R-associated regulation of the intercellular exchange in ventricular myocytes. Representative images (inset) and traces of the bleached cell indicate 6-CFDA transfer through GJs from the connected NRVMs monitored by the FRAP method (A). I, I0, It and It1/2 stand for the fluorescence intensity at the initial, after bleaching, recovery at 400 s, and at the time for 50% recovery, respectively. Effects of IP3/BM (20 μm, 6 minutes), ATP (5 μm, 3 minutes), 2-APB (3 μm, 10 minutes), heptanol (1 mM, 2 minutes), Gap 27 (300 μm, 30 minutes) and BAPTA/AM (200 μm, 10 minutes) on the fluorescence recovery in bleached cells are indicated with the percentage of two parameters; It/I (B) and CFIRR (C). A rescue effect of IP3/BM was found on heptanol- or Gap 27-suppressed GJ, but not on 2-APB-inhibited GJ permeability (D and E). Knockdown of pan-IP3R expression was obtained in NRVMs by shRNA against specific IP3R isoforms (Additional file 1: Figure S1). The traces of 6-CFDA recovery after bleaching (F) and their summarized data (G and H) between scramble control and IP3R deficient myocytes illustrate the effect of IP3R deficiency on the intercellular exchange. *P <0.05 and **P <0.01 vs. Con (vehicle) or scramble shRNA, and ##P <0.01 vs. heptanol or Gap 27 treated cells, n = 7–25 independent experiments for each bar. Representative confocal images (I) of paired end-end cardiomyocytes isolated from mouse ventricles illustrate the fluorescence recovery in bleached cell 1 due to 6-CFDA diffusion through GJs from the connected cell (cell 2) monitored by FRAP method. Cell 3 is a background control. The statistical data depict the effects of IP3/BM (20 μm, 6 minutes), 2-APB (5 μm, 10 minutes) and XeC (10 μm, 20 minutes) in bleached cells (J and K). **P <0.01 vs. Con (0.1% DMSO), n = 15–20 paired cells for each bar.