Fig. 2.
Effects of metaflumizone (10 μM) on the voltage dependence of activation, steady-state fast inactivation and slow inactivation. A, conductance-voltage plots of activation measured upon depolarization from −120 mV to test potentials ranging from −80 to +40 mV. Peak sodium currents were transformed to conductances (G) using the equation G = INa/(Vtest − Vrev), where INa is the peak sodium current during test depolarization (V), and Vrev is the sodium current reversal potential. Data were normalized to maximum peak conductance (GMax) and fitted using the Boltzmann equation; values are means ± S.E. from five oocytes. The asterisks indicate test potentials of submaximal activation at which the measured sodium current amplitude in the presence of metaflumizone was significantly (*, P < 0.05; **, P < 0.001; paired t test) different from the control. B, representative normalized sodium current traces recorded from an oocyte before or after metaflumizone exposure upon depolarization from −120 to −20 mV. C, voltage dependence of steady-state fast inactivation; conditioning pulses (200 ms) from −120 mV to potentials ranging from −100 to 0 mV were followed immediately by 20-ms test pulses to −10 mV. Peak sodium currents were normalized to the maximum current obtained during the inactivation protocol for that oocyte and plotted versus the conditioning potential; curves were fitted using the Boltzmann equation; values are means ± S.E. from five oocytes. D, voltage dependence of slow inactivation; amplitudes of peak transient currents measured during a 20-ms depolarization to −10 mV after a 100-s conditioning prepulse from a holding potential (Vhold) of −120 mV to potentials ranging from −90 to 0 mV and a 50-ms hyperpolarization to −120 mV were normalized to the maximum current obtained during the inactivation protocol for that oocyte and plotted as a function of the conditioning potential. Values are means ± S.E. from six (control) or five (metaflumizone) separate experiments in different oocytes; curves are fitted to the Boltzmann equation.