed in spinal cord terminals. In EAE mice, mGlu2/3 autoreceptors completely lost their inhibitory activity in cortical, but not in spinal cord synaptosomes. In vivo LY379268 administration restored the glutamate exocytosis capability in spinal cord but not in cortical terminals in EAE mice. CONCLUSIONS AND IMPLICATIONS We propose the existence of mGlu2-preferring and mGlu3-preferring autoreceptors in mouse cortex and spinal cord respectively. The mGlu3 -preferring autoreceptors could represent a target for new pharmacological approaches for treating demyelinating diseases.
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Affiliation(s)
- Silvia Di Prisco
- Department of Pharmacy, DiFAR, Pharmacology and Toxicology Section, University of Genoa, Genoa, Italy
| | - Elisa Merega
- Department of Pharmacy, DiFAR, Pharmacology and Toxicology Section, University of Genoa, Genoa, Italy
| | - Tommaso Bonfiglio
- Department of Pharmacy, DiFAR, Pharmacology and Toxicology Section, University of Genoa, Genoa, Italy
| | - Guendalina Olivero
- Department of Pharmacy, DiFAR, Pharmacology and Toxicology Section, University of Genoa, Genoa, Italy
| | - Chiara Cervetto
- Department of Pharmacy, DiFAR, Pharmacology and Toxicology Section, University of Genoa, Genoa, Italy
| | - Massimo Grilli
- Department of Pharmacy, DiFAR, Pharmacology and Toxicology Section, University of Genoa, Genoa, Italy
| | - Cesare Usai
- Institute of Biophysics, National Research Council, Genoa, Italy
| | - Mario Marchi
- Department of Pharmacy, DiFAR, Pharmacology and Toxicology Section, University of Genoa, Genoa, Italy.,Center of Excellence for Biomedical Research, University of Genoa, Genoa, Italy
| | - Anna Pittaluga
- Department of Pharmacy, DiFAR, Pharmacology and Toxicology Section, University of Genoa, Genoa, Italy.,Center of Excellence for Biomedical Research, University of Genoa, Genoa, Italy
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19
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Chiechio S. Modulation of Chronic Pain by Metabotropic Glutamate Receptors. PHARMACOLOGICAL MECHANISMS AND THE MODULATION OF PAIN 2016; 75:63-89. [DOI: 10.1016/bs.apha.2015.11.001] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
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20
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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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21
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Li C, Rainnie DG. Bidirectional regulation of synaptic plasticity in the basolateral amygdala induced by the D1-like family of dopamine receptors and group II metabotropic glutamate receptors. J Physiol 2014; 592:4329-51. [PMID: 25107924 PMCID: PMC4215780 DOI: 10.1113/jphysiol.2014.277715] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Accepted: 07/22/2014] [Indexed: 12/31/2022] Open
Abstract
Competing mechanisms of long-term potentiation (LTP) and long-term depression (LTD) in principal neurons of the basolateral amygdala (BLA) are thought to underlie the acquisition and consolidation of fear memories, and their subsequent extinction. However, no study to date has examined the locus of action and/or the cellular mechanism(s) by which these processes interact. Here, we report that synaptic plasticity in the cortical pathway onto BLA principal neurons is frequency-dependent and shows a transition from LTD to LTP at stimulation frequencies of ∼10 Hz. At the crossover point from LTD to LTP induction we show that concurrent activation of D1 and group II metabotropic glutamate (mGluR2/3) receptors act to nullify any net change in synaptic strength. Significantly, blockade of either D1 or mGluR2/3 receptors unmasked 10 Hz stimulation-induced LTD and LTP, respectively. Significantly, prior activation of presynaptic D1 receptors caused a time-dependent attenuation of mGluR2/3-induced depotentiation of previously induced LTP. Furthermore, studies with cell type-specific postsynaptic transgene expression of designer receptors activated by designer drugs (DREADDs) suggest that the interaction results via bidirectional modulation of adenylate cyclase activity in presynaptic glutamatergic terminals. The results of our study raise the possibility that the temporal sequence of activation of either presynaptic D1 receptors or mGluR2/3 receptors may critically regulate the direction of synaptic plasticity in afferent pathways onto BLA principal neurons. Hence, the interaction of these two neurotransmitter systems may represent an important mechanism for bidirectional metaplasticity in BLA circuits and thus modulate the acquisition and extinction of fear memory.
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Affiliation(s)
- Chenchen Li
- Division of Behavioural Neuroscience & Psychiatric Disorders, Yerkes National Primate Research Center, Atlanta, GA, 30329, USA Department of Psychiatry, Emory University School of Medicine, Atlanta, GA, 30329, USA
| | - Donald G Rainnie
- Division of Behavioural Neuroscience & Psychiatric Disorders, Yerkes National Primate Research Center, Atlanta, GA, 30329, USA Department of Psychiatry, Emory University School of Medicine, Atlanta, GA, 30329, USA
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22
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Palazzo E, Marabese I, de Novellis V, Rossi F, Maione S. Supraspinal metabotropic glutamate receptors: a target for pain relief and beyond. Eur J Neurosci 2014; 39:444-54. [PMID: 24494684 DOI: 10.1111/ejn.12398] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2013] [Revised: 09/20/2013] [Accepted: 09/23/2013] [Indexed: 01/09/2023]
Abstract
Glutamate is the main excitatory neurotransmitter in the central nervous system, controlling the majority of synapses. Apart from neurodegenerative diseases, growing evidence suggests that glutamate is involved in psychiatric and neurological disorders, including pain. Glutamate signaling is mediated via ionotropic glutamate receptors (iGluRs) and metabotropic glutamate receptors (mGluRs). So far, drugs acting via modulation of glutamatergic system are few in number, and all are associated with iGluRs and important side effects. The glutamatergic system may be finely modulated by mGluRs. Signaling via these receptors is slower and longer-lasting, and permits fine-tuning of glutamate transmission. There have been eight mGluRs cloned to date (mGluR1-mGluR8), and these are further divided into three groups on the basis of sequence homology, pharmacological profile, and second messenger signaling. The pattern of expression of mGluRs along the pain neuraxis makes them suitable substrates for the design of novel analgesics. This review will focus on the supraspinal mGluRs, whose pharmacological manipulation generates a variety of effects, which depend on the synaptic location, the cell type on which they are located, and the expression in particular pain modulation areas, such as the periaqueductal gray, which plays a major role in the descending modulation of pain, and the central nucleus of the amygdala, which is an important center for the processing of emotional information associated with pain. A particular emphasis will also be given to the novel selective mGluR subtype ligands, as well as positive and negative allosteric modulators, which have permitted discrimination of the individual roles of the different mGluR subtypes, and subtle modulation of central nervous system functioning and related disorders.
