Figure 1. Open state inactivation. (A) Ik evoked by a 30 ms pulse to 0 mV (Na_o/K_i). (B) I_K evoked by a 12 sec pulse as in (A). (C) Normalized inactivation phase of I_K in (B), fitted with the equation (solid line): Ik(t)/Io = Af_Na*exp(−t/τ_f,_OI,Na) + As_Na*exp(−t/τ_s,_OI,Na) + C_Na; where: Io is peak I_K; Af_Na = 0.39, τ_f,_OI,Na = 0.83sec; As_Na = 0.55, τ_s,_OI,Na = 3.2sec; and C_Na = 0.03 (see Text). The inset shows the residuals of the fit. (D) Inactivation time constants at 0 mV, obtained as in (B). (E) Fast (closed symbols) and slow (open symbols) time constants vs. Vm. n = 8