EFFECTS OF CYHALOTHRIN ON THE SODIUM AND CALCIUM CHANNELS IN CENTRAL NEURONS OF Helicoverpa armigera
三氟氯氰菊酯对棉铃虫神经细胞钠及钙通道作用机理研究

The properties of sodium currents of the central neurons isolated from the thoracic and abdominal ganglia of susceptible (S) and cyhalothrin-resistant (R) cotton bollworm, Helicoverpa armigera (Hübner) were studied with the whole-cell patch clamp technique.The effects of cyhalothrin upon the sodium and calcium channels of S and R neurons were also analyzed. The results showed that the sodium channels of R neurons had altered gating properties. Voltage-dependent activation of S sodium channels began from -50 to -40 mV and reached peak value at approximately -20 mV. In contrast, R channels were activated at approximately -40 mV and reached peak around –10~0 mV. Thus, the voltage-dependent activation and inactivation potential of sodium channels of R neurons was shifted approximately 10 mV in the positive direction. Consistent with these changes in gating behavior, R central neurons were less sensitive to the cyhalothrin, as evidenced by the blocking time. The sodium currents of S neurons were entirely sup-pressed by 1.0×10-7 mmol·L-1 cyhalothrin within 20 min, while it required more than 90 min to block the R currents. The current-voltage relationships for the sodium channels of S and R neurons shifted towards more negative potentials (10 mV or more) in 5 min when the cyhalothrin was added to the external solution. Further, the value of R currents varied several times during recording, which indicated that there were other mechanisms involved in the detoxification. The current-voltage relationships for the calcium channels of S and R neurons was shifted 10~20 mV in the negative direction after the action of cyhalothrin, indicating that the cyhalothrin can also affect the gating behavior of calcium channels. Taken together, the results suggest that the cyhalothrin can affect the gating behavior of both sodium and calcium channels of S and R neurons. The sodium channels of R have altered properties, and are less sensitive to cyhalothrin. This is related to the nervous system insensitivity.