马桑内酯对大鼠海马锥体神经元钙激活钾通道的影响

目的　了解致痫剂马桑内酯 (CL)对培养的大鼠海马锥体神经元细胞膜钙激活钾通道 (KCa)的调节作用及癫痫的发病机理。方法　采用膜片钳单通道电流记录技术进行定量研究。结果　 1在内面向外式膜片下 ,KCa(12 0 .34± 2 5 .12 ) p S表现出钙离子浓度依赖性 (n=6 )、电压依赖性 (n=17)和四乙基胺 (TEA)阻断特点 ;2在细胞贴附式膜片下 ,浴液中加入 CL 可明显激活 KCa(P<0 .0 1) ;3在对称性高钾溶液中 ,使浴液 [Ca2 + ]i 为 10 - 8m ol/L,维持神经元膜电位为 2 0 m V,当 CL 为 0 μl/ m l和 1.0 μl/ m l时 ,可分别使 KCa开放概率从 0 .0 2 5增加到 0 .5 5 3(P<0 .0 1) ,通道活动的平均开放时间 (ms)从 1.875± 0 .4 12增加到 6 .82 9± 0 .136 ,平均关闭时间 (m s)从 179.342±13.831降低到 6 .4 12± 1.383(n=2 5 ,P<0 .0 1)。结论　在 CL 诱导的癫痫发病中 ,钙激活钾通道活化可能起重要的负反馈调节作用。

Effect of Coriaria Lactone on the Activation of Ca2+-activated K+ Channel in Hippocampal Pyrimidal Neurons of Rats

OBJECTIVE: This research sought to disclose the regulatory effect of Coriaria lactone (CL) on the Ca(2+)-activated K+ channel in hippocampal pyrimidal neurons of Wistar rats in epileptogenesis. METHODS: Cell-attached and inside-out methods of patch clamp technique were used to record the activity of single channel. The sample data were stored in a computer and analyzed by the application of Pclamp softwares. RESULTS: 1. By means of inside-out method, the KCa channels (120.34 +/- 25.12) pS on the membrane of hippocampal pyrimidal neurons showed a distinct dependence on calcium concentration (n = 6) and on voltage (n = 17), and the channels could be blocked by TEA. 2. With the use of cell-attached method, the KCa channels could be activated by CL apparently (n = 25, P < 0.01). 3. In the conditions where the neuronal membranous voltage was kept at 20 mV and the [Ca2+]i at 10(-8) mol/L in bath solution, the CL at concentrations from 0 microliter/ml to 1.0 microliter/ml could make the open state probability of KCa to increase from 0.025 to 0.553 (P < 0.01), the mean opening time (ms) to prolong from 1.875 +/- 0.412 to 6.829 +/- 0.136, and the mean closing time (ms) to decrease from 179.342 +/- 13.831 to 6.412 +/- 1.383 (n = 25, P < 0.01). CONCLUSION: The membranous KCa activation induced by CL may play an important negative feedback regulating role in the mechanism of epileptogenesis.