Representative line-scan confocal images show fluo-4 signals in permeabilized CMs. [Ca2+]i,=50 nM. A, C. Scan Images (2 sec) and traces for nuclear (Nu, upper panels) and cytosolic (Cy, lower panels) regions show fluo-4 signals and intensity profiles (F/F0) at basal condition (Ctl) and after sequential addition of IP3 (10 μM), anti-PLB Fab (100μg/ml), and 2-APB (10 μM). M indicates minutes after addition of the reagents. B.D, Bar graphs show F/F0 at rest for Nu (left panels) and Cy (right panels) in each condition. * indicates p<0.05. n=12 CMs, 6 mice for WT; n= 13 CMs, 6 mice for PLB-KO.