Arginine vasopressin modulates the central action of angiotensin II in the dog.

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Abstract
Endogenous vasopressin may interact with central autonomic nervous system factors in the regulation of cardiovascular function. In 25 morphine/chloralose-anesthetized dogs, we studied the magnitude of the pressor response produced by an infusion of angiotensin II (AII) into the vertebral arteries (VA), before and after intracisternal (n = 10), intravertebral (n = 9), or intravenous (n = 6) administration of a competitive antagonist of arginine vasopressin (AVP) [d(CH2)5Tyr(Me) AVP]. The dose response curve to vertebral artery infusion of AII (range 2-20 ng/kg/min) was significantly (p less than 0.05) shifted to the right of control after injection of the AVP antagonist (10 micrograms/kg) into the cisterna magna; the ED at 20 mm Hg being almost double after central AVP blockade. This effect of AVP blockade was confined only to the cardiovascular response mediated by AII via the vertebral arteries. When pressor doses of AII were injected into either a vein (i.v.) or the cisterna magna of these same dogs, the increases in mean blood pressure were the same before and after AVP antagonist treatment. In another group of anesthetized dogs, we investigated whether the reduced reactivity to intravertebral AII could be duplicated by giving the AVP antagonist either via the vertebral artery or i.v. Only the cisterna magna route was effective in causing a blunting of the pressor response to vertebral artery AII. These data demonstrate a previously unknown interaction between vasopressin and the centrally mediated pressor response to intravertebral AII.

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