Figure 7.

P2X₂ receptor. (A) ATP dependence of transient currents obtained with membrane vesicles from a rP2X₂ HEK293 cell line. The plot shows average values (and SE) of four different experiments. Each was normalized to the saturation value of a fit with a Hill function. Subsequently, combined data were fitted with the Hill function, yielding an EC₅₀ of 17.4 ± 5.5 μM and a Hill coefficient of 1.15 ± 0.44. Experimental conditions as in Fig. 6 but different ATP concentrations (1–1000 mM) were used. (B) Inhibition of the P2X₂ receptor by suramin. The receptor was activated using a solution exchange protocol as in Fig. 6 with 100 μM ATP in the presence of different concentrations of suramin (0.3–1000 μM) in all buffers. The plot shows mean values (and SE) of six independent experiments. The data were fitted with a Hill function with constant offset yielding an IC₅₀ of 6.4 ± 0.4 μM and a Hill coefficient of 1.55 ± 0.13.