Figure 4.

Inactivation and recovery kinetics of Na⁺ channels. (A) Voltage dependence of fast and slow time constants of I_Na decay. The time constants were obtained by fitting the decay portions of I_Na in response to the voltage protocol in the inset of Figure 1B with a two-exponential function, A_f×exp(−t/τ_f)+A_s×exp(−t/τ_s)+offset, where t is time and τ_f and τ_s are fast and slow time constants, respectively. (B and C) Steady-state and fast inactivation, respectively. (D) Kinetics of Na⁺ channel recovery from fast inactivation. The peak I_Na elicited by a test pulse in the voltage protocols depicted in the left panels was plotted against the voltage (V) of the conditioning pulse that preceded the test pulse. Labels are the same as for Figure 1.