Fig. 3
Effects of ryanodine receptor inhibitors on [Ca2+]i. a Representative trace of [Ca2+]i produced by repeated additions of Lys-[Des-Arg9]BK (white boxes at top of graph) in the presence (2.0 mM; gray segments of lower bar) or absence of extracellular Ca2+ (white segment of lower bar) is shown. The increase in [Ca2+]i induced by 10 nM Lys-[Des-Arg9]BK was inhibited by the application of 1.0 μM dantrolene (upper black box) in the absence of external Ca2+. Gray box on the upper-right side of graph indicates the timing of application of the high-extracellular-K+ (50 mM) solution. b Summary bar graph showing [Ca2+]i increases following the first (upper bar), second (second bar from the top) and third (lowermost bar) application of 10 nM Lys-[Des-Arg9]BK in the presence of external Ca2+ (2.0 mM; gray boxes on right side of graph), and following the application of 10 nM Lys-[Des-Arg9]BK in the presence of 1.0 μM dantrolene (third bar from the top) in the absence of external Ca2+ (white box on the right side of graph). Each bar denotes the mean ± SE of seven experiments. c Following the repetitive Lys-[Des-Arg9]BK-induced [Ca2+]i increases (upper white boxes) in the presence (2.0 mM: lower gray bar) of extracellular Ca2+, we applied 1.0 μM dantrolene (upper black box). The increase in [Ca2+]i induced by 10 nM Lys-[Des-Arg9]BK was inhibited by the application of 1.0 μM dantrolene in the presence of external Ca2+. The gray boxes on the upper-right side of the graphs in a and c indicate the timing for application of high-extracellular-K+ (50 mM) solution. d Summary bar graph showing the [Ca2+]i increases following the first (upper bar) and second (middle bar) application of 10 nM Lys-[Des-Arg9]BK with external Ca2+ (2.0 mM; vertical gray bar on the right side of graph), and following the application of 10 nM Lys-[Des-Arg9]BK with 1.0 μM dantrolene (lowermost bar). Each bar denotes the mean ± SE of the mean of three experiments. In b and d, the statistical significance between bars (shown by solid lines) is indicated by asterisks: *p < 0.05