Fig. 4. Dose-response curve for the caffeine-induced cytosolic Ca²⁺ signals. ^wtRyR3- (filled squares) and ^V2322DRyR3- (open squares) expressing HEK293 cells were stimulated with increasing caffeine concentrations. Each data point is the averaged maximal amplitude of two to three independent experiments. EC₅₀ values amounted to 0.3 mM and 5.2 mM for the ^wtRyR3 and the ^V2322DRyR3 group, respectively. Sigmoidal fitting was performed using Microcal^TM Origin (version 6.0) software.