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Titolo:
THE GNRH SYSTEM OF SEASONAL BREEDERS - ANATOMY AND PLASTICITY
Autore:
LEHMAN MN; GOODMAN RL; KARSCH FJ; JACKSON GL; BERRIMAN SJ; JANSEN HT;
Indirizzi:
UNIV CINCINNATI,COLL MED,DEPT CELL BIOL,231 BETHESDA AVE CINCINNATI OH 45267 UNIV CINCINNATI,COLL MED,DEPT NEUROBIOL CINCINNATI OH 45267 UNIV CINCINNATI,COLL MED,DEPT ANAT CINCINNATI OH 45267 W VIRGINIA UNIV,DEPT PHYSIOL MORGANTOWN WV 26506 UNIV MICHIGAN,REPROD SCI PROGRAM ANN ARBOR MI 49109 UNIV ILLINOIS,DEPT VET BIOSCI URBANA IL 61801
Titolo Testata:
Brain research bulletin
fascicolo: 4, volume: 44, anno: 1997,
pagine: 445 - 457
SICI:
0361-9230(1997)44:4<445:TGSOSB>2.0.ZU;2-5
Fonte:
ISI
Lingua:
ENG
Soggetto:
HORMONE-RELEASING HORMONE; ESTRADIOL NEGATIVE FEEDBACK; STEROID-DEPENDENT SUPPRESSION; LUTEINIZING-HORMONE; MEDIAN-EMINENCE; IMMUNOCYTOCHEMICAL LOCALIZATION; ANESTROUS EWE; PREOPTIC AREA; THYROID-GLAND; RHESUS-MONKEY;
Keywords:
SEASONAL BREEDING; SHEEP; HAMSTERS; GNRH; LHRH; ESTRADIOL; NEGATIVE FEEDBACK; THYROID HORMONE; ENDOGENOUS OPIOID PEPTIDES;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
93
Recensione:
Indirizzi per estratti:
Citazione:
M.N. Lehman et al., "THE GNRH SYSTEM OF SEASONAL BREEDERS - ANATOMY AND PLASTICITY", Brain research bulletin, 44(4), 1997, pp. 445-457

Abstract

Seasonal breeders, such as sheep and hamsters, by virtue of their annual cycles of reproduction, represent valuable models for the study ofplasticity in the adult mammalian neuroendocrine brain. A major factor responsible for the occurrence of seasonal reproductive transitions is a striking change in the responsiveness of gonadotropin-releasing hormone (GnRH) neurons to the inhibitory effects of gonadal steroids. However, the neural circuitry mediating these seasonal changes is stillrelatively unexplored. In this article, we review recent findings that have begun to define that circuitry and its plasticity in a well-studied seasonal breeder, the ewe. Tract tracing studies and immunocytochemical analyses using Fos and FRAs as markers of activation point to asubset of neuroendocrine GnRH neurons in the MBH as potential mediators of pulsatile GnRH secretion. Because the vast majority of GnRH neurons lack estrogen receptors, seasonal changes in responsiveness to estradiol are most probably conveyed by afferents. Two possible mediatorsof this influence are dopaminergic cells in the A14/A15 cell groups of the hypothalamus, and estrogen receptor-containing cells in the arcuate nucleus that project to the median eminence. The importance of GnRH afferents in the regulation of season breeding is underscored by observations of seasonal changes in the density of synaptic inputs onto GnRH neurons. Thyroid hormones may participate in this remodeling, because they are important in seasonal reproduction, influence the morphology of other brain systems, and thyroid hormone receptors are expressed within GnRH neurons. Finally, in the hamster, neonatal hypothyroidism affects the number of caudally placed GnRH neurons in the adult brain, suggesting that thyroid hormones may influence development of the GnRH system as well as its reproductive functions in the adult brain. (C) 1997 Elsevier Science Inc.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 29/11/20 alle ore 18:12:41