Differential effects of LH-RH immunoneutralization on LH and FSH secretion in the ewe

Fraser, H. M.; McNeilly, Alan S.

doi:10.1530/jrf.0.0690569

Cited by 26 publications

(10 citation statements)

References 29 publications

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“…Thus, the basal secre tion of FSH persisted for 2 weeks in the presumed absence of pulsatile GnRH release. A differential regulation of LH and FSH secretion, like that shown here, has been observed in other situations and species [10,14,18,23,48]. In a directly analogous study, Clarke et al [10] observed con tinuing FSH secretion for up to I week in ewes after pulsa tile GnRH and LH secretion were abolished by surgical dis connection of the pituitary from the hypothalamus.…”

Section: Discussionsupporting

confidence: 81%

Hypophyseal Actions of Pulsatile Gonadotropin-Releasing Hormone in the Ewe: Development and Application of a New Experimental Model

Kaynard

Karsch²

1988

Neuroendocrinology

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Ovariectomy of ewes during seasonal anestrus and immediate replacement with subcutaneous Silastic progesterone implants which maintained a midluteal-phase level of circulating progesterone obliterated pulsatile luteinizing hormone (LH) secretion for up to 2 weeks without preventing a normal response of the pituitary to exogenous pulses of gonadotropin-releasing hormone (GnRH). Consideration was given to the possibility that such ‘progesterone-suppressed ewes’ would be useful as an animal model for isolating the pituitary from pulsatile GnRH secretion, and for testing the hypophyseotropic actions of exogenous GnRH. Two experiments were conducted using this progesterone-suppressed ewe as an animal model. In the first, the amplitude of LH pulses elicited by episodic delivery of GnRH was found to depend upon the frequency of exogenous GnRH pulses. Hourly frequency produced larger LH pulses than a 30-min frequency of GnRH. In the second experiment, LH surges were induced in progesterone-suppressed ewes by a combined treatment of estradiol and GnRH in patterns designed to approximate those secreted in the follicular phase of the estrous cycle. Our findings suggest that the progesterone-suppressed ewe is a suitable animal model for studying the hypophyseotropic actions of GnRH. Further, they are consistent with two hypotheses concerning the regulation of the tonic and surge modes of LH secretion. (1) The inverse relationship between LH pulse frequency and amplitude observed in a number of situations can be accounted for, at least in part, by a differential response of the pituitary to GnRH. (2) Progesterone can block the LH surge by an action on the brain and an inhibition of pulsatile GnRH release.

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Section: Discussionsupporting

confidence: 81%

Hypophyseal Actions of Pulsatile Gonadotropin-Releasing Hormone in the Ewe: Development and Application of a New Experimental Model

Kaynard

Karsch²

1988

Neuroendocrinology

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“…This slow and incomplete effect was reflected in the lack of responsiveness to the pulses of analogue. These observations are consistent with those of Lincoln and Short (1980) (Clarke et al, 1978), and passive immunization against LH-RH in entire ewes during the follicular phase leads to an increase in the levels of FSH, probably through deprivation of oestrogen (Fraser and McNeilly, 1983). Normally, FSH levels fall during the follicular phase due to the build-up in oestrogen levels (Baird and McNeilly, 19811.…”

Section: Introductionsupporting

confidence: 77%

A new method for studying pituitary responsiveness in vivo using pulses of LH-RH analogue in ewes passively immunized against native LH-RH

Caraty¹,

Martin²,

Montgomery³

1984

Reprod. Nutr. Dévelop.

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“…2) supports a previous hypothesis (Goodman et ai, 1982) that during seasonal anoestrus oestradiol can suppress LH pulse frequency with a corresponding increase in LH pulse amplitude. The conclusion that oestradiol acts on the LHRH pulse generating system is further supported by reports that a pulse of LH is preceded or accompanied by a pulse of LHRH from the hypothalamus (Clarke & Cummins, 1982 ; Levine, Pan, Ramirez & Jackson, 1982 (Fraser & McNeilly, 1983).…”

Section: Peripheral Plasma Fsh Concentrationsmentioning

confidence: 78%

Control of gonadotrophin release in Scottish Blackface and Finnish Landrace ewes during seasonal anoestrus

Webb¹,

Baxter²,

Preece³

et al. 1985

Reproduction

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Differential effects of LH-RH immunoneutralization on LH and FSH secretion in the ewe

Cited by 26 publications

References 29 publications

Hypophyseal Actions of Pulsatile Gonadotropin-Releasing Hormone in the Ewe: Development and Application of a New Experimental Model

Hypophyseal Actions of Pulsatile Gonadotropin-Releasing Hormone in the Ewe: Development and Application of a New Experimental Model

A new method for studying pituitary responsiveness in vivo using pulses of LH-RH analogue in ewes passively immunized against native LH-RH

Control of gonadotrophin release in Scottish Blackface and Finnish Landrace ewes during seasonal anoestrus

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