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Wang WT, Feng F, Zhang MM, Tian X, Yang QQ, Li YJ, Tao XX, Xu YL, Dou E, Wang JY, Zeng XY. Red nucleus mGluR2 but not mGluR3 mediates inhibitory effect in the development of SNI-induced neuropathological pain by suppressing the expressions of TNF-α and IL-1β. Neurochem Int 2024; 179:105840. [PMID: 39181245 DOI: 10.1016/j.neuint.2024.105840] [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: 07/08/2024] [Revised: 08/08/2024] [Accepted: 08/21/2024] [Indexed: 08/27/2024]
Abstract
Our previous study has verified that activation of group Ⅰ metabotropic glutamate receptors (mGluRⅠ) in the red nucleus (RN) facilitate the development of neuropathological pain. Here, we further discussed the functions and possible molecular mechanisms of red nucleus mGluR Ⅱ (mGluR2 and mGluR3) in the development of neuropathological pain induced by spared nerve injury (SNI). Our results showed that mGluR2 and mGluR3 both were constitutively expressed in the RN of normal rats. At 2 weeks post-SNI, the protein expression of mGluR2 rather than mGluR3 was significantly reduced in the RN contralateral to the nerve lesion. Injection of mGluR2/3 agonist LY379268 into the RN contralateral to the nerve injury at 2 weeks post-SNI significantly attenuated SNI-induced neuropathological pain, this effect was reversed by mGluR2/3 antagonist EGLU instead of selective mGluR3 antagonist β-NAAG. Intrarubral injection of LY379268 did not alter the PWT of contralateral hindpaw in normal rats, while intrarubral injection of EGLU rather than β-NAAG provoked a significant mechanical allodynia. Further studies indicated that the expressions of nociceptive factors TNF-α and IL-1β in the RN were enhanced at 2 weeks post-SNI. Intrarubral injection of LY379268 at 2 weeks post-SNI significantly suppressed the overexpressions of TNF-α and IL-1β, these effects were reversed by EGLU instead of β-NAAG. Intrarubral injection of LY379268 did not influence the protein expressions of TNF-α and IL-1β in normal rats, while intrarubral injection of EGLU rather than β-NAAG significantly boosted the expressions of TNF-α and IL-1β. These findings suggest that red nucleus mGluR2 but not mGluR3 mediates inhibitory effect in the development of SNI-induced neuropathological pain by suppressing the expressions of TNF-α and IL-1β. mGluR Ⅱ may be potential targets for drug development and clinical treatment of neuropathological pain.
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Affiliation(s)
- Wen-Tao Wang
- Department of Laboratory Medicine, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, 710061, Shaanxi, China; Department of Pathogenic Biology and Immunology, Xi'an Jiaotong University Health Science Center, Xi'an, 710061, Shaanxi, China
| | - Fan Feng
- Department of Pathogenic Biology and Immunology, Xi'an Jiaotong University Health Science Center, Xi'an, 710061, Shaanxi, China
| | - Miao-Miao Zhang
- Department of Pathogenic Biology and Immunology, Xi'an Jiaotong University Health Science Center, Xi'an, 710061, Shaanxi, China
| | - Xue Tian
- Department of Pathogenic Biology and Immunology, Xi'an Jiaotong University Health Science Center, Xi'an, 710061, Shaanxi, China
| | - Qing-Qing Yang
- Department of Laboratory Medicine, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, 710061, Shaanxi, China; Department of Pathogenic Biology and Immunology, Xi'an Jiaotong University Health Science Center, Xi'an, 710061, Shaanxi, China
| | - Yue-Jia Li
- Department of Pathogenic Biology and Immunology, Xi'an Jiaotong University Health Science Center, Xi'an, 710061, Shaanxi, China
| | - Xiao-Xia Tao
- Department of Pathogenic Biology and Immunology, Xi'an Jiaotong University Health Science Center, Xi'an, 710061, Shaanxi, China
| | - Ya-Li Xu
- Department of Pathogenic Biology and Immunology, Xi'an Jiaotong University Health Science Center, Xi'an, 710061, Shaanxi, China; Department of Blood Transfusion, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, 710061, Shaanxi, China
| | - E Dou
- Department of Pathogenic Biology and Immunology, Xi'an Jiaotong University Health Science Center, Xi'an, 710061, Shaanxi, China
| | - Jun-Yang Wang
- Department of Pathogenic Biology and Immunology, Xi'an Jiaotong University Health Science Center, Xi'an, 710061, Shaanxi, China.
| | - Xiao-Yan Zeng
- Department of Laboratory Medicine, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, 710061, Shaanxi, China.
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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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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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Ghosh K, Zhang GF, Chen H, Chen SR, Pan HL. Cannabinoid CB2 receptors are upregulated via bivalent histone modifications and control primary afferent input to the spinal cord in neuropathic pain. J Biol Chem 2022; 298:101999. [PMID: 35500651 PMCID: PMC9168157 DOI: 10.1016/j.jbc.2022.101999] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2021] [Revised: 04/25/2022] [Accepted: 04/26/2022] [Indexed: 11/24/2022] Open
Abstract
Type-2 cannabinoid receptors (CB2, encoded by the Cnr2 gene) are mainly expressed in immune cells, and CB2 agonists normally have no analgesic effect. However, nerve injury upregulates CB2 in the dorsal root ganglion (DRG), following which CB2 stimulation reduces neuropathic pain. It is unclear how nerve injury increases CB2 expression or how CB2 activity is transformed in neuropathic pain. In this study, immunoblotting showed that spinal nerve ligation (SNL) induced a delayed and sustained increase in CB2 expression in the DRG and dorsal spinal cord synaptosomes. RNAscope in situ hybridization also showed that SNL substantially increased CB2 mRNA levels, mostly in medium and large DRG neurons. Furthermore, we found that the specific CB2 agonist JWH-133 significantly inhibits the amplitude of dorsal root-evoked glutamatergic excitatory postsynaptic currents in spinal dorsal horn neurons in SNL rats, but not in sham control rats; intrathecal injection of JWH-133 reversed pain hypersensitivity in SNL rats, but had no effect in sham control rats. In addition, chromatin immunoprecipitation-qPCR analysis showed that SNL increased enrichment of two activating histone marks (H3K4me3 and H3K9ac) and diminished occupancy of two repressive histone marks (H3K9me2 and H3K27me3) at the Cnr2 promoter in the DRG. In contrast, SNL had no effect on DNA methylation levels around the Cnr2 promoter. Our findings suggest that peripheral nerve injury promotes CB2 expression in primary sensory neurons via epigenetic bivalent histone modifications and that CB2 activation reduces neuropathic pain by attenuating nociceptive transmission from primary afferent nerves to the spinal cord.
