Insecticidal activity of oxadiazine insecticide indoxacarb and its N-decarbomethoxylated metabolite and their modulations of voltage-gated sodium channels.

Insecticidal bioassays on Plutella xylostella (Linneaus) of an oxadiazine insecticide indoxacarb and its N-decarbomethoxylated metabolite (DCJW), and their modulation of voltage-gated sodium channels in rat dorsal root ganglion neurons were examined. No significant difference was observed in insecticidal activity between indoxacarb and DCJW in ingestion and contact tests. In patch-clamp experiments, both indoxacarb and DCJW suppressed the peak sodium currents in a time- and dose-dependent manner. DCJW at 1 μM blocked the sodium currents to 62.7±3.0% (n=5) of the control after 25 min of bath application. In contrast, in the presence of 1 μM indoxacarb, currents were blocked to 4.5±0.6% (n=4) of control. Thus, the potency of DCJW in blocking sodium currents was higher than that of indoxacarb in rat dorsal root ganglion neurons.