A transient voltage-dependent outward potassium current in mammalian cerebellar Purkinje cells.

Utilizing the single electrode voltage clamp technique applied to rat Purkinje cells (PCs), we have recorded a transient outward voltage-dependent potassium current, Ito. Half maximal values for inactivation and activation were -65 mV and -39 mV, respectively. Ito decays as a single exponential with a time constant of 95 ms and is reduced by 4-aminopyridine. Based on criteria of voltage dependency of activation and inactivation, kinetics of inactivation, ionic selectivity and pharmacologic sensitivity, we have verified a strong resemblance between the typical A current in other neurons, and Ito in PCs. As in other cells, Ito may be important in shaping PC output by modulating intrinsic and extrinsic factors that govern PC firing.