Centrally Mediated Effects of Sodium and Angiotensin II on Arterial Blood Pressure and Fluid Balance

Abstract

Four kinds of infusions were made for 1 h periods into the 3rd cerebral ventricle of hydrated, conscious goats: 1) Angiotensin in hypertonic NaCI, 2) angiotensin in slightly hypotonic NaCI, 3) angiotensin in isotonic d‐glucose, and 4) hypertonic NaCI. The influence of these infusions on carotid blood pressure and fluid balance was studied. The infusions of angiotensin in hypertonic NaCl had conspicuous hypertensive, dipsogenic, antidiuretic and natriuretic effects. More moderate responses of the same kinds were obtained during the infusions of hypertonic NaCl and of angiotensin in slightly hypotonic NaCI. In contrast, no or only weak effects were obtained by the infusions of angiotensin in isotonic d‐glucose. The results are taken as support for the idea that a Na+ sensitive system in the vicinity of the 3rd ventricle may be of importance in the central contml of fluid balance and arterial blood pressure. Such a system may be influenced by the Na+ concentration of the cerebrospinal fluid, and angiotensin may either sensitize it to Na+ or make it more exposed to Na+ ions.

Pressor response to small elevations of cerebroventricular pressure in conscious rats.

“…The first solution was composed of 7.597 g of NaCl, 0.231 g of KC1, 0.203 g of MgCl 2 , 2.058 g of NaHCO 3 ,0.69 g of NaH 2 PO 4 , and 500 ml of H 2 O. The second solution was prepared with 5.376 g of glucose, 0.175 g of CaCl 2 , and 500 ml of H 2 O.…”

Review: AT1-receptors in the central nervous system

“…105 It is unlikely that this is a direct action via AT 1 -receptors on the AVP-containing neurons of the supraoptic and paraventricular nuclei of the hypothalamus. 9,23 Neuronal inputs to the supraoptic and paraventricular nuclei come from several regions rich in Ang II receptors and Ang II-containing terminals, including the caudal ventrolateral medulla, NTS and the lamina terminalis.…”

“…113,115 The rapid natriuresis following ICV injection of Ang II may come about because BP increases (causing a pressure natriuresis), renal sympathetic nerve activity is suppressed, 79 plasma levels of renin fall, 116 vasopressin secretion increases, 105,117 or a natriuretic agent is released into the circulation. One of these factors, alone or in combination with one or more of the others, may be the link between brain and kidney mediating this response.…”

Effects of chronic intraventricular sodium on blood pressure and fluid balance.

“…The depressor response to </(CH2) 3 H ypertonic NaCI administered into the central nervous system influences cardiovascular and body fluid conditions by producing blood pressure elevation, tachycardia, drinking response, and natriuresis. 1 …”

“…1 ' 35 - 8 Both the sympathetic nervous system and vasopressin appear to mediate the pressor response to intracerebroventricularly administered hypertonic NaCI. 59 The central action of sodium might play an important role in the relation between salt and hypertension.…”