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Titolo:
Importance of photoperiodic signal quality to entrainment of the circannual reproductive rhythm of the ewe
Autore:
Barrell, GK; Thrun, LA; Brown, ME; Viguie, C; Karsch, FJ;
Indirizzi:
Univ Michigan, Reprod Sci Program, Dept Physiol, Ann Arbor, MI 48109 USA Univ Michigan Ann Arbor MI USA 48109 ept Physiol, Ann Arbor, MI 48109 USA
Titolo Testata:
BIOLOGY OF REPRODUCTION
fascicolo: 3, volume: 63, anno: 2000,
pagine: 769 - 774
SICI:
0006-3363(200009)63:3<769:IOPSQT>2.0.ZU;2-M
Fonte:
ISI
Lingua:
ENG
Soggetto:
NEGATIVE FEEDBACK ACTION; INDUCTIVE PHOTOPERIOD; MELATONIN SECRETION; LUTEINIZING-HORMONE; GROUND-SQUIRRELS; BREEDING-SEASON; DAY LENGTH; DURATION; PATTERN; SYNCHRONIZATION;
Keywords:
anterior pituitary; circadian rhythm; estradiol; GnRH; hypothalamus; LH; melatonin; pineal; seasonal reproduction;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
33
Recensione:
Indirizzi per estratti:
Indirizzo: Karsch, FJ Univ Michigan, Reprod Sci Program, Dept Physiol, 300 N Ingalls Bldg, Ann Arbor, MI 48109 USA Univ Michigan 300 N Ingalls Bldg Ann Arbor MIUSA 48109 109 USA
Citazione:
G.K. Barrell et al., "Importance of photoperiodic signal quality to entrainment of the circannual reproductive rhythm of the ewe", BIOL REPROD, 63(3), 2000, pp. 769-774

Abstract

An endogenous circannual rhythm drives the seasonal reproductive cycle of a broad spectrum of species. This rhythm is synchronized to the seasons (i.e,, entrained) by photoperiod, which acts by regulating the circadian pattern of melatonin secretion from the pineal gland. Prior work has revealed that melatonin patterns secreted in spring/summer entrain the circannual rhythm of reproductive neuroendocrine activity in sheep, whereas secretions in winter do not. The goal of this study was to determine if inability of the winter-melatonin pattern to entrain the rhythm is due to the specific melatonin pattern secreted in winter or to the stage of the circannual rhythm atthat time of year. Either a summer- or a winter-melatonin pattern was infused for 70 days into pinealectomized ewes, centered around the summer solstice, when an effective stimulus readily entrains the rhythm, The ewes were ovariectomized and treated with constant-release estradiol implants, and circannual cycles of reproductive neuroendocrine activity were monitored by serum LH concentrations. Only the summer-melatonin pattern entrained the circannual reproductive rhythm. The inability of the winter pattern to do so indicates that the mere presence of a circadian melatonin pattern, in itself, is insufficient for entrainment. Rather, the characteristics of the melatonin pattern, in particular a pattern that mimics the photoperiodic signalsof summer, determines entrainment of the circannual rhythm of reproductiveneuroendocrine activity in the ewe.

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Documento generato il 29/11/20 alle ore 17:42:34