2型大麻素受体通过抑制脊髓小胶质细胞活化减轻神经病理性疼痛小鼠痛觉过敏

目的 探讨脊髓大麻素受体2（CB2R）与小胶质细胞激活对小鼠神经病理性疼痛中痛觉过敏的影响。方法 采用脊神经结扎（SNL）创建神经病理性疼痛模型，C57/BL小鼠60只随机分为六组：假手术组（Sham）、模型组（SNL）、模型+ CB2R激动剂组（SNL+AM1241）、模型+小胶质细胞抑制剂组（SNL+Min）、模型+CB2R小干扰RNA组（SNL+siRNA）、模型+CB2R小干扰RNA+小胶质细胞抑制剂组（SNL+siRNA+Min）。Western blot测定小鼠脊髓CB2R蛋白表达，Von Frey测定各组小鼠机械性痛阈变化，免疫荧光观察脊髓背角小胶质细胞激活情况，PCR测定小鼠脊髓内炎症因子释放，电生理技术观察CB2R激动剂对脊髓背角抑制性突触后电流（sIPSC）的影响。结果 同Sham组相比，SNL小鼠脊髓CB2R表达明显减少，痛阈降低，小胶质细胞激活明显增强，且炎症因子释放增加；鞘内注射CB2R激动剂或小胶质细胞抑制剂后，同SNL相比SNL+AM1241、SNL+Min组痛阈增加，小胶质细胞激活减弱且炎症因子有所减少；而siRNA干扰CB2R表达后同SNL相比，SNL+siRNA小鼠痛阈降低，小胶质细胞激活明显增强，且炎症因子释放增加，同时鞘内注射Min逆转siRAN介导的变化。电生理结果显示AM1241显著增强脊髓背角sIPSC频率和振幅，而Min持续灌流抑制AM1241的效应。结论 CB2R通过抑制脊髓小胶质细胞活化减轻神经炎性反应并增强抑制性电活动，从而减轻神经病理性疼痛的痛觉过敏。

Cannabinoid type 2 receptor alleviates hyperalgesia in neuropathic pain mice by inhibiting spinal microglia activation

Objective To investigate the effects of spinal cannabinoid receptor 2 (CB2R) and microglia activation on hyperalgesia in neuropathic pain mice. Methods Neuropathic pain model was established by spinal nerve ligation (SNL), and sixty C57/BL mice were randomly divided into six groups: sham, SNL, SNL+CB2R agonist AM1241 (SNL+AM1241), SNL+microglia inhibitor minocycline (SNL+Min), SNL+CB2R small interfering RNA (SNL+siRNA), SNL+siRNA+Min groups. The expression of spinal CB2R protein was determined by Western blot, mechanical pain thresholds in six groups were measured by Von Frey, spinal microglia activation was observed by immunofluorescence, and the releases of inflammatory factors in spinal cord were determined by PCR. Electrophysiology was applied to observe the effect of CB2R agonist on spontaneous inhibitory postsynaptic currents (sIPSC) in spinal dorsal horn. Results Compared with Sham group, SNL mice acquired significantly decreased CB2R expression, decreased pain thresholds, enhanced microglia activation and increased inflammatory factors releases. After intrathecal injection of CB2R agonist or microglial inhibitor, SNL+AM1241 and SNL+Min groups acquired increased pain thresholds, weakened microglia activation and decreased inflammatory factors releases compared with SNL group. Through interfering CB2R expression by siRNA, SNL+siRNA group got significantly decreased pain threshold, enhanced microglia activation and increased inflammatory factors releases compared with SNL group, while Min intrathecally reversed these changes. Electrophysiological results showed that AM1241 significantly enhanced the frequency and amplitude of sIPSC in spinal dorsal horn, while Min perfusion inhibited the effects of AM1241. Conclusion CB2R reduces neuroinflammatory responses and enhances inhibitory electrical activity in spinal cord by inhibiting spinal microglia activation, thereby alleviating hyperalgesia in neuropathic pain.