Figure 7. Concentration–response curves for ATP in inducing [Ca²⁺]_i increase in 1321N1 cells stably expressing the wild-type and mutant P2Y₁₁–GFP receptors.

Cells pre-incubated with 2 μM fura 2/AM were stimulated with various concentrations of ATP and the change in fluorescence (ΔF_{340 nm}/F_{380 nm}) was detected. Results represent the mean values and S.E.M. from 40–70 single cells. Results were obtained in at least three separate experiments. Filled circles (●) represent results obtained with the wild-type receptor, open circles (○) the F109I mutant, filled triangles (▼) the E186A mutant, open triangles (▽) the R268A mutant, filled squares (■) the R268Q mutant and open squares (□) the A313N mutant receptor.