Figure 6. Perturbations of NavMs channel kinetics and voltage dependence by W77 mutations.

(a) The voltage dependence of NavMs channels. Top, grey lines indicate voltage protocol use to open and inactivate the sodium channels. Middle, exemplar sodium currents conducted by the indicated wild type (WT) and mutant NavMs channels with expanded time scale indicated by the dashed line. Bottom, resulting voltage dependence of normalized channel conductance and inactivation. (b) Current density of Wt and W77 mutant NavMs channels (c) Average time constants of entry into activation (τ_act.) and inactivation (τ_inact.) obtained by fitting the initial rise and subsequent decay of the sodium currents (see Methods) to a single exponential. The star indicates P<0.05 resulting from a two tailed Student's t-test compared with the Wt values. (d) Rate of recovery from inactivation. Top, exemplar sodium currents were completely inactivated by a 150 ms depolarization 40 mV positive to the V_1/2 of activation. The membrane potential was then held at −180 mV for varying time intervals; recovery was assessed by a second depolarization. The proportion of second to the first depolarization is the normalized recovery from inactivation. For all of the results in this figure, N=8 cells, Error=s.d.