Carotid arterial control of vasopressin secretion in sheep

The purpose of this study was to test the role of carotid arterial mechanoreceptors in the control of vasopressin secretion in conscious 6- to 7-wk-old lambs. Bilateral carotid occlusion decreased lingual arterial pressure and stimulated reflex increases in heart rate and femoral arterial blood pressure but did not significantly alter plasma concentrations of vasopressin. Acute vagosympathetic blockade, produced by injection of 2% lidocaine onto the vagosympathetic trunks, did not significantly alter heart rate or blood pressure but did stimulate a slow increase in plasma vasopressin concentration, suggesting that afferent vagal fibers tonically inhibit vasopressin secretion. Bilateral carotid occlusion after vagosympathetic blockade stimulated a brisk increase in plasma vasopressin that was larger than the response to vagosympathetic blockade alone. These results suggest that vasopressin secretion in lambs is partially controlled by arterial mechanoreceptors in the carotid sinus and by extracarotid receptors with vagosympathetic afferent fibers.