Increased dietary sodium alters neural control of blood pressure during intravenous ANG II infusion

Department of Pharmacology and Toxicology, College of Pharmacy, University of Utah, Salt Lake City, Utah 84112 Increased dietary sodium enhances both excitatory and inhibitory blood pressure responses to stimulation of the central sympathetic nervous system (SNS) centers. In addition, long-term (hours to days) administration of ANG II increases blood pressure by activation of the SNS. These studies investigated the effects of increased dietary sodium on SNS control of blood pressure during 0- to 24-h infusion of ANG II in conscious, male rats consuming either tap water or isotonic saline (Iso) for 2 to 3 wk. The SNS component (evaluated by ganglionic blockade with trimetaphan) of both control blood pressure and the pressor response to intravenous ANG II was reduced in Iso animals. Furthermore, although the pressor response to intravenous ANG II infusion was similar between groups, the baroreflex-induced bradycardia during the initial 6 h of ANG II infusion was significantly greater, whereas the tachycardia accompanying longer infusion periods was significantly attenuated in Iso animals. These data suggest that in normal rats increased dietary sodium enhances sympathoinhibitory responses during intravenous ANG II. baroreflex; heart rate; sympathoexcitation; sympathoinhibition; hypertension