FIGURE 4.

Interaction between open-channel block and slow inactivation in Purkinje cells. (A, left) Voltage protocols and representative traces for detecting the extent of block during long (50- to 500-ms) conditioning steps to different potentials, as labeled. (A, right) Normalized peak resurgent current versus conditioning pulse duration. Data are fitted with a single exponential, with parameters given in Results. For the +60-mV step, N = 6; for the +30-mV step, N = 7, and for the 0-mV step, N = 8. (B, upper) Voltage protocol and representative traces to test the effect of conditioning voltage on slow inactivation. (B, lower) Reference and test steps at higher gain, illustrating the onset of the difference in availability at longer conditioning durations. Test currents evoked after all four conditioning voltages are shown; arrows indicate largest and smallest amounts of recovery and are labeled with the corresponding conditioning voltages. (C) Plot of the percent availability increase after steps to −30, +30, and +60 mV relative to that after steps to 0 mV, as a function of conditioning duration. All recovery intervals were 100 ms. For intervals <100 ms, N = 8; for intervals >100 ms, N = 10. Dotted line indicates no change relative to 0 mV.