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

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Helicoverpa armigera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（I_Na）先增大，同时通道的激活电压向负电位方向移动约10 mV，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10 min后，I_Na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I_Na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I_Na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。

Effect of optically-active pyrethroid on sodium channels in the central neurons of Helicoverpa armigera

Effects of the optically-active pyrethroids, alpha-cypermethrin and theta cypermethrin upon the voltage dependent sodium channels of central neurons of larval Helicoverpa armigera (Hübner) were studied using the whole-cell patch clamp technique. Results show that the sodium currents (I_Na) of central neurons 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 direction of hyperpolarization, which indicated that alpha-cypermethrin caused sodium channels of larval H. armigera to be more easily activated. After treatment with alpha cypermethrin for 10－15 min, I_Na decreased quickly, which revealed that alpha cypermethrin also had an effect on opening sodium channels. The latency to peak current was shortened after the application of alpha-cypermethrin, while the time constants of decay did not change. The activation voltage of the sodium channel also shifted towards more negative potentials (around 10 mV) after the application of theta-cypermethrin. I_Na decreased slowly during the action of theta cypermethrin and more time was required to depress it. In conclusion, these data indicate that alpha cypermethrin and theta-cypermethrin have effects on both closed and open states of sodium channels in the central neurons of larval H. armigera and that alpha-cypermethrin is the more effective of these two pyrethroids.