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Affiliation(s)
- Krishna Ghosh
- Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA
| | - Guang-Fen Zhang
- Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA
| | - Hong Chen
- Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA
| | - Shao-Rui Chen
- Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA.
| | - Hui-Lin Pan
- Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA.
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Mazzitelli M, Neugebauer V. Amygdala group II mGluRs mediate the inhibitory effects of systemic group II mGluR activation on behavior and spinal neurons in a rat model of arthritis pain. Neuropharmacology 2019; 158:107706. [PMID: 31306647 DOI: 10.1016/j.neuropharm.2019.107706] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Revised: 07/03/2019] [Accepted: 07/10/2019] [Indexed: 12/16/2022]
Abstract
The amygdala plays a critical role in emotional-affective aspects of behaviors and pain modulation. The central nucleus of amygdala (CeA) serves major output functions, and neuroplasticity in the CeA is linked to pain-related behaviors in different models. Activation of Gi/o-coupled group II metabotropic glutamate receptors (mGluRs), which consist of mGluR2 and mGluR3, can decrease neurotransmitter release and regulate synaptic plasticity. Group II mGluRs have emerged as targets for neuropsychiatric disorders and can inhibit pain-related processing and behaviors. Surprisingly, site and mechanism of antinociceptive actions of systemically applied group II mGluR agonists are not clear. Our previous work showed that group II mGluR activation in the amygdala inhibits pain-related CeA activity, but behavioral and spinal consequences remain to be determined. Here we studied the contribution of group II mGluRs in the amygdala to the antinociceptive effects of a systemically applied group II mGluR agonist (LY379268) on behavior and spinal dorsal horn neuronal activity, using the kaolin/carrageenan-induced knee joint arthritis pain model. Audible and ultrasonic vocalizations (emotional responses) and mechanical reflex thresholds were measured in adult rats with and without arthritis (5-6 h postinduction). Extracellular single-unit recordings were made from spinal dorsal horn wide dynamic range neurons of anesthetized (isoflurane) rats with and without arthritis (5-6 h postinduction). Systemic (intraperitoneal) application of a group II mGluR agonist (LY379268) decreased behaviors and activity of spinal neurons in the arthritis pain model but not under normal conditions. Stereotaxic administration of LY379268 into the CeA mimicked the effects of systemic application. Conversely, stereotaxic administration of a group II mGluR antagonist (LY341495) into the CeA reversed the effects of systemic application of LY379268 on behaviors and dorsal horn neuronal activity in arthritic rats. The data show for the first time that the amygdala is the critical site of action for the antinociceptive behavioral and spinal neuronal effects of systemically applied group II mGluR agonists.
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Affiliation(s)
- Mariacristina Mazzitelli
- Department of Pharmacology and Neuroscience, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX, 79430-6592, USA
| | - Volker Neugebauer
- Department of Pharmacology and Neuroscience, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX, 79430-6592, USA; Center of Excellence for Translational Neuroscience and Therapeutics, Texas Tech University Health Sciences Center, Lubbock, TX, 79430-6592, USA; Garrison Institute on Aging, Texas Tech University Health Sciences Center, Lubbock, TX, 79430-6592, USA.
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6
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A Systematic Review of NMDA Receptor Antagonists for Treatment of Neuropathic Pain in Clinical Practice. Clin J Pain 2019; 34:450-467. [PMID: 28877137 DOI: 10.1097/ajp.0000000000000547] [Citation(s) in RCA: 90] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
OBJECTIVE To investigate the efficacy of N-methyl-D-aspartate receptor (NMDAR) antagonists for neuropathic pain (NeuP) and review literature to determine if specific pharmacologic agents provide adequate NeuP relief. METHODS Literature was reviewed on PubMed using a variety of key words for 8 NMDAR antagonists. These key words include: "Ketamine and Neuropathy," "Ketamine and Neuropathic Pain," "Methadone and Neuropathy," "Methadone and Neuropathic Pain," "Memantine and Neuropathic pain," "Memantine and Neuropathy," "Amantadine and Neuropathic Pain," "Amantadine and Neuropathy," "Dextromethorphan and Neuropathic Pain," "Dextromethorphan and Neuropathy," "Carbamazepine and Neuropathic Pain," "Carbamazepine and Neuropathy," "Valproic Acid and Neuropathy," "Valproic Acid and Neuropathic Pain," "Phenytoin and Neuropathy," and "Phenytoin and Neuropathic Pain." With the results, the papers were reviewed using the PRISMA (Preferred Reporting in Systematic and Meta-Analyses) guideline. RESULTS A total of 58 randomized controlled trials were reviewed among 8 pharmacologic agents, which are organized by date and alphabetical order. Of the trials for ketamine, 15 showed some benefit for analgesia. Methadone had 3 positive trials, while amantadine and memantine each only had 2 trials showing NeuP analgesic properties. Dextromethorphan and valproic acid both had 4 randomized controlled trials that showed some NeuP treatment benefit while carbamazepine had over 8 trials showing efficacy. Finally, phenytoin only had 1 trial that showed clinical response in treatment. CONCLUSIONS There are a variety of NMDAR antagonist agents that should be considered for treatment of NeuP. Nevertheless, continued and further investigation of the 8 pharmacologic agents is needed to continue to evaluate their efficacy for treatment of NeuP.
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7
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Pereira V, Goudet C. Emerging Trends in Pain Modulation by Metabotropic Glutamate Receptors. Front Mol Neurosci 2019; 11:464. [PMID: 30662395 PMCID: PMC6328474 DOI: 10.3389/fnmol.2018.00464] [Citation(s) in RCA: 69] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Accepted: 11/30/2018] [Indexed: 12/20/2022] Open
Abstract
Pain is an essential protective mechanism meant to prevent tissue damages in organisms. On the other hand, chronic or persistent pain caused, for example, by inflammation or nerve injury is long lasting and responsible for long-term disability in patients. Therefore, chronic pain and its management represents a major public health problem. Hence, it is critical to better understand chronic pain molecular mechanisms to develop innovative and efficient drugs. Over the past decades, accumulating evidence has demonstrated a pivotal role of glutamate in pain sensation and transmission, supporting glutamate receptors as promising potential targets for pain relieving drug development. Glutamate is the most abundant excitatory neurotransmitter in the brain. Once released into the synapse, glutamate acts through ionotropic glutamate receptors (iGluRs), which are ligand-gated ion channels triggering fast excitatory neurotransmission, and metabotropic glutamate receptors (mGluRs), which are G protein-coupled receptors modulating synaptic transmission. Eight mGluRs subtypes have been identified and are divided into three classes based on their sequence similarities and their pharmacological and biochemical properties. Of note, all mGluR subtypes (except mGlu6 receptor) are expressed within the nociceptive pathways where they modulate pain transmission. This review will address the role of mGluRs in acute and persistent pain processing and emerging pharmacotherapies for pain management.
