Fig. 3

Effects of depolarization on [Ca²⁺]_i increase following the reintroduction of Ca²⁺ during IM stimulation. The experimental protocol is shown in Figs. 1 and 2. Cells were perfused with a Ca²⁺-free solution for 5 min prior to the IM addition. Cells were treated with IM for 10 min, and then Ca²⁺ (1.5 mM) was reintroduced. In these figures, changes in the [Ca²⁺]_i increase for 2 min were shown (9.5–11.5 min from the start of IM stimulation). The figure clearly shows decreases in the rate of [Ca²⁺]_i increase following the reintroduction of Ca²⁺ with increasing [K⁺]_o. a IM (1 μM). With increasing [K⁺]_o, the rate of [Ca²⁺]_i increase decreased, and the final [Ca²⁺]_i also decreased. b IM (5 μM). With increasing [K⁺]_o, the rate of [Ca²⁺]_i increase decreased. The final [Ca²⁺]_is decreased by 10% at 151 mM [K⁺]_o