Fig. 4. A shift in the steady-state inactivation toward negative voltage. A two-pulse voltage protocol (top ) was used to determine the voltage dependence of steady-state inactivation for WT-β1and F1579A-β1. (A–D ) Representative current traces elicited by the test pulse following the indicated prepulse voltages in control (Ctl) and ketamine (KET). (E ) A plot of test Na+current (INa) normalized to control INaamplitude (test pulse with no prepulse) versus prepulse voltage without (solid) and with (open) 1 mm ketamine for WT-β1.Smooth curves are Boltzmann function fits to the data with the indicated parameters. (F ) Same as above ( E ) but for F1579A-β1and 2 mm ketamine. The dashed line indicates the fraction of channels not inactivated even at large depolarized prepulse voltages. For both summary figures, n = 5.