EFFECT OF 5-HYDROXYTRYPTAMINE AND PINEAL METABOLITES ON THE SECRETIONOF NEUROHYPOPHYSEAL HORMONES

It has been shown that 5-hydroxytryptamine and melatonin, an indoleami ne for which 5-hydroxytryptamine is a precursor, influence the release of vasopressin and oxytocin from the rat hypothalamus both in vivo an d in vitro. The oral administration of melatonin has been shown to dec rease oxytocin release and modulate the nocturnal vasopressin release in humans. B-Hydroxytryptamine and its metabolites, 5-hydroxytryptopho l, 5-methoxytryptamine and 5-methoxytryptophol, are detected within th e pineal, and there is evidence that 5-methoxytryptamine and 5-methoxy tryptophol may have some physiological role. The aim of this study was to evaluate the effects of 5-hydroxytryptamine, 5-hydroxytryptophol, 5-methoxytryptamine and 5-methoxytryptophol on neurohypophysial hormon e release from the rat hypothalamus in vitro. It was found that 5-hydr oxytryptamine and 5-hydroxytryptophol increased neurohypophysial hormo ne release, 5-methoxytryptamine decreased the release of vasopressin a nd oxytocin and 5-methoxytryptophol was found to have no effect, thus providing further evidence for a role of indole compounds in the contr ol of neurohypophysial hormone secretion. (C) 1998 Elsevier Science In c.