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Affiliation(s)
- Enza Palazzo
- Department of Anaesthesiology, Surgery and Emergency, The Second University of Naples, Piazza Luigi Miraglia 2, 80138, Naples, Italy
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23
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Ohi Y, Kimura S, Haji A. Modulation of glutamatergic transmission by metabotropic glutamate receptor activation in second-order neurons of the guinea pig nucleus tractus solitarius. Brain Res 2014; 1581:12-22. [DOI: 10.1016/j.brainres.2014.04.031] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Revised: 04/10/2014] [Accepted: 04/23/2014] [Indexed: 11/30/2022]
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24
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Chen SR, Chen H, Yuan WX, Wess J, Pan HL. Differential regulation of primary afferent input to spinal cord by muscarinic receptor subtypes delineated using knockout mice. J Biol Chem 2014; 289:14321-30. [PMID: 24695732 DOI: 10.1074/jbc.m114.550384] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Stimulation of muscarinic acetylcholine receptors (mAChRs) inhibits nociceptive transmission at the spinal level. However, it is unclear how each mAChR subtype regulates excitatory synaptic input from primary afferents. Here we examined excitatory postsynaptic currents (EPSCs) of dorsal horn neurons evoked by dorsal root stimulation in spinal cord slices from wild-type and mAChR subtype knock-out (KO) mice. In wild-type mice, mAChR activation with oxotremorine-M decreased the amplitude of monosynaptic EPSCs in ∼67% of neurons but increased it in ∼10% of neurons. The inhibitory effect of oxotremorine-M was attenuated by the M2/M4 antagonist himbacine in the majority of neurons, and the remaining inhibition was abolished by group II/III metabotropic glutamate receptor (mGluR) antagonists in wild-type mice. In M2/M4 double-KO mice, oxotremorine-M inhibited monosynaptic EPSCs in significantly fewer neurons (∼26%) and increased EPSCs in significantly more neurons (33%) compared with wild-type mice. Blocking group II/III mGluRs eliminated the inhibitory effect of oxotremorine-M in M2/M4 double-KO mice. In M2 single-KO and M4 single-KO mice, himbacine still significantly reduced the inhibitory effect of oxotremorine-M. However, the inhibitory and potentiating effects of oxotremorine-M on EPSCs in M3 single-KO and M1/M3 double-KO mice were similar to those in wild-type mice. In M5 single-KO mice, oxotremorine-M failed to potentiate evoked EPSCs, and its inhibitory effect was abolished by himbacine. These findings indicate that activation of presynaptic M2 and M4 subtypes reduces glutamate release from primary afferents. Activation of the M5 subtype either directly increases primary afferent input or inhibits it through indirectly stimulating group II/III mGluRs.
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Affiliation(s)
- Shao-Rui Chen
- From the Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030 and
| | - Hong Chen
- From the Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030 and
| | - Wei-Xiu Yuan
- From the Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030 and
| | - Jürgen Wess
- the Laboratory of Bioorganic Chemistry, NIDDK, National Institutes of Health, Bethesda, Maryland 20892
| | - Hui-Lin Pan
- From the Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030 and
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25
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Abstract
Metabotropic glutamate receptors (mGluRs) are found throughout thalamus and cortex and are clearly important to circuit behavior in both structures, and so considering only participation of ionotropic glutamate receptors (e.g., [R,S]-α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid [AMPA] and N-methyl-d-aspartate receptors [NMDA] receptors) in glutamatergic processing would be an unfortunate oversimplification. These mGluRs are found both postsynaptically, on target cells of glutamatergic afferents, and presynaptically, on various synaptic terminals themselves, and when activated, they produce prolonged effects lasting at least hundreds of msec to several sec and perhaps longer. Two main types exist: activation of group I mGluRs causes postsynaptic depolarization, and group II, hyperpolarization. Both types are implicated in synaptic plasticity, both short term and long term. Their evident importance in functioning of thalamus and cortex makes it critical to develop a better understanding of how these receptors are normally activated, especially because they also seem implicated in a wide range of neurological and cognitive pathologies.
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Bardoni R. Role of presynaptic glutamate receptors in pain transmission at the spinal cord level. Curr Neuropharmacol 2014; 11:477-83. [PMID: 24403871 PMCID: PMC3763755 DOI: 10.2174/1570159x11311050002] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2013] [Revised: 02/21/2013] [Accepted: 03/16/2013] [Indexed: 12/27/2022] Open
Abstract
Nociceptive primary afferents release glutamate, activating postsynaptic glutamate receptors on spinal cord dorsal horn neurons. Glutamate receptors, both ionotropic and metabotropic, are also expressed on presynaptic terminals, where they regulate neurotransmitter release. During the last two decades, a wide number of studies have characterized the properties of presynaptic glutamatergic receptors, particularly those expressed on primary afferent fibers. This review describes the subunit composition, distribution and function of presynaptic glutamate ionotropic (AMPA, NMDA, kainate) and metabotropic receptors expressed in rodent spinal cord dorsal horn. The role of presynaptic receptors in modulating nociceptive information in experimental models of acute and chronic pain will be also discussed.
