Fig. 3.

Use of ryanodine receptor antagonist to demonstrate signal specificity. Representative optical action potential (a) and calcium transient (b) recorded under control perfusion (Ctrl) or immediately after administration of ryanodine (Ry, 30 s – 3 min). Ryanodine (Ry) administration significantly reduced peak calcium transient amplitudes (a, c), with no effect on optical action potential amplitudes (b, d). Normalized fluorescent signals were used for time measurements. Calcium transient (c, e, g) and action potential (d, f, h) parameters are shown before and 1 min after ryanodine administration at a pacing frequency of 180 msec cycle length. Mean ± SEM, n = 3 juvenile rat hearts