cAMP inhibition curves for 7 and 17. After 30 min incubation with increasing concentrations of 7 or 17, forskolin was added to CHO cells expressing A1 or A3 ARs to increase adenylyl cylase. The inhibition of adenylyl cylase was measured using the Direct cAMP Enzyme Immunoassay. For a summary of EC50 values obtained, see Table 2. The results shown are means ± S.E.M. of three independent experiments.