Fig. 1. Inhibitory effect of verapamil on hKv1.5 current. (A) Superimposed current traces of hKv1.5 current activated by 300-ms depolarizing voltage-clamp steps to test potentials of -50 to +50 mV applied from a holding potential of -50 mV, before and 5 min after exposure to 10 mM verapamil. (B and C) Initial (B) and late (C) current levels during test potentials measured in the absence and presence of verapamil. (D) Current ratio of initial and late currents, measured by dividing the hKv1.5 current in the presence of verapamil by that in its absence. *, P<0.05 compared with the initial current ratio.