Figure 4. The effect of exposure to BAPTA AM on the [Ca²⁺]_i and the spontaneous action potential recorded from different toad pacemaker cells.

A, [Ca²⁺]_i recorded under control and after 5 and 8 min exposure to 10 μm BAPTA AM. B, the effects of BAPTA AM on spontaneous action potential were recorded from a non-indo loaded cell. The panels show control, 5 and 8 min exposure. C and D, the correlations between firing rate and [Ca²⁺]_i from 12 measurements of 5 cells. C shows diastolic [Ca²⁺]_i and D shows systolic [Ca²⁺]_i. The correlation coefficients are shown (r) on each panel and are statistically significant (P < 0.01).