Figure 3.

Genistein-induced block of closed f-channels. A train of activating/deactivating steps (−105 mV*3 s/+5 mV*0.75 s; 1/6 Hz) was delivered to the cell under study and stable I_f traces were recorded (left). Current stimulation was then stopped for 72 s by clamping the cell at the holding potential (−35 mV). Genistein (50 μM) superfusion started at the beginning of this silent period, and was maintained throughout the whole time of the experiment. Train stimulation was then resumed (right). When traces recorded just after the interruption (b) and at the end of the experiment (c) were compared to the trace recorded just before the interruption (a), the calculated ratios b/a and c/a were 0.63 and 0.64, respectively, while the c/b ratio yielded a value of 1.01.