DIV voltage-sensor movement is rate limiting for recovery from fast inactivation. (A) Representative families of traces illustrating current responses to a −20-mV test pulse after recovery from inactivation during a variable duration conditioning pulse at −140 mV after initially inactivating the channels for 30 ms at −20 mV. See Results for a detailed description of the voltage-pulse protocol. (B) Summary of the time course of recovery from fast inactivation for conditioning voltages spanning −180 to −110 mV. (C and D) For each conditioning voltage, the time course of recovery from fast inactivation shown in B was fit to the bi-exponential rise ${A1(1−e−(t−t0)/τ1)+A2(1−e−(t−t0)/τ2)}H(t−t0),$ where t is the duration of the conditioning pulse, A_i and τ_i are the amplitudes and time constants of the rise (i = 1,2), H is the unit step function, and t₀ is the delay after onset of the conditioning pulse to initiation of recovery from fast inactivation. The voltage dependence of the delay and fast time constant for each construct is summarized in C and D, respectively (mean ± SEM).