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Titolo:
EVIDENCE FOR SHORT OR ULTRASHORT LOOP NEGATIVE FEEDBACK OF GONADOTROPIN-RELEASING-HORMONE SECRETION
Autore:
PADMANABHAN V; EVANS NP; DAHL GE; MCFADDEN KL; MAUGER DT; KARSCH FJ;
Indirizzi:
UNIV MICHIGAN,REPROD SCI PROGRAM,300 N INGALLS BLDG,ROOM 1101 SW ANN ARBOR MI 48109 UNIV MICHIGAN,DEPT PEDIAT ANN ARBOR MI 48109 UNIV MICHIGAN,DEPT PHYSIOL ANN ARBOR MI 48109 UNIV MICHIGAN,DEPT BIOSTAT ANN ARBOR MI 48109 UNIV MICHIGAN,NATL CTR INFERTIL RES MICHIGAN ANN ARBOR MI 48109
Titolo Testata:
Neuroendocrinology
fascicolo: 3, volume: 62, anno: 1995,
pagine: 248 - 258
SICI:
0028-3835(1995)62:3<248:EFSOUL>2.0.ZU;2-T
Fonte:
ISI
Lingua:
ENG
Soggetto:
BLOOD-BRAIN-BARRIER; LUTEINIZING-HORMONE; PREOPTIC AREA; HYPOTHALAMIC NEURONS; GNRH SECRETION; LH-SECRETION; EWE; ESTRADIOL; RAT; PROGESTERONE;
Keywords:
GONADOTROPINS; GONADOTROPIN-RELEASING HORMONE; GONADOTROPIN-RELEASING-HORMONE ANTAGONISTS; SHEEP;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Science Citation Index Expanded
Citazioni:
52
Recensione:
Indirizzi per estratti:
Citazione:
V. Padmanabhan et al., "EVIDENCE FOR SHORT OR ULTRASHORT LOOP NEGATIVE FEEDBACK OF GONADOTROPIN-RELEASING-HORMONE SECRETION", Neuroendocrinology, 62(3), 1995, pp. 248-258

Abstract

The present studies tested the hypothesis that either short or ultrashort loop negative feedback regulation of gonadotropin-releasing hormone (GnRH) secretion occurs in the ewe. As part of ongoing studies investigating the regulation of follicle-stimulating-hormone secretion, weobtained the unexpected result that a GnRH antagonist (Nal-Glu) may stimulate GnRH secretion. In that experiment, hypophyseal portal blood was collected from five short-term ovariectomized ewes at 5-min intervals for 6 h before and 6 h after intravenous injection of Nal-Glu (10 mu g/kg body weight). An increase in GnRH pulse frequency in association with the blockade of luteinizing hormone (LH) release was evident in 3 of the 5 animals. To determine if an effect of Nal-Glu on episodicGnRH secretion would be more evident in an animal model in which low-frequency pulses of GnRH prevail, the study was repeated in six ewes in the midluteal phase of the estrous cycle and six ovariectomized ewesbearing estradiol and progesterone implants to suppress GnRH release (artificial luteal model). In luteal-phase ewes, administration of Nal-Glu was followed by an increase in GnRH pulse frequency, pulse size and the secretion of GnRH between pulses, and by a blockade of LH release. In ovariectomized ewes treated with estradiol and progesterone, Nal-Glu administration also stimulated GnRH and inhibited LH secretion. Our finding that the GnRH antagonist stimulated GnRH secretion is consistent with the hypothesis that endogenous GnRH may influence its own release via either a short or ultrashort loop feedback mechanism.

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Documento generato il 27/11/20 alle ore 22:35:30