A, Effects of T529 mutations on the rate of deactivation at −80 mV. Recordings were made in 98 mM [K]o using the voltage clamp protocol shown on top left: the membrane was depolarized to +60 mV for 100 msec followed by repolarization to −80 mV. Inward tail currents at −80 mV are shown. In each panel, the tail current from one of the T529 mutants (depicted by the thick trace) is superimposed on the WT tail current (thin trace). To facilitate comparison, the gain of display is adjusted so that the tail current amplitudes match each other. Note the differences in the time calibration. B, Correlating effects of T529 mutations on 4AP’s blocking potency with effects on the rate of deactivation. 4AP’s Kd values from figure 11 are plotted against τ of deactivation at −80 mV on a double logarithmic scale. The dotted lines are drawn by eye. The following are values of τ of deactivation (in msec, numbers of measurements in parentheses):