Figure 7.
Kinetics of endogenous resurgent Na current are more closely replicated by β4 peptides derived from various species than by mutant peptides. A, Voltage dependence of resurgent currents in mouse and chick Purkinje neurons and mouse CA3 neurons with various β4 peptides. All currents were evoked by repolarization to indicated voltage for 100 ms following a 10 ms conditioning step to +30 mV and are normalized to the peak resurgent current evoked at 0 mV; 7≤ n ≤12. Error bars indicate ±SEM. B, Mean resurgent currents (gray) and fits (black), at −30 mV (left) and at −10 mV (right). C, Left, Blocker Kd obtained from fits by ratio of BO rate to OB rate, corrected for concentration of 200 μm. Right, Keq of inactivation, calculated from ratio of the rate of IO to that of OI. D, Kinetics of resurgent Na currents. Currents evoked as in A. x-axis, time to peak resurgent current from onset of voltage step; y-axis, decay time constant (τ) of resurgent current, fit with a single exponential.