Figure 1.

Purkinje neurons from embryonic chick have resurgent Na current with kinetics similar to those in mouse Purkinje neurons. A, Alignment of sequences of the initial segment of the cytoplasmic tail of Na_Vβ4, corresponding to residues 154–173 of the mouse protein and 1–20 of the extended β4 peptide. Na_Vβ2 residues correspond to 151–162 of the mouse protein. Black with white lettering indicates conservation with mouse Na_Vβ4 sequence; gray with white lettering indicates conservative substitutions; white with black lettering indicates lack of conservation. B, Top, “Resurgent current” voltage protocol, applied in all experiments. Bottom, Representative whole-cell TTX-sensitive Na currents recorded from an acutely dissociated Purkinje cell from late-stage embryonic chick (bottom). C, Mean resurgent Na currents in mouse and chick Purkinje neurons, normalized to transient current evoked at +30 mV. Inset, Overlay of mean resurgent currents individually normalized to peak resurgent current. D, Voltage dependence of amplitude of resurgent currents evoked by repolarization following a 10 ms step to +30 mV; amplitudes normalized to that of the transient current evoked at +30 mV. E, Time to peak and decay time constant (τ) of resurgent current evoked at −30 mV. Black, chick, n = 12; gray, mouse, n = 7.