The effect of stimulation of atrial receptors on the plasma concentration of vasopressin.

The effect of stimulation of the left atrial receptors on plasma concentration of vasopressin and urine flow was studied in dogs anaesthetized 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 an 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 had been administered. In these dogs distension of the small balloons was not associated with significant changes in heart rate, left atrial pressure or arterial blood pressure and consistently resulted in a decrease in plasma vasopressin and an increase in urine flow. It is concluded that this decrease in the plasma concentration of vasopressin is a direct result of discrete stimulation of the atrial receptors and is not secondary to any haemodynamic 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.