Voltage dependence of relief of inhibition by A-887826, VX-548, and LTGO-33. (A) Voltage protocol for assaying relief of inhibition. A 100-ms prepulse to varying voltages is followed by a test pulse to +10 mV to assay channel availability after returning to −80 mV for 10 ms to allow channels to recover from fast inactivation. (B) Examples of test pulse currents evoked after the prepulses to −80 and +120 mV in control (left) and after application of each inhibitor (right). (C) Test pulse currents versus prepulse voltage in control (black) and with 300 nM A-887826 (blue, mean ± SEM, n = 7). Solid line: Boltzmann function with midpoint +13 mV and slope factor 9.6 mV (mean values for individual fits to data from the seven cells). (D) Same for 1 nM VX-548 (red, n = 7). Solid line: Boltzmann function with midpoint +33 mV, slope factor 16.3 mV. (E) Same for 300 nM LTGO-33 (green, n = 7). Solid line: Boltzmann function with midpoint −11 mV, slope factor 16.5 mV.