Voltage-gated ion channels in central neurons of Helicoverpa armigera as potential targets for cycloxaprid: a cis-configuration neonicotinoid insecticide

Cycloxaprid is a novel cis-neonicotinoid, mainly acting on the nicotinic acetylcholine receptor; however, it is not clear whether cycloxaprid can act on voltage-gated ion channels. In this study, the effects of cycloxaprid on the sodium, calcium and potassium channels in central neurons acutely dissociated from Helicoverpa armigera Hübner (Lepidoptera: Noctuidae) were investigated by the whole-cell patch clamp technique. With the application of cycloxaprid, the half voltage (V_0.5) of activation and inactivation of sodium channels exhibited an obvious hyperpolarizing shift around 4–16 mV and 4–14 mV, respectively. The window currents of sodium channels increased by 35.04–88.89%. The time course of recovery from inactivation was also significantly prolonged by 0.25–0.43 ms. The V_0.5 of activation and inactivation of calcium channels exhibited a marked hyperpolarizing shift around 6–9 mV and 13–19 mV, respectively. The window currents of calcium channels increased by 13.82–28.97%. The time course of recovery from inactivation for calcium channels was prolonged by 0.76–16.85 ms, although not significantly. Comparatively, the peak currents and the V_0.5 of activation of potassium channels showed no significant change. These results indicate that sodium and calcium channels of H. armigera are potential target sites of cycloxaprid.