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Affiliation(s)
- Vanessa Pereira
- IGF, CNRS, INSERM, Univ. de Montpellier, Montpellier, France
| | - Cyril Goudet
- IGF, CNRS, INSERM, Univ. de Montpellier, Montpellier, France
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Bae C, Wang J, Shim HS, Tang SJ, Chung JM, La JH. Mitochondrial superoxide increases excitatory synaptic strength in spinal dorsal horn neurons of neuropathic mice. Mol Pain 2018; 14:1744806918797032. [PMID: 30152257 PMCID: PMC6113735 DOI: 10.1177/1744806918797032] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Reactive oxygen species has been suggested as a key player in neuropathic pain, causing central sensitization by changing synaptic strengths in spinal dorsal horn neurons. However, it remains unclear as to what type of reactive oxygen species changes what aspect of synaptic strengths for central sensitization in neuropathic pain conditions. In this study, we investigated whether mitochondrial superoxide affects both excitatory and inhibitory synaptic strengths in spinal dorsal horn neurons after peripheral nerve injury. Upregulation of mitochondrial superoxide level by knockout of superoxide dismutase-2 exacerbated neuropathic mechanical hypersensitivity caused by L5 spinal nerve ligation, whereas downregulation of mitochondrial superoxide level by overexpression of superoxide dismutase-2 alleviated the hypersensitivity. In spinal nerve ligation condition, the frequency of miniature excitatory postsynaptic currents increased, while that of miniature inhibitory postsynaptic currents decreased in spinal dorsal horn neurons. Superoxide dismutase-2-knockout augmented, whereas superoxide dismutase-2-overexpression prevented, the spinal nerve ligation-increased miniature excitatory postsynaptic currents frequency. However, superoxide dismutase-2-knockout had no effect on the spinal nerve ligation-decreased miniature inhibitory postsynaptic current frequency, and superoxide dismutase-2-overexpression unexpectedly decreased miniature inhibitory postsynaptic current frequency in the normal condition. When applied to the spinal cord slice during in vitro recordings, mitoTEMPO, a specific scavenger of mitochondrial superoxide, reduced the spinal nerve ligation-increased miniature excitatory postsynaptic currents frequency but failed to normalize the spinal nerve ligation-decreased miniature inhibitory postsynaptic current frequency. These results suggest that in spinal dorsal horn neurons, high levels of mitochondrial superoxide increase excitatory synaptic strength after peripheral nerve injury and contribute to neuropathic mechanical hypersensitivity. However, mitochondrial superoxide does not seem to be involved in the decreased inhibitory synaptic strength in this neuropathic pain condition.
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Affiliation(s)
- Chilman Bae
- 1 Department of Neuroscience, Cell Biology, and Anatomy, University of Texas Medical Branch, Galveston, TX, USA
| | - Jigong Wang
- 1 Department of Neuroscience, Cell Biology, and Anatomy, University of Texas Medical Branch, Galveston, TX, USA
| | - Hyun Soo Shim
- 1 Department of Neuroscience, Cell Biology, and Anatomy, University of Texas Medical Branch, Galveston, TX, USA
| | - Shao-Jun Tang
- 1 Department of Neuroscience, Cell Biology, and Anatomy, University of Texas Medical Branch, Galveston, TX, USA
| | - Jin Mo Chung
- 1 Department of Neuroscience, Cell Biology, and Anatomy, University of Texas Medical Branch, Galveston, TX, USA
| | - Jun-Ho La
- 1 Department of Neuroscience, Cell Biology, and Anatomy, University of Texas Medical Branch, Galveston, TX, USA
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Mazzitelli M, Palazzo E, Maione S, Neugebauer V. Group II Metabotropic Glutamate Receptors: Role in Pain Mechanisms and Pain Modulation. Front Mol Neurosci 2018; 11:383. [PMID: 30356691 PMCID: PMC6189308 DOI: 10.3389/fnmol.2018.00383] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2018] [Accepted: 09/24/2018] [Indexed: 12/12/2022] Open
Abstract
Glutamate is the main excitatory neurotransmitter in the nervous system and plays a critical role in nociceptive processing and pain modulation. G-protein coupled metabotropic glutamate receptors (mGluRs) are widely expressed in the central and peripheral nervous system, and they mediate neuronal excitability and synaptic transmission. Eight different mGluR subtypes have been identified so far, and are classified into Groups I-III. Group II mGluR2 and mGluR3 couple negatively to adenylyl cyclase through Gi/Go proteins, are mainly expressed presynaptically, and typically inhibit the release of neurotransmitters, including glutamate and GABA. Group II mGluRs have consistently been linked to pain modulation; they are expressed in peripheral, spinal and supraspinal elements of pain-related neural processing. Pharmacological studies have shown anti-nociceptive/analgesic effects of group II mGluR agonists in preclinical models of acute and chronic pain, although much less is known about mechanisms and sites of action for mGluR2 and mGluR3 compared to other mGluRs. The availability of orthosteric and new selective allosteric modulators acting on mGluR2 and mGluR3 has provided valuable tools for elucidating (subtype) specific contributions of these receptors to the pathophysiological mechanisms of pain and other disorders and their potential as therapeutic targets. This review focuses on the important role of group II mGluRs in the neurobiology of pain mechanisms and behavioral modulation, and discusses evidence for their therapeutic potential in pain.
