A specific antagonist of vasopressin produced plasma hyperosmolality and reduced ischemic-induced cerebral edema in rats.

Water diuresis was produced in rats after s.c. injections of d(CH2)5,D-Ile2,Ile4-AVP (compound 1) and d(CH2)5,Tyr(OEt)2Val4-AVP (compound 2). Compound 1 is known to be a more potent antagonist against the antidiuretic effect, while Compound 2 is a more potent antagonist against the vasopressor effect of vasopressin. Compound 1 (but not compound 2) also increased plasma osmolality significantly at the diuretic doses. In rats rendered ischemic of the forebrain by 4-hour occlusion of both common carotid arteries, the resulting increases in brain water were significantly reversed by the injection of compound 1. Compound 2 did not reduce the edema. The results suggests a novel approach to the treatment of cerebral edema.