苯妥英与加巴喷丁对藜芦碱致大鼠海马CA1神经元癫痫样放电的不同影响

Effects of phenytoin and gabapentin on veratridine-induced epileptiform discharge in rats' hippocampal CA1 neurones

目的观察治疗剂量的苯妥英与加巴喷丁对小剂量(0·5μmol/L)藜芦碱诱发大鼠海马神经元癫痫样放电的作用,分析其可能的细胞学机制。方法通过膜片钳全细胞记录技术,胞外灌流0·5μmol/L藜芦碱,制作大鼠海马CA1锥体神经元癫痫样放电模型,如果在灌流30min内出现振荡样放电[长簇(bursting)放电],即认为造模成功。分别在电压钳模式下观察2·5、5、10、15μmol/L苯妥英和2·5、5、10μmol/L加巴喷丁对这种癫痫活动的影响;测定藜芦碱灌流后CA1锥体神经元Ih电流的变化规律。结果藜芦碱(0·5μmol/L)灌流9～16min后,海马CA1锥体神经元出现节律性巨大慢波振荡,100～200Hz的连续高频放电骑跨其上,类似于癫痫生理学中的阵发性去极化漂移(PDS)现象,证明造模成功。苯妥英可阻断藜芦碱诱发的癫痫样活动,且随浓度递增,簇放电间期逐渐延长,但单个簇放电持续时间并不缩短。在藜芦碱致痫过程中,Ih电流并无增大反而明显减小。加巴喷丁不能阻断藜芦碱引起的癫痫样活动。结论在藜芦碱致海马CA1神经元癫痫样活动模型中,苯妥英对藜芦碱致痫的阻断作用具有浓度依赖性,可能通过抑制持续性钠电流的产生而消除癫痫活动。加巴喷丁不能阻断藜芦碱诱发的癫痫样活动,其机制可能与加巴喷丁对持续性钠电流没有作用和藜芦碱致痫并不增加Ih电流有关。

Objective To observe the effects of phenytoin and gabapentin in therapeutic dosage on low-dose veratridine-induced epileptiform discharge in rats＇ hippocampal CA1 neurons,and explore the involved mechanisms.Methods By means of whole-cell patch clamp technique,the epileptiform discharge model of rats＇ hippocampal CA1 neurons was constructed with extracellular perfusion of 0.5μmol/L veratridine,and the model should be regarded as successfully estabilshed if bursting discharge emerged within 30min perfusion.The effects of phenytoin（2.5,5,10 and 15μmol/L） and gabapentin（2.5,5 and 10μmol/L） on the epileptiform activity were observed under the voltage-clamp configuration,and the current changes for 1 hour in CA1 neurons was also observed.Results Nine-sixteen minutes after veratridine perfusion,the huge,rhythmic slow oscillation emerged,with 100～200Hz high-frequency discharge,in the hippocampal CA1 neurons,which was similar to the paroxysmal depolarization shifts（PDS）,implying that the epileptiform activity was reproduced.Therapeutic dose of phenytoin blocked the veratridine-induced epileptiform activity.The bursting interval of the epileptiform activity was prolonged along with the increased phenytoin concentration,and the duration of bursting was not shortened.1h current decreased gradually in the generation of veratridine-induced epileptiform activity.Therapeutic dose of gabapentin did not block the epileptiform activity in this model.Conclusions In the epileptiform discharge model of rats＇ hippocampal CA1 neurons,phenytoin can block the epileptic activity in a dose-dependent manner,and the effect may be related to the inhibition of 1h currents.Gabapentin shows no influence on the epileptiform activity,and the possible mechanism may be its ineffectiveness to the persistent sodium currents,and vertridine-induced epileptiform activity does not enhance the 1h currents.