R1629Q enhances Nav1.5 channel into intermediate inactivation.
(A) Time dependence of intermediate inactivation for WT and R1629Q.The two-pulse protocol is shown in the Inset. Differences between WT (open circle, n=9) and R1629Q (filled squre, n=8) were significant at all prepulse durations from 1 to 1000ms. (B)Activity-dependent loss of sodium channel availability. Sodium currents are recorded during series trains of 300ms depolarization to -20mV from holding potential -120mV.Currents are normalized to the value obtained after the first pulse and plotted against the successive pulse number. The residual normalized current level recorded after 30th pulse is 39.4%±2.1% for WT (open circles, n=14) and 18.7%±2.1% for R1629Q (filled squares, n=15) (P<0.01).