Fig. 2. Time constant of verapamil blockade of hKv1.5 current during depolarization. (A) Superimposed hKv1.5 currents recorded during the depolarizing step to 0 mV in the absence and presence of verapamil (upper panel). The current ratio was obtained by dividing hKv1.5 current in the presence of verapamil (I_Verapamil) by that in control (I_Control) and fitted with a single exponential function, yielding the time constant for channel blockade (t). (B) Time constant (t) for channel blockade at various test potentials. *, P<0.05 versus -10 mV.