Response of large hindlimb veins of dog to aortic arch chemoreceptor stimulation.

Experiments were performed in chloralose-anesthetized dogs to examine the reflex effects on tone in the saphenous vein of stimulating the aortic arch chemoreceptors. The saphenous vein was perfused with cooled (30 degrees C) aortic blood at constant flow, and perfusion pressure was measured. In 13 animals the aortic arch chemoreceptors were stimulated by injection of cyanide (0.1 mg/kg) into the root of the aorta. Cyanide caused a decrease (20 +/- 2 mmHg) in saphenous vein perfusion pressure and an increase (44 +/- 4) in aortic pressure. These changes that occurred subsequent to aortic root cyanide injections were abolished by vagotomy or section of the aortic nerves (afferent pathway); section of the lumbar sympathetic chain at L4 and L5 abolished the dilator response of the vein (efferent pathway) but did not alter the increase in aortic pressure. Four dogs were prepared for cardiopulmonary bypass and separate perfusion of the systemic circulation and the isolated aortic arch. Delivery of hypoxic-hypercapnic blood to the isolated aortic arch caused a dilation of the saphenous vein and an increase in systemic arterial perfusion pressure. From these results we conclude that cutaneous venomotor tone can be reflexly reduced through the aortic chemoreflex.