Figure 2.

Strong local β₂-AR/cAMP signals in the PLM/NKA microdomain. (A, B) Representative FRET traces for Epac1-camps and PLM-Epac1 expressing ARVMs upon β₁-AR-selective stimulation (100 nmol/L ISO plus 50 nmol/L of the β₂-AR blocker ICI118551). (C, D) Representative FRET traces for β₂-AR-selective stimulation (100 nmol/L ISO plus 100 nmol/L of the β₁-AR blocker CGP20712A). Maximal stimulation of cAMP was subsequently achieved by the PDE2 selective inhibitor (BAY 60-7550, 100 nmol/L used in C and D, see Figure 4), the unselective PDE inhibitor IBMX (100 μmol/L), and the adenylyl cyclase activator forskolin (10 μmol/L). (E) Quantification of FRET responses to selective β₁- and β₂-AR stimulations shown in A–D. Number of cells (n) and hearts (N) per condition were as follows—n/N = 40/6 and n/N = 33/6 for β₁-AR and n/N = 31/9 and n/N = 38/8 for β₂-AR, respectively. *—significant difference, P < 0.05 by mixed ANOVA followed by Wald χ²-test.