Regulation of corticosterone production by vasopressin during water restriction and after drinking in rats

Plasma vasopressin (VP) and corticosterone have each been shown to be rapidly suppressed after drinking in different models of osmotic stimulation in rats; however, no causal relationship between these responses has been investigated. Studies were performed to determine if plasma VP and corticosterone are reduced in parallel after drinking and if manipulation of plasma VP affects plasma, ACTH corticotropins and corticosterone in a model of water restriction. A strong correlation between changes in plasma VP and corticosterone, but not between plasma ACTH and corticosterone, was observed after drinking induced by 6 days of water restriction. Similarly, ingestion of isotonic saline resulted in a biphasic VP response that was paralleled by adrenal and plasma corticosterone, but not by plasma ACTH. Administration of an immunoneutralizing antibody directed against VP resulted in a rapid decrease in plasma corticosterone, but not ACTH, in water-restricted rats, but not in rats receiving water ad libitum. These data suggest that during dehydration, elevated plasma VP can stimulate the production of corticosterone by the adrenal, independently of ACTH. Moreover, they support the hypothesis that the decline in corticosterone after restriction-induced drinking is due, in part, to a decline in plasma VP.