The ability of low concentrations of dopamine to stimulate prolactin secretion from the anterior pituitary gland was examined. Pituitary cells in dynamic culture increased prolactin secretion in response to a reduction of dopamine concentration (100 nM to 1 pM) much more robustly than in response to a simple removal of dopamine (100 nM to no dopamine). The stimulatory activity of low doses of dopamine is dose dependent (1 pM-100 pM is stimulatory and doses above 100 nM are inhibitory). In rats, dopamine infused at doses 100 times less than the maximal inhibitory doses also stimulates prolactin secretion. These data indicate that low doses of dopamine have prolactin releasing properties. In a static culture system, pharmacological experiments indicated that the dopamine receptor mediating the stimulatory effect was most similar to the D$\sb2$ receptor. This receptor was found to be distinct from the D$\sb2$ receptor coupled to inhibition of prolactin secretion and the two receptors utilized different G-proteins. The reverse hemolytic plaque assay identified a relatively small subpopulation of lactotrophs that responded to stimulatory doses of dopamine. Neither the short nor the long form of the D$\sb2$ receptor could mediate dopaminergic stimulation of prolactin secretion when expressed in a prolactin secreting cell line. These two receptors mediated inhibition of PRL secretion and the signal transduction mechanisms utilized were identical. The receptor mediating dopaminergic stimulation of prolactin secretion has not been identified; however, this receptor is coupled to the G$\sb{\rm s}$ G-protein and mediates an increase in cytosolic calcium. / Source: Dissertation Abstracts International, Volume: 54-03, Section: B, page: 1190. / Major Professor: Marc E. Freeman. / Thesis (Ph.D.)--The Florida State University, 1993.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_76891 |
| Contributors | Burris, Thomas Patrick., Florida State University |
| Source Sets | Florida State University |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | 199 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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