Figure 1. Simultaneous recording of inward current and Ca²⁺ release.

A, activation of the L-type Ca²⁺ current (200 ms) elicited a substantial Ca²⁺ release signal. Both the current and the Ca²⁺ signal were markedly enhanced by administration of 1 μm isoproterenol in the bathing solution. B, in an analogous experiment, activation of the Na⁺ current (50 ms) in a different cell showed smaller Ca²⁺ signal amplitudes but similar β-adrenergic potentiation. Traces show from top to bottom: voltage protocol (mV), current record, line-scan image, mean Ca²⁺ concentration profile, same current record expanded 10 times (red traces, not temporally aligned to the other signals).