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Affiliation(s)
- Rita Bardoni
- Department of Biomedical, metabolic and neural sciences, University of Modena and Reggio Emilia, Italy
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Onofrj M, Ciccocioppo F, Varanese S, di Muzio A, Calvani M, Chiechio S, Osio M, Thomas A. Acetyl-L-carnitine: from a biological curiosity to a drug for the peripheral nervous system and beyond. Expert Rev Neurother 2014; 13:925-36. [DOI: 10.1586/14737175.2013.814930] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Yan X, 严 喜, Weng HR, 翁 汉. Endogenous interleukin-1β in neuropathic rats enhances glutamate release from the primary afferents in the spinal dorsal horn through coupling with presynaptic N-methyl-D-aspartic acid receptors. J Biol Chem 2013; 288:30544-30557. [PMID: 24003233 DOI: 10.1074/jbc.m113.495465] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Excessive activation of glutamate receptors and overproduction of proinflammatory cytokines, including interleukin-1β (IL-1β) in the spinal dorsal horn, are key mechanisms underlying the development and maintenance of neuropathic pain. In this study, we investigated the mechanisms by which endogenous IL-1β alters glutamatergic synaptic transmission in the spinal dorsal horn in rats with neuropathic pain induced by ligation of the L5 spinal nerve. We demonstrated that endogenous IL-1β in neuropathic rats enhances glutamate release from the primary afferent terminals and non-NMDA glutamate receptor activities in postsynaptic neurons in the spinal dorsal horn. Myeloid differentiation primary response protein 88 (MyD88) is a mediator used by IL-1β to enhance non-NMDA glutamate receptor activities in postsynaptic neurons in the spinal dorsal horn. Presynaptic NMDA receptors are effector receptors used by the endogenous IL-1β to enhance glutamate release from the primary afferents in neuropathic rats. This is further supported by the fact that NMDA currents recorded from small neurons in the dorsal root ganglion of normal rats are potentiated by exogenous IL-1β. Furthermore, we provided evidence that functional coupling between IL-1β receptors and presynaptic NMDA receptors at the primary afferent terminals is mediated by the neutral sphingomyelinase/ceramide signaling pathway. Hence, functional coupling between IL-1β receptors and presynaptic NMDA receptors at the primary afferent terminals is a crucial mechanism leading to enhanced glutamate release and activation of non-NMDA receptors in the spinal dorsal horn neurons in neuropathic pain conditions. Interruption of such functional coupling could be an effective approach for the treatment of neuropathic pain.
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Affiliation(s)
- Xisheng Yan
- From the Department of Pharmaceutical and Biomedical Sciences, University of Georgia College of Pharmacy, Athens, Georgia 30602
| | - 喜胜 严
- From the Department of Pharmaceutical and Biomedical Sciences, University of Georgia College of Pharmacy, Athens, Georgia 30602
| | - Han-Rong Weng
- From the Department of Pharmaceutical and Biomedical Sciences, University of Georgia College of Pharmacy, Athens, Georgia 30602
| | - 汉荣 翁
- From the Department of Pharmaceutical and Biomedical Sciences, University of Georgia College of Pharmacy, Athens, Georgia 30602.
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De Pasquale R, Sherman SM. A modulatory effect of the feedback from higher visual areas to V1 in the mouse. J Neurophysiol 2013; 109:2618-31. [PMID: 23446698 PMCID: PMC3653048 DOI: 10.1152/jn.01083.2012] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2012] [Accepted: 02/26/2013] [Indexed: 11/22/2022] Open
Abstract
Using a mouse brain slice preparation, we studied the modulatory effects of a feedback projection from higher visual cortical areas, mostly or exclusively area LM (or V2), on two inputs to layer 4 cells in the first visual area (V1). The two inputs to these cells were geniculocortical and an unspecified intracortical input, possibly involving layer 6 cells. We found that activation of metabotropic glutamate receptors (mGluRs) from stimulation of the feedback projection reduced the evoked excitatory postsynaptic currents of both of these inputs to layer 4 but that this modulation acts in an input-specific way. Reducing the strength of the geniculocortical input in adults involved both presynaptic and postsynaptic group I mGluRs (although in younger animals presynaptic group II mGluRs were also involved), whereas modulation of the intracortical input acted entirely via postsynaptic group II mGluRs. These results demonstrate that one of the effects of this feedback pathway is to control the gain of geniculocortical transmission.
