Fig. 5. Recovery from block of inactivated human heart (hH1) mutant Na⁺channels by R  (+)- (filled squares) and S  (−)-bupivacaine (filled diamonds) at a concentration of 100 μm. Cells were conditioned with a 10-s depolarizing pulse to −70 mV from a holding potential of −160 mV. Recovery was determined by applying a test pulse to +30 mV at various times after the conditioning pulse. The data were normalized to the amplitude of the test pulse obtained after 50-s recovery time. The data were best fitted by the sum of two exponentials. The control data (open circles) for experiments with R  (+)- and S  (−)-bupivacaine were combined. The data for recovery of hH1 wild-type currents from block by 100 μm R  (+)- (dashed lines) and S  (−)-bupivacaine (dotted lines) are given for comparison. For fast and slow time constants of recovery (Τ1 and Τ2) for wild-type and mutant channels, see table 3.