Feedback effects of ovarian steroids on the hypothalamic-hypophyseal axis in the rabbit

K. Y. Francis Pau, K. M. Orstead, David Hess, H. G. Spies

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    Abstract

    The feedback effects of two ovarian steroids, estradiol-17β (E2) and 20α-hydroxypregn-4-en-3-one (20αOH), were examined in both intact (INT) and ovariectomized (OVEX) does. We measured (1) steroid-induced alterations in endogenous gonadotropin-releasing hormone (GnRH) from sequential 10-min samples of hypothalamic perfusates, (2) simultaneous changes in peripheral plasma luteinizing hormone (LH) and follicle-stimulating hormone (FSH), and (3) the modification of pituitary responsiveness, i.e., increments in plasma LH (Δ LH) and plasma FSH (Δ FSH), after 50 ng, 250 ng, and 1 μg of exogenous GnRH in individual does of 6 treatment groups. The groups were: INT does, OVEX does, OVEX does receiving either one (1 E2) or two (2 E2) E2-filled Silastic capsules, OVEX does receiving a 20αOH-filled capsule (20αOH), and OVEX does receiving both capsules of E2 and 20αOH (1 E2 + 20αOH). Ovariectomy enhanced the pulsatile release of hypothalamic GnRH and pituitary LH and FSH, and increased the LH response (Δ LH) to exogenous GnRH (OVEX vs. INT, p2 at the time of ovariectomy prevented the increased GnRH and gonadotropin secretion as well as the enhanced Δ LH that were observed in untreated OVEX does. The release of hypothalamic GnRH in the 20αOH group was lower (p2 + 20αOH group was lower (p2 or the 20αOH group, but the Δ LH in the 1 E2 + 20αOH group was not different from that in either the 1 E2 or the 20αOH group. The highest dose (1 μg) of exogenous GnRH stimulated a modest increase in FSH in the OVEX, 20αOH, 1 E2 + 20αOH, and 1 E2 groups; but a steroid effect on Δ FSH among these 4 groups was not apparent. These results suggest that in the rabbit, E2 exerts its inhibitory effects on both the hypothalamus and the pituitary, whereas 20αOH suppresses hypothalamic GnRH release and facilitates pituitary LH responsiveness.

    Original languageEnglish (US)
    Pages (from-to)1009-1023
    Number of pages15
    JournalBiology of Reproduction
    Volume35
    Issue number4
    StatePublished - 1986

    Fingerprint

    Luteinizing Hormone
    Gonadotropin-Releasing Hormone
    Steroids
    Follicle Stimulating Hormone
    Rabbits
    Pituitary Hormone-Releasing Hormones
    Capsules
    Pituitary Hormones
    Ovariectomy
    Gonadotropins
    Hypothalamus
    Estradiol

    ASJC Scopus subject areas

    • Cell Biology
    • Developmental Biology
    • Embryology

    Cite this

    Francis Pau, K. Y., Orstead, K. M., Hess, D., & Spies, H. G. (1986). Feedback effects of ovarian steroids on the hypothalamic-hypophyseal axis in the rabbit. Biology of Reproduction, 35(4), 1009-1023.

    Feedback effects of ovarian steroids on the hypothalamic-hypophyseal axis in the rabbit. / Francis Pau, K. Y.; Orstead, K. M.; Hess, David; Spies, H. G.

    In: Biology of Reproduction, Vol. 35, No. 4, 1986, p. 1009-1023.

    Research output: Contribution to journalArticle

    Francis Pau, KY, Orstead, KM, Hess, D & Spies, HG 1986, 'Feedback effects of ovarian steroids on the hypothalamic-hypophyseal axis in the rabbit', Biology of Reproduction, vol. 35, no. 4, pp. 1009-1023.
    Francis Pau, K. Y. ; Orstead, K. M. ; Hess, David ; Spies, H. G. / Feedback effects of ovarian steroids on the hypothalamic-hypophyseal axis in the rabbit. In: Biology of Reproduction. 1986 ; Vol. 35, No. 4. pp. 1009-1023.
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    abstract = "The feedback effects of two ovarian steroids, estradiol-17β (E2) and 20α-hydroxypregn-4-en-3-one (20αOH), were examined in both intact (INT) and ovariectomized (OVEX) does. We measured (1) steroid-induced alterations in endogenous gonadotropin-releasing hormone (GnRH) from sequential 10-min samples of hypothalamic perfusates, (2) simultaneous changes in peripheral plasma luteinizing hormone (LH) and follicle-stimulating hormone (FSH), and (3) the modification of pituitary responsiveness, i.e., increments in plasma LH (Δ LH) and plasma FSH (Δ FSH), after 50 ng, 250 ng, and 1 μg of exogenous GnRH in individual does of 6 treatment groups. The groups were: INT does, OVEX does, OVEX does receiving either one (1 E2) or two (2 E2) E2-filled Silastic capsules, OVEX does receiving a 20αOH-filled capsule (20αOH), and OVEX does receiving both capsules of E2 and 20αOH (1 E2 + 20αOH). Ovariectomy enhanced the pulsatile release of hypothalamic GnRH and pituitary LH and FSH, and increased the LH response (Δ LH) to exogenous GnRH (OVEX vs. INT, p2 at the time of ovariectomy prevented the increased GnRH and gonadotropin secretion as well as the enhanced Δ LH that were observed in untreated OVEX does. The release of hypothalamic GnRH in the 20αOH group was lower (p2 + 20αOH group was lower (p2 or the 20αOH group, but the Δ LH in the 1 E2 + 20αOH group was not different from that in either the 1 E2 or the 20αOH group. The highest dose (1 μg) of exogenous GnRH stimulated a modest increase in FSH in the OVEX, 20αOH, 1 E2 + 20αOH, and 1 E2 groups; but a steroid effect on Δ FSH among these 4 groups was not apparent. These results suggest that in the rabbit, E2 exerts its inhibitory effects on both the hypothalamus and the pituitary, whereas 20αOH suppresses hypothalamic GnRH release and facilitates pituitary LH responsiveness.",
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