Figure 2. Shab deactivation in the presence of quinidine.

A, superimposed I_K recorded either in control solutions (5K_o/K_i) or with 0.05 Qd present, as indicated. I_K was evoked either by a +30 mV or a +50 mV pulse, respectively (see Text). B, deactivation tails at −80 mV in A shown on an expanded scale. The lines are the single exponential fit of either the control tail or the monotonically declining phase of the tail in the presence of Qd. C, comparison of the deactivation time constant of control I_K (n= 6) against the time constant of the monotonically declining phase of tails with Qd (n= 4) at −80 mV, obtained as in B. D, tail I_K in the presence of Qd in B. The continuous line is the fit of the sample points with the numerical solution of scheme 2(see text). The dotted line indicates the zero current level.