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Titolo:
Thyroid hormones act primarily within the brain to promote the seasonal inhibition of luteinizing hormone secretion in the ewe
Autore:
Viguie, C; Battaglia, DF; Krasa, HB; Thrun, LA; Karsch, FJ;
Indirizzi:
Univ Michigan, Dept Biol, Reprod Sci Program, Ann Arbor, MI 48109 USA UnivMichigan Ann Arbor MI USA 48109 Sci Program, Ann Arbor, MI 48109 USA Univ Michigan, Dept Physiol, Ann Arbor, MI 48109 USA Univ Michigan Ann Arbor MI USA 48109 ept Physiol, Ann Arbor, MI 48109 USA
Titolo Testata:
ENDOCRINOLOGY
fascicolo: 3, volume: 140, anno: 1999,
pagine: 1111 - 1117
SICI:
0013-7227(199903)140:3<1111:THAPWT>2.0.ZU;2-4
Fonte:
ISI
Lingua:
ENG
Soggetto:
GONADOTROPIN-RELEASING-HORMONE; NEGATIVE FEEDBACK ACTION; REPRODUCTIVE NEUROENDOCRINE ACTIVITY; ANESTROUS EWE; CEREBROSPINAL-FLUID; STARLINGS STURNUS; PLASMA PROLACTIN; RHESUS-MONKEY; LH-SECRETION; GNRH NEURONS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
54
Recensione:
Indirizzi per estratti:
Indirizzo: Karsch, FJ UnivSW,chigan, Dept Biol, Reprod Sci Program, 300 N Ingalls Bldg,Room 1101 Univ Michigan 300 N Ingalls Bldg,Room 1101 SW Ann Arbor MI USA 48109
Citazione:
C. Viguie et al., "Thyroid hormones act primarily within the brain to promote the seasonal inhibition of luteinizing hormone secretion in the ewe", ENDOCRINOL, 140(3), 1999, pp. 1111-1117

Abstract

In the ewe, thyroid hormones are required for the seasonal suppression of GnRH and LH secretion, thereby maintaining an annual rhythm in reproductiveactivity. The primary site of action of thyroid hormones is unknown; in particular, there is no evidence to distinguish a central from a peripheral action. In this study, we test the hypothesis that thyroid hormones can act directly within the brain to promote GnRH/LH seasonal inhibition. Ovariectomized estradiol-treated ewes were thyroidectomized late in the breeding season to prevent seasonal LH inhibition. T-4 was then infused for 3 months, either peripherally or centrally. Neuroendocrine reproductive state was monitored by assaying the LH concentration in biweekly blood samples. Central infusion of low dose T-4, which restored a physiological concentration of the hormone in cerebrospinal fluid of these thyroidectomized ewes, promoted the neuroendocrine changes that lead to anestrus. The serum LH concentrationin these animals fell at the same time as the seasonal LH decline in euthyroid controls. Neither this same T-4 dose infused peripherally nor vehicle infused centrally was effective; LH remained elevated, signifying blockade of the mechanism for anestrus. Our results provide strong evidence that thyroid hormones can act directly within the brain to promote seasonal inhibition of neuroendocrine reproductive function in the ewe.

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Documento generato il 02/12/20 alle ore 07:11:12