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Evidence that progesterone modulates anterior pituitary neuropeptide Y levels during the progesterone-induced gonadotropin surge in the estrogen-primed intact immature female rat.
J Steroid Biochem Mol Biol. 1995 May; 52(5):497-504.JS

Abstract

In a previous study we reported that in vivo estrogen-priming alone, without subsequent progesterone-treatment, was sufficient to maximize NPY potentiation of gonadotropin hormone-releasing hormone responsiveness exhibited in vitro by the rat anterior pituitary. This observation suggests that the necessity, as reported by others, for both estrogen-priming and progesterone-treatment to maximize NPY potentiation of GnRH responsiveness in vivo may be due to progesterone acting primarily at the hypothalamus. Consequently, the current study was performed to determine whether progesterone facilitates gonadotropin secretion in vivo by acting to stimulate hypothalamic synthesis of NPY and the subsequent elevation of anterior pituitary tissue levels of NPY. Intact immature female rats were injected with estradiol at 1700 h on days 27 and 28. On day 29 at 0900 h, the animals received an injection of progesterone (2 mg/kg) or vehicle and were subsequently sacrificed at 1200, 1330 and 1500 h. Rats which received only estradiol injections were used as controls. Surge levels of serum LH and FSH were observed at 1330 and 1500 h. Hypothalamic levels of NPY mRNA at 1200 h on day 29 were higher (P < 0.01) in estradiol-primed rats which received progesterone; there was no accompanying statistically significant change in hypothalamic NPY content. NPY content in the anterior pituitary was significantly increased (P < 0.01) at 1200 h on day 29 in estradiol-primed rats which received progesterone; there was no accompanying significant change in anterior pituitary NPY mRNA levels. Hypothalamic GnRH mRNA content was significantly increased (P < 0.01) at 1330 h on day 29 concomitant with the peak of the gonadotropin surge in the estradiol-primed, progesterone-treated rat. The data indicate that progesterone modulates hypothalamic NPY mRNA and anterior pituitary NPY levels as well as GnRH mRNA levels and that modulation of NPY levels in the hypothalamic-pituitary axis occurs prior to modulation of GnRH gene expression. These studies support the hypothesis that in the estrogen-primed rat, progesterone facilitates the induction of the gonadotropin surge by maintaining hypothalamic synthesis of NPY as well as by modulating anterior pituitary NPY tissue levels.

Authors+Show Affiliations

Department of Physiology and Endocrinology, Medical College of Georgia, Augusta 30912-3000, USA.No affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

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

Language

eng

PubMed ID

7748815

Citation

O'Conner, J L., et al. "Evidence That Progesterone Modulates Anterior Pituitary Neuropeptide Y Levels During the Progesterone-induced Gonadotropin Surge in the Estrogen-primed Intact Immature Female Rat." The Journal of Steroid Biochemistry and Molecular Biology, vol. 52, no. 5, 1995, pp. 497-504.
O'Conner JL, Wade MF, Brann DW, et al. Evidence that progesterone modulates anterior pituitary neuropeptide Y levels during the progesterone-induced gonadotropin surge in the estrogen-primed intact immature female rat. J Steroid Biochem Mol Biol. 1995;52(5):497-504.
O'Conner, J. L., Wade, M. F., Brann, D. W., & Mahesh, V. B. (1995). Evidence that progesterone modulates anterior pituitary neuropeptide Y levels during the progesterone-induced gonadotropin surge in the estrogen-primed intact immature female rat. The Journal of Steroid Biochemistry and Molecular Biology, 52(5), 497-504.
O'Conner JL, et al. Evidence That Progesterone Modulates Anterior Pituitary Neuropeptide Y Levels During the Progesterone-induced Gonadotropin Surge in the Estrogen-primed Intact Immature Female Rat. J Steroid Biochem Mol Biol. 1995;52(5):497-504. PubMed PMID: 7748815.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Evidence that progesterone modulates anterior pituitary neuropeptide Y levels during the progesterone-induced gonadotropin surge in the estrogen-primed intact immature female rat. AU - O'Conner,J L, AU - Wade,M F, AU - Brann,D W, AU - Mahesh,V B, PY - 1995/5/1/pubmed PY - 1995/5/1/medline PY - 1995/5/1/entrez SP - 497 EP - 504 JF - The Journal of steroid biochemistry and molecular biology JO - J Steroid Biochem Mol Biol VL - 52 IS - 5 N2 - In a previous study we reported that in vivo estrogen-priming alone, without subsequent progesterone-treatment, was sufficient to maximize NPY potentiation of gonadotropin hormone-releasing hormone responsiveness exhibited in vitro by the rat anterior pituitary. This observation suggests that the necessity, as reported by others, for both estrogen-priming and progesterone-treatment to maximize NPY potentiation of GnRH responsiveness in vivo may be due to progesterone acting primarily at the hypothalamus. Consequently, the current study was performed to determine whether progesterone facilitates gonadotropin secretion in vivo by acting to stimulate hypothalamic synthesis of NPY and the subsequent elevation of anterior pituitary tissue levels of NPY. Intact immature female rats were injected with estradiol at 1700 h on days 27 and 28. On day 29 at 0900 h, the animals received an injection of progesterone (2 mg/kg) or vehicle and were subsequently sacrificed at 1200, 1330 and 1500 h. Rats which received only estradiol injections were used as controls. Surge levels of serum LH and FSH were observed at 1330 and 1500 h. Hypothalamic levels of NPY mRNA at 1200 h on day 29 were higher (P < 0.01) in estradiol-primed rats which received progesterone; there was no accompanying statistically significant change in hypothalamic NPY content. NPY content in the anterior pituitary was significantly increased (P < 0.01) at 1200 h on day 29 in estradiol-primed rats which received progesterone; there was no accompanying significant change in anterior pituitary NPY mRNA levels. Hypothalamic GnRH mRNA content was significantly increased (P < 0.01) at 1330 h on day 29 concomitant with the peak of the gonadotropin surge in the estradiol-primed, progesterone-treated rat. The data indicate that progesterone modulates hypothalamic NPY mRNA and anterior pituitary NPY levels as well as GnRH mRNA levels and that modulation of NPY levels in the hypothalamic-pituitary axis occurs prior to modulation of GnRH gene expression. These studies support the hypothesis that in the estrogen-primed rat, progesterone facilitates the induction of the gonadotropin surge by maintaining hypothalamic synthesis of NPY as well as by modulating anterior pituitary NPY tissue levels. SN - 0960-0760 UR - https://www.unboundmedicine.com/medline/citation/7748815/Evidence_that_progesterone_modulates_anterior_pituitary_neuropeptide_Y_levels_during_the_progesterone_induced_gonadotropin_surge_in_the_estrogen_primed_intact_immature_female_rat_ L2 - https://linkinghub.elsevier.com/retrieve/pii/0960-0760(95)00011-N DB - PRIME DP - Unbound Medicine ER -