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The preovulatory prolactin surge is prolonged by a progesterone-dependent dopaminergic mechanism.
Endocrinology. 1990 Jan; 126(1):246-52.E

Abstract

The preovulatory PRL surge consists of a sharp peak, a prolonged plateau, and a termination phase. This study examined the role of progesterone in maintaining elevated PRL release during the plateau phase and its effect on dopaminergic (DA) neuronal activity. Immature rats were injected with PMSG on day 28, and blood was collected during the periovulatory period. Plasma estradiol levels were elevated before and during the PRL peak and declined during the plateau. Plasma progesterone levels were low before and during the peak, rose 4- to 5-fold during the plateau, and decreased to basal levels at the termination phase. In a second experiment rats were subjected to acute ovariectomy (OVEX) or sham surgery (SHAM) just before the onset of the PRL surge. Some OVEX rats were either immediately implanted with an estradiol-containing capsule or given three injections of progesterone during the time of the plateau phase. Blood PRL levels in SHAM rats showed the typical peak, plateau, and termination phases. The PRL peak was evident, but the plateau was missing in OVEX rats with or without estradiol treatment. Replacement with progesterone restored the plateau. In a third experiment, the stalk-median eminence, posterior pituitary, and striatum were removed during the time of the midplateau phase. Tyrosine hydroxylase activity was determined in tissue homogenates by a coupled hydroxylation-decarboxylation assay. Tyrosine hydroxylase activity in the stalk-median eminence of SHAM and progesterone-treated OVEX rats was similar, but was significantly lower than that in OVEX rats with or without estradiol. Tyrosine hydroxylase activity in the posterior pituitary and striatum was unchanged. To assess the functional DA input to the anterior pituitary, haloperidol, a DA antagonist, was injected during the midplateau phase. It induced a 12- to 17-fold rise in plasma PRL in both untreated and estradiol-treated OVEX rats, but failed to increase PRL above the plateau levels in SHAM and progesterone-treated OVEX rats. We conclude that the plateau phase of the preovulatory PRL surge is dependent on the concomitant rise in progesterone. Progesterone probably acts by reducing the DA neuronal activity in the SME, resulting in an absence of functional DA input to anterior pituitary lactotrophs.

Authors+Show Affiliations

Department of Physiology and Biophysics, Indiana University School of Medicine, Indianapolis 46223.No affiliation info available

Pub Type(s)

Journal Article
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

1967162

Citation

Arbogast, L A., and N Ben-Jonathan. "The Preovulatory Prolactin Surge Is Prolonged By a Progesterone-dependent Dopaminergic Mechanism." Endocrinology, vol. 126, no. 1, 1990, pp. 246-52.
Arbogast LA, Ben-Jonathan N. The preovulatory prolactin surge is prolonged by a progesterone-dependent dopaminergic mechanism. Endocrinology. 1990;126(1):246-52.
Arbogast, L. A., & Ben-Jonathan, N. (1990). The preovulatory prolactin surge is prolonged by a progesterone-dependent dopaminergic mechanism. Endocrinology, 126(1), 246-52.
Arbogast LA, Ben-Jonathan N. The Preovulatory Prolactin Surge Is Prolonged By a Progesterone-dependent Dopaminergic Mechanism. Endocrinology. 1990;126(1):246-52. PubMed PMID: 1967162.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - The preovulatory prolactin surge is prolonged by a progesterone-dependent dopaminergic mechanism. AU - Arbogast,L A, AU - Ben-Jonathan,N, PY - 1990/1/1/pubmed PY - 1990/1/1/medline PY - 1990/1/1/entrez SP - 246 EP - 52 JF - Endocrinology JO - Endocrinology VL - 126 IS - 1 N2 - The preovulatory PRL surge consists of a sharp peak, a prolonged plateau, and a termination phase. This study examined the role of progesterone in maintaining elevated PRL release during the plateau phase and its effect on dopaminergic (DA) neuronal activity. Immature rats were injected with PMSG on day 28, and blood was collected during the periovulatory period. Plasma estradiol levels were elevated before and during the PRL peak and declined during the plateau. Plasma progesterone levels were low before and during the peak, rose 4- to 5-fold during the plateau, and decreased to basal levels at the termination phase. In a second experiment rats were subjected to acute ovariectomy (OVEX) or sham surgery (SHAM) just before the onset of the PRL surge. Some OVEX rats were either immediately implanted with an estradiol-containing capsule or given three injections of progesterone during the time of the plateau phase. Blood PRL levels in SHAM rats showed the typical peak, plateau, and termination phases. The PRL peak was evident, but the plateau was missing in OVEX rats with or without estradiol treatment. Replacement with progesterone restored the plateau. In a third experiment, the stalk-median eminence, posterior pituitary, and striatum were removed during the time of the midplateau phase. Tyrosine hydroxylase activity was determined in tissue homogenates by a coupled hydroxylation-decarboxylation assay. Tyrosine hydroxylase activity in the stalk-median eminence of SHAM and progesterone-treated OVEX rats was similar, but was significantly lower than that in OVEX rats with or without estradiol. Tyrosine hydroxylase activity in the posterior pituitary and striatum was unchanged. To assess the functional DA input to the anterior pituitary, haloperidol, a DA antagonist, was injected during the midplateau phase. It induced a 12- to 17-fold rise in plasma PRL in both untreated and estradiol-treated OVEX rats, but failed to increase PRL above the plateau levels in SHAM and progesterone-treated OVEX rats. We conclude that the plateau phase of the preovulatory PRL surge is dependent on the concomitant rise in progesterone. Progesterone probably acts by reducing the DA neuronal activity in the SME, resulting in an absence of functional DA input to anterior pituitary lactotrophs. SN - 0013-7227 UR - https://www.unboundmedicine.com/medline/citation/1967162/The_preovulatory_prolactin_surge_is_prolonged_by_a_progesterone_dependent_dopaminergic_mechanism_ L2 - https://academic.oup.com/endo/article-lookup/doi/10.1210/endo-126-1-246 DB - PRIME DP - Unbound Medicine ER -