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Affiliation(s)
- Mariacristina Mazzitelli
- Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center, Lubbock, TX, United States
| | - Enza Palazzo
- Section of Pharmacology L. Donatelli, Department of Experimental Medicine, University of Campania Luigi Vanvitelli, Naples, Italy
| | - Sabatino Maione
- Section of Pharmacology L. Donatelli, Department of Experimental Medicine, University of Campania Luigi Vanvitelli, Naples, Italy
| | - Volker Neugebauer
- Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center, Lubbock, TX, United States
- Center of Excellence for Translational Neuroscience and Therapeutics, Texas Tech University Health Sciences Center, Lubbock, TX, United States
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10
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Lian YN, Lu Q, Chang JL, Zhang Y. The role of glutamate and its receptors in central nervous system in stress-induced hyperalgesia. Int J Neurosci 2017; 128:283-290. [DOI: 10.1080/00207454.2017.1387112] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Yan-Na Lian
- Department of Physiology, Harbin Medical University, Harbin, P. R. China
| | - Qi Lu
- Department of Physiology, Harbin Medical University, Harbin, P. R. China
| | - Jin-Long Chang
- Department of Physiology, Harbin Medical University, Harbin, P. R. China
| | - Ying Zhang
- Department of Physiology, Harbin Medical University, Harbin, P. R. China
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11
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Notartomaso S, Mascio G, Bernabucci M, Zappulla C, Scarselli P, Cannella M, Imbriglio T, Gradini R, Battaglia G, Bruno V, Nicoletti F. Analgesia induced by the epigenetic drug, L-acetylcarnitine, outlasts the end of treatment in mouse models of chronic inflammatory and neuropathic pain. Mol Pain 2017; 13:1744806917697009. [PMID: 28326943 PMCID: PMC5407675 DOI: 10.1177/1744806917697009] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Background L-acetylcarnitine, a drug marketed for the treatment of chronic pain, causes analgesia by epigenetically up-regulating type-2 metabotropic glutamate (mGlu2) receptors in the spinal cord. Because the epigenetic mechanisms are typically long-lasting, we hypothesized that analgesia could outlast the duration of L-acetylcarnitine treatment in models of inflammatory and neuropathic pain. Results A seven-day treatment with L-acetylcarnitine (100 mg/kg, once a day, i.p.) produced an antiallodynic effect in the complete Freund adjuvant mouse model of chronic inflammatory pain. L-Acetylcarnitine-induced analgesia persisted for at least 14 days after drug withdrawal. In contrast, the analgesic effect of pregabalin, amitryptiline, ceftriaxone, and N-acetylcysteine disappeared seven days after drug withdrawal. L-acetylcarnitine treatment enhanced mGlu2/3 receptor protein levels in the dorsal region of the spinal cord. This effect also persisted for two weeks after drug withdrawal and was associated with increased levels of acetylated histone H3 bound to the Grm2 gene promoter in the dorsal root ganglia. A long-lasting analgesic effect of L-acetylcarnitine was also observed in mice subjected to chronic constriction injury of the sciatic nerve. In these animals, a 14-day treatment with pregabalin, amitryptiline, tramadol, or L-acetylcarnitine produced a significant antiallodynic effect, with pregabalin displaying the greatest efficacy. In mice treated with pregabalin, tramadol or L-acetylcarnitine the analgesic effect was still visible 15 days after the end of drug treatment. However, only in mice treated with L-acetylcarnitine analgesia persisted 37 days after drug withdrawal. This effect was associated with an increase in mGlu2/3 receptor protein levels in the dorsal horns of the spinal cord. Conclusions Our findings suggest that L-acetylcarnitine has the unique property to cause a long-lasting analgesic effect that might reduce relapses in patients suffering from chronic pain.
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Affiliation(s)
| | | | | | | | | | | | | | - Roberto Gradini
- 1 I.R.C.C.S. Neuromed, Pozzilli, Italy.,2 Department of Experimental Medicine, Sapienza University, Rome, Italy
| | | | - Valeria Bruno
- 1 I.R.C.C.S. Neuromed, Pozzilli, Italy.,3 Department of Physiology and Pharmacology, Sapienza University, Rome, Italy
| | - Ferdinando Nicoletti
- 1 I.R.C.C.S. Neuromed, Pozzilli, Italy.,3 Department of Physiology and Pharmacology, Sapienza University, Rome, Italy
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12
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Spontaneous Release Regulates Synaptic Scaling in the Embryonic Spinal Network In Vivo. J Neurosci 2017; 36:7268-82. [PMID: 27383600 DOI: 10.1523/jneurosci.4066-15.2016] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2015] [Accepted: 05/26/2016] [Indexed: 12/13/2022] Open
Abstract
UNLABELLED Homeostatic plasticity mechanisms maintain cellular or network spiking activity within a physiologically functional range through compensatory changes in synaptic strength or intrinsic cellular excitability. Synaptic scaling is one form of homeostatic plasticity that is triggered after blockade of spiking or neurotransmission in which the strengths of all synaptic inputs to a cell are multiplicatively scaled upward or downward in a compensatory fashion. We have shown previously that synaptic upscaling could be triggered in chick embryo spinal motoneurons by complete blockade of spiking or GABAA receptor (GABAAR) activation for 2 d in vivo Here, we alter GABAAR activation in a more physiologically relevant manner by chronically adjusting presynaptic GABA release in vivo using nicotinic modulators or an mGluR2 agonist. Manipulating GABAAR activation in this way triggered scaling in a mechanistically similar manner to scaling induced by complete blockade of GABAARs. Remarkably, we find that altering action-potential (AP)-independent spontaneous release was able to fully account for the observed bidirectional scaling, whereas dramatic changes in spiking activity associated with spontaneous network activity had little effect on quantal amplitude. The reliance of scaling on an AP-independent process challenges the plasticity's relatedness to spiking in the living embryonic spinal network. Our findings have implications for the trigger and function of synaptic scaling and suggest that spontaneous release functions to regulate synaptic strength homeostatically in vivo SIGNIFICANCE STATEMENT Homeostatic synaptic scaling is thought to prevent inappropriate levels of spiking activity through compensatory adjustments in the strength of synaptic inputs. Therefore, it is thought that perturbations in spike rate trigger scaling. Here, we find that dramatic changes in spiking activity in the embryonic spinal cord have little effect on synaptic scaling; conversely, alterations in GABAA receptor activation due to action-potential-independent GABA vesicle release can trigger scaling. The findings suggest that scaling in the living embryonic spinal cord functions to maintain synaptic strength and challenge the view that scaling acts to regulate spiking activity homeostatically. Finally, the results indicate that fetal exposure to drugs that influence GABA spontaneous release, such as nicotine, could profoundly affect synaptic maturation.
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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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Cao DY, Bai G, Ji Y, Karpowicz JM, Traub RJ. EXPRESS: Histone hyperacetylation modulates spinal type II metabotropic glutamate receptor alleviating stress-induced visceral hypersensitivity in female rats. Mol Pain 2016; 12:1744806916660722. [PMID: 27385724 PMCID: PMC4956148 DOI: 10.1177/1744806916660722] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Revised: 06/13/2016] [Accepted: 06/27/2016] [Indexed: 12/14/2022] Open
Abstract
Stress is often a trigger to exacerbate chronic pain including visceral hypersensitivity associated with irritable bowel syndrome, a female predominant functional bowel disorder. Epigenetic mechanisms that mediate stress responses are a potential target to interfere with visceral pain. The purpose of this study was to examine the effect of a histone deacetylase inhibitor, suberoylanilide hydroxamic acid, on visceral hypersensitivity induced by a subchronic stressor in female rats and to investigate the involvement of spinal glutamate receptors. Three daily sessions of forced swim induced visceral hypersensitivity. Intrathecal suberoylanilide hydroxamic acid prevented or reversed the stress-induced visceral hypersensitivity, increased spinal histone 3 acetylation and increased mGluR2 and mGluR3 expression. Chromatin immunoprecipitation (ChIP) analysis revealed enrichment of H3K9Ac and H3K18Ac at several promoter Grm2 and Grm3 regions. The mGluR2/3 antagonist LY341495 reversed the inhibitory effect of suberoylanilide hydroxamic acid on the stress-induced visceral hypersensitivity. In surprising contrast, stress and/or suberoylanilide hydroxamic acid had no effect on spinal NMDA receptor expression or function. These data reveal histone modification modulates mGluR2/3 expression in the spinal cord to attenuate stressinduced visceral hypersensitivity. HDAC inhibitors may provide a potential approach to relieve visceral hypersensitivity associated with irritable bowel syndrome.
