PD 116,948, a highly selective A1 adenosine receptor antagonist

(R)-N-(1-Methyl-2-phenylethyl) adenosine (R-PIA), an Adenosine Receptor agonist has both negative chronotropic activity and coronary vasodilator activity. These actions of R-PIA are proposed to be mediated by subtypes (A1 and A2) of adenosine receptors. PD 116,948 is a xanthine derivative which is a highly selective A1 Adenosine Receptor ligand. In this study PD 116,948 selectively antagonized the negative chronotropic activity of R-PIA in the isolated rat heart. These results are consistent with, and add further support to the hypothesis that Adenosine Receptor agonists mediate their negative chronotropic activity via A1 receptors and their vasodilator activity via A2 receptors.