Differential effects of the allosteric enhancer (2-amino-4,5-dimethyl-trienyl)[3-(trifluoromethyl) phenyl]methanone (PD81,723) on agonist and antagonist binding and function at the human wild-type and a mutant (T277A) adenosine A1 receptor11Abbreviations: CCPA, 2-chloro-N6-cyclopentyladenosine; DPCPX, 1,3-dipropyl-8-cyclopentylxanthine; CPA, N6-cyclopentyladenosine, R-PIA, N6-[-(R)-1-methyl-2-phenylethyl]adenosine; NECA, 5′-(N-ethyl)-carboxamidoadenosine; N-0840, N6-cyclopentyl-9-methyladenine; theophylline, 1,3-dimethylxanthine; PD81,723, (2-amino-4,5-dimethyl-trienyl)[3-(trifluoromethyl) phenyl]methanone; BCA, bicinchoninic acid; BCS, bovine calf serum; cAMP, adenosine 3′,5′-cyclic monophosphate; DMEM, Dulbecco’s modified Eagle’s medium; CHO, Chinese hamster ovary; and wt, wild-type