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Affiliation(s)
| | - Guang Bai
- University of Maryland School of Dentistry
| | - Yaping Ji
- University of Maryland School of Dentistry
| | - Jane M Karpowicz
- University of Maryland School of DentistryUniversity of Maryland School of DentistryUniversity of Maryland School of Dentistry
| | - Richard J Traub
- University of Maryland School of DentistryUniversity of Maryland School of DentistryUniversity of Maryland School of Dentistry
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Kiritoshi T, Neugebauer V. Group II mGluRs modulate baseline and arthritis pain-related synaptic transmission in the rat medial prefrontal cortex. Neuropharmacology 2015; 95:388-94. [PMID: 25912637 DOI: 10.1016/j.neuropharm.2015.04.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Revised: 03/26/2015] [Accepted: 04/02/2015] [Indexed: 01/02/2023]
Abstract
The medial prefrontal cortex (mPFC) serves executive control functions that are impaired in neuropsychiatric disorders and pain. Therefore, restoring normal synaptic transmission and output is a desirable goal. Group II metabotropic glutamate receptors mGluR2 and mGluR3 are highly expressed in the mPFC, modulate synaptic transmission, and have been targeted for neuropsychiatric disorders. Their pain-related modulatory effects in the mPFC remain to be determined. Here we evaluated their ability to restore pyramidal output in an arthritis pain model. Whole-cell patch-clamp recordings of layer V mPFC pyramidal cells show that a selective group II mGluR agonist (LY379268) decreased synaptically evoked spiking in brain slices from normal and arthritic rats. Effects were concentration-dependent and reversed by a selective antagonist (LY341495). LY379268 decreased monosynaptic excitatory postsynaptic currents (EPSCs) and glutamate-driven inhibitory postsynaptic currents (IPSCs) in the pain model. Effects on EPSCs preceded those on IPSCs and could explain the overall inhibitory effect on pyramidal output. LY379268 decreased frequency, but not amplitude, of miniature EPSCs without affecting miniature IPSCs. LY341495 alone increased synaptically evoked spiking under normal conditions and in the pain model. In conclusion, group II mGluRs act on glutamatergic synapses to inhibit direct excitatory transmission and feedforward inhibition onto pyramidal cells. Their net effect is decreased pyramidal cell output. Facilitatory effects of a group II antagonist suggest the system may be tonically active to control pyramidal output. Failure to release the inhibitory tone and enhance mPFC output could be a mechanism for the development or persistence of a disease state such as pain.
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Affiliation(s)
- Takaki Kiritoshi
- Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center (TTUHSC), School of Medicine, 3601 4th Street, Mail Stop 6592, Lubbock, TX 79430-6592, USA
| | - Volker Neugebauer
- Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center (TTUHSC), School of Medicine, 3601 4th Street, Mail Stop 6592, Lubbock, TX 79430-6592, USA; Center of Excellence for Translational Neuroscience and Therapeutics, Texas Tech University Health Sciences Center (TTUHSC), School of Medicine, 3601 4th Street, Mail Stop 6592, Lubbock, TX 79430-6592, USA.
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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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17
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Patel R, Gonçalves L, Leveridge M, Mack SR, Hendrick A, Brice NL, Dickenson AH. Anti-hyperalgesic effects of a novel TRPM8 agonist in neuropathic rats: a comparison with topical menthol. Pain 2014; 155:2097-107. [PMID: 25083927 PMCID: PMC4220012 DOI: 10.1016/j.pain.2014.07.022] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2014] [Revised: 07/21/2014] [Accepted: 07/25/2014] [Indexed: 11/27/2022]
Abstract
Menthol has historically been used topically to alleviate various pain conditions. At low concentrations, this non-selective TRPM8 agonist elicits a cooling sensation, however higher concentrations result in cold hyperalgesia in normal subjects and paradoxically analgesia in neuropathic patients. Through behavioural and electrophysiological means, we examined whether this back-translated into a pre-clinical rodent model. Menthol was applied topically to the hind paws of naive and spinal nerve-ligated (SNL) rats. In behavioural assays, menthol did not affect withdrawal thresholds to mechanical stimulation and 10% and 40% menthol rarely sensitised withdrawals to innocuous cooling in naïve rats. However, in SNL rats, 10% and 40% menthol alleviated cold hypersensitivity. This was partly corroborated by in vivo electrophysiological recordings of dorsal horn lamina V/VI neurones. As several studies have implicated TRPM8 in analgesia, we examined whether a novel systemically available TRPM8 agonist, M8-Ag, had more potent anti-hyperalgesic effects than menthol in neuropathic rats. In vitro, M8-Ag activates TRPM8, expressed in HEK293 cells, with an EC50 of 44.97 nM. In vivo, M8-Ag inhibited neuronal responses to innocuous and noxious cooling in SNL rats with no effect in sham-operated rats. This effect was modality selective; M8-Ag did not alter neuronal responses to mechanical, heat or brush stimulation. In addition, M8-Ag attenuated behavioural hypersensitivity to innocuous cooling but not mechanical stimulation. These data suggest that menthol induced hyperalgesia is not consistently replicable in the rat and that the analgesic properties are revealed by injury. Systemic TRPM8 agonists might be beneficial in neuropathy without affecting normal cold sensitivity.
