丙戊酸对大鼠臂丛损伤后脊髓运动神经元Ca^2＋及凋亡的影响

Effect of valproic acid on Ca^2＋ and cell apoptosis in spinal cord motor neurons after brachial plexusinjury in rats

目的探讨丙戊酸（VPA）对大鼠臂丛损伤后脊髓前角运动神经元Ca^2＋的影响，以及对神经元的保护作用。方法健康成年雄性Wistar大鼠210只，随机分为假手术组（显露臂丛不做处理）、对照组（臂丛根性切断伤组）、VPA组（臂丛根性切断伤加饲喂丙戊酸钠组），每组70只大鼠，分别在术后12、24、48、72h和1、2、4周7个时间点取臂丛对应的C5-T1脊髓节段。利用全细胞膜片钳技术检测L-型钙离子通道电流，采用荧光分光光度计测定脊髓前角运动神经元内游离Ca^2＋（[Ca^2＋]i）浓度，TUNEL法检测脊髓前角运动神经元的凋亡。所得数据进行统计学分析（P〈0．05为差异有统计学意义）。结果假手术组各组指标无变化。对照组在神经损伤后12h至1周时，L-型钙离子通道电流值和细胞内[Ca^2＋]浓度与假手术组相比显著升高。在神经损伤后12h直至4周，对照组凋亡神经元数明显高于假手术组。VPA组的L一型钙离子通道电流值与对照组相比各时间点差异无统计学意义，但在神经损伤后48h至1周，细胞内[Ca^2＋]i浓度显著降低，在伤后24h至2周，脊髓前角运动神经元的凋亡数目显著降低。结论臂丛根性切断伤可以引起脊髓前角运动神经元内[Ca^2＋]i浓度升高及神经元的凋亡，VPA对神经元L-型钙离子通道无影响，但可以在一定程度上降低受损运动神经元胞内的[Ca^2＋i的浓度，并减少神经元的凋亡。

Objective To examine the effect of valproic acid （VPA） on concentration of Intracellular Ca^2＋ and on cell apoptosis in spinal cord motor neurons after brachial plexus injury in rats. Methods Totally 210 adult male Wistar rats were randomly divided into Sham operation group （disposed the brachial plexus nerve root, but not cutted it off）, control group （rats with brachial plexus nerve root amputating wound）and VPA group（rats with brachial plexus nerve root amputating wound and fed by VPA water）, with 70 rats in each group. The specimens were taken at 12, 24, 48, 72 h, 1, 2 and 4 weeks after operation. Whole-cell patch-clamp recording techniques were used to assayed the L-type calcium channel of motoneuron and monitored the changes in intracellular concentration of Ca^2＋ with spectrofluorometer. The motoneruron apoptosis was detected by TUNEL. Results The set of indicators did not change in the sham group. From 12h to 1 weeks after the operation, the electrical current of L-type calcium channel and the intra-cellular Ca^2＋ concentration of the neuron were obviously more in control group than in sham operation group （P 〈 0.05）. From 12 h to g weeks after the injury, there were more apoptosis neurons in control group than in sham operation group （P 〈 0.05）. There was no obviously difference in electrical current of L-type calcium channel between the VPA group and the control group at each time point（P 〉 0.05）. Compared to the control group, the intra-cellular Ca2~ concentration was lower in VPA group from 48 h to 1 week after nerve injury （P 〈 0.05）; the number of apoptosis neurons were less in VPA group from 24 h to 2 weeks after the injury （P 〈 0.05）. Conclusions Brachial plexus nerve root amputating wound in rats can increase the intra-cellular Ca^2＋ concentration and apoptosis of the motor neuron. VPA can reduce the intra-cellular Ca^2＋concentration and aoootosis, but has no effect on the L-tyoe calcium channel of the motor neuron.