Figure 3. Effects of repetitive stimulation on [Ca²⁺]_i.

A, traces show: top, [Ca²⁺]_i; bottom, I_Ca. During the periods of stimulation (shown by the spikes in the current record) 100 ms duration depolarizing pulses were applied from a holding potential of -80 to 0 mV at 3 Hz. B, changes in I_Ca and Δ[Ca²⁺]_i during repetitive stimulation. I_Ca was normalized to the value of the first I_Ca in the burst. [Ca²⁺]_i transients were normalized to the maximal Δ[Ca²⁺]_i occurring during the train of voltage steps. Graphs labelled a-c correspond to transients a-c shown in A.