Fig. 3.

4-AP differentially blocks rapidly and slowly deactivating currents. A, Currents evoked in the presence of different concentrations of 4-AP by the voltage-clamp protocol shown above the traces. B, Tail currents at −40 mV obtained during the experiment shown inA. C, Rapidly deactivating tail currents in increasing concentrations of 4-AP obtained by the subtraction method described in Figure 1. D, Slowly deactivating tail currents in increasing concentrations of 4-AP. E, Plot of rapidly and slowly deactivating tail current amplitudes as a function of 4-AP concentration. The lines represent Langmuir first-order fits of experimental data.