神经病理性痛大鼠背根神经节神经元电生理学的改变

目的 探讨神经病理性痛大鼠背根神经节(DRG)神经元电生理学的改变.方法 成年雄性sD大鼠20只,周龄3～4周,体重100～150 g,随机分为对照组(C组,n=5)和神经病理性痛组(NP组,n=15).采用坐骨神经慢性压迫性损伤(CCI)法制备神经病理性痛模型.于CCI前1d和CCI 后第4天测定热痛阈和机械痛阈.痛阈测定后,急性分离大鼠DRG神经元,采用全细胞膜片钳技术记录其电生理学活动.结果 与CCI前1d比较,NP组CCI后第4天热痛阈和机械痛阈均降低(P<0.05);与c组比较,NP组DRG小神经元基强度降低,膜电位、重复放电率和自发放电率均升高(P<0.05或0.01),阚电位和超射值差异无统计学意义(P>0.05),DRG中神经元膜电位、阈电位、自发放电率升高,基强度降低(P<0.05或0.01),超射值差异无统计学意义(P>0.05),DRG大神经元阈电位升高(P<0.05),其余指标差异无统计学意义(P>0.05).结论 神经病理性痛大鼠DRG神经元电生理学的改变主要发生在DRG中、小神经元上,表现为兴奋性升高、重复放电和自发放电现象增多.

Electrophysiological changes of dorsal root ganglion neurons in rats with neuropathic pain

Objective To investigate the electrophysiological changes of the dorsal root ganglion (DRG) neurons in rats with neuropathic pain.Methods Twenty adult male SD rats, 3-4 weeks old, weighing 100-150 g, were randomly divided into 2 groups: control group (group C, n = 5), and neuropathic pain group (group NP, n = 15). The neuropathic pain was induced by chronic constrictive injury (CCI) of their right side sciatic nerve. The thermal and mechanical pain thresholds were measured at 1 d before and at 4 d after CCI. The DRG neurons were isolated acutely after the measurement of pain threshold and then whole-cell current clamp was used to record the electrophysiological activity. Results The thermal and mechanical pain thresholds were significantly lower at 4 d after CCI than at 1 d before CCI in group NP ( P < 0.05) . The rheobase was significantly lower, and membrane potential, repetitive firing rate and spontaneous discharge rate were significantly higher in the small DRG neurons in group NP than in group C (P < 0.05 or 0.01), but there was no significant difference in threshold potential and overshoot between the 2 groups (P > 0.05). The membrane potential, threshold potential, and spontaneous discharge rate were significantly higher, the reobase was significantly lower in the medium DRG neurons in group NP than in group C ( P < 0.05 or 0.01), but there was no significant difference in overshoot between the 2 groups ( P > 0.05) . The threshold potential was significantly higher in the large DRG neurons in group NP than in group C ( P < 0.05) , but there was no significant difference in the other indices ( P > 0.05) . Conclusion The electrophysiological changes of the DRG neurons mainly occurs in the small and medium DRG neurons in the rats with neuropathic pain, which leads to an increase in the excitability, repetitive firing rate and spontaneous discharge rate.