神经病理性痛大鼠背根神经节神经元高电压激活钙电流的变化

目的 观察神经病理性痛大鼠损伤和邻近未损伤背根神经节神经元高电压激活钙电流的变化.方法 雄性SD大鼠,周龄4～6周,采用结扎左侧L5脊神经的方法制备神经病理性痛模型.于结扎后14 d时采用酶消化法急性分离结扎侧邻近未损伤L4背根神经节神经元(L4组)和损伤L5背根神经节神经元(L5组),另取正常大鼠L4.5背根神经节神经元作为对照组(C组).采用全细胞膜片钳技术记录神经元高电压激活钙电流,绘制钙电流激活曲线及稳态失活曲线;记录各亚型高电压激活钙电流.结果 与C组比较,L4组和L5组峰电流密度降低,L5组钙电流激活曲线向超极化方向移动,N型钙电流比例升高,L型钙电流比例降低(P＜0.05);与L4组比较,L5组峰电流密度降低,钙电流激活曲线向超极化方向移动,N型钙电流比例升高,L型钙电流比例降低(P＜0.05).3组钙电流半数失活电压差异无统计学意义(P＞0.05).结论 损伤背根神经节神经元高电压激活钙电流可能在诱发大鼠神经病理性痛的过程中起主要作用.

Changes in high voltage-activated calcium current in dorsal root ganglion neurons isolated from rats with neuropathic pain

Objective To investigate the changes in high voltage-activated (HVA) calcium current in dorsal root ganglion (DRG) neurons isolated from rats with neuropathic pain. Methods Pathogen-free male SD rats aged 4-6 weeks weighing 180-220 g were used in this study. The animals were anesthetized with intraperitoneal pentobarbital sodium 50 mg/kg. Neuropathic pain was induced by ligation of L5 spinal nerve between DRG and sciatic nerve. The nerve was transected distal to the ligature. The animals which showed positive signs of neuropathic pain were decapitated on the 14th postoperative day. L5 and L4 DRGs were isolated and the neurons in the ganglia were enzymatically dissociated (group L5 and L4). The control group received no surgery (group C). The HVA Ca2+ current was recorded using whole-cell patch clamp technique. Results Peak calcium current density was significantly lower in group L5 and L4 than in group C, and was significantly lower in group L5 than in group L4 . Halfactivation value (Va 1/2) was also significantly lower in group L5 than in group C and L4 (P ＜ 0.05). The relative contribution of N-type to the total HVA Ca2+ current was significantly greater in group L5 than in group C and L4(P ＜ 0.05). There was no significant difference in the steady-state inactivation curves among the 3 groups. Conclusion In rats with neuropathic pain, the HVA Ca2+ current in the injured DRG neurons may play a key role in the induction of neuropathic pain.