Inhibition by antiserum to vasoactive intestinal polypeptide (VIP) of prolactin secretion induced by serotonin in the rat.

Intraventricular (i.c.v.) injection of serotonin (5HT) or intravenous (i.v.) injection of 5-hydroxytryptophan (5HTP), a precursor of 5HT, raised plasma prolactin (PRL) levels in urethane-anesthetized rats pretreated with normal rabbit serum. When the animals were injected i.c.v. or i.v. with specific anti-VIP rabbit serum, the plasma PRL responses to 5HT and 5HTP were blunted. These findings suggest that hypothalamic VIP is involved, at least in part, in PRL secretion induced by central serotonergic stimulation in the rat.