Tonic GABA and Glycine Inhibition Control Pain Hypersensitivity via Limiting α2δ-1- and mGluR5-Dependent NMDA Receptor Activity at Primary Afferent-Excitatory Neuron Synapses.

IF 4 2区 医学 Q1 NEUROSCIENCES
Yuying Huang 黄玉莹,Hong Chen 陈红,Shao-Rui Chen 陈少瑞,Hui-Lin Pan 潘惠麟
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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.
强直性GABA和甘氨酸抑制通过限制初级传入-兴奋神经元突触α2δ-1-和mglur5依赖的NMDA受体活性来控制疼痛超敏反应。
GABA和甘氨酸突触抑制受损导致慢性神经性疼痛相关脊髓兴奋-抑制失衡;然而,潜在的机制仍不清楚。在这项研究中,我们研究了gaba能和甘氨酸能输入如何调节雄性和雌性小鼠脊髓背角兴奋性和抑制性神经元突触NMDA受体(NMDAR)的活性。表达谷氨酸转运蛋白-2 (VGluT2)的水疱性神经元和表达γ-氨基丁酸转运蛋白(VGAT)的水疱性神经元表现出相似的gaba能和甘氨酸能混合IPSCs。加巴嗪阻断GABAA受体或士的宁阻断甘氨酸受体可增强NMDA介导的微型EPSC (mEPSC)的频率、背根单突触诱发的EPSC的振幅和VGluT2神经元的NMDA电流,而VGAT神经元则没有。用河豚毒素或Cacna2d1敲除小鼠沉默神经元活动可消除这些影响。在初级感觉神经元gr1基因有条件敲除的小鼠(gr1 - cko)中,加巴嗪和士的宁不影响mEPSC频率,但仍能增强背角神经元的膨化NMDA电流。此外,通过敲除Grin1-cKO、Cacna2d1或α2δ-1 c端肽,可减少鞘内加巴嗪或士的宁诱导的伤害性超敏反应。此外,阻断代谢性谷氨酸受体5可防止加巴嗪和士的宁诱导的NMDA介导的mEPSC频率增加、诱发的EPSCs和VGluT2神经元中膨化的NMDA电流以及伤害性超敏反应。我们的研究结果表明,正常的gaba能抑制和甘氨酸能抑制突触前和突触后NMDAR在初级传入-兴奋神经元突触的活性。α2δ-1和代谢性谷氨酸受体5在去抑制诱导的脊髓痛觉超敏和突触NMDAR亢进中起重要作用。本研究首次确定了抑制信号- gaba和甘氨酸-通常抑制谷氨酸NMDA受体(NMDAR)活性以调节疼痛传递的特定脊髓神经元和突触。这种抑制控制的丧失通过选择性地增加遗传标记的兴奋性神经元的突触前和突触后NMDAR活性导致疼痛敏感性升高。从初级感觉神经元中去除NMDARs或阻断与NMDARs-α2δ-1和mglur5相关的两种蛋白可显著降低这种疼痛超敏反应。这些发现揭示了突触抑制中断如何驱动慢性疼痛,并强调α2δ-1和mGluR5是恢复脊髓兴奋-抑制平衡的有希望的治疗靶点。这项工作促进了我们对慢性神经性疼痛的关键细胞和分子底物的理解。
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来源期刊
Journal of Neuroscience
Journal of Neuroscience 医学-神经科学
CiteScore
9.30
自引率
3.80%
发文量
1164
审稿时长
12 months
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
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