Tonic GABA and Glycine Inhibition Control Pain Hypersensitivity via Limiting α2δ-1- and mGluR5-Dependent NMDA Receptor Activity at Primary Afferent-Excitatory Neuron Synapses.
Yuying Huang 黄玉莹,Hong Chen 陈红,Shao-Rui Chen 陈少瑞,Hui-Lin Pan 潘惠麟
{"title":"Tonic GABA and Glycine Inhibition Control Pain Hypersensitivity via Limiting α2δ-1- and mGluR5-Dependent NMDA Receptor Activity at Primary Afferent-Excitatory Neuron Synapses.","authors":"Yuying Huang 黄玉莹,Hong Chen 陈红,Shao-Rui Chen 陈少瑞,Hui-Lin Pan 潘惠麟","doi":"10.1523/jneurosci.1469-25.2025","DOIUrl":null,"url":null,"abstract":"Impaired synaptic inhibition by GABA and glycine contributes to excitatory-inhibitory imbalance in the spinal cord associated with chronic neuropathic pain; however, the underlying mechanisms remain unclear. In this study, we investigated how GABAergic and glycinergic inputs regulate synaptic NMDA receptor (NMDAR) activity in both excitatory and inhibitory neurons of the spinal dorsal horn in male and female mice. Vesicular glutamate transporter-2 (VGluT2)-expressing excitatory neurons and vesicular γ-aminobutyric acid transporter (VGAT)-expressing inhibitory neurons exhibited comparable mixed GABAergic and glycinergic IPSCs. Blockade of GABAA receptors with gabazine or glycine receptors with strychnine potentiated NMDAR-mediated miniature EPSC (mEPSC) frequency, the amplitude of EPSCs monosynaptically evoked from the dorsal root, and puff NMDA currents in VGluT2, but not VGAT, neurons. These effects were abolished by silencing neuronal activity with tetrodotoxin or in Cacna2d1 knockout mice. In mice with conditional Grin1 knockout in primary sensory neurons (Grin1-cKO), gabazine and strychnine did not affect mEPSC frequency but still enhanced puff NMDA currents in dorsal horn neurons. Furthermore, intrathecal gabazine- or strychnine-induced nociceptive hypersensitivity was diminished by Grin1-cKO, Cacna2d1 knockout, or α2δ-1 C-terminus peptide. Additionally, blocking metabotropic glutamate receptor 5 prevents gabazine- and strychnine-induced increases in NMDAR-mediated mEPSC frequency, evoked EPSCs, and puff NMDA currents in VGluT2 neurons as well as nociceptive hypersensitivity. Our findings reveal that normal GABAergic and glycinergic inhibition tonically suppresses both presynaptic and postsynaptic NMDAR activity at primary afferent-excitatory neuron synapses. α2δ-1 and metabotropic glutamate receptor 5 are essential for disinhibition-induced nociceptive hypersensitivity and synaptic NMDAR hyperactivity in the spinal cord.Significance Statement This study identifies for the first time the specific spinal cord neurons and synapses where inhibitory signals-GABA and glycine-normally suppress glutamate NMDA receptor (NMDAR) activity to regulate pain transmission. Loss of this inhibitory control leads to heightened pain sensitivity by selectively increasing presynaptic and postsynaptic NMDAR activity in genetically tagged excitatory neurons. Eliminating NMDARs from primary sensory neurons or blocking two proteins linked to NMDARs-α2δ-1 and mGluR5-markedly reduces this pain hypersensitivity. These findings uncover how disrupted synaptic inhibition drives chronic pain and highlight α2δ-1 and mGluR5 as promising therapeutic targets for restoring excitation-inhibition balance in the spinal cord. This work advances our understanding of key cellular and molecular substrates underlying chronic neuropathic pain.","PeriodicalId":50114,"journal":{"name":"Journal of Neuroscience","volume":"39 1","pages":""},"PeriodicalIF":4.0000,"publicationDate":"2025-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Neuroscience","FirstCategoryId":"3","ListUrlMain":"https://doi.org/10.1523/jneurosci.1469-25.2025","RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"NEUROSCIENCES","Score":null,"Total":0}
引用次数: 0
Abstract
Impaired synaptic inhibition by GABA and glycine contributes to excitatory-inhibitory imbalance in the spinal cord associated with chronic neuropathic pain; however, the underlying mechanisms remain unclear. In this study, we investigated how GABAergic and glycinergic inputs regulate synaptic NMDA receptor (NMDAR) activity in both excitatory and inhibitory neurons of the spinal dorsal horn in male and female mice. Vesicular glutamate transporter-2 (VGluT2)-expressing excitatory neurons and vesicular γ-aminobutyric acid transporter (VGAT)-expressing inhibitory neurons exhibited comparable mixed GABAergic and glycinergic IPSCs. Blockade of GABAA receptors with gabazine or glycine receptors with strychnine potentiated NMDAR-mediated miniature EPSC (mEPSC) frequency, the amplitude of EPSCs monosynaptically evoked from the dorsal root, and puff NMDA currents in VGluT2, but not VGAT, neurons. These effects were abolished by silencing neuronal activity with tetrodotoxin or in Cacna2d1 knockout mice. In mice with conditional Grin1 knockout in primary sensory neurons (Grin1-cKO), gabazine and strychnine did not affect mEPSC frequency but still enhanced puff NMDA currents in dorsal horn neurons. Furthermore, intrathecal gabazine- or strychnine-induced nociceptive hypersensitivity was diminished by Grin1-cKO, Cacna2d1 knockout, or α2δ-1 C-terminus peptide. Additionally, blocking metabotropic glutamate receptor 5 prevents gabazine- and strychnine-induced increases in NMDAR-mediated mEPSC frequency, evoked EPSCs, and puff NMDA currents in VGluT2 neurons as well as nociceptive hypersensitivity. Our findings reveal that normal GABAergic and glycinergic inhibition tonically suppresses both presynaptic and postsynaptic NMDAR activity at primary afferent-excitatory neuron synapses. α2δ-1 and metabotropic glutamate receptor 5 are essential for disinhibition-induced nociceptive hypersensitivity and synaptic NMDAR hyperactivity in the spinal cord.Significance Statement This study identifies for the first time the specific spinal cord neurons and synapses where inhibitory signals-GABA and glycine-normally suppress glutamate NMDA receptor (NMDAR) activity to regulate pain transmission. Loss of this inhibitory control leads to heightened pain sensitivity by selectively increasing presynaptic and postsynaptic NMDAR activity in genetically tagged excitatory neurons. Eliminating NMDARs from primary sensory neurons or blocking two proteins linked to NMDARs-α2δ-1 and mGluR5-markedly reduces this pain hypersensitivity. These findings uncover how disrupted synaptic inhibition drives chronic pain and highlight α2δ-1 and mGluR5 as promising therapeutic targets for restoring excitation-inhibition balance in the spinal cord. This work advances our understanding of key cellular and molecular substrates underlying chronic neuropathic pain.
期刊介绍:
JNeurosci (ISSN 0270-6474) is an official journal of the Society for Neuroscience. It is published weekly by the Society, fifty weeks a year, one volume a year. JNeurosci publishes papers on a broad range of topics of general interest to those working on the nervous system. Authors now have an Open Choice option for their published articles