Arterial baroreceptors control plasma vasopressin responses to graded hypotension in conscious dogs

We studied the role of cardiac and arterial baroreceptors in the reflex con trol of arginine vasopressin (AVP) and renin secretion during graded hypote nsion in conscious dog;. The dogs were prepared with Silastic cuffs on the thoracic inferior vena cava and catheters in the pericardial space. Each ex periment consisted of a control period followed by four periods of inferior vena caval constriction, during which mean arterial pressure (MAP) was red uced in increments of similar to 10 mmHg. The hormonal responses were measu red in five dogs under four treatment conditions: 1) intact, 2) acute cardi ac denervation (CD) by intrapericardial infusion of procaine, 3) after sino aortic denervation (SAD), and 4) during combined SAD+CD. The individual slo pes relating MAP to plasma AVP and plasma renin activity (PRA) were used to compare the treatment effects using a 2 x 2 factorial: analysis. There was a significant (P < 0.01) effect of SAD on the slope relating plasma AVP to MAP but no effect of CD and no SAD X CD interaction. In contrast, the slop e relating PRA and MAP was increased (P < 0.05) by SAD but was not affected by CD. These results support the hypothesis that stimulation of AVP secret ion in response to graded hypotension is primarily driven by unloading arte rial baroreceptors in the dog.