CALCIUM-INDUCED CALCIUM-RELEASE IN CEREBELLAR PURKINJE-CELLS

Depolarization-induced intracellular Ca2+ rises were measured in fura-2-loaded, voltage-clamped Purkinje cells. The peak Ca2+ rise increased more than linearly with voltage step duration, suggesting the presence of Ca2+-induced Ca2+ release. In cells from young animals, in which Ca2+ currents could be satisfactorily recorded, a supralinear relation was also found between peak Ca2+ rise and Ca2+ current integral. Responses to long pulses were inhibited in cells dialyzed with 20 mu M ruthenium red and potentiated in cells bathed in the presence of 20 mu M ryanodine. Upon repetitive depolarization, increasing Ca2+ rises were elicited by successive voltage pulses, probably because of a potentiating effect of residual Ca2+. Altogether, the results indicate an important contribution of Ca2+-induced Ca2+ release to Ca2+ signals of Purkinje cells.