PARENT SESSION
MINISYMPOSIUM VI. NEUROENDOCRINOLOGY OF DOMESTIC ANIMALS

Tuesday, August 3, 2004
9:00 AM–10:30 AM
Buchanan A202
Chair: Thomas R. Hansen (University of Wyoming, Laramie, WY), Co-Chair: Debora L. Hamernik (USDA-CSREES, Washington, DC)

(MS16) NEUROENDOCRINOLOGY OF PROLACTIN REGULATION IN THE DOMESTIC TURKEY.

El Halawani, Mohamed¹, Kang, Seong¹, Chaiseha, Yupaporn², Youngren, Orlan¹, ¹ University of Minnesota, St. Paul, MN, USA² Suranaree University of Technology, Nakhom Ratchasima, Thailand

ABSTRACT- Prolactin (PRL) secretion, which is under tonic control in avian species, is stimulated by vasoactive intestinal peptide (VIP), which meets the classical criteria required for releasing factors. VIP mediates PRL gene expression via a 35-bp VIP response element located between position −74 and − 40 on the turkey proximal PRL promoter. The group of VIP neurons regulating PRL secretion is located in the infundibular nuclear complex (INF) of the caudal hypothalamus. While neurotransmitters regulating the VIP/PRL system remain uncertain, groups of dopamine (DA) cells are prominent in the avian hypothalamus. Both D₁ and D₂ DA receptors display abundant mRNA in the hypothalamus and pituitary, and have been shown to mediate, respectively, the stimulatory and inhibitory influences on PRL release and gene expression. The stimulatory effect is mediated by dopaminergic neurons in the preoptic area which stimulate hypothalamic VIP release and gene expression. The inhibitory effect occurs when DA neurons in the dorsolateral INF secrete DA to the pituitary where it overrides the stimulating effect of VIP on PRL secretion. The interaction between VIP and DA at the pituitary level is mediated by the intracellular Ca²⁺ signaling pathway, with VIP stimulating extracellular Ca²⁺ influx, and DA blocking Ca²⁺ channels. Supported by USDA grant # 00-35203-91−

KEY WORDS: dopamine, prolactin, avian, vasoactive intestinal peptide