Figure 9. Representative experiments showing the effect of isoprenaline as studied by Fluo-4 fluorescence confocal images.

The overall intensity of Fluo-4 fluorescence is significantly higher in the presence of isoprenaline during the pacing stage of experiment (A). The original recordings (B, C) and the corrected images (D, E) show a larger spark frequency in the presence of isoprenaline (B–E have the same scale). We also observed the occurrence of longer calcium release events (F) and multiple sparks occurring at the same location in the experiments with isoprenaline (G).