Expression of vasoactive intestinal peptide receptor messenger RNA in the hypothalamus and pituitary throughout the turkey reproductive cycle.

Vasoactive intestinal peptide (VIP) has been implicated in the regulation of avian reproductive activity and appears to act at the level of the hypothalamus and pituitary. This in situ hybridization histochemistry study describes the distribution of VIP receptor mRNA expression in the hypothalamus and the pituitary of reproductively active (laying) and quiescent (nonphotostimulated, incubating, and photorefractory) female turkeys and characterizes the differences observed in VIP receptor gene expression. VIP receptor mRNA, while expressed throughout the hypothalamus, was specifically expressed in areas known to contain GnRH-I neurons in the chicken, i.

Expression of D1 and D2 dopamine receptors in the hypothalamus and pituitary during the turkey reproductive cycle: colocalization with vasoactive intestinal peptide.

The regulation of avian prolactin (PRL) secretion and PRL gene expression is influenced by hypothalamic vasoactive intestinal peptide (VIP), the PRL-releasing factor in avian species. Recent evidence indicates that D(1) and D(2) dopamine (DA) receptors play a pivotal role in VIP and PRL secretion. The differential expression of DA receptors located on hypothalamic VIP neurons and anterior pituitary cells may affect the degree of prolactinemia observed during the turkey reproductive cycle.

Dopamine infusion into the third ventricle increases gene expression of hypothalamic vasoactive intestinal peptide and pituitary prolactin and luteinizing hormone beta subunit in the turkey.

Turkey prolactin (PRL) secretion is controlled by vasoactive intestinal peptide (VIP) neurons residing in the infundibular nuclear complex (INF) of the hypothalamus. The VIPergic activity is modulated by dopamine (DA) via stimulatory D(1) DA receptors. DA (10 nmol/min for 40 min) was infused into the third ventricle of laying turkey hens to study its effect on circulating PRL, hypothalamic VIP and pituitary PRL and LHbeta subunit mRNA levels.

Influence of VIP on prolactinemia in turkey anterior pituitary cells: role of cAMP second messenger in VIP-induced prolactin gene expression.

Vasoactive intestinal peptide (VIP) is the avian prolactin (PRL)-releasing factor. In the turkey, hypothalamic VIP immunoreactivity and mRNA content, as well as VIP levels in hypophyseal portal blood, are closely related to the state of prolactinemia and the reproductive stage. The present study investigated the role of VIP on prolactinemia in turkey anterior pituitary (AP) cells through PRL gene expression and the role of a cAMP second messenger system on VIP-induced PRL expression.

Regulation of prolactin secretion by dopamine at the level of the hypothalamus in the turkey.

Avian prolactin (PRL) secretion is regulated by vasoactive intestinal peptide (VIP) neurons residing in the infundibular nuclear complex (INF) of the hypothalamus. This VIPergic activity is modulated by stimulatory dopaminergic inputs. Dynorphin, serotonin (5-HT), dopamine (DA) and VIP all appear to stimulate PRL secretion along a hypothalamic pathway, expressing kappa opioid, serotonergic, dopaminergic and VIPergic receptors in succession, with the VIPergic system as the final mediator.