Potentiated SkEIIIK conducts inward Ca²⁺ current. Representative currents are shown for a ±Bay K 8644–treated (5 μM) dysgenic myotube expressing SkEIIIK (A) and a ±Bay K 8644–treated, uninjected dysgenic myotube (B). The inset illustrates the tail currents shown in A on an expanded time base. (C) Summary of amplitudes (left) and deactivation time constants (right) of SkEIIIK tail currents recorded in the absence (n = 9) and presence (n = 10) of ±Bay K 8644. (D) Total charge moved obtained by integration of tail currents recorded in the absence (n = 9) and presence (n = 10) of ±Bay K 8644 from dysgenic myotubes expressing SkEIIIK. Asterisks indicate significant differences between untreated and ±Bay K 8644–treated cells (*, P < 0.05; **, P < 0.01, t test).