Fig. 7. Effect of BTP2 and BEL on caffeine-induced Mn²⁺ entry in C57BL/6J and mdx^5cv fibers. (A) Left panel: Ca²⁺ transients triggered by caffeine (50 mM) in C57BL/6J and mdx^5cv fibers. Right panel: plot of average [Ca²⁺]_i at the base line (b) and at the peak of caffeine-induced Ca²⁺ transients (p) for both C57BL/6J and mdx^5cv fibers. (B) Effect of BTP2 (5 µM) and BEL (5 µM) on Mn²⁺ entry triggered by caffeine in C57BL/6J and mdx^5cv fibers. Prior to caffeine application, fibers were incubated with a solution containing 1 mM MnCl₂ and 1.7 mM CaCl₂. On the same graph and for each type of fibers are shown results from a control experiment and from experiments performed on fibers preincubated with either BTP2 (5 µM) for 10 minutes or BEL (5 µM) for 20 minutes (hatched trace). As caffeine triggered small increase in Fura-2 fluorescence even when excitation was set to 360 nm, maximal fluorescence was set to 100% and fluorescence quench was measured 90 seconds after caffeine application. (C) Compiled data showing the percentage of fluorescence decrease 90 seconds after caffeine application in control condition and when fibers had been preincubated with either BTP2 or BEL. Vertical hatched line on recordings shown in B indicates the time for measurements of fluorescence decrease. Numbers of fibers tested (from four C57BL/6J mice and four mdx^5cv mice) are indicated on bar graphs.