Kinetics and distribution of voltage-gated Ca, Na and K channels on the somata of rat cerebellar Purkinje cells.

Voltage gated ion channels on the somatic membrane of rat cerebellar Purkinje cells were studied in dissociated cell culture with the combination of cell-attached and whole-cell variation of patch clamp technique. The method enables us to record local somatic membrane current under an improved space clamp condition. Transient (fast-inactivating) and steady (slow inactivating) Ca channel currents, Na current, transient (fast-inactivating) and steady (slow-inactivating) K currents, were observed. Transient and steady Ca channel currents were activated at test potentials more positive than -40 mV and -20 mV, respectively (in 50 mM external Ba). The transient current inactivated with a half-decay time of 10-30 ms during maintained depolarizing pulses, while the steady current showed relatively little inactivation. Na current was activated at more positive potentials than -60 mV, and inactivated with a half-decay time of less than 5 ms. Transient and steady K outward currents were recorded at more positive potential than -20 mV and -40 mV, respectively. The transient current inactivated with a half-decay time of 2-8 ms. Ca, Na and K channels showed different patterns of distribution on the somatic membrane. Steady Ca channels tended to cluster compared with Na or K channels.