低频海马电刺激增加耐药性颞叶癫痫大鼠脑细胞外液γ-氨基丁酸含量和抑制癫痫发作及杏仁核后放电

Low-frequency hippocampal stimulation increases the extracellular γ-aminobutyrate level in the brain, inhibits the epileptic seizures and after discharges of the amygdala in pharmacoresistant temporal lobe epileptic rats

目的 建立多药耐药性颞叶癫痫模型,以杏仁核后放电频率、癫痫发作频率、海马细胞外液γ-氨基丁酸（GABA）浓度为指标,观察海马电刺激治疗耐药性颞叶癫痫的疗效及可能机制.方法 选用Wistar大鼠120只,制作慢性杏仁核点燃癫痫模型,模型制作成功后,应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性癫痫大鼠及药物敏感大鼠,将耐药性癫痫大鼠分为耐药对照组（n=8）及海马刺激组（n=8）,对耐药性癫痫大鼠进行低频海马电刺激,用微透析方法收集脑组织细胞外液,采用高效液相色谱法检测海马电刺激后GABA含量的变化.结果 海马刺激组经过2周的低频电刺激后,癫痫发作受到明显抑制,杏仁核后放电频率及波幅降低,8：00-9：00 am和8：00-9：00 pm 2个时段的GABA浓度（μg/ml）分别为32.69±7.80、35.76±6.27,2个时段的GABA浓度（μg/ml）都明显高于耐药对照组（26.58±6.87,t=-21.45,P=0.000;31.50 ±4.87,t=-15.74,P=0.000）,差异具有统计学意义.结论 低频电刺激海马可以明显抑制点燃模型的癫痫发作,抑制耐药性颞叶癫痫模型的后放电,降低杏仁核后放电频率及波幅、缩短后放电持续时间,该作用可能是通过增加脑细胞外液GABA浓度而实现的.

Objective To establish a multi-drug resistant model of temporal lobe epilepsy and observe the effect of hippocampal stimulation on pharmacoresistant epileptic rats and its possible mechanism with the use of indexes including after discharges （AD） of the amygdalae,the stimulus-induced seizures and the extracellular levels of γ-aminobutyrate （GABA）.Methods Totally,120 Wistar rats were used for the amygdaloid kindled model of epilepsy by chronic stimulation of amygaloid basal lateral nucleus.Based on the successful kindled model of epilepsy,we selected the pharmacoresistant and pharmacosensitive epileptic rats according to their response to phenobabital and phenytoin.We then divided the pharmacoresistant epileptic rats into the hippocampal stimulation group and control group,with 8 rats in each group.Low-frequency stimulus was conducted for two weeks in the hippocampal stimulation group.The hippocampus extracellular fluid collected by microdialysis was then used to determine the levels of GABA by a high performance liquid chromatography method after hippocampal stimulation.Results The stimulus-induced seizures were inhibited significantly,and the frequency of the AD was decreased,as well as the amplitude,compared with the control group.The extracellular level of GABA in the 8：00-9：00 am and the 8：00-9：00 pm was （32.69 ± 7.80） and （35.76 ± 6.27） μg/ml,respectively,both significantly increased as compared with the control （（26.58 ± 6.87） μg/ml,t =-21.45,P =0.000 ; （31.50 ± 4.87） μg/ml,t =-15.74,P =0.000）.Conclusions The low-frequency hippocampal stimulation inhibits the seizures of the kindled model of epilepsy and decreases the frequency,the amplitude,as well as the duration of the amygdale AD in the pharmacoresistant epileptic rats,which may be contributed to the increased GABA content in extracellular fluid of the brain after stimulation.