Fig. 2.
Voltage dependence of activation and steady-state inactivation for wild-type rNav1.1 and GEFS+ 2 mutant channels. The voltage dependencies of activation (circles) and inactivation (diamonds) were determined for the wild-type rNav1.1 (white symbols), DII (gray symbols), and DIV (black symbols) mutants expressed as α subunits alone (A) and as α + β1 subunits (B). Sodium currents were recorded from a holding potential of −100 mV by depolarizations to a range of potentials from −95 to +50 mV in 5 mV increments. Conductance values were calculated by dividing the peak current amplitude by the driving force at each potential and normalizing to the maximum conductance, as described in Materials and Methods. The values shown are averages; the error bars indicate SD. The data were fit with a two-state Boltzmann equation, and the parameters of the fits are shown in Table 1. The voltage dependence of inactivation was determined by using a two-step protocol in which a conditioning pulse was applied from a holding potential of −100 mV, consisting of 100 msec depolarizations to a range of potentials from −100 to +15 mV in 5 mV increments, followed by a test pulse to −5 mV. The peak current amplitude during each test pulse was normalized to the current amplitude of the first test pulse and plotted as a function of the conditioning pulse potential. The values shown are averages; the error bars indicate SD. The data were fit with a two-state Boltzmann equation, and the parameters of the fits are shown in Table 1.