Vasopressin-induced pressor responses to carotid occlusion in the rat

We studied the effect of carotid occlusion on blood pressure in cordotomized rats. Occlusion of both common carotid arteries resulted in an increase in blood pressure. This response was unaffected by denervation of the sinus and aortic nerves, and vagi. The response to occlusion was blocked by intravenous administration of a vasopressin antagonist, d(CH2)5Tyr(Me)arginine-vasopressin, but not by intravenous administration of hexamethonium or captopril. Further, microinjection of procaine into the paraventricular nuclei abolished the pressor response to occlusion. Thus, it appears that in cordotomized rats carotid occlusion causes release of vasopressin and this in turn results in an elevation of blood pressure. The arterial baroreceptors are not essential for the pressor response.