Aortic arch reflex control of total systemic vascular capacity.

The ability of the aortic arch baroreceptors to change vascular capacity was measured and, in the same animal, compared with carotid sinus reflex changes in capacity. Seven dogs were anesthetized with pentobarbital sodium and perfused with constant flow. Changes in external reservoir volume reflected reciprocal changes in total systemic vascular capacity and changes in arterial pressure parallel changes in total peripheral resistance. The aortic arch and carotid sinus baroreceptor areas were isolated, and the pressures were controlled separately. With carotid sinus pressure held constant at 125 mmHg, aortic arch pressure was increased and decreased between 225 and 50 mmHg, and the changes in reservoir volume and systemic arterial pressure were measured. Results from increasing and decreasing aortic arch or carotid sinus pressure were not significantly different and were averaged. The mean change in reservoir volume was 1.9 +/- 0.2 ml/kg and the change in mean arterial pressure was 18.7 +/- 3.7 mmHg. The changes in reservoir volume and arterial pressure caused by the aortic arch reflex were not influenced by the level of carotid sinus pressure. Carotid sinus pressure changes between 200 and 50 mmHg at a constant aortic arch pressure caused reservoir volume and arterial pressure to change by 7.2 +/- 0.9 ml/kg and 45.1 +/- 4.1 mmHg, respectively. The level of aortic arch pressure did not modify these responses.