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Affiliation(s)
- Roberto De Pasquale
- Department of Neurobiology, University of Chicago, Chicago, Illinois 60637, USA
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Matsuta Y, Mally AD, Zhang F, Shen B, Wang J, Roppolo JR, de Groat WC, Tai C. Contribution of opioid and metabotropic glutamate receptor mechanisms to inhibition of bladder overactivity by tibial nerve stimulation. Am J Physiol Regul Integr Comp Physiol 2013; 305:R126-33. [PMID: 23576608 DOI: 10.1152/ajpregu.00572.2012] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The contribution of metabotropic glutamate receptors (mGluR) and opioid receptors to inhibition of bladder overactivity by tibial nerve stimulation (TNS) was investigated in cats under α-chloralose anesthesia using LY341495 (a group II mGluR antagonist) and naloxone (an opioid receptor antagonist). Slow infusion cystometry was used to measure the volume threshold (i.e., bladder capacity) for inducing a large bladder contraction. After measuring the bladder capacity during saline infusion, 0.25% acetic acid (AA) was infused to irritate the bladder, activate the nociceptive C-fiber bladder afferents, and induce bladder overactivity. AA significantly (P < 0.0001) reduced bladder capacity to 26.6 ± 4.7% of saline control capacity. TNS (5 Hz, 0.2 ms) at 2 and 4 times the threshold (T) intensity for inducing an observable toe movement significantly increased bladder capacity to 62.2 ± 8.3% at 2T (P < 0.01) and 80.8 ± 9.2% at 4T (P = 0.0001) of saline control capacity. LY341495 (0.1-5 mg/kg iv) did not change bladder overactivity, but completely suppressed the inhibition induced by TNS at a low stimulus intensity (2T) and partially suppressed the inhibition at high intensity (4T). Following administration of LY341495, naloxone (0.01 mg/kg iv) completely eliminated the high-intensity TNS-induced inhibition. However, without LY341495 treatment a 10 times higher dose (0.1 mg/kg) of naloxone was required to completely block TNS inhibition. These results indicate that interactions between group II mGluR and opioid receptor mechanisms contribute to TNS inhibition of AA-induced bladder overactivity. Understanding neurotransmitter mechanisms underlying TNS inhibition of bladder overactivity is important for the development of new treatments for bladder disorders.
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Affiliation(s)
- Yosuke Matsuta
- Department of Urology, University of Pittsburgh, Pittsburgh, PA 15213, USA
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Yan X, Jiang E, Gao M, Weng HR. Endogenous activation of presynaptic NMDA receptors enhances glutamate release from the primary afferents in the spinal dorsal horn in a rat model of neuropathic pain. J Physiol 2013; 591:2001-19. [PMID: 23359671 DOI: 10.1113/jphysiol.2012.250522] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Activation of N-methyl-D-aspartate (NMDA) receptors (NMDARs) is a crucial mechanism underlying the development and maintenance of pain. Traditionally, the role of NMDARs in the pathogenesis of pain is ascribed to their activation and signalling cascades in postsynaptic neurons. In this study, we determined if presynaptic NMDARs in the primary afferent central terminals play a role in synaptic plasticity of the spinal first sensory synapse in a rat model of neuropathic pain induced by spinal nerve ligation. Excitatory postsynaptic currents (EPSCs) were recorded from superficial dorsal horn neurons of spinal slices taken from young adult rats. We showed that increased glutamate release from the primary afferents contributed to the enhanced amplitudes of EPSCs evoked by input from the primary afferents in neuropathic rats. Endogenous activation of presynaptic NMDARs increased glutamate release from the primary afferents in neuropathic rats. Presynaptic NMDARs in neuropathic rats were mainly composed of NR2B receptors. The action of presynaptic NMDARs in neuropathic rats was enhanced by exogenous D-serine and/or NMDA and dependent on activation of protein kinase C. In contrast, glutamate release from the primary afferents in sham-operated rats was not regulated by presynaptic NMDARs. We demonstrated that the lack of NMDAR-mediated regulation of glutamate release in sham-operated rats was not attributable to low extracellular levels of the NMDAR agonist and/or coagonist (D-serine), but rather was due to the insufficient function and/or number of presynaptic NMDARs. This was supported by an increase of NR2B receptor protein expression in both the dorsal root ganglion and spinal dorsal horn ipsilateral to the injury site in neuropathic rats. Hence, suppression of the presynaptic NMDAR activity in the primary sensory afferents is an effective approach to attenuate the enhanced glutamatergic response in the spinal first sensory synapse induced by peripheral nerve injury, and presynaptic NMDARs might be a novel target for the development of analgesics.
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Affiliation(s)
- Xisheng Yan
- Department of Pharmaceutical and Biomedical Sciences, The University of Georgia College of Pharmacy, Athens, GA 30602, USA
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Bernabucci M, Notartomaso S, Zappulla C, Fazio F, Cannella M, Motolese M, Battaglia G, Bruno V, Gradini R, Nicoletti F. N-Acetyl-cysteine causes analgesia by reinforcing the endogenous activation of type-2 metabotropic glutamate receptors. Mol Pain 2012; 8:77. [PMID: 23088864 PMCID: PMC3543227 DOI: 10.1186/1744-8069-8-77] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2012] [Accepted: 09/28/2012] [Indexed: 01/21/2023] Open
Abstract
Background Pharmacological activation of type-2 metabotropic glutamate receptors (mGlu2 receptors) causes analgesia in experimental models of inflammatory and neuropathic pain. Presynaptic mGlu2 receptors are activated by the glutamate released from astrocytes by means of the cystine/glutamate antiporter (System xc- or Sxc-). We examined the analgesic activity of the Sxc- activator, N-acetyl-cysteine (NAC), in mice developing inflammatory or neuropathic pain. Results A single injection of NAC (100 mg/kg, i.p.) reduced nocifensive behavior in the second phase of the formalin test. NAC-induced analgesia was abrogated by the Sxc- inhibitor, sulphasalazine (8 mg/kg, i.p.) or by the mGlu2/3 receptor antagonist, LY341495 (1 mg/kg, i.p.). NAC still caused analgesia in mGlu3−/− mice, but was inactive in mGlu2−/− mice. In wild-type mice, NAC retained the analgesic activity in the formalin test when injected daily for 7 days, indicating the lack of tolerance. Both single and repeated injections of NAC also caused analgesia in the complete Freund’s adjuvant (CFA) model of chronic inflammatory pain, and, again, analgesia was abolished by LY341495. Data obtained in mice developing neuropathic pain in response to chronic constriction injury (CCI) of the sciatic nerve were divergent. In this model, a single injection of NAC caused analgesia that was reversed by LY341495, whereas repeated injections of NAC were ineffective. Thus, tolerance to NAC-induced analgesia developed in the CCI model, but not in models of inflammatory pain. The CFA and CCI models differed with respect to the expression levels of xCT (the catalytic subunit of Sxc-) and activator of G-protein signaling type-3 (AGS3) in the dorsal portion of the lumbar spinal cord. CFA-treated mice showed no change in either protein, whereas CCI mice showed an ipislateral reduction in xCT levels and a bilateral increase in AGS3 levels in the spinal cord. Conclusions These data demonstrate that pharmacological activation of Sxc- causes analgesia by reinforcing the endogenous activation of mGlu2 receptors. NAC has an excellent profile of safety and tolerability when clinically used as a mucolytic agent or in the management of acetaminophen overdose. Thus, our data encourage the use of NAC for the experimental treatment of inflammatory pain in humans.
