马桑内酯对锥体神经元三磷酸腺苷敏感钾通道的作用

背景神经元异常放电的基础是细胞膜离子通道的激活与离子的跨膜运动.三磷酸腺苷敏感钾通道是将细胞电活动与代谢联系在一起的重要通道.三磷酸腺苷敏感钾通道是否参与癫痫的发病过程,马桑内酯是否具有调节三磷酸腺苷敏感钾通道的作用尚不清楚.目的了解致痫剂马桑内酯对大鼠海马锥体神经细胞膜三磷酸腺苷敏感钾通道的影响及三磷酸腺苷敏感钾通道在癫痫发病中的作用.设计随机对照实验.单位四川大学华西医院神经内科和四川大学华西基础医学与法医学院生理学教研室.材料实验于2000-05/12在泸州医学院完成.将Wistar乳鼠的培养的海马锥体神经元,随机分为正常对照组,四乙基胺组,二磷酸核苷组,马桑内酯组,电导与动力学组.方法Wistar乳鼠在麻醉和无菌条件下分离出海马组织,接种、培养24 h后加入10 μmol/L的阿糖胞苷,选择培养7～10 d、生长良好、形态典型的锥体神经元进行膜片钳试验.正常对照组加入生理盐水;四乙基胺组加入5 mmol/L氯化四乙基胺;二磷酸核苷组先加入30 μmoL/L的二磷酸核苷,后加入0.5 mol/L的三磷酸腺苷;致痫组先加入1.0 mL/L的马桑内酯,后加入1 μmol/L的优降糖;对电导与动力学组,先调节钳制电压的大小,了解通道开放及通道形态,后加入马桑内酯.主要观察指标①观察神经元三磷酸腺苷敏感钾通道的活动及形态.②观察不同钳制电压对通道活动的影响;了解二磷酸核苷、三磷酸腺苷和氯化四乙铵对通道的影响.③观察致痫剂马桑内酯对神经元细胞膜三磷酸腺苷敏感钾通道的激活作用及优降糖的影响.结果①对称性高钾溶液条件下,通道的翻转电位接近0 mV.三磷酸腺苷敏感钾通道开放随着钳制电压绝对值的增大而增多,具有电压依赖性,该通道可被氯化四乙铵阻断.②其电流-电压(Ⅰ-Ⅴ)曲线可被直线拟合,电导值为(78.23±12.04)pS.③30μmol/L的二磷酸核苷可使通道开放增多,0.5 mol/L的三磷酸腺苷可抑制通道活动.④1.0mL/L的马桑内酯诱导通道开放数量明显增多,1μmol/L的优降糖可抑制通道活动.⑤通道开放时间,致痫神经元τ01为(1.754±0.060)ms,正常神经元为(1.733±0.046)ms,无显著性差异(n=25,t=0.147,P＞0.05);而τ02正常组为(2.441±0.265)ms,致痫组延长,为(10.446±0.579)ms(n=25,t=0.000,P＜0.01).结论在马桑内酯诱导的癫痫发作中,三磷酸腺苷敏感钾通道开放的作用是降低动作电位频率、保护神经元,可能起一种负反馈调节作用.

Effect of coriaria lactone on adenosine triphosphate-sensitive potassium channels in pyramidal neurons

BACKGROUND: Abnormal neuronal discharge arose from the activation of cell membrane ion channels and transmembrane ion transport. The electric activity of the cells is associated with cell metabolism fundamentally through adenosine triphosphate (ATP)-sensitive potassium(KATP) channels.Currently the involvement of KATP channels in the pathogenesis of epilepsy and the regulation of KATP channels by coriaria lacton (EL) remain unknown.OBJETCIVE: To investigate the changes of cell membrane KATP channels in rat hippocampal neurons in response to CL as an epilepsy-inducing agent, and explore the role of KATP channels in the pathogenesis of epilepsy.DESIGN: Randomized controlled experiment.SETTING: Department of Neurology, West China Hospital Affiliated to Sichuan University, and Teaching and Research Section of Physiology,West China College of Preclinical Medicine and Forensic Medicine of Sichuan University.MATERIALS: This experiment was carried out at Luzhou Medical College between May and December 2000. Hippocampus pyramidal neurons were obtained from neonatal Wistar rats and randomized into normal control group, tetraethylammonium chloride (TEA) group, DNP group, CL group, and electric conductance and dynamics group.METHODS: The hippocampus of newborn Wistar rats was separated under aseptic condition and cultured for 24 hours prior to treatment with 10 μmol/L cytarabine for selective cell culture for 7-10 days. The cells in good growth exhibiting typical morphology of pyramidal neurons were then selected for patch-clamp experiment. The cells in the normal control group were treated with normal saline, which was replaced by 5 mmol/L TEA in TEA group, by 30 μmol/L DNP then 0.5 mol/L ATP in DNP group, and by 1.0 mL/L CL then 1 μmol/L glibenclamide in CL group. In electric conductance and dynamics group, the clamp voltage was firstly adjusted to investigate the channel opening before CL was added to the cells.MAIN OUTCOME MEASURES: ① Activity and curve of neuronal KATP channels; ② Effects of various clamp voltages on the channels activity and the effects of interventions with DNP, ATP and TEA; ③ Activation of neuronal membrane KATP channels induced by CL and the influence of glibenclamide.RESULTS: The reversal potential of the channels approximated 0 mV in homologous high-potassium solution. The opening of KATP channels increased along with the absolute value of the clamp voltage in a voltage-dependent manner, which was blocked by TEA. The electric current-voltage (Ⅰ-Ⅴ)curve could be fitted to a straight line with the electric conductance of (78.23±12.04) pS. Administration of 30 μmol/L DNP enhances the opening of the channels, which could be suppressed by 0.5 mol/L ATP.Addition of 1.0 mL/L CL to the cells caused obviously increased channel opening, which was suppressed by 1 μmol/L glibenclamide. The channel opening time was (1.754±0.060) ms for epileptic neuron τ01and (1.733±0.046) ms for normal neurons, showing no significant difference between them (n=25, t=0.147, P ＞ 0.05), but compared with the channel opening time of (2.441±0.265) ms for τ02 normal neurons, and duration was significantly prolonged in the epileptic neurons to reach (10.446±0.579)ms (n=25, t=0.000, P ＜ 0.01).CONCLUSION: The opening of KATP channels is responsible for reducing the action potential frequency for neuronal protection, which might be a negative feedback mechanism.