Figure 3.

Window currents of the Na_v1.5 WT and mutant channels. (A) The overlap between activation and inactivation defines the window current. The predicted window current was obtained using the following equation: (1/(1 + exp((V_{1/2activation} − V)/k_activation))((1 − C)/(1 + exp((V − V_{1/2inactivation})/k_inactivation)) + C). The presence of the mutation increased the predicted window current over 2.3-fold. (B–E) Ramp protocols (see protocol in inset) were imposed (0.64 mV/ms) to study the window current. As predicted in A, the window currents of the mutant channels were higher than that of the WT channel. (B) Ramp current traces normalized to the α peak current. (C) Histogram showing the peak window current normalized to the α peak current (% of peak current). (D) Average traces of ramp currents normalized to cell capacitance to study ramp current density. (E) Peak ramp current density (pA/pF). Data are expressed as means ± SEM. Differences were considered significant at P < 0.05 (*) or < 0.001 (***).