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Osikowicz M, Mika J, Przewlocka B. The glutamatergic system as a target for neuropathic pain relief. Exp Physiol 2012; 98:372-84. [PMID: 23002244 DOI: 10.1113/expphysiol.2012.069922] [Citation(s) in RCA: 100] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Glutamate is the major excitatory neurotransmitter in the mammalian CNS. The understanding of glutamatergic transmission in the nervous system has been greatly expanded with the discovery and investigation of the family of ionotropic and metabotropic glutamate receptors (mGluRs). Metabotropic glutamate receptors are localized at nerve terminals, postsynaptic sites and glial cells and thus, they can influence and modulate the action of glutamate at different levels in the synapse. Moreover, there is substantial evidence of glial participation in glutamate nociceptive processes and neuropathic pain. Metabotropic glutamate receptors have been shown to play a role in neuropathic pain, which is one of the most troublesome illnesses because the therapy is still not satisfactory. Recently, the development of selective mGluR ligands has provided important tools for further investigation of the role of mGluRs in the modulation of chronic pain processing. This paper presents a review of the literature of glutamate receptors in neuropathic pain and the role of glia in these effects. Specifically, pharmacological interventions aimed at inhibiting group I mGluRs and/or potentiating group II and III mGluR-mediated signalling is discussed. Moreover, we introduce data about the role of glutamate transporters. They are responsible for the level of glutamate in the synaptic cleft and thus regulate the effects of all three groups of mGluRs and, in consequence, the activity of this system in nociceptive transmission. Additionally, the question of how the modulation of the glutamatergic system influences the effectiveness of analgesic drugs used in neuropathic pain therapy is addressed.
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Affiliation(s)
- Maria Osikowicz
- Department of Pain Pharmacology, Institute of Pharmacology, Polish Academy of Sciences, Krakow, Poland
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Abstract
Glutamatergic pathways in various thalamic and cortical circuits have been classified into two types: Class 1 and Class 2, where it has been suggested that Class 1 carries the main information for processing, and Class 2 is mainly modulatory. We now extend this to the local circuitry of visual cortex of the mouse by demonstrating the modulatory actions on the Class 1 pathway from layer 4 to layers 2/3 of a Class 2 input from adjacent locations in layers 2/3. We found that this Class 2 input produces a long-lasting hyperpolarization and suppresses the initial responses of input from layer 4 and that this involves the postsynaptic activation of Group II metabotropic glutamate receptors. This modulation also shifts the paired pulse ratio of the layer 4 input from depression to facilitation.
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Romei C, Raiteri M, Raiteri L. Glycine release is regulated by metabotropic glutamate receptors sensitive to mGluR2/3 ligands and activated by N-acetylaspartylglutamate (NAAG). Neuropharmacology 2012; 66:311-6. [PMID: 22659408 DOI: 10.1016/j.neuropharm.2012.05.030] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2012] [Revised: 04/30/2012] [Accepted: 05/22/2012] [Indexed: 10/28/2022]
Abstract
The presence of metabotropic glutamate receptors (mGluRs) of group II modulating glycine exocytosis from glycinergic nerve endings of mouse spinal cord was investigated. Purified synaptosomes were selectively prelabeled with [(3)H]glycine through the neuronal transporter GlyT2 and subsequently depolarized by superfusion with 12 mM KCl. The selective mGluR2/3 agonist LY379268 inhibited the K(+)-evoked overflow of [(3)H]glycine in a concentration-dependent manner (EC(50) about 0.2 nM). The effect of LY379268 was prevented by the selective mGluR2/3 antagonist LY341495 (IC(50) about 1 nM). N-acetylaspartylglutamate (NAAG) inhibited [(3)H]glycine overflow with extraordinary potency (EC(50) about 50 fmol). In contrast, glutamate was ineffective up to 0.1 nM, excluding that glutamate contamination of commercial NAAG samples is responsible for the reported activity of NAAG at mGluR3. LY341495 antagonized the NAAG inhibition of [(3)H]glycine release. The effect of a combination of maximally effective concentrations of LY379268 and NAAG exhibited no additivity. The non-hydrolysable NAAG analogue N-acetylaspartyl-β-linked glutamate (β-NAAG) antagonized NAAG and LY379268. In conclusion, our results show that glycinergic nerve endings in spinal cord are endowed with group II mGluRs mediating inhibition of glycine exocytosis. NAAG can activate these presynaptic receptors with extremely high affinity and with characteristics compatible with the reported mGluR3 pharmacology. This article is part of a Special Issue entitled 'Metabotropic Glutamate Receptors'.
