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

Abstract

SUMMARY 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 (All) 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(CH 2 )5iyr(Me) AVP]. The dose response curve to vertebral artery infusion of AH (range 2-20 ng/ kg/mih) was significantly (p < 0.05) shifted to the right of control after injection of the AVP antagonist (10 Mg/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 All via the vertebral arteries. When pressor doses of All 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 All 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 AH. These data demonstrate a previously unknown interaction between vasopressin and the centrally mediated pressor response to intravertebral AH. T is well established that in the dog the area postrema of the fourth ventricle has a role in the neural control of cardiovascular function by acting, in part, to enhance central vasomotor sympathetic activity in response to increased blood levels of angiotensin II (All).1 " 5 In addition, recent data suggest that the effects of AH at the dog's area postrema may depend upon the activity of endogenous brain peptides such as the opioid system. 6 Other studies have indicated that there are reciprocal direct connections between the supraoptic (SON) and paraventricular nuclei (PVN) of the hypothalamus and the nucleus tractus solitarii (NTS) in the brain stem. These observations, in conjunction with the recent reports that hypertension is associated with alterations in vasopressin levels in the brain stem of spontaneously hypertensive rats (SHRs), 10 make this peptide another possible candidate to interact with AH in determining the degree of sympathetic activation at the brain stem. To investigate one facet of the function of brain vasopressin upon the reflex regulation of arterial pressure, we determined whether blockade of the activity of this neuropeptide system alters the ability of AH to exert an increase in sympathetic activity via the area postrema pressor pathway. MethodsExperiments were performed in 25 male mongrel dogs (body weight = 21.6 ± 0.4 kg) anesthetized with alpha-chloralose (65 mg/kg, i.v.) after premedication with morphine (2 mg/kg, i.m.) and respirated mechanically. S...

Endogenous Vasopressin Modulates the Cardiovascular Responses to Exercise

“…32, 33 Peripheral and central vasopressin administration produced hypertension with different heart rate responses: bradycardia and tachycardia, respectively. 34–36 On the basis of these data we hypothesize that vasopressinergic input could adjust the heart rate response to the circulatory demands during exercise. To accomplish this, vasopressinergic projections to NTS should modulate baroreceptor reflex control of heart rate, be stimulated during exercise and change heart rate response during exercise.…”

Role of central AT1 and V1 receptors in cardiovascular adaptation to hemorrhage in SD and renin TGR rats

“…angiotensin; hypertension; losartan; vasopressin; TGR (mRen2)27 NUMEROUS STUDIES INDICATE that the cardiovascular brain regions are innervated by angiotensinergic and vasopressinergic neurons (5,8,13,28) and that the intracranial administration of angiotensin II (ANG II) or arginine vasopressin (AVP) results in significant alterations of the cardiovascular functions (3,13,18,20,27,42). However, the role of these two neuropeptides in the regulation of blood pressure under specific physiological and pathophysiological conditions is not yet well established.…”