Prolactin secretion is regulated by an endogenous rhythm of prolactin-releasing factors. This rhythm has a bimodal periodicity with distinct nocturnal and diurnal phases. Oxytocin, vasoactive intestinal peptide and serotonin play different roles in generating this endogenous stimulatory rhythm. We proposed that oxytocin is the neurohormone of this rhythm, whereas vasoactive intestinal peptide and serotonin act as neurotransmitters to release oxytocin. We investigated the role of this rhythm in female rats under varying physiological paradigms. Infusion of antagonists to oxytocin, vasoactive intestinal peptide and serotonin in ovariectomized, cervically stimulated rats were consistent with a role for the endogenous stimulatory rhythm in regulating mating-induced prolactin surges. Study of the ontogeny of this rhythm was also consistent with a role for this mechanism in driving mating-induced prolactin surges. / This endogenous rhythm is also important to prolactin secretion during lactation. Suckling-induced prolactin release was greater during the nocturnal and diurnal phases. Freely lactating rats secreted prolactin in a bimodal rhythm similar in periodicity to the endogenous rhythm. / Oxytocinergic neurons were analyzed for the presence of Fos protein as a marker of neuronal activity. A bimodal rhythm of oxytocinergic activity was present in the paraventricular nucleus. There was also a bimodal rhythm of oxytocin detected in the anterior pituitary coincident with the phases of the endogenous rhythm. / A diurnal rhythm of activity of vasoactive intestinal peptide neurons was detected coincident with the nocturnal phase of the endogenous rhythm in the paraventricular nucleus. / A diurnal rhythm of activity of serotonergic neurons was detected in the paraventricular nucleus coincident with the diurnal phase of the endogenous stimulatory rhythm. / These data clearly show that the endogenous stimulatory rhythm is an important regulator of prolactin secretion. Activity of oxytocin, vasoactive intestinal peptide and serotonin neurons are consistent with their proposed roles in generating the endogenous rhythm. The endogenous rhythm may be a common regulatory mechanism to prolactin secretion under varying physiological conditions. / Source: Dissertation Abstracts International, Volume: 53-03, Section: B, page: 1213. / Major Professor: Marc E. Freeman. / Thesis (Ph.D.)--The Florida State University, 1992.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_76625 |
| Contributors | Arey, Brian Joseph., Florida State University |
| Source Sets | Florida State University |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | 150 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
Page generated in 0.0151 seconds