The effect of stimulation of the atrial receptors on plasma renin activity in the dog.

1. To determine whether stimulation of atrial receptors reflexly results in a consistent change in plasma renin activity experiments were performed in dogs anaesthetized with alpha-chloralose. Either a large balloon in the lumen of the left atrium or small balloons positioned at the upper and middle pulmonary vein-atrial junctions and atrial appendage were distended. Plasma samples obtained from these dogs during control periods and during periods of stimulation were assayed for plasma renin activity. 2. In the first series of experiments, stimulation of left atrial receptors by either large or small balloon distension was shown to result in an increase in urine flow and a decrease in plasma renin activity. 3. In a second series of experiments, cooling of the cervical vagosympathetic nerve trunks abolished the response of an increase to balloon distension in urine flow and decrease in plasma renin activity. 4. It was shown that a decrease in plasma renin activity resulted in response to stimulation of atrial receptors, and that this decrease is reflex in nature and is likely to involve only atrial receptors discharging into myelinated vagal fibres.