Panel A: Representative normalized cyto-iATP confocal line-scan traces of normalized fluorescence from superior and inferior SA nodes under control conditions, after I f inhibition with ivabradine, and following SERCA inhibition with thapsigargin. Panel B: Scatter plot of cyto-iATP transient frequency for superior and inferior SA nodes across different conditions. Panel C: Scatter plot of cyto-iATP peak amplitude for superior and inferior SA nodes across different conditions. The horizontal axis represents different treatments, and the vertical axis represents the measured values. Data points are shown for individual biological replicates and per-animal means. P-values indicate statistical significance between conditions.
SR Ca 2+ release drives beat-to-beat ATP oscillations, while I f modulates metabolic frequency. (A) Representative normalized cyto-iATP confocal line-scan traces from superior (top) and inferior (bottom) SA nodes acquired under control conditions (left), after If inhibition with ivabradine (30 µM; middle), and following SERCA inhibition with thapsigargin (1 µM; right). Traces are shown as normalized fluorescence (F/F0). The dashed line indicates baseline fluorescence (F/F0 = 1). (B and C) Summary quantification of cyto-iATP oscillation frequency (B) and peak cyto-iATP oscillation amplitude (C) across conditions (N = 6 mice per group). P values are shown above comparisons. Large circles denote per-animal means; small circles indicate individual biological replicates. N represents the number of independent mice.