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, I to. Half maximal values for inactivation and activation were −65 mV and −39 mV, respectively. I to 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 I to in PCs. As in other cells, I to may be important in shaping PC output by modulating intrinsic and extrinsic factors that govern PC firing.