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Affiliation(s)
- Ryan Patel
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, UK.
| | - Leonor Gonçalves
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, UK
| | | | | | | | | | - Anthony H Dickenson
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, UK
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18
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Chen SR, Zhou HY, Byun HS, Chen H, Pan HL. Casein kinase II regulates N-methyl-D-aspartate receptor activity in spinal cords and pain hypersensitivity induced by nerve injury. J Pharmacol Exp Ther 2014; 350:301-12. [PMID: 24898266 DOI: 10.1124/jpet.114.215855] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Increased N-methyl-d-aspartate receptor (NMDAR) activity and phosphorylation in the spinal cord are critically involved in the synaptic plasticity and central sensitization associated with neuropathic pain. However, the mechanisms underlying increased NMDAR activity in neuropathic pain conditions remain poorly understood. Here we show that peripheral nerve injury induces a large GluN2A-mediated increase in NMDAR activity in spinal lamina II, but not lamina I, neurons. However, NMDAR currents in spinal dorsal horn neurons are not significantly altered in rat models of diabetic neuropathic pain and resiniferatoxin-induced painful neuropathy (postherpedic neuralgia). Inhibition of protein tyrosine kinases or protein kinase C has little effect on NMDAR currents potentiated by nerve injury. Strikingly, casein kinase II (CK2) inhibitors normalize increased NMDAR currents of dorsal horn neurons in nerve-injured rats. In addition, inhibition of calcineurin, but not protein phosphatase 1/2A, augments NMDAR currents only in control rats. CK2 inhibition blocks the increase in spinal NMDAR activity by the calcineurin inhibitor in control rats. Furthermore, nerve injury significantly increases CK2α and CK2β protein levels in the spinal cord. In addition, inhibition of CK2 or CK2β knockdown at the spinal level substantially reverses pain hypersensitivity induced by nerve injury. Our study indicates that neuropathic pain conditions with different etiologies do not share the same mechanisms, and increased spinal NMDAR activity is distinctly associated with traumatic nerve injury. CK2 plays a prominent role in the potentiation of NMDAR activity in the spinal dorsal horn and may represent a new target for treatments of chronic pain caused by nerve injury.
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Affiliation(s)
- Shao-Rui Chen
- Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative Medicine, University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Hong-Yi Zhou
- Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative Medicine, University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Hee Sun Byun
- Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative Medicine, University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Hong Chen
- Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative Medicine, University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Hui-Lin Pan
- Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative Medicine, University of Texas MD Anderson Cancer Center, Houston, Texas
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Zhou C, Luo ZD. Electrophysiological characterization of spinal neuron sensitization by elevated calcium channel alpha-2-delta-1 subunit protein. Eur J Pain 2013; 18:649-58. [PMID: 24151064 DOI: 10.1002/j.1532-2149.2013.00416.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/10/2013] [Indexed: 12/21/2022]
Abstract
BACKGROUND Voltage-gated calcium channel α2 δ1 subunit is the binding site for gabapentin, an effective drug in controlling neuropathic pain states including thermal hyperalgesia. Hyperalgesia to noxious thermal stimuli in both spinal nerve-ligated (SNL) and voltage-gated calcium channel α2 δ1 overexpressing transgenic (Tg) mice correlates with higher α2 δ1 levels in dorsal root ganglia and dorsal spinal cord. In this study, we investigated whether abnormal synaptic transmission is responsible for thermal hyperalgesia induced by elevated α2 δ1 expression in these models. METHODS Behavioural sensitivities to thermal stimuli were test in L4 SNL and sham mice, as well as in α2 δ1 Tg and wild-type mice. Miniature excitatory (mEPSC) and inhibitory (mIPSC) post-synaptic currents were recorded in superficial dorsal spinal cord neurons from these models using whole-cell patch clamp slice recording techniques. RESULTS The frequency, but not amplitude, of mEPSC in superficial dorsal horn neurons was increased in SNL and α2 δ1 Tg mice, which could be attenuated by gabapentin dose dependently. Intrathecal α2 δ1 antisense oligodeoxynucleotide treatment diminished increased mEPSC frequency and gabapentin's inhibitory effects in elevated mEPSC frequency in the SNL mice. In contrast, neither the frequency nor the amplitude of mIPSC was altered in superficial dorsal horn neurons from the SNL and α2 δ1 Tg mice. CONCLUSIONS Our findings support a role of peripheral nerve injury-induced α2 δ1 in enhancing pre-synaptic excitatory input onto superficial dorsal spinal cord neurons that contributes to nociception development.
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Affiliation(s)
- C Zhou
- Department of Pharmacology, School of Medicine, University of California Irvine, USA
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20
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Chen SR, Zhou HY, Byun HS, Pan HL. Nerve injury increases GluA2-lacking AMPA receptor prevalence in spinal cords: functional significance and signaling mechanisms. J Pharmacol Exp Ther 2013; 347:765-72. [PMID: 24030012 DOI: 10.1124/jpet.113.208363] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The glutamate α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptors (AMPARs) are critically involved in the excitatory synaptic transmission, and blocking AMPARs at the spinal level reverses neuropathic pain. However, little is known about changes in the composition of synaptic AMPARs in the spinal dorsal horn after peripheral nerve injury. AMPARs lacking the GluA2 subunit are permeable to Ca(2+), and their currents show unique inward rectification. We found that AMPAR-mediated excitatory postsynaptic currents (AMPAR-EPSCs) of spinal dorsal horn neurons exhibited a linear current-voltage relationship in control rats, whereas AMPAR-EPSCs of dorsal horn neurons displayed inward rectification in rats with spinal nerve injury. In nerve-injured rats, compared with control rats, the GluA2 protein level was significantly less in the plasma membrane but was greater in the cytosolic vesicle fraction in the dorsal spinal cord. However, the GluA1 protein levels in these fractions did not differ significantly between nerve-injured and control rats. Blocking N-methyl-d-aspartate receptors (NMDARs) abolished inward rectification of AMPAR-EPSCs of dorsal horn neurons in nerve-injured rats. Furthermore, inhibition of calpain or calcineurin, but not protein kinase C, completely blocked nerve injury-induced inward rectification of AMPAR-EPSCs of dorsal horn neurons. In addition, blocking GluA2-lacking AMPARs at the spinal cord level reduced nerve injury-induced pain hypersensitivity. Our study suggests that nerve injury increases GluA2 internalization and the prevalence of GluA2-lacking AMPARs in the spinal dorsal horn to maintain chronic neuropathic pain. Increased prevalence of spinal GluA2-lacking AMPARs in neuropathic pain is mediated by NMDARs and subsequent stimulation of calpain and calcineurin signaling.
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Affiliation(s)
- Shao-Rui Chen
- Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative Medicine, The University of Texas M.D. Anderson Cancer Center, Houston, Texas (S.-R.C., H.-Y.Z., H.S.B., H.-L.P.); Graduate Program in Neuroscience, The University of Texas Graduate School of Biomedical Sciences, Houston, Texas (H.-L.P.)
