title: Development of melatonin rhythