The effect of stimulation of left atrial receptors on coronary blood flow in anaesthetized dogs.

1. To determine whether stimulation of atrial receptors reflexly affects coronary blood flow, experiments were performed in seven dogs anaesthetized with alpha-chloralose. The left upper and middle pulmonary vein-atrial junctions and atrial appendage were stretched by distension of small balloons. Coronary blood flow was measured using an electromagnetic flowmeter positioned around the origin of the left anterior descending or circumflex coronary artery. 2. Following prevention of the reflex increase in heart rate by atrial pacing or propranolol, distension of the small balloons was shown to result in a decrease in mean coronary blood flow. 3. Cooling of the cervical vagosympathetic nerve trunks to 9 degrees C abolished the response of a decrease in mean coronary blood flow to distension of the balloons. 4. The response of a decrease in mean coronary blood flow was abolished by bretylium tosylate. 5. It was shown that a decrease in mean coronary blood flow occurred in response to stimulation of left atrial receptors, and that this decrease was reflex in nature. This reflex response is likely to involve atrial receptors discharging into afferent myelinated vagal fibres, and the efferent limb involves cardiac sympathetic pathways.