REFLEX VASCULAR-RESPONSES TO ALTERATIONS IN ABDOMINAL ARTERIAL-PRESSURE AND FLOW IN AN ANESTHETIZED DOGS

The existence of abdominal arterial baroreceptors has long been contro versial. Previously difficulties have been encountered in localizing a stimulus to abdominal arteries without affecting reflexogenic areas e lsewhere. In these experiments, using anaesthetized dogs, the abdomen was vascularly isolated at the level of the diaphragm, perfused throug h the aorta, and drained from the inferior vena cava to a reservoir. C hanges in abdominal arterial pressure were effected by changing the pe rfusion pump speed. During this procedure the flow back to the animal from the venous outflow reservoir was held constant. Increases and dec reases in abdominal arterial pressure resulted, respectively, in decre ases and increases in perfusion pressure to a vascularly isolated hind limb and in some dogs also a forelimb Responses were significantly lar ger when carotid sinus pressure was high (120-180 mmHg) than when it w as low (60 mmHg). Responses were still obtained after cutting vagus, p hrenic and splanchnic nerves, but were abolished by spinal cord lesion at T12. These experiments provide evidence For the existence of abdom inal arterial baroreceptors. The afferent pathway for the reflex vasod ilatation appears to run in the spinal cord.