A型肉毒毒素通过调控大鼠背根神经节神经元中钠离子通道缓解神经病理性疼痛的研究

Research on analgesic effect of Botulinum neurotoxin type A on neuropathic pain by regulating sodium channels in dorsal root ganglion neurons

目的:观察A型肉毒毒素(BoNT/A)对大鼠L5脊神经前根切断(L5 VRT)疼痛模型大鼠的镇痛效果,研究BoNT/A对未受损的背根神经节(DRG)神经元中不同类型钠通道电流和神经元兴奋性的影响。方法:建立L5 VRT神经病理性疼痛大鼠模型。实验大鼠分成3组:假手术组(Sham)、VRT+生理盐水注射组(VRT+Saline)、VRT+BoNT/A注射组(VRT+BoNT/A)。造模后第5天给药,测量不同时间点各组大鼠机械撤足阈值和热撤足潜伏期的变化。电生理膜片钳方法观察BoNT/A对DRG神经元中不同类型钠通道电流的影响,电流钳检测神经元动作电位阈值变化情况。结果:足底皮下注射BoNT/A(7U/kg)可显著缓解L5 VRT介导的机械触痛敏和热痛敏症状(P<0.01);BoNT/A干预后可显著减小L5 VRT术后DRG神经元中河豚毒素敏感型(TTX-S)和河豚毒素抵抗型(TTX-R)钠通道电流密度(P<0.05);BoNT/A可升高VRT术后原本下降的神经元动作电位阈值(P<0.05)。结论:BoNT/A可减小未损伤DRG神经元中TTX-S和TTX-R钠电流,降低神经元兴奋性,缓解L5 VRT介导的神经病理性疼痛症状。

Objective:To investigate the analgesic effect of Botulinum neurotoxin type A(BoNT/A)on neuropathic pain induced by Lumbar 5 ventral root transaction(L5 VRT)and further to observe the effect of BoNT/A on sodium currents and excitability in uninjured dorsal root ganglion(DRG)neurons.Method:The animal model of neuropathic pain was induced by L5 VRT in adult Sprague-Dawley rats.A single BoNT/A or saline was subcutaneously injected into the hindpaws'plantar surface 5 days after L5 VRT.By using behavioral tests,the effect of BoNT/A on the paw withdrawal threshold and thermal withdrawal latency of L5 VRT rats was investigated,the effect of BoNT/A on tetrodotoxin-sensitive(TTX-S)and tetrodotoxin-resistant(TTX-R)sodium current densities in DRG neurons of L5 VRT rats was observed by patch clamp,and the threshold of action potential in DRG neurons was recorded as well.Result:Injection of BoNT/A at 7 U/kg reversed L5 VRT-induced mechanical allodynia and thermal hyperalgesia(P<0.01).Administration of BoNT/A significantly decreased the current densities of TTX-S and TTX-R sodium channels in uninjured DRG neurons of L5 VRT rats(P<0.05).In addition,BoNT/A significantly increased the threshold of action potential in DRG neurons of L5 VRT rats(P<0.05).Conclusion:Administration of BoNT/A is capable of decreasing current densities of TTX-S and TTX-R sodium channels and increasing the threshold of action potential in uninjured DRG neurons following L5 VRT,thus contributes to its analgesic effect.