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Affiliation(s)
- Cristina Romei
- Department of Experimental Medicine, Pharmacology and Toxicology Unit, University of Genoa, Genoa, Italy
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37
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Doehring A, Geisslinger G, Lötsch J. Epigenetics in pain and analgesia: An imminent research field. Eur J Pain 2012; 15:11-6. [DOI: 10.1016/j.ejpain.2010.06.004] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2010] [Revised: 04/15/2010] [Accepted: 06/01/2010] [Indexed: 01/13/2023]
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Chiechio S, Nicoletti F. Metabotropic glutamate receptors and the control of chronic pain. Curr Opin Pharmacol 2011; 12:28-34. [PMID: 22040745 DOI: 10.1016/j.coph.2011.10.010] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2011] [Revised: 10/10/2011] [Accepted: 10/10/2011] [Indexed: 01/13/2023]
Abstract
Over the past two decades metabotropic glutamate (mGlu) receptor ligands have been investigated for their potential therapeutic effects in different disorders of the central nervous system (CNS), including anxiety, depression, schizophrenia, and neurodegenerative diseases. In addition, it has been widely demonstrated that mGlu receptors are able to modulate pain transmission both in inflammatory and neuropathic pain models. A large number of preclinical studies combining the use of selective ligands with the knockout strategy have revealed more details about the role of the different mGlu receptor subtypes in the modulation of pain information. This review will address the role of mGlu receptors in pain sensitivity focusing on different strategies to achieve pain control by targeting specific mGlu receptor subtypes. Specifically, pharmacological interventions aimed at inhibiting group I mGlu receptor-mediated signaling and/or potentiating groups II and III mGlu receptor signaling together with an epigenetic approach leading to an increased expression of mGlu2 receptors will be discussed.
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Carlton SM, Zhou S, Govea R, Du J. Group II/III metabotropic glutamate receptors exert endogenous activity-dependent modulation of TRPV1 receptors on peripheral nociceptors. J Neurosci 2011; 31:12727-37. [PMID: 21900552 PMCID: PMC3209953 DOI: 10.1523/jneurosci.6558-10.2011] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2010] [Revised: 07/07/2011] [Accepted: 07/14/2011] [Indexed: 12/13/2022] Open
Abstract
There is pharmacological evidence that group II and III metabotropic glutamate receptors (mGluRs) function as activity-dependent autoreceptors, inhibiting transmission in supraspinal sites. These receptors are expressed by peripheral nociceptors. We investigated whether mGluRs function as activity-dependent autoreceptors inhibiting pain transmission to the rat CNS, particularly transient receptor potential vanilloid 1 (TRPV1)-induced activity. Blocking peripheral mGluR activity by intraplantar injection of antagonists LY341495 [(2S)-2-amino-2-[(1S,2S)-2-carboxycycloprop-1-yl]-3-(xanth-9-yl) propanoic acid] (LY) (20, 100 μm, group II/III), APICA [(RS)-1-amino-5-phosphonoindan-1-carboxylic acid] (100 μm, group II), or UBP1112 (α-methyl-3-methyl-4-phosphonophenylglycine) (30 μm, group III) increased capsaicin (CAP)-induced nociceptive behaviors and nociceptor activity. In contrast, group II agonist APDC [(2R,4R)-4-aminopyrrolidine-2,4-dicarboxylate] (0.1 μm) or group III agonist l-(+)-2-amino-4-phosphonobutyric acid (l-AP-4) (10 μm) blocked the LY-induced increase. Ca(2+) imaging in dorsal root ganglion (DRG) cells confirmed LY enhanced CAP-induced Ca(2+) mobilization, which was blocked by APDC and l-AP-4. We hypothesized that excess glutamate (GLU) released by high intensity and/or prolonged stimulation endogenously activated group II/III, dampening nociceptor activation. In support of this, intraplantar GLU + LY produced heat hyperalgesia, and exogenous GLU + LY applied to nociceptors produced enhanced nociceptor activity and thermal sensitization. Intraplantar Formalin, known to elevate extracellular GLU, enhanced pain behaviors in the presence of LY. LY alone produced no pain behaviors, no change in nociceptor discharge rate or heat-evoked responses, and no change in cytosolic Ca(2+) in DRG cells, demonstrating a lack of tonic inhibitory control. Group II/III mGluRs maintain an activity-dependent autoinhibition, capable of significantly reducing TRPV1-induced activity. They are endogenously activated after high-frequency and/or prolonged nociceptor stimulation, acting as built-in negative modulators of TRPV1 and nociceptor function, reducing pain transmission to the CNS.
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Affiliation(s)
- Susan M Carlton
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, Texas 77555-1069, USA.
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mGlu2 metabotropic glutamate receptors restrain inflammatory pain and mediate the analgesic activity of dual mGlu2/mGlu3 receptor agonists. Mol Pain 2011; 7:6. [PMID: 21235748 PMCID: PMC3030510 DOI: 10.1186/1744-8069-7-6] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2010] [Accepted: 01/14/2011] [Indexed: 02/07/2023] Open
Abstract
Group II metabotropic glutamate receptors (mGluRs) couple to the inhibitory G-protein Gi. The group II mGluRs include two subtypes, mGlu2 and mGlu3, and their pharmacological activation produces analgesic effects in inflammatory and neuropathic pain states. However, the specific contribution of each one of the two subtypes has not been clarified due to the lack of selective orthosteric ligands that can discriminate between mGlu2 and mGlu3 subtypes. In this study we used mGlu2 or mGlu3 knock-out mice to dissect the specific role for these two receptors in the endogenous control of inflammatory pain and their specific contribution to the analgesic activity of mixed mGlu2/3 receptor agonists. Our results showed that mGlu2-/- mice display a significantly greater pain response compared to their wild type littermates. Interestingly the increased pain sensitivity in mGlu2-/- mice occurred only in the second phase of the formalin test. No differences were observed in the first phase. In contrast, mGlu3-/- mice did not significantly differ from their wild type littermates in either phase of the formalin test. When systemically injected, a single administration of the mGlu2/3 agonist, LY379268 (3 mg/kg, ip), showed a significant reduction of both phases in wild-type mice and in mGlu3-/- but not in mGlu2-/- mice. However tolerance to the analgesic effect of LY379268 (3 mg/kg, ip) in mGlu3-/- mice developed following 5 consecutive days of injection. Taken together, these results demonstrate that: (i) mGlu2 receptors play a predominant role over mGlu3 receptors in the control of inflammatory pain in mice; (ii) the analgesic activity of mixed mGlu2/3 agonists is entirely mediated by the activation of the mGlu2 subtype and (iii) the development of tolerance to the analgesic effect of mGlu2/3 agonists develops despite the lack of mGlu3 receptors.
