Fig. 1. β-AR-stimulated augmentation of I_Ca and Ca²⁺ transients is diminished in aging.

a Representative whole-cell currents elicited from young and old ventricular myocytes before (control; black) and during application of ISO (blue). b Dot-plots showing the fold-change in peak current with ISO in young and old myocytes. c Dot-plots showing peak I_Ca density before and after ISO. d Plots showing the voltage dependence of I_Ca density for both groups before and after ISO. e Voltage dependence of the normalized conductance (G/G_max) fit with Boltzmann functions and f dot-plots showing the V_1/2 of activation for each group. N-numbers for patch clamp data in (b–f ) is as follows: young (N = 9, n = 13) and old (N = 5, n = 11). g Representative Ca²⁺ transients recorded before (black) and after ISO (blue) from paced young and old myocytes. h Dot-plots showing the fold increase in Ca²⁺ transient amplitude after ISO and i Ca²⁺ transient amplitude before and after ISO. N-numbers for Ca²⁺ transient data in (h, i) is as follows: young (N = 5, n = 15) and old (N = 3, n = 15). Unpaired two-tailed Student’s t-tests were performed on data sets displayed in (b, h). Two-way ANOVAs with multiple comparison post-hoc tests were performed on data displayed in (c, f, i). Young data in (b–f ) is pooled from NIA young and JAX young myocytes, as no significant differences were found in I_Ca when NIA young and JAX young myocytes were compared (see Supplementary Fig. 1a–e). Young data in (h, i) is from NIA young. Data are presented as mean ± SEM. Source data are provided in the Source Data file.