Figure 11.
Resurgent sodium current promotes the recovery of NaV channels. (A and E) Representative current traces recorded from mid- to high-frequency (A) NM and (E) NMc neurons, in response to two voltage-clamp protocols (for details, please refer Hong et al.43,50). In short, a conditioning step was applied to neurons followed by recovery period at rest for the varying amounts of time. After recovery, a pulse to 0 mV was applied to evoke a transient NaV current. The conditioning step is +30 mV at 5 ms in Open-Block Condition and −30 mV at 40 ms in Inactivation Condition. Recovery time varied from 2 to 50 ms for mid- to high-frequency NM neurons and from 2 to 30 ms for NMc neurons. (B and F) Population data showing the NaV channel availability (%) as a function of recovery time. To calculate NaV channel availability, a reference pulse to 0 mV was applied to neurons (not shown in the figure), and the amplitude of transient NaV current after the recovery was normalized to this “reference amplitude.” The recovery trajectory was fit by a single exponential, to obtain recovery tau (time constant). (C and G) Population data showing the recovery tau under two different condition states. Error bar = standard error. (D and H) Representative NaV current traces taken from respective (A) and (E) were normalized and overlaid for recovery time periods of 2 and 20 ms. Data were adapted from Hong et al.43,50 NM indicates nucleus magnocellularis.