ROLE OF VASOACTIVE-INTESTINAL-PEPTIDE IN THE CONTROL OF PROLACTIN-INDUCED TURKEY INCUBATION BEHAVIOR .2. CHRONIC INFUSION OF VASOACTIVE-INTESTINAL-PEPTIDE

Hyperprolactinemia is associated with incubation behavior in avian spe cies. Increased nesting activity is a major indication of incubation b ehavior. Vasoactive intestinal peptide (VIP) stimulates prolactin (PRL ) secretion from the anterior pituitary. The goal of this study was to induce incubation behavior by stimulating PRL through chronically inf using VIP into the third ventricle of turkey brains. In experiment 1, porcine VIP (pVIP) was infused into the median eminence at a rate of 6 0 ng/min for 7 days by means of osmotic pumps implanted s.c.. Plasma P RC increased significantly in the pVIP-treated turkeys (p < 0.001). Al though egg laying was not affected by the pVIP infusion, the mean ovid uct weight decreased (p < 0.057). In experiment 2, saline or pVIP (30 or 60 ng/min) was infused into the third ventricle of laying turkeys f or 12 days. Both pVIP treatments increased plasma PRL for 9 days (p < 0.05). The 30-ng pVIP/min infusion decreased nesting activity, plasma W, ovary and oviduct weight, hypothalamic GnRH I, and anterior pituita ry VIP receptors (p < 0.1). However, ovine PRL infusion (20.8 ng/min) into the same turkey flock increased nesting activity (p < 0.01). In c onclusion, pVIP does not induce incubation behavior in laying turkeys.