光学活性拟除虫菊酯对棉铃虫神经细胞钠通道电流的影响

Effect of optically ctive pyrethroid on sodium channels in th e central neurons of Helicoverpa armigera

用全细胞膜片钳技术对比分析了alpha体氯氰菊酯与theta体氯氰菊酯对棉铃虫Helicoverpaarmigera幼虫离体培养中枢神经细胞Na+ 通道门控过程的影响。结果表明 ,alpha体氯氰菊酯作用后 ,神经细胞Na+ 通道电流 (INa)先增大 ,同时通道的激活电压向负电位方向移动约 10mV ,提示alpha体氯氰菊酯使通道激活电位降低 ,通道更容易被激活。药剂作用约 10min后 ,INa又迅速降低 ,表明alpha体氯氰菊酯对开放状态的Na+ 通道有抑制作用。另外 ,alpha体氯氰菊酯使INa到达峰值的时间缩短 ,但对失活时间无明显影响。theta体氯氰菊酯也使INa激活电位左移 ,幅值降低 ,但降低速率较慢。总的结果表明alpha体氯氰菊酯与theta体氯氰菊酯对棉铃虫中枢神经细胞处于关闭和开放状态的钠通道均有作用 ,且alpha体氯氰菊酯对钠通道电流的抑制作用强于theta体氯氰菊酯。

Effects of the optically-active pyrethroids, alpha- cypermethrin and theta-cypermethrin upon the voltage dependent sodium chann els of cen tral neurons of larval Helicoverpa armigera(Hübner) were studied using the whole-cell p atch clamp technique. Results show that the sodium currents (I Na) of central n eurons increased quickly after the application of alpha-cypermethrin. At the same time , the activation voltage of the sodium channel shifted about 10 mV in the direct ion of hyperpolarization, which indicated that alpha-cypermethrin caused so dium channels of larval H. armigera to be more easily activated. After treatment with alpha-cypermethrin for 10－15?min, I Na decreased quickly, which rev ealed that alpha-cypermethrin also had an effect on opening sodium channels . The latency to peak current was shortened after the application of alpha-cypermethrin, whi le th e time constants of decay did not change. The activation voltage of the sodium c hannel also shifted towards more negative potentials (around 10 mV) after the ap plication of theta-cypermethrin. I Na decreased slowly during the acti on of theta-cypermethrin and more time was required to depress it. In concl usion, these data indicate that alpha-cypermethrin and theta-cypermeth rin have effects on both closed and open states of sodium channels in the centra l neurons of larval H. armigera and that alpha-cypermethrin is the more effective of these two pyrethroids.