Calcium-induced calcium release in cerebellar purkinje cells

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