小剂量藜芦碱诱发大鼠脑海马CA1区锥体神经元异常放电癫痫脑片模型的特征

背景阵发性去极化漂移是癫痫活动的脑神经元的细胞学特征,过去认为其产生与突触传递异常有关.近年来,阵发性去极化漂移的内因机制得到进一步关注和重视.;目的观察小剂量藜芦碱诱发大鼠脑海马CA1区锥体神经元产生癫痫样活动的特征,探讨其可能的离子机制.设计探索性观察实验.单位解放军第四军医大学的神经科学研究所.材料实验于2002-10/2004-10在解放军第四军医大学神经科学研究所完成.选择出生后14 d的健康SD大鼠40只,所需试剂购自天津市医药公司和Sigma公司.干预大鼠经腹腔麻醉后取脑切片,通过0.5 μmol/L藜芦碱诱发癫痫样活动.在6张脑片上诱发产生阵发性去极化飘移样放电后,灌流液中加入80 nmol/L河豚毒素,在另外5张脑片上,用抗癫痫药物苯妥英(5μmol/L)替换河豚毒素,观察在不同药物作用下细胞电生理特性的变化.主要观察指标①细胞放电模式.②电压钳模式下通过细胞Ⅰ-Ⅴ反应计算河豚毒素敏感性持续性钠电流的大小.结果小剂量藜芦碱细胞外灌流后,随着神经元膜的超极化,大鼠CA1区锥体细胞表现出固定模式的阵发性去极化漂移串样放电,这种电活动可被小剂量(80 nmol/L)河豚毒素或(5 μmol/L)苯妥英所阻断.电压钳模式下测量阈下河豚毒素敏感性钠电流,在膜电位-55,-60,-65mV范围内,癫痫放电神经元测值明显增大,表明小剂量藜芦碱可增强持续性钠电流,并具有电压依赖性.结论小剂量藜芦碱可在大鼠脑海马CA1区锥体神经元上诱发出阵发性去极化漂移样癫痫活动.小剂量河豚毒素或苯妥英可阻断这种癫痫活动,其离子机制可能与持续性钠电流的增强有关.

Epileptiform activities of pyramidal neurons in rat CA1 area induced by low-dosage veratridine

BACKGROUND: The event of paroxysmal deplorizing shift (PDS) is the cellular hallmark of brain neurons of epileptiform activities. Its development used to be considered to be related to abnormal synaptic interactions. Recertly, the intrinsic nature of PDS has received more attention.OBJECTIVE: To observe the characteristics of epileptiform activities of rat hippocampal CA1 pyramidal neurons induced by low-dosage veratridine and investigate its possible ion mechanism.DESIGN: An exploratory and observational trial.SETTING: Institute of Neuroscience, Fourth Military Medical University of Chinese PLA.MATERIALS: This study was conducted at the Institute of Neuroscience,Fourth Military Medical University of Chinese PLA, from October 2002 to October 2004. Forty healthy SD rats of 14 days old were selected. Drugs were provided from Tianjin Drug Company and Sigma Company.METHODS: Rats were anesthetized by intraperitoneal injection, and their brain was removed and cut into slices. Epileptiform activities were induced by 0.5 μ mol/L veratridine. Then 80 nmol/L tetrodotoxin was added into the perfused solution on 6 cerebral slices, and 5 μmol/L phenytoin was used on another 5 cerebral slices. The electrophysiological characteristics of the cells under the effect of different kinds of drugs were observed.MAIN OUTCOME MEASURE: Discharge pattern of cells and tetrodotoxin-sensitive sodium currents under voltage-clamp configuration through Ⅰ-Ⅴ reaction.RESULTS: After perfusion of 0.5 μmol/L veratridine, the rat pyramidal neurons in CA1 area displayed relatively fixed-mode of runs of PDS bursting,followed by the hyperpolarization of cell membrane. Such epileptiform activities were blocked either by 80 nmol/L tetrodotoxin or 5 μnol/L phenytoin. The tetrodotoxin-sensitive sodium currents in epileptic neurons and normal controls under voltage-clamp configuration on holding potential of -55 rmV, -60 rmV, -65 mV. This shows that persistent sodium currents could be improved by low-dosage veratridine in a voltage-dependent manner.CONCLUSION: Low-dosage veratridine may induce runs of PDS like epileptiform activities on rat CA1 pyramidal neurons. Such changes can be blocked by low-dosage tetrodotoxin or phenytoin. Its ion mechanism may be related to persistent sodium currents.