THE EFFECT OF STIMULATION OF ATRIAL RECEPTORS ON THE PLASMA CONCENTRATION OF VASOPRESSIN

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Abstract
The effect of stimulation of the left atrial receptors on plasma concentration of vasopressin and urine flow was studied in dogs anesthetized with chloralose. Distending a large balloon in the left atrium, so as to occlude the mitral valve and increase left atrial pressure, consistently resulted in a decrease in plasma vasopressin and increase in urine flow. Discrete stimulation of the left atrial receptors, by distending small balloons in the pulmonary vein-left atrial junctions and in the left atrial appendage, consistently resulted in a decrease in plasma vasopressin and an increase in urine flow. The left atrial receptors were stimulated discretely in dogs in which bretylium tosylate, atropine and atenolol were administered. In these dogs distension of the small balloons was not associated with significant changes in heart rate, left atrial pressure or pressure or arterial blood pressure and consistently resulted in a decrease in plasma vasopressin and an increase in urine flow. This decrease in the plasma concentration of vasopressin is evidently a direct result of discrete stimulation of the atrial receptors and is not secondary to any hemodynamic changes. The exact role of this decrease in plasma concentrations of vasopressin in the diuretic response to stimulation of the left atrial receptors remains to be established.