Stimulatory effect of intracerebroventricularly administered dopamine on vasopressin release in rats

Experiments were designed to investigate the effects of the intracerebroventricular administration of dopamine (DA) and a DA antagonist (pimozide) on the immunoreactive-vasopressin (IR-VP) contents of the rat magnocellular nuclei (MCN), neurohypophysis (NH) and plasma. The IR-VP levels in the MCN and NH were decreased 5 min after administration of DA in a dose of 20 nmol, but that in the plasma was increased. This effect was not observed after pretreatment with pimozide. Administration of pimozide alone did not affect the IR-VP contents of the MCN, NH or plasma. The results suggest that DA given icv. has a stimulatory effect on VP release from the neurohypophysial system.