Figure 5. The effects of low doses of caffeine on Ca²⁺ wave propagation at increased SR Ca²⁺ load.

A, linescan images of fluorescence changes induced by focal applications of caffeine (10 mM) before (a) and 20 s after introducing 0.5 mM caffeine to the bath (b), as illustrated by the scheme at the top. [Ca²⁺]_o was 3 mM. Calibration bars: horizontal, 18 μm; vertical, 0.66 s. B, linear fits to the positions of the Ca²⁺ waves for sections defined by arrows in corresponding images; the values of mean wave velocities are indicated. C, time-dependent changes in fluorescence at the sites of caffeine applications (marked in the corresponding images by bars) with (black traces) and without (grey traces) conditioning by 0.5 mM caffeine.