海马电刺激对耐药性颞叶癫痫大鼠CA1区神经元钠通道电流的影响

Effect of hippocampal electrical stimulation on the sodium channel current in CA~ region neurons in rats with pharmacoresistant temporal lobe epilepsy

目的建立多药耐药性颞叶癫痫模型，以海马CA，区锥体细胞钠通道电流的变化为观察指标，探讨海马电刺激治疗耐药性颞叶癫痫的可能机制。方法选用Wistar大鼠80只制作慢性杏仁核点燃癫痫模型，制作成功后用经典抗癫痫药苯妥英钠和苯巴比妥进行筛选，根据癫痫大鼠对药物的反应区别出耐药癫痫大鼠及药物敏感大鼠，将筛选出的耐药性癫痫大鼠分为海马刺激组（n=6）及耐药对照组（n=6），用膜片钳全细胞记录模式观察海马电刺激后脑细胞钠通道电流的变化。结果进行海马电刺激2周后，刺激杏仁核诱发的癫痫发作明显减轻，海马刺激组与耐药对照组Racine分级分别为（2．32±0．38）级和（4．45±0．42）级，差异具有统计学意义（t=84．600，P=0．000），后放电各项参数也明显改善，膜片钳全细胞记录结果表明，海马刺激组钠通道电流峰值及激活曲线向去极化方向偏移，失活曲线向超极化方向偏移，海马刺激组钠通道失活后恢复时间[（17．94-0．6）S]较耐药对照组[（16．3±0．3）S]明显延长（t=-25．420，P=0．000）。结论海马电刺激可以抑制钠通道电流，其治疗耐药性癫痫的作用可能是通过抑制钠通道电流而降低脑细胞兴奋性，从而减少癫痫性电活动的产生而实现的。

Objective To establish a muhi-drug resistant model of temporal lobe epilepsy, and then the sodium current of pyramidal neurons in CA areas of the hippocampus was used as as index to observe the effect of hippocampal stimulation on pharmacoresistant epileptic rats. Methods Eighty Wistar rats were selected to prepare an amygdaloid kindled model of epilepsy by chronic stimulation of amygaloid basal lateral nucleus. When the kindled model of epilepsy was prepared successfully, the pharmacoresistant epileptic rats were selected according their response to phenobabital and phenytoin. The selected pharmacoresistant epileptic rats were divided into a hippocampal stimulation group （HS group） and a pharmacoresistant control group （PR group）. A low-frequency hippocampal stimulation was performed in the HS group, while the PR group received sham stimulation. The whole-cell recording technique by patch-clamp was used to observe the changes of sodium current of hippocampal pyramidal neurons after the hippocampal stimulation. Results Compared with the PR group, the pharmacoresistant epileptic rats in HS group underwent low-frequency stimulation for 2 weeks showed that the amygdale stimulus-induced seizures were decreased （2. 32 ± 0. 38 in HS group and 4.45 ± 0. 42 in PR group, t = 84. 600, P = 0. 000） and the parameters of the after-discharges were improved significantly. In HS group, the peak current shifted towards depolarization, the sodium channels were difficult to activate, and were more susceptible to inactivation. Moreover, the recovery time after the sodium channel inactivation was slower in HS group （ （ 17.9±0. 6） s） than in PR group（ （ 16. 3 ±0. 3 ） s, t = - 25. 420,P = 0. 000）. Conclusions Hippocampal stimulation may inhibit the sodium channel current of pyramidal neurons in CA1 areas of hippocampus. The mechanism of hippocampal stimulation in the treatment of pharmacoresistant epilepsy might he achieved partly by inhibiting the sodium channel current so as to decrease the excitability of hippocampal neurons.