Fig. 2. Spontaneous and triggered Ca²⁺ events in WT and RyR1^–/– urinary bladder myocytes. (A-C) Typical confocal line-scan images of (A) spontaneous, (B) caffeine-activated or (C) depolarization-activated Ca²⁺ events in WT (left) and RyR1^–/– (right) myocytes. Caffeine (10 mM) was applied near the cell by pressure ejection from a glass pipette while depolarizing pulses of 50 mV, 100 mseconds from a holding potential of –40 mV were applied to whole-cell patch-clamped myocytes. Fluo-4 fluorescence averaged from a 2-µm region indicated by the bar on the line-scan image is illustrated under each image. Myocytes were loaded with Fluo4-AM and when patch-clamped, 50 µM Fluo-4 was added to the intracellular medium. Spatio-temporal parameters of these Ca²⁺ events are given in Table 1.