PD 81723 is an allosteric potentiator at Adenosine A1-R that acts via agonist-dependent and independent mechanisms. PD 81723 enhances the functional effects of adenosine and adenosine analogs. This compound also inhibits basal and forskolin-stimulated A cyclase (adenylyl cyclase, AC) activity in Adensosine A1-R expressed in CHO cells, possibly via direct potentiation of constitutive receptor activity or by direct inhibition of A cyclase (adenylyl cyclase, AC).