Figure 7. Slow inactivation properties of WT and mutant SCN1A channels.

A, onset of slow inactivation. Cells were stepped to −10 mV for 0.001–100 s, allowed to recover from fast inactivation at −120 mV for 50 ms, and subjected to a −10 mV test pulse. B, steady-state slow inactivation after a 30 s depolarization to potentials between −140 and −10 mV. Cells were allowed to recover from fast inactivation at −120 mV for 50 ms before a test pulse to −10 mV. C, recovery from slow inactivation. Cells were conditioned at −10 mV for 30 s, allowed to recover at −120 mV for 0.1–100 s, and immediately tested at −10 mV. Because the recovery period always exceeded 100 ms, effects of fast inactivation were considered negligible. Data were fitted to a two-exponential (A and C) or a Boltzmann function (B), as described in the Methods. Fitted values from all experiments are provided in Table 2.