GABAergic Inhibition of Hypertonic Saline-Induced Vasopressin- Dependent Hypertension1

Previous studies have shown that hypotension produced by drugs facilitating y-aminobutyric acid (GABA) transmission was caused by a decrease in sympathetic nervous system outflow. We attempted to determine if GABA agonists and GABA uptake inhibitors could also lower arterial pressure that was elevated by increasing the secretion of endogenous vasopressin. GABA and nipecotic acid, an uptake inhibitor of GABA, were administered intraventricularly to determine the cardiovascular effects of these agents in nephrectomized rats made acutely hypertensive with hypertonic saline. A 2-hr i.v. infusion of hypertonic saline (3.0 mEq/ml) increased arterial pressure from 1 1 9 ± 2 to 1 57 ± 2 mm Hg. lntraventncular administration of artificial cerebrospinal fluid, 1 00 g of GABA and 1 75 zg of nipecotic acid produced a peak decrease in blood pressure of 0 ± 0, 30 ± 4 and 22 ±