Figure 4 Recovery from inactivated state for human wild-type and mutant (E1211K, I1473M, and A575V) Na_v1.2 channels

(A) Recovery from inactivated state for WT (closed circle), E1211K (closed triangle), I1473M (open triangle), and A575V (open circle). Two depolarizing pulses (step to 10 mV, 10 msec in duration) with various interpulse intervals (from 0.5 msec to 50 msec) were successively applied to activate Na⁺ currents. The peak amplitude of Na⁺ currents evoked by the second pulse (I₂) was normalized to the peak amplitude of Na⁺ currents evoked by the first pulse (I₁) and I₂/I₁ is expressed as recovery ratios. Data were fitted by the equation I₂/I₁ = 1 − exp(−A_rect), where A_rec is the factor to determine the speed of recovery. The data points represent the average of I₂/I₁. Note that the recovery for E1211K was significantly prolonged. (B) A_rec of Na_v1.2 channels. A_rec was calculated for individual cells and averaged. Values represent means ± SEM, *p < 0.05, **p < 0.01.