Fig. 2

Effects of sarcoplasmic reticulum Ca²⁺-ATPase inhibitors on [Ca²⁺]_i. a Representative [Ca²⁺]_i trace upon additions of Lys-[Des-Arg⁹]BK (upper white boxes) is shown. Application of 100 nM of cyclopiazonic acid (CPA; black bar at top of graph) gradually elicited an increase in [Ca²⁺]_i, and the subsequent application of Lys-[Des-Arg⁹]BK (10 nM) induced a further increase in transient [Ca²⁺]_i. b Summary bar graph showing [Ca²⁺]_i increases following the first (upper bar) and second (middle bar) application of 10 nM Lys-[Des-Arg⁹]BK in the presence of external Ca²⁺ (2.0 mM) and following the application of 10 nM Lys-[Des-Arg⁹]BK with 100 nM CPA (lowermost bar) in the presence of extracellular Ca²⁺ (gray box on the upper-right side of graph). Each bar denotes the mean ± SE of seven experiments. c Following the repetitive [Ca²⁺]_i increases triggered by Lys-[Des-Arg⁹]BK (white boxes at top of graph), extracellular Ca²⁺ was removed and 100 nM CPA was applied (black bar at top of graph), which gradually elicited an increase in [Ca²⁺]_i, with the subsequent application of Lys-[Des-Arg⁹]BK (10 nM) inducing a considerably small transient [Ca²⁺]_i increase. Gray boxes on the upper-right side of graphs in a and c indicates the timing for application of the high extracellular-K⁺ (50 mM) solution. d Summary bar graph showing [Ca²⁺]_i increases following the first (upper bar) and second (middle bar) application of 10 nM Lys-[Des-Arg⁹]BK in the presence of external Ca²⁺ (2.0 mM) (gray box on the right side of graph) and following the application of 10 nM Lys-[Des-Arg⁹]BK with 100 nM CPA (lowermost bar) in the absence of extracellular Ca²⁺ (white box on the right side of graph). Each bar denotes the mean ± SE of the mean of four experiments. Statistical significance between the bars in b and d (shown by solid lines) is indicated by asterisks: *p < 0.05.