Effects of prepulse voltage Mg²⁺ on activation kinetics of specific split channels. (A) Representative currents of the wild type, L341 split, Y347 split, and Δ342–348 split elicited with the indicated voltage protocol, with (left) and without (right) 5 mM Mg²⁺ in the extracellular medium. In the voltage protocol, the duration of the conditioning prepulse was 5 s. (B) Time needed for current to reach 90% of the maximal value plotted against the prepulse voltage (mean ± SEM; n = 7–10). (C) The ratio of peak currents with and without Mg²⁺ in the extracellular medium (mean ± SEM; n = 7–10; asterisks indicate P < 0.05 in t test with Bonferroni correction with respect to the continuous channel).