Arginine vasotocin stimulates glucocorticoid secretion in male rats

The endocrine effects of the putative pineal peptide arginine vasotocin (AVT) were compared with those of the pineal indoleamines melatonin and N-acetylserotonin and passive immunization against these indoleamines in male rats injected at 1200 hr or 2400 hr. A pharmacologic dose of AVT markedly enhanced both day and night serum glucocorticoid levels but lowered prolactin levels at both time points. Melatonin decreased night prolactin and corticosterone levels whereas passive immunization against circulating melatonin and N-acetylserotonin elevated night levels of these hormones. Preliminary evidence that AVT (10 microM) produces a guanosine triphosphate (GTP)-dependent stimulation of adenylate cyclase activity in the hypothalamus, anterior pituitary and adrenal gland suggests that the endocrine effects of this peptide may involve alterations in cAMP levels at one or more of these sites.