Potentiation of the negative chronotropic and inotropic effects of adenosine by 2-phenylaminoadenosine.

1. Effects of 2-phenylaminoadenosine on SA nodal pacemaker activity and atrial contractility were studied, using eleven isolated, blood-perfused dog atrial preparations. The compounds were administered via the cannulated sinus node artery of the isolated atrium. 2. 2-Phenylaminoadenosine induced negative chronotropic and inotropic effects and was 100 times less potent than adenosine in this action. 3. The interaction between adenosine and 2-phenylaminoadenosine was studied. 2-Phenylaminoadenosine potentiated the effect of adenosine on atrial muscle, but not that of acetylcholine.