Prolactin Regulation by the Pars Tuberalis

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Many hormones follow seasonal rhythms, but none more so than prolactin. Prolactin is secreted by the pituitary gland at the base of the brain and is high in summer and low in winter. These seasonal changes are driven by the changes in daylight that are transformed into a chemical signal in the body by another hormone, melatonin. Melatonin acts on an enigmatic subdivision of the pituitary gland, the pars tuberalis, to regulate the secretion of an unknown factor that, in turn, drives seasonal prolactin release. In the current project it is hypothesized that the identity of this unknown factor is a "tachykinin". Using sheep as a model, this project will investigate the release of tachykinins by the pars tuberalis and the effect of these tachykinins on prolactin secretion during the different seasons of the year. It is expected that tachykinin production or receptor regulation will differ between seasons and, accordingly, its ability to modulate prolactin release will be seasonally dependent. This research will drive forward an important basic scientific question - establishing what the enigmatic pars tuberalis secretes. This research may also resolve why chromophobic tumors of the pars tuberalis region induce hyperprolactinemia and address the common link between hyperprolactinemia and infertility in mammals. The project will offer unique training opportunities for students who will be expected to present their findings at national and international conferences and these students will have the opportunity to become co-authors on peer-reviewed publications.