Figure 8. Original trace depicting the effects of morphine on the rate of Ca²⁺uptake and content in isolated sarcoplasmic reticulum vesicles (A). Adenosine triphosphate was used to trigger Ca²⁺uptake into the vesicles. Caffeine was used to trigger Ca²⁺release. The concentrations of morphine are shown. (B) Summarized data for the effects of morphine on the rate of Ca²⁺uptake. *Significant change from control (P < 0.05). n = 4 individual experiments.