FIGURE 2.
Rates of entry into inactivation, recovery from fast inactivation, and use-dependent inactivation for wild-type Nav1.2 and Nav1.3 channels. A, entry into inactivation was analyzed for wild-type Nav1.2 and Nav1.3 channels expressed as α subunits alone (circles) and as α + β1 subunits (triangles). The symbols represent means, and the error bars indicate S.D. values. The parameters of the fits are shown in Table 1. B, recovery from inactivation was determined using three two-pulse protocols, and the data were fit with either a triple or a double exponential equation, as described under “Experimental Procedures.” The symbols represent means, and the error bars indicate S.D. values. Sample sizes were 5 for Nav1.2, 8 for Nav1.3, 6 for Nav1.2 + β1, and 11 for Nav1.3 + β1. C, use-dependent inactivation was analyzed at 39 Hz for wild-type Nav1.2 and Nav1.3. Currents were elicited during 17.5-ms depolarizations to −10 mV from a holding potential of −100 mV, normalized to the initial peak current amplitude, and plotted against the start time of the first depolarization in the pulse train. The values shown are means, and the error bars show S.D. values. Sample sizes were 8 for Nav1.2, 8 for Nav1.3, 6 for Nav1.2 + β1, and 8 for Nav1.3 + β1.