Figure 2.

Verapamil blocks currents through the voltage-gated K⁺ channel Kv1.3 in a cumulative manner. Current through Kv1.3 channels were elicited by 200 ms depolarizing pulses from a holding potential of −80 to 40 mV every 30 s. Current traces were obtained before (1) and after (2–10) the addition of 20 μM verapamil to the external solution (left panel). Only the first 60 ms of the current traces are shown for clarity. Time course of peak Kv1.3 current reduction by verapamil (accumulation of block) (right panel). Application of 20 μM verapamil to the bath solution is indicated by an arrow. Time course of peak current reduction could be fitted by a single exponential function to the data points and yielded a τ_acc=31 s in this experiment.