Properties and expression of Kv3 channels in cerebellar Purkinje cells.

In cerebellar Purkinje cells, Kv3 potassium channels are indispensable for firing at high frequencies. In Purkinje cells from young mice (P4-P7), Kv3 currents, recorded in whole-cell in slices, activated at -30 mV, with rapid activation and deactivation kinetics, and they were partially blocked by blood depressing substance-I (BDS-I, 1 microM). At positive potentials, Kv3 currents were slowly but completely inactivating, while the recovery from inactivation was about eightfold slower, suggesting that a previous firing activity or a small change of the resting potential could in principle accumulate inactivated Kv3 channels, thereby finely tuning Kv3 current availability for subsequent action potentials. Single-cell RT-PCR analysis showed the expression by all Purkinje cells (n=10 for each subunit) of Kv3.1, Kv3.3 and Kv3.4 mRNA, while Kv3.2 was not expressed. These results add to the framework for interpreting the physiological function and the molecular determinants of Kv3 currents in cerebellar Purkinje cells.