The neurohypophyseal vasopressin content under conditions of inhibited synthesis of prostaglandins in euhydrated and dehydrated rats.

Rats euhydrated or dehydrated up to eight days were given intraperitoneally indomethacin (IM) twice daily in a dose of 0.2 mg/100 g of initial body weight. A single dose of IM injected to euhydrated animals did not affect the neurohypophyseal vasopressor activity; however, when administered repeatedly during four or eight days, IM increased significantly the neurohypophyseal vasopressor activity. Under conditions of severe dehydration (eight days of water deprivation) the known depletion of neurohypophyseal vasopressin store was not significantly affected by indomethacin. It is, therefore, suggested that impulses of osmoreceptor origin are of distinct importance in determining the function of vasopressinergic neurons under conditions of inhibited prostaglandin synthesis.