Abstract
This study used an isolated right atrial preparation, cross-perfused with arterial blood from a support dog. We investigated the effects of dibutyryl cyclic AMP (DBcAMP) on heart rate and arterial blood pressure of the support dog and on the sinus rate and atrial contractile force of the isolated perfused atrium. DBcAMP was injected into the external jugular vein of the support dog or into the sinus node artery of the isolated atrium. DBcAMP to the support dog induced a small increase and/or decrease in arterial blood pressure at a dose of 3 or 10 mg/Kg i.v. It produced a decrease, with or without an increase in blood pressure, at a dose of 30 mg/Kg i.v., and a dose-dependent increase in heart rate in the support dog. In the isolated atrium, positive chronotropic and inotropic effects were observed. Direct injection of DBcAMP (3-30 mg) into the sinus node artery of the isolated atrium induced positive chronotropic and inotropic effects, after initial brief negative effects, in a dose-dependent manner. DBcAMP did not change norepinephrine-induced positive chronotropic and inotropic effects in the isolated atrium. These results demonstrate that DBcAMP induces a decrease in systemic arterial blood pressure with increases in sinus rate and atrial contractile force, and acts additively with the norepinephrine-induced positive cardiac effects in the dog heart.
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