Central vasopressin raises arterial pressure by sympathetic activation and vasopressin release.

Abstract

Although central administration of arginine vasopressin (AVP) has been reported to increase arterial pressure mediated by activation of the sympathetic system, we found that peripheral blockade of sympathetic transmission did not attenuate this pressor response. To elucidate the mechanism, rats were pretreated with either phentolamine (3 mg/kg), chlorisondamine (2.5 mg/kg), a vasopressin V! receptor antagonist d(CH 2 )sTyr(Me)AVP (AVP-X) (10 /xg/kg), or the combinations of phentolamine and AVP-X or chlorisondamine and AVP-X. The pressor response to intracerebroventricular injection of AVP in unrestrained conscious rats was reduced but not significantly altered by intravenous injection of phentolamine or AVP-X; however, combined treatment with these agents abolished the response. To determine that the amount of central AVP leaked to the periphery did not contribute to the pressor effect, tritiated AVP and AVP (100 ng total) were injected intracerebroventricularly. Blood samples collected at 0, 3, and 30 minutes after injection showed that radioactivity in plasma was primarily metabolites and that the amount of intact AVP estimated to leak from the brain was too low to produce a pressor effect. 1 Despite the number of papers related to central actions of AVP, the mechanism of the pressor action induced by this centrally injected peptide remains unclear.AVP-containing neurons project from the paraventricular and supraoptic nuclei to brainstem regions such as the nucleus tractus solitarius (NTS). Also, in several regions of the brain specific binding sites for AVP that play a role in central regulation of arterial pressure have been reported.2 MicroinjecFrom the Department of Pharmacology and the Cardiovascular Center, the University of Iowa College of Medicine, Iowa City, Iowa.Supported by Grant HLB-14388 from the National Institutes of Health and by Roussel-Uclaf, Paris, France.This manuscript from the University of Iowa was sent to Carlos M. Ferrario, Guest Editor, for review by expert referees, for editorial decision, and for final disposition.Address for reprints: Michael J. Brody, PhD, University of Iowa, Department of Pharmacology, 2-210 Bowen Science Building, Iowa City, IA 52242. tions of AVP in the NTS raise arterial pressure 34 and increase turnover of catecholamine in this nucleus.5 AVP is stored in the neural lobe of the pituitary gland and can be released into the bloodstream by several central 6 -9 and peripheral 10 stimuli. It has also been indicated that this peptide is present in the cerebrospinal fluid. 11It has been reported that the increase in arterial pressure produced by central injection of AVP is mediated by increased sympathetic outflow.1213 If this were the only mechanism, then blockade of sympathetic transmission should prevent this pressor effect. However, in recent studies, we found that neither ganglionic nor a-adrenergic blockade significantly altered the pressor response. Therefore, the purpose of the present study was to characterize the mechanism of the pressor action evoked by...

Arginine-vasopressin mediates central and peripheral glucose regulation in response to carotid body receptor stimulation with Na-cyanide

“…Central AVP infusion may also activate sympathoadrenal outflow, enhancing cortisol and catecholamine secretion (21), to trigger protective counterregulatory neurohormonal responses. The results obtained in the present study were not due to peripheral leakage of AVP; at the concentrations we used, AVP does not leak into the circulation for at least 30 min after the beginning of intracerebral infusion (27).…”

Furosemide inhibits the centrally‐mediated pressor response to clonidine in conscious, normotensive rats

“…clonidine in conscious rats (Nakamura et al, 1990). In addition, central administration of AVP has been shown to increase blood pressure in conscious rats (Janiak et al, 1989). On the other hand, it is well known that reduction of body fluid volume activates the reninangiotensin system.…”

Central .ALPHA.2-Adrenoceptor-Mediated Pressor Response to Clonidine in Conscious, Spontaneously Hypertensive Rats.

“…clonidine in con scious rats (23). In addition, central adiministration of AVP has been shown to increase blood pressure in con scious rats (24). Further studies are needed to clarify the mechanism of this effect.…”