Figure 6. Comparative inhibition of Na_v1.4 and Na_v1.4/V787K sodium channels by SCI insecticides.

(A) Representative sodium current traces from an oocyte expressing Na_v1.4/V787K at a holding potential (V_h) of −140 mV and −110 mV in the absence of insecticides. (B) Representative sodium current traces from an oocyte expressing Na_v1.4 sodium channels at a V_h of −120 mV and −30 mV in the absence of SCI insecticides. (C) Time course of inhibition of Na_v1.4/V787K by SCI insecticides; oocytes were clamped at a V_h of −110 mV and stimulated once every minute with a test pulse (20 ms) to −10 mV preceded by a hyperpolarization (2 s) to − 140 mV; currents measured in the presence of an insecticide were normalized to the peak sodium current recorded in that oocyte prior to insecticide perfusion; values are means ± S.E. of 5-7 separate experiments with different oocytes; curves were fitted to the mean values using a single-exponential decay equation. (D) Comparison of the fractional inhibition of Na_v1.4 (Fig. 4A) and Na_v1.4/V787K channels by SCI insecticides after 15 min of insecticide perfusion at a V_h of either −30 (Na_v1.4) or −110 mV (Na_v1.4/V787K).