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21
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Ye ZY, Li DP, Pan HL. Regulation of Hypothalamic Presympathetic Neurons and Sympathetic Outflow by Group II Metabotropic Glutamate Receptors in Spontaneously Hypertensive Rats. Hypertension 2013; 62:255-62. [PMID: 23716583 DOI: 10.1161/hypertensionaha.113.01466] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Increased glutamatergic input in the hypothalamic paraventricular nucleus (PVN) plays an important role in the development of hypertension. Group II metabotropic glutamate receptors are expressed in the PVN, but their involvement in regulating synaptic transmission and sympathetic outflow in hypertension is unclear. Here, we show that the group II metabotropic glutamate receptors agonist (2S,2'R,3'R)-2-(2',3'-dicarboxycyclopropyl)glycine (DCG-IV) produced a significantly greater reduction in the frequency of spontaneous and miniature excitatory postsynaptic currents and in the amplitude of electrically evoked excitatory postsynaptic currents in retrogradely labeled spinally projecting PVN neurons in spontaneously hypertensive rats (SHRs) than in normotensive control rats. DCG-IV similarly decreased the frequency of GABAergic inhibitory postsynaptic currents of labeled PVN neurons in the 2 groups of rats. Strikingly, DCG-IV suppressed the firing of labeled PVN neurons only in SHRs. DCG-IV failed to inhibit the firing of PVN neurons of SHRs in the presence of ionotropic glutamate receptor antagonists. Lowering blood pressure with celiac ganglionectomy in SHRs normalized the DCG-IV effect on excitatory postsynaptic currents to the same level seen in control rats. Furthermore, microinjection of DCG-IV into the PVN significantly reduced blood pressure and sympathetic nerve activity in SHRs. Our findings provide new information that presynaptic group II metabotropic glutamate receptor activity at the glutamatergic terminals increases in the PVN in SHRs. Activation of group II metabotropic glutamate receptors in the PVN inhibits sympathetic vasomotor tone through attenuation of increased glutamatergic input and neuronal hyperactivity in SHRs.
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Affiliation(s)
- Zeng-You Ye
- Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd, Houston, TX 77030-4009, 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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Zhou HY, Chen SR, Byun HS, Chen H, Li L, Han HD, Lopez-Berestein G, Sood AK, Pan HL. N-methyl-D-aspartate receptor- and calpain-mediated proteolytic cleavage of K+-Cl- cotransporter-2 impairs spinal chloride homeostasis in neuropathic pain. J Biol Chem 2012; 287:33853-64. [PMID: 22854961 PMCID: PMC3460480 DOI: 10.1074/jbc.m112.395830] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2012] [Revised: 07/31/2012] [Indexed: 12/31/2022] Open
Abstract
Loss of synaptic inhibition by γ-aminobutyric acid and glycine due to potassium chloride cotransporter-2 (KCC2) down-regulation in the spinal cord is a critical mechanism of synaptic plasticity in neuropathic pain. Here we present novel evidence that peripheral nerve injury diminishes glycine-mediated inhibition and induces a depolarizing shift in the reversal potential of glycine-mediated currents (E(glycine)) in spinal dorsal horn neurons. Blocking glutamate N-methyl-D-aspartate (NMDA) receptors normalizes synaptic inhibition, E(glycine), and KCC2 by nerve injury. Strikingly, nerve injury increases calcium-dependent calpain activity in the spinal cord that in turn causes KCC2 cleavage at the C terminus. Inhibiting calpain blocks KCC2 cleavage induced by nerve injury and NMDA, thereby normalizing E(glycine). Furthermore, calpain inhibition or silencing of μ-calpain at the spinal level reduces neuropathic pain. Thus, nerve injury promotes proteolytic cleavage of KCC2 through NMDA receptor-calpain activation, resulting in disruption of chloride homeostasis and diminished synaptic inhibition in the spinal cord. Targeting calpain may represent a new strategy for restoring KCC2 levels and tonic synaptic inhibition and for treating chronic neuropathic pain.
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Affiliation(s)
- Hong-Yi Zhou
- From the Center for Neuroscience and Pain Research
- Department of Anesthesiology and Perioperative Medicine
| | - Shao-Rui Chen
- From the Center for Neuroscience and Pain Research
- Department of Anesthesiology and Perioperative Medicine
| | - Hee-Sun Byun
- From the Center for Neuroscience and Pain Research
- Department of Anesthesiology and Perioperative Medicine
| | - Hong Chen
- From the Center for Neuroscience and Pain Research
- Department of Anesthesiology and Perioperative Medicine
| | - Li Li
- From the Center for Neuroscience and Pain Research
- Department of Anesthesiology and Perioperative Medicine
| | - Hee-Dong Han
- Department of Experimental Therapeutics
- Center for RNA Interference and Non-Coding RNA, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030
| | - Gabriel Lopez-Berestein
- Department of Experimental Therapeutics
- Center for RNA Interference and Non-Coding RNA, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030
| | - Anil K. Sood
- Department of Gynecologic Oncology, and
- Center for RNA Interference and Non-Coding RNA, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030
| | - Hui-Lin Pan
- From the Center for Neuroscience and Pain Research
- Department of Anesthesiology and Perioperative Medicine
- Center for RNA Interference and Non-Coding RNA, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030
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Zhou HY, Chen SR, Pan HL. Targeting N-methyl-D-aspartate receptors for treatment of neuropathic pain. Expert Rev Clin Pharmacol 2012; 4:379-88. [PMID: 21686074 DOI: 10.1586/ecp.11.17] [Citation(s) in RCA: 136] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Neuropathic pain remains a major clinical problem and a therapeutic challenge because existing analgesics are often ineffective and can cause serious side effects. Increased N-methyl-d-aspartate receptor (NMDAR) activity contributes to central sensitization in certain types of neuropathic pain. NMDAR antagonists can reduce hyperalgesia and allodynia in animal models of neuropathic pain induced by nerve injury and diabetic neuropathy. Clinically used NMDAR antagonists, such as ketamine and dextromethorphan, are generally effective in patients with neuropathic pain, such as complex regional pain syndrome and painful diabetic neuropathy. However, patients with postherpetic neuralgia respond poorly to NMDAR antagonists. Recent studies on identifying NMDAR-interacting proteins and molecular mechanisms of increased NMDAR activity in neuropathic pain could facilitate the development of new drugs to attenuate abnormal NMDAR activity with minimal impairment of the physiological function of NMDARs. Combining NMDAR antagonists with other analgesics could also lead to better management of neuropathic pain without causing serious side effects.
