FIGURE 1.

Stretch protocol applied to trabeculae at 20 °C and at the initial SL 1.9 μm. Top panel, force response to photolytic release of ATP at time zero. Dots, trabeculae in 32 μmol/liter of Ca²⁺. Solid line, trabeculae in 1 μmol/liter of Ca²⁺. Middle panel, P_i release derived from the change in fluorescence of MDCC-PBP and corrected for saturation of MDCC-PBP with P_i (see ”Experimental Procedures“). Bottom panel, motor movement, with stretch beginning at 0.4 s and ending at 0.7 s after photolytic release of ATP, and the release beginning at 1 s and ending at 1.3 s. Vertical lines across the panels indicate the timing of changes in motor movement. The figure shows the average of five experiments for each Ca²⁺ concentration.