This Article Full Text (PDF) Submit a related Letter to the Editor Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints, Permissions and Rights Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by KHORRAM, O. Articles by MCCANN, S. M. Search for Related Content PubMed PubMed Citation Articles by KHORRAM, O. Articles by MCCANN, S. M.

Hypothalamic Control of Prolactin Secretion during the Perinatal Period in the Rat

O. KHORRAM, L. R. DEPALATIS^* and S. M. MCCANN

Department of Physiology, University of Texas Health Science Center Dallas, Texas 75235

Address requests for reprints to: Dr. S. M. McCann, Department Physiology, University of Texas Health Science Center, 5323 Harry Hines Boulevard, Dallas, Texas 75235.

Abstract

The development of hypothalamic control of PRL secretion in the late prenatal and early postnatal periods i n the rat was studied by employing a static system for incubation of pituitaries. PRL was detected in the incubation medium after incubating fetal pituitaries as early as day 18. A gradual increase i n the amount of hormone released into the medium occurred during development, with the greatest change occurring between days 20 and 21 prenatally. A progressive increase in the pituitary content of PRL occurred during development. The percentage of PRL released from the gland was higher pre- (19–39%) than postnatally (17%).

Hypothalamic extracts from fetuses and neonates stimulated the secretion of PRL when coincubated with pituitaries from animals of the same age. However, extracts from 1-day-old neonates inhibited PRL secretion from adult male hemipituitar-ies. Extracts prepared from adult male hypothalami stimulated PRL secretion from neonatal pituitaries from rats at 1 day of age, as did cerebral cortical extracts from adults, but not 1-day-old, rats.

TRH significantly stimulated PRL secretion in vitro from pituitaries of donors as early as day 19 of the fetal period. The response of the pituitaries to this peptide diminished by day 8 postnatally. Immunoneutralization of hypothalamic TRH significantly decreased but did not abolish the PRL-releasing activity of hypothalamic extracts, whereas this procedure had no effect on the GH-releasing activity of the extracts.

The dopamine receptor agonist apomorphine (10^–6 M) inhibited PRL secretion in vitro on day 19 of the fetal period and postnatally starting on day 1. The response to apomorphine increased with advancing age.

The results suggest that a combination of factors contribute to maintaining high circulating PRL levels during the late fetal and early neonatal periods. These include high rates of PRL release by the pituitary and a relative insensitivity of the pituitary to dopamine in the face of high sensitivity to PRL-releasing factors such as TRH. (Endocrinology 115: 1698–1704, 1984)

Footnotes

^* Present address: Dow Chemical Company, 1701 Building, Midland, Michigan 48640.

Supported by PHS Grants AM-10073 and HD-09988.

Received February 10, 1984.

This article has been cited by other articles:

				M.G. Rosenfeld, C.K. Glass, S. Adler, E.B. Crenshaw III, X. He, S.A. Lira, H.P. Elsholtz, H.J. Mangalam, J.M. Holloway, C. Nelson, et al. Response and Binding Elements for Ligand-dependent Positive Transcription Factors Integrate Positive and Negative Regulation of Gene Expression Cold Spring Harb Symp Quant Biol, January 1, 1988; 53(0): 545 - 556. [Abstract] [PDF]