FUNCTIONAL DIVERSITY OF L-TYPE CALCIUM CHANNELS IN RAT CEREBELLAR NEURONS

Single-channel recordings show that functionally different L-type Ca2+ channels coexist in rat cerebellar granules. Besides two different dihydropyridine (DHP)sensitive gating patterns with properties similar to those of cardiac L-type channels, cerebellar granules contain a third DHP-sensitive gating pattern with unusual voltage-dependent properties and slightly different conductance. This ''anomalous gating'' is characterized, on one hand, by rare, short openings with very low open probability even at high positive voltages and, on the other hand, by long openings with high open probability at negative voltages after a predepolarization. L-type channels with anomalous gating appear suited to generate a surge of Ca2+ influx following strong neuronal activity. The anomalous gating can be explained by a model in which voltage controls the equilibrium between two gating modes.