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Affiliation(s)
- Hong-Yi Zhou
- Department of Anesthesiology and Perioperative Medicine, Unit 110, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA
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25
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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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Li L, Cao XH, Chen SR, Han HD, Lopez-Berestein G, Sood AK, Pan HL. Up-regulation of Cavβ3 subunit in primary sensory neurons increases voltage-activated Ca2+ channel activity and nociceptive input in neuropathic pain. J Biol Chem 2011; 287:6002-13. [PMID: 22187436 DOI: 10.1074/jbc.m111.310110] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
High voltage-activated calcium channels (HVACCs) are essential for synaptic and nociceptive transmission. Although blocking HVACCs can effectively reduce pain, this treatment strategy is associated with intolerable adverse effects. Neuronal HVACCs are typically composed of α(1), β (Cavβ), and α(2)δ subunits. The Cavβ subunit plays a crucial role in the membrane expression and gating properties of the pore-forming α(1) subunit. However, little is known about how nerve injury affects the expression and function of Cavβ subunits in primary sensory neurons. In this study, we found that Cavβ(3) and Cavβ(4) are the most prominent subtypes expressed in the rat dorsal root ganglion (DRG) and dorsal spinal cord. Spinal nerve ligation (SNL) in rats significantly increased mRNA and protein levels of the Cavβ(3), but not Cavβ(4), subunit in the DRG. SNL also significantly increased HVACC currents in small DRG neurons and monosynaptic excitatory postsynaptic currents of spinal dorsal horn neurons evoked from the dorsal root. Intrathecal injection of Cavβ(3)-specific siRNA significantly reduced HVACC currents in small DRG neurons and the amplitude of monosynaptic excitatory postsynaptic currents of dorsal horn neurons in SNL rats. Furthermore, intrathecal treatment with Cavβ(3)-specific siRNA normalized mechanical hyperalgesia and tactile allodynia caused by SNL but had no significant effect on the normal nociceptive threshold. Our findings provide novel evidence that increased expression of the Cavβ(3) subunit augments HVACC activity in primary sensory neurons and nociceptive input to dorsal horn neurons in neuropathic pain. Targeting the Cavβ(3) subunit at the spinal level represents an effective strategy for treating neuropathic pain.
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Affiliation(s)
- Li Li
- Department of Anesthesiology and Perioperative Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030, USA
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Investigation on quantitative structure activity relationships and pharmacophore modeling of a series of mGluR2 antagonists. Int J Mol Sci 2011; 12:5999-6023. [PMID: 22016641 PMCID: PMC3189765 DOI: 10.3390/ijms12095999] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2011] [Revised: 09/01/2011] [Accepted: 09/09/2011] [Indexed: 11/30/2022] Open
Abstract
MGluR2 is G protein-coupled receptor that is targeted for diseases like anxiety, depression, Parkinson’s disease and schizophrenia. Herein, we report the three-dimensional quantitative structure–activity relationship (3D-QSAR) studies of a series of 1,3-dihydrobenzo[ b][1,4]diazepin-2-one derivatives as mGluR2 antagonists. Two series of models using two different activities of the antagonists against rat mGluR2, which has been shown to be very similar to the human mGluR2, (activity I: inhibition of [3H]-LY354740; activity II: mGluR2 (1S,3R)-ACPD inhibition of forskolin stimulated cAMP.) were derived from datasets composed of 137 and 69 molecules respectively. For activity I study, the best predictive model obtained from CoMFA analysis yielded a Q2 of 0.513, R2ncv of 0.868, R2pred = 0.876, while the CoMSIA model yielded a Q2 of 0.450, R2ncv = 0.899, R2pred = 0.735. For activity II study, CoMFA model yielded statistics of Q2 = 0.5, R2ncv = 0.715, R2pred = 0.723. These results prove the high predictability of the models. Furthermore, a combined analysis between the CoMFA, CoMSIA contour maps shows that: (1) Bulky substituents in R7, R3 and position A benefit activity I of the antagonists, but decrease it when projected in R8 and position B; (2) Hydrophilic groups at position A and B increase both antagonistic activity I and II; (3) Electrostatic field plays an essential rule in the variance of activity II. In search for more potent mGluR2 antagonists, two pharmacophore models were developed separately for the two activities. The first model reveals six pharmacophoric features, namely an aromatic center, two hydrophobic centers, an H-donor atom, an H-acceptor atom and an H-donor site. The second model shares all features of the first one and has an additional acceptor site, a positive N and an aromatic center. These models can be used as guidance for the development of new mGluR2 antagonists of high activity and selectivity. This work is the first report on 3D-QSAR modeling of these mGluR2 antagonists. All the conclusions may lead to a better understanding of the mechanism of antagonism and be helpful in the design of new potent mGluR2 antagonists.
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Jin XG, Chen SR, Cao XH, Li L, Pan HL. Nitric oxide inhibits nociceptive transmission by differentially regulating glutamate and glycine release to spinal dorsal horn neurons. J Biol Chem 2011; 286:33190-202. [PMID: 21813646 DOI: 10.1074/jbc.m111.270967] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Nitric oxide (NO) is involved in many physiological functions, but its role in pain signaling remains uncertain. Surprisingly, little is known about how endogenous NO affects excitatory and inhibitory synaptic transmission at the spinal level. Here we determined how NO affects excitatory and inhibitory synaptic inputs to dorsal horn neurons using whole-cell recordings in rat spinal cord slices. The NO precursor L-arginine or the NO donor SNAP significantly increased the frequency of glycinergic spontaneous and miniature inhibitory postsynaptic currents (IPSCs) of lamina II neurons. However, neither L-arginine nor SNAP had any effect on GABAergic IPSCs. L-arginine and SNAP significantly reduced the amplitude of monosynaptic excitatory postsynaptic currents (EPSCs) evoked from the dorsal root with an increase in paired-pulse ratio. Inhibition of the soluble guanylyl cyclase abolished the effect of L-arginine on glycinergic IPSCs but not on evoked monosynaptic EPSCs. Also, inhibition of protein kinase G blocked the increase in glycinergic sIPSCs by the cGMP analog 8-bromo-cGMP. The inhibitory effects of L-arginine on evoked EPSCs and high voltage-activated Ca(2+) channels expressed in HEK293 cells and dorsal root ganglion neurons were abolished by blocking the S-nitrosylation reaction with N-ethylmaleimide. Intrathecal injection of L-arginine and SNAP significantly increased mechanical nociceptive thresholds. Our findings suggest that spinal endogenous NO enhances inhibitory glycinergic input to dorsal horn neurons through sGC-cGMP-protein kinase G. Furthermore, NO reduces glutamate release from primary afferent terminals through S-nitrosylation of voltage-activated Ca(2+) channels. Both of these actions probably contribute to inhibition of nociceptive transmission by NO at the spinal level.
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Affiliation(s)
- Xiao-Gao Jin
- Department of Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA
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