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Zhou HY, Chen SR, Chen H, Pan HL. Functional plasticity of group II metabotropic glutamate receptors in regulating spinal excitatory and inhibitory synaptic input in neuropathic pain. J Pharmacol Exp Ther 2010; 336:254-64. [PMID: 20923868 DOI: 10.1124/jpet.110.173112] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Metabotropic glutamate receptors (mGluRs) are involved in the modulation of synaptic transmission and plasticity. Group II mGluRs in the spinal cord regulate glutamatergic input, but their functional changes in neuropathic pain are not clear. In this study, we determined the plasticity of spinal group II mGluRs in controlling excitatory and inhibitory synaptic transmission and nociception in neuropathic pain. Neuropathic pain was induced by spinal nerve ligation in rats, and whole-cell voltage-clamp recordings of glutamatergic excitatory postsynaptic currents (EPSCs) and spontaneous and miniature GABAergic and glycinergic inhibitory postsynaptic currents (sIPSCs and mIPSCs, respectively) were performed in spinal cord slices. The specific group II mGluR agonist (2S,2'R,3'R)-2-(2',3'-dicarboxycyclopropyl)glycine (DCG-IV) had a similar inhibitory effect on monosynaptic EPSCs evoked from the dorsal root in sham and nerve-injured rats. However, DCG-IV produced a greater inhibitory effect on evoked polysynaptic EPSCs and the frequency of spontaneous EPSCs in nerve-injured rats than in control rats. Although DCG-IV similarly reduced the frequency of GABAergic sIPSCs and mIPSCs in both groups, it distinctly inhibited the frequency of glycinergic sIPSCs and mIPSCs only in nerve-injured rats. The DCG-IV effect was blocked by the group II mGluR antagonist but not by the N-methyl-D-aspartate receptor antagonist. Strikingly, intrathecal injection of DCG-IV dose-dependently attenuated allodynia and hyperalgesia in nerve-injured rats but produced hyperalgesia in control rats. Our study provides new information that nerve injury up-regulates group II mGluRs present on glutamatergic and glycinergic interneurons in the spinal cord. Activation of group II mGluRs reduces neuropathic pain probably by attenuating glutamatergic and glycinergic input to spinal dorsal horn neurons.
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Affiliation(s)
- Hong-Yi Zhou
- Department of Anesthesiology and Perioperative Medicine, Unit 110, University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX 77030, USA
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42
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A new metabotropic glutamate receptor agonist with in vivo anti-allodynic activity. Bioorg Med Chem 2010; 18:6089-98. [DOI: 10.1016/j.bmc.2010.06.051] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2010] [Revised: 06/16/2010] [Accepted: 06/17/2010] [Indexed: 11/19/2022]
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43
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Liu XJ, Salter MW. Glutamate receptor phosphorylation and trafficking in pain plasticity in spinal cord dorsal horn. Eur J Neurosci 2010; 32:278-89. [PMID: 20629726 DOI: 10.1111/j.1460-9568.2010.07351.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Glutamate is the major excitatory neurotransmitter in the central nervous system. Considerable evidence suggests that both ionotropic and metabotropic glutamate receptors are involved in pain hypersensitivity. However, glutamate receptor-based therapies are limited by side-effects because the activities of glutamate receptors are essential for many important physiological functions. Here, we review recent key findings in molecular and cellular mechanisms of glutamate receptor regulation and their roles in triggering and sustaining pain hypersensitivity. Targeting these molecular mechanisms could form the basis for new therapeutic strategies for the treatment of chronic pain.
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Affiliation(s)
- Xue Jun Liu
- Program in Neurosciences & Mental Health, the Hospital for Sick Children, Toronto, ON, Canada
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Wu SX, Wang W, Li H, Wang YY, Feng YP, Li YQ. The synaptic connectivity that underlies the noxious transmission and modulation within the superficial dorsal horn of the spinal cord. Prog Neurobiol 2010; 91:38-54. [DOI: 10.1016/j.pneurobio.2010.01.005] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2009] [Revised: 12/10/2009] [Accepted: 01/14/2010] [Indexed: 01/27/2023]
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Kumar N, Laferriere A, Yu JSC, Poon T, Coderre TJ. Metabotropic glutamate receptors (mGluRs) regulate noxious stimulus-induced glutamate release in the spinal cord dorsal horn of rats with neuropathic and inflammatory pain. J Neurochem 2010; 114:281-90. [PMID: 20412385 DOI: 10.1111/j.1471-4159.2010.06761.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
In rats with persistent pain, spinal group I metabotropic glutamate receptor (mGluR) activity has been shown to be pronociceptive, whereas spinal group II/III activity is anti-nociceptive. In brain, group I mGluR activity produces positive feedback effects on glutamate release, whereas group II/III activity produces negative feedback effects. It is unknown whether the nociceptive versus anti-nociceptive effects of spinal group I versus group II/III mGluR activity depend on differential regulation of spinal glutamate release. Here, we used behavioral nociceptive testing and in vivo microdialysis to assess the effect of intrathecal treatment with group I mGluR antagonists [cyclopropan[b] chromen-1a-carboxylate, (CPCCOEt), 2-methyl-6-(phenylethynyl) pyridine (MPEP)] or groups II [aminopyrrolidine-2R,4R-dicarboxylate (APDC)] and III [l-2-amino-4-phosphonobutyrate (l-AP4)] mGluR agonists or vehicle, on nociception and noxious stimulus-induced increases in glutamate release in the spinal cord dorsal horn of rats with a chronic constriction injury (CCI) of the sciatic nerve or hind paw injection of complete Freund's adjuvant (CFA). None of the treatments significantly influenced basal spinal glutamate concentrations in either CCI or CFA rats. In CCI rats, formalin-induced nociception and increases in spinal glutamate concentrations were significantly attenuated by pre-treatment with CPCCOEt, MPEP, APDC, or l-AP4. In CFA rats, capsaicin-induced increases in nociception and spinal glutamate concentrations were significantly attenuated by pre-treatment with CPCCOEt, MPEP, or APDC, but not l-AP4. This study demonstrates that group I antagonists and group II/III mGluR agonists attenuated the enhanced nociception and noxious stimulus-induced glutamate release in spinal cord dorsal horn of CCI and/or CFA rats in vivo, and suggests a possible mechanism for their anti-hyperalgesic effects.
