Pharmacological parameters for A2AR antagonist binding to A2AR, A1R-A2AR and A2AR-D2R CHO cells.

Competition experiments of [3H]ZM-241385 (2 nM) binding versus increasing concentrations of A2A receptor antagonists were performed as indicated in Methods in membrane preparations from CHO cells expressing A2AR or A1R and A2AR or A2AR and D2R. Binding data were fitted assuming that receptors (also when heteromerizing) form homodimers, and cooperativity (DCB ≠ 0, fitting to eq. 2; Materials and Methods) or non-cooperativity (DCB = 0, fitting to eq. 3; Materials and Methods) for competitor ligand binding was statistically tested (F test). Only KDB1 values (equilibrium dissociation constant of the first binding of B: ZM-241385, MSX-2, SCH-58261, SCH-420814 or KW-6002) are shown, since the analysis demonstrated non-cooperativity for the five A2AR antagonists. Data are mean ± S.E.M. values of three experiments.*: pDB1 values in A2AR cells; one-way ANOVA, followed by Newman-Keuls test.