Pituitary Responsiveness to LRH in the Short-Term Ovariectomized Rat1

Baldwin, David M.; Ramírez, Victor D.; Sawyer, Charles H.

doi:10.1095/biolreprod13.5.535

Cited by 6 publications

(3 citation statements)

References 18 publications

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“…At that time in control ovariectomized rats, serum LH values were suppressed to low values. It is well known that in ovariectomized rats the enhancement of pituitary responsiveness to LH-RH is observed 8-10 h after OB injection (Libertun et al 1974) and lasts for at least 3 days (Baldwin, Ramirez & Sawyer, 1975;Aiyer et al 1976). In spite of very high pituitary responsiveness to LH-RH 1 day after OB administration, the animals had low basal LH concentrations, suggesting that OB inhibited LH-RH secretion from the hypothalamus.…”

Section: Discussionmentioning

confidence: 99%

Feedback Effect of Oestrogen on Luteinizing Hormone Secretion by the Rat Pituitary Gland

Higuchi¹,

Kawakami²

1982

Journal of Endocrinology

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Ovariectomized rats with neural deafferentation at the level of the posterior border of the anterior hypothalamic area (AC rats) were used to re-evaluate the direct feedback effect of oestrogen on the regulation of LH secretion by the pituitary gland. Synthetic LH releasing hormone (LH-RH; 300 ng/kg), injected at 30 min intervals into AC rats with undetectable basal LH, induced pulsatile increase of serum LH concentrations. Oestradiol-7Beta (5 micrograms), administered i.v. just before the first LH-RH injection, significantly decreased the LH response to a second injection of LH-RH given 30 min later and to subsequent injections. Maximal inhibition was 58%. Oestradiol 17 beta (5 micrograms) given i.v. to control ovariectomized rats decreased serum LH concentrations 40 min after administration; the maximum reduction being 52%. An s.c. injection of oestradiol benzoate (5 micrograms) increased pituitary responsiveness to LH-RH by the next day in AC rats but decreased serum LH levels in control ovariectomized rats. These results indicate that acute inhibitory and chronic facilitatory effects of oestrogen on LH secretion are exerted at the pituitary gland, without a change in LH-RH secretion. The prolonged inhibitory effect of oestrogen is at the level of the hypothalamus and causes a reduction in LH-RH secretion.

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Section: Discussionmentioning

confidence: 99%

Feedback Effect of Oestrogen on Luteinizing Hormone Secretion by the Rat Pituitary Gland

Higuchi¹,

Kawakami²

1982

Journal of Endocrinology

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“…Since in vivo treatment with estrogens can lead to decreased plasma LH levels in the presence of increased pituitary responsiveness to LHRH, it is probable that estrogens exert an inhibitory effect on LHRH secretion at the hypothalamic level . The possibility does, however, remain that estrogens could, as clearly demonstrated in the female animal (Baldwin et al 1974;Ferland et al 1976) exert also a positive action on LHRH secretion. Fig.…”

Section: Discussionmentioning

confidence: 99%

Interactions Between LHRH, Sex Steroids and “Inhibin” in the Control of LH and FSH Secretion

et al. 1978

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Using anterior pituitary cells obtained from adult male rats, 17β‐estradiol stimulated both spontaneous and LHRH‐induced LH and FSH secretion. After in vivo administration, estrogens showed inhibitory or stimulatory effects on gonadotropin secretion, the effect being dose‐ and time‐dependent. Contrary to estrogens, androgens had differential effects at the anterior pituitary level: they inhibited LH but stimulated FSH secretion. These in vitro data were confirmed by in vivo experiments using anti‐androgens. Sertoli cell culture medium was found to be a potent inhibitor of spontaneous FSH secretion while no effect was detected on LH release. When the gonadotropin response to LHRH was studied, Sertoli cell culture medium was a more potent inhibitor of FSH than LH release although clear inhibition of LHRH‐induced LH release did occur.

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“…Feedback effects are generally negative as in adrenal glucocorticoid inhibition of corticotropin-releasing factor and adrenocorticotropin (ACTH) release from the hypothalamus and the pituitary, respectively (see Keller-Wood and Dallman, 1984 for review); feedback of gonadal steroids on gonadotropin release is predominantly negative although positive effects are seen under certain physiological circumstances (Baldwin et al, 1974;Martin et al, 1974;Labrie et al, 1978). Feedback effects are generally negative as in adrenal glucocorticoid inhibition of corticotropin-releasing factor and adrenocorticotropin (ACTH) release from the hypothalamus and the pituitary, respectively (see Keller-Wood and Dallman, 1984 for review); feedback of gonadal steroids on gonadotropin release is predominantly negative although positive effects are seen under certain physiological circumstances (Baldwin et al, 1974;Martin et al, 1974;Labrie et al, 1978).…”

Section: Introductionmentioning

confidence: 99%

Evidence for Ecdysteroid Feedback on Release of Molt-Inhibiting Hormone From Crab Eyestalk Ganglia

Mattson¹,

Spaziani²

1986

The Biological Bulletin

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JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.Marine Biological Laboratory is collaborating with JSTOR to digitize, preserve and extend access to Biological Bulletin This content downloaded from 128.252.67.66 on Mon, ABSTRACT The content and release of molt-inhibiting hormone activity (MIH) in isolated eyestalk ganglia of crabs (Cancer antennarius S.) were measured in vitro as a function of exposure in vivo to elevated or reduced hemolymph ecdysteroid levels. Ecdysteroid titers of intermolt crabs injected with 20-hydroxyecdysone (two 45 tug injections/24 h) rose 8-to 10-fold; MIH released from subsequently isolated ganglia was significantly less than that released from ganglia of saline-injected controls, while MIH content of ganglia from treated crabs was increased. The hemolymph ecdysteroid level of intermolt crabs was low (6 ng/ml) and was further reduced by 40% 6 days after Y-organectomy. MIH release from ganglia of both Y-organectomized and sham-operated control crabs was high, similar to that of unoperated controls, but MIH content of ganglia from both Y-organectomized and sham groups was significantly reduced relative to controls. The results indicate a negative feedback regulation of MIH release but not synthesis by ecdysteroids and are discussed in relation to the patterns of ecdysteroid titers observed in the normal crustacean molt cycle.

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Pituitary Responsiveness to LRH in the Short-Term Ovariectomized Rat1

Cited by 6 publications

References 18 publications

Feedback Effect of Oestrogen on Luteinizing Hormone Secretion by the Rat Pituitary Gland

Feedback Effect of Oestrogen on Luteinizing Hormone Secretion by the Rat Pituitary Gland

Interactions Between LHRH, Sex Steroids and “Inhibin” in the Control of LH and FSH Secretion

Evidence for Ecdysteroid Feedback on Release of Molt-Inhibiting Hormone From Crab Eyestalk Ganglia

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