R-associated regulation of electronic spreading among monolayer neonatal ventricular myocytes. Coordinated spontaneous Ca2+ oscillations were measured by confocal microscopy in cultured NRVMs loaded with fluo-4. Representative images and traces illustrate the global Ca2+ transients prior to and after 2-APB (3 μm, 10 minutes) or heptanol (1 mM, 2 minutes) treatment followed by addition of IP3/BM (20 μm, 6 minutes) or ATP (5 μm, 3 minutes) (A). Ca2+ transient uncoupling, represented by the percentage of dysynchronous transients in four to five connected cells indicated with circles in control image, were found in heptanol, 2-APB (B and C), or pan-IP3R shRNA (D) treated cells. IP3/BM and ATP could rescue the uncoupled transients induced by heptanol but not by 2-APB or pan-IP3R shRNA. Nifedipine (0.3 μm, 10 minutes), PMA (1 μm, 20 minutes) or isoprenaline (Iso, 0.1 μm, 2 minutes) did not mimic the effect of 2-APB or IP3/BM on coupled spontaneous Ca2+ oscillations (E). **P <0.01 vs. the cells treated with vehicle or scramble shRNA; ##P <0.01 vs. heptanol alone, n = 10–23 independent determinations for each bar.