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Titolo:
CENTRAL REGULATION OF PULSATILE GONADOTROPIN-RELEASING-HORMONE (GNRH)SECRETION BY ESTRADIOL DURING THE PERIOD LEADING UP TO THE PREOVULATORY GNRH SURGE IN THE EWE
Autore:
EVANS NP; DAHL GE; GLOVER BH; KARSCH FJ;
Indirizzi:
UNIV MICHIGAN,REPROD SCI PROGRAM,300 N INGALLS BLDG,ROOM 1101 SW ANN ARBOR MI 48109 UNIV MICHIGAN,REPROD SCI PROGRAM,300 N INGALLS BLDG,ROOM 1101 SW ANN ARBOR MI 48109
Titolo Testata:
Endocrinology
fascicolo: 4, volume: 134, anno: 1994,
pagine: 1806 - 1811
SICI:
0013-7227(1994)134:4<1806:CROPG(>2.0.ZU;2-A
Fonte:
ISI
Lingua:
ENG
Soggetto:
TONIC LH-SECRETION; LUTEINIZING-HORMONE; PROGESTERONE; PULSE; RAM;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
19
Recensione:
Indirizzi per estratti:
Citazione:
N.P. Evans et al., "CENTRAL REGULATION OF PULSATILE GONADOTROPIN-RELEASING-HORMONE (GNRH)SECRETION BY ESTRADIOL DURING THE PERIOD LEADING UP TO THE PREOVULATORY GNRH SURGE IN THE EWE", Endocrinology, 134(4), 1994, pp. 1806-1811

Abstract

An experiment was conducted to investigate the central regulatory effects of estradiol on GnRH secretion leading up to the preovulatory LH surge in the ewe. Midluteal phase ewes were ovariectomized, treated with steroid implants to maintain luteal phase concentrations of progesterone and estradiol, and fitted with an apparatus for collection of hypophyseal portal blood. After simulated luteolysis (removal of progesterone implants), the ewes were allocated to one of three groups: estradiol withdrawn, estradiol maintained at a luteal phase level, or estradiol raised from a luteal phase level to a peak follicular phase levelin two increments. The results demonstrated that during the interval between luteolysis and the preovulatory gonadotropin surge, estradiol exerts a dose-dependent suppression of GnRH secretion from the hypothalamus. This effect reflects a suppression of GnRH pulse size and occurs despite a stimulatory action of estradiol on GnRH pulse frequency. The suppressive effect of estradiol on GnRH secretion, however, was delayed relative to that on LH. We conclude that during the period leading up to the preovulatory surge in the ewe, estradiol acts centrally, reducing GnRH secretion by suppressing GnRH pulse size.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 26/11/20 alle ore 13:43:31