PMID: 8609596Aug 1, 1995Paper

Plasma melatonin in the horse: measurements in natural photoperiod and in acutely extended darkness throughout the year

Journal of Pineal Research
M V GuerinC D Matthews

Abstract

Plasma melatonin was measured at the winter and summer solstices and the autumn and spring equinoxes in four mares held under natural conditions at 35 degrees S. At all seasons the onset of the nightly elevated melatonin was coincident with or after the time of sunset and the melatonin offset after the time of sunrise. The duration of elevated melatonin was not different from the duration of natural scotophase for each season, with the duration of elevated melatonin longer in winter than the other seasons. Immediately following each 24 hr sampling two mares were resampled in acutely extended darkness to determine the melatonin profile of the endogenous rhythm of the circadian pacemaker, originating from the suprachiasmatic nuclei (SCN). At each season melatonin secretion commenced earlier and decreased later than that measured under the natural photoperiodic condition, suggesting that the expression of the melatonin rhythm is normally gated by natural environmental light both at dusk and dawn. The interval from the onset of melatonin measured under acutely extended darkness to the time of sunset was greater in the spring/summer than the autumn/winter suggesting a possible alternating signal throughout the year. Thus the mare ap...Continue Reading

References

Feb 1, 1979·Endocrinology·L TamarkinD C Klein
Aug 1, 1992·Journal of Reproduction and Fertility·C D MatthewsM V Guerin
Jan 1, 1991·Comparative Biochemistry and Physiology. A, Comparative Physiology·A Flisińska-BojanowskaJ Gill
Jan 1, 1990·Journal of Pineal Research·C R EarlR F Seamark
Jan 1, 1986·Journal of Biological Rhythms·M S Carmichael, I Zucker
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Oct 1, 1985·Journal of Animal Science·K MalinowskiC G Scanes
Apr 1, 1993·Journal of Pineal Research·C D MatthewsJ R Deed

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Citations

Mar 10, 2000·Animal Reproduction Science·T Gerlach, J E Aurich
Mar 24, 2011·Reproduction, Fertility, and Development·Marcos PedrerosMontserrat Guerra
May 17, 2011·Journal of Circadian Rhythms·Barbara A MurphyJeffrey A Elliott
May 12, 2009·The Veterinary Journal·Barbara A Murphy
Jan 2, 2007·Research in Veterinary Science·G PiccioneR Refinetti
Feb 24, 2005·Journal of Pineal Research·Marie-Laure Garidou-BoofBerthe Vivien-Roels
Apr 12, 2002·General and Comparative Endocrinology·Michaela HauThomas J Van't Hof
Jun 16, 2001·Journal of Biological Rhythms·A Alila-JohanssonM L Laakso
Jun 15, 2019·Chronobiology International·David J Kennaway
Mar 11, 2003·American Journal of Physiology. Regulatory, Integrative and Comparative Physiology·Marie-Laure GaridouValerie Simonneaux
Apr 14, 2020·Journal of Pineal Research·David J Kennaway
Dec 5, 2002·Journal of Animal Science·M A DiekmanD Cook

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