Thyrotropin-releasing hormone (TRH) inhibits vasopressin release from hypothalamo-neurohypophysial system of rats drinking hypertonic saline.

Rats drinking ad libitum tap water or hypertonic (i.e. 2%) sodium chloride solution were given intracerebroventricularly (i.c.v.) for three days, thyrotropin-releasing hormone (TRH) in a daily dose of 200 ng dissolved in 10 microliters of 0.9% sodium chloride. Treatment with TRH resulted in significantly increased hypothalamic vasopressin content in both euhydrated (i.e. given tap water ad libitum) and salt-loaded rats. In rats given hypertonic saline, neurohypophysial vasopressin content increased. Plasma vasopressin concentration was distinctly diminished under TRH treatment, the respective difference being significant, however, barely in salt-loaded rats. The present data suggest that TRH may be involved in some regulatory processes related to vasopressin biosynthesis and release from the rat hypothalamo-neurohypophysial system.