FACULTY MEMBER, retired
Dr. Marc E. Freeman
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Lloyd M. Beidler Professor of Biological Science;
Ph.D., West Virginia University, 1970
Retired graduate faculty status
Research and Professional Interests:
We study the way an important area of the brain, the hypothalamus, regulates the secretion of hormones from the pituitary gland that are involved in reproductive processes.
We are particularly interested in the control of secretion of prolactin, the hormone that controls milk synthesis in the mammary gland. The hypothalamus controls prolactin secretion from the anterior pituitary gland in an inhibitory manner. The inhibitory chemical made by nerve cells in the hypothalamus is dopamine. When released into the small blood supply connecting the hypothalamus with the pituitary gland, dopamine inhibits prolactin secretion. Prolactin-releasing stimuli, such as nursing by the hungry infant, inhibit dopamine release from the hypothalamus.
Using approaches such as culture of pituitary cells, radioimmunoassay for measuring prolactin, immunocytochemistry for visualizing dopamine nerve cells and their gene activity and high performance liquid chromatography along with electrochemical detection for measuring changes in dopamine in the brain we are pursuing the following problems:
- It was previously believed that only one population of dopamine nerve cells in the hypothalamus affect prolactin secretion. We have identified two others that directly affect prolactin secretion and are in the process of characterizing the relative contribution of each
- Prolactin inhibits its own secretion by activating dopamine nerve cells in the hypothalamus. We have identified prolactin receptors on dopamine nerve cells and are in the process of determining how prolactin regulates the activity of these cells.
- We have found that dopamine is not only inhibitory to prolactin secretion, but under certain circumstances it can be stimulatory. We are in the process of determining how dopamine can both stimulate and inhibit the same pituitary cell that secretes prolactin.
- We have discovered that a chemical found in the cells lining the blood vessels of all mammals, endothelin, affects the secretion of most of the anterior pituitary hormones. We are now determining the role endothelin plays in the secretion of each.
Olah, M., P. Feher, Z. Ihm, I. Bacskay, T. Kiss, and M. E. Freeman (2010) Central clock regulates the cervically-stimulated prolactin surges by modulation of dopamine and vasoactive intestinal polypeptide release in ovariectomized rat. Neuroendocrinology 90: 391-401.
Poletini, M. O., J. E. Kennett, D. T. McKee, and M. E. Freeman (2010) Central clock regulates the cervically-stimulated prolactin surges by modulation of dopamine and vasoactive intestinal polypeptide release in ovariectomized rat. Neuroendocrinology 91: 179-188.
Tabak, J., A. E. Gonzalez-Iglesia, N. Toporikova, R. Bertram, and M. E. Freeman (2010) Variations in the response of pituitary lactotrophs to oxytocin during the rat estrous cycle. Endocrinology 151: 1806-1813.
Bertram, R., C. Helena, A. E. Gonzalez-Iglesia, J. Tabak, and M. E. Freeman (2010) A tale of two rhythms: the emerging roles of oxytocin in rhythmic prolactin release. Neuroendocrinology 22: 778-784.
Kennett, J. E., M. O. Poletini, C. A. Fitch, and M. E. Freeman (2009) Antagonism of oxytocin prevents suckling- and estradiol-induced, but not progesterone-induced, secretion of prolactin. Endocrinology 150: 2292-2299.
Helena, C. V., D. T. McKee, R. Bertram, A. M. Walker, and M. E. Freeman (2009) The rhythmic secretion of mating-induced prolactin secretion is controlled by prolactin acting centrally. Endocrinology 150: 3245-3251.
Freeman, M. E., D. T. McKee, M. Egli, and R. Bertram (2008) Biological and mathematical modeling approaches to defining the role of oxytocin and dopamine in the control of mating-induced PRL secretion. Neurobiology of the Parental Brain 235-247.
Toporikova, N., J. Tabak, M. E. Freeman, and R. Bertram (2008) A-type K+ current can act as a trigger for bursting in the absence of a slow variable. Neural Computation 20: 436-451.
Kennett, J. E., M. O. Poletini, and M. E. Freeman (2008) Vasoactive intestinal polypeptide modulates the estradiol-induced prolactin surge by entraining oxytocin neuronal activity. Brain Research 1196: 65-73.
Freeman, M. E., B. Kanyicska, A. Lerant, and G. Nagy (2000) Prolactin: structure, function and regulation of secretion. Physiological Reviews 80: 1523-1631.