Fig. 5.

AC3-I SAN cells fail to increase diastolic Ca²⁺ spark frequency or DDR with ISO. (A–C) Representative line scan confocal images of Rhod-2 fluorescence and simultaneously recorded spontaneous APs (Upper) and spatially averaged Ca²⁺ transients (Lower) at baseline and after ISO (1 μM). (Insets) Superimposed DDR for each genotype, before and after ISO, corresponding to the dashed boxes marking the confocal images. (D–G) Summary data for DDR (D), Ca²⁺ spark frequency (E), Ca²⁺ transient (F), and diastolic Ca²⁺ (G) before and after ISO (1 μM) (n = 13–21 per group). *, P <0.05; **, P <0.01 compared with baseline.