Visualization of DICR by laser scanning confocal microscopy. (A) Typical results of time-lapse R-CEPIA1er fluorescence measurement of individual 5 BV-infected RyR1/R-CEPIA1er HEK293 cells using a laser scanning confocal microscope (see also Video 1). Cells were incubated with normal Krebs solution and high [K⁺] (50 mM) solution was perfused during measurements (arrow). Note that R-CEPIA1er fluorescence was transiently decreased by high [K⁺] solution and recovered after replacement with normal Krebs solution. (B) Percent responding cells to high [K⁺] (50 mM) or caffeine (10 mM) solution. 100 cells were randomly picked from each of No BV or 5 BV cells. Whereas 95% of 5 BV cells responded to high [K⁺], <1% of No BV cells responded. All the cells responded to caffeine. Data are means ± SD (n = 3, N = 3). n is the number of cells and N is the number of independent experiments. Related to Fig. 1 A and Video 1.