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Affiliation(s)
- Naresh Kumar
- Department of Anesthesia, McGill University, Montreal, Quebec, Canada H3G 1Y6
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The selective metabotropic glutamate receptor 7 allosteric agonist AMN082 inhibits inflammatory pain-induced and incision-induced hypersensitivity in rat. Behav Pharmacol 2009; 20:596-604. [DOI: 10.1097/fbp.0b013e32832ec5d1] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Chiechio S, Zammataro M, Caraci F, Rampello L, Copani A, Sabato AF, Nicoletti F. Pregabalin in the treatment of chronic pain: an overview. Clin Drug Investig 2009; 29:203-13. [PMID: 19243212 DOI: 10.2165/00044011-200929030-00006] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Chronic 'pathological' pain is sustained by mechanisms of peripheral and central sensitization, which are being increasingly investigated at the molecular and cellular levels. The molecular determinants of nociceptive sensitization are natural targets for potential analgesic drugs used in the treatment of different forms of pain. Most of these determinants are common to all forms of chronic pain, and it is therefore not surprising that drugs specifically targeted for the treatment of neuropathic pain are effective in relieving nociceptive inflammatory pain and vice versa. The molecular mechanisms of sensitization that occur in peripheral nociceptors and the dorsal horns of the spinal cord are putative targets for context-dependent drugs, i.e. drugs that are able to discriminate between 'normal' and 'pathological' pain transmission. Among these, pregabalin and gabapentin bind to the alpha(2)delta subunit of voltage-sensitive Ca2+ channels, which sustain the enhanced release of pain transmitters at the synapses between primary afferent fibres and second-order sensory neurons under conditions of chronic pain. Pregabalin in particular represents a remarkable example of a context-dependent analgesic drug that acts at a critical step of nociceptive sensitization. Preclinical and clinical data suggest that pregabalin is more than a structural and functional analogue of gabapentin and may be effective in the treatment of nociceptive inflammatory pain that is resistant to gabapentin.
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Affiliation(s)
- S Chiechio
- Department of Pharmaceutical Sciences, University of Catania, Catania, Italy
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Chiechio S, Zammataro M, Morales ME, Busceti CL, Drago F, Gereau RW, Copani A, Nicoletti F. Epigenetic Modulation of mGlu2 Receptors by Histone Deacetylase Inhibitors in the Treatment of Inflammatory Pain. Mol Pharmacol 2009; 75:1014-20. [DOI: 10.1124/mol.108.054346] [Citation(s) in RCA: 152] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
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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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Zhang HM, Chen SR, Pan HL. Effects of activation of group III metabotropic glutamate receptors on spinal synaptic transmission in a rat model of neuropathic pain. Neuroscience 2008; 158:875-84. [PMID: 19017536 DOI: 10.1016/j.neuroscience.2008.10.042] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2008] [Revised: 10/15/2008] [Accepted: 11/20/2008] [Indexed: 11/18/2022]
Abstract
Chronic neuropathic pain remains an unmet clinical problem because it is often resistant to conventional analgesics. Metabotropic glutamate receptors (mGluRs) are involved in nociceptive processing at the spinal level, but their functions in neuropathic pain are not fully known. In this study, we investigated the role of group III mGluRs in the control of spinal excitatory and inhibitory synaptic transmission in a rat model of neuropathic pain induced by L5/L6 spinal nerve ligation. Whole-cell recording of lamina II neurons was performed in spinal cord slices from control and nerve-ligated rats. The baseline amplitude of glutamatergic EPSCs evoked from primary afferents was significantly larger in nerve-injured rats than in control rats. However, the baseline frequency of GABAergic and glycinergic inhibitory postsynaptic currents (IPSCs) was much lower in nerve-injured rats than in control rats. The group III mGluR agonist l(+)-2-amino-4-phosphonbutyric acid (l-AP4) produced a greater inhibition of the amplitude of monosynaptic and polysynaptic evoked EPSCs in nerve-injured rats than in control rats. l-AP4 inhibited the frequency of miniature EPSCs in 66.7% of neurons in control rats but its inhibitory effect was observed in all neurons tested in nerve-injured rats. Furthermore, l-AP4 similarly inhibited the frequency of GABAergic and glycinergic IPSCs in control and nerve-injured rats. Our study suggests that spinal nerve injury augments glutamatergic input from primary afferents but decreases GABAergic and glycinergic input to spinal dorsal horn neurons. Activation of group III mGluRs attenuates glutamatergic input from primary afferents in nerve-injured rats, which could explain the antinociceptive effect of group III mGluR agonists on neuropathic pain.
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Affiliation(s)
- H-M Zhang
- Department of Anesthesiology and Pain Medicine, Unit 110, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA
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