Effects of repetitive stimulation. (A) Representative traces for mag-fluo-4 fluorescence in WT and EK FDB fibers subjected to a single 50 Hz train of stimulation for one second and the response was acquired in the line scan mode of a confocal microscope. (B) Tetanic calcium response averaged from first to 50th peak (50 pulses for one second) and the calculated averaged response was plotted. (C) Effects of fatiguing stimulation (100 Hz) on the amplitude of the Ca2+ transients in WT and EK fibers measured with mag-fluo-4. (D) Average amplitude of the 4CmC releasable Ca2+ stores after repetitive stimulation (100 Hz) measured with mag-fluo-4. (E) Cytosolic Ca2+ concentrations measured with Fura-2 before and after electrical stimulation using the same stimulation protocol as in (C). Values represent the average values over one second at 30 seconds after stimulation. Data are shown as mean ± SEM. *P <0.05, **P <0.01, and ***P <0.001.