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Titolo:
SEASONAL-CHANGES IN GONADOTROPIN-RELEASING-HORMONE SECRETION IN THE EWE - ALTERATION IN RESPONSE TO THE NEGATIVE FEEDBACK ACTION OF ESTRADIOL
Autore:
KARSCH FJ; DAHL GE; EVANS NP; MANNING JM; MAYFIELD KP; MOENTER SM; FOSTER DL;
Indirizzi:
UNIV MICHIGAN,REPROD SCI PROGRAM ANN ARBOR MI 48109 UNIV MICHIGAN,DEPT BIOL ANN ARBOR MI 48109 UNIV MICHIGAN,DEPT PHYSIOL ANN ARBOR MI 48109 UNIV MICHIGAN,DEPT OBSTET & GYNECOL ANN ARBOR MI 48109
Titolo Testata:
Biology of reproduction
fascicolo: 6, volume: 49, anno: 1993,
pagine: 1377 - 1383
SICI:
0006-3363(1993)49:6<1377:SIGSIT>2.0.ZU;2-P
Fonte:
ISI
Lingua:
ENG
Soggetto:
LUTEINIZING-HORMONE; PULSATILE SECRETION; ESTROUS-CYCLE; OVARIAN-STEROIDS; FOLLICULAR PHASE; PULSE FREQUENCY; GNRH SECRETION; LH-SECRETION; SHEEP; SURGE;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
38
Recensione:
Indirizzi per estratti:
Citazione:
F.J. Karsch et al., "SEASONAL-CHANGES IN GONADOTROPIN-RELEASING-HORMONE SECRETION IN THE EWE - ALTERATION IN RESPONSE TO THE NEGATIVE FEEDBACK ACTION OF ESTRADIOL", Biology of reproduction, 49(6), 1993, pp. 1377-1383

Abstract

Two experiments were performed to test the hypothesis that there is aseasonal change in the negative feedback effect of estradiol on episodic secretion of GnRH in the ewe. The first experiment identified a specific estradiol treatment (delivered by s.c. Silastic implant) that produced a 50% decrease in the frequency of pulsatile secretion of LH in ovariectomized ewes during the anestrous season. In the second experiment, theis estradiol treatment was administered to ovariectomized ewes during the mid-breeding and anestrous seasons. Separate groups of ovariectomized ewes not treated with estradiol were included during each season to test for a seasonal difference in the effect of estradiol on episodic GnRH and LH secretion. Samples of hypophyseal portal blood(for GnRH) and jugular blood (for LH) were obtained at 5-min intervals approximately one month after placement of the estradiol implants. During the breeding season, no effect of estradiol was observed on either the frequency or size of GnRH and LH pulses. During anestrus, however, estradiol produced a profound suppression of the frequency of GnRHand LH pulses, and an increase in GnRH pulse size. No significant seasonal change was observed in the characteristics of GnRH and LH pulsesin ovariectomized ewes in the absence of estradiol treatment. These findings lead to the conclusion that there is a marked seasonal change in the negative feedback effect of estradiol on episodic GnRH secretion in the ewe, with the steroid being maximally effective during anestrus.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 29/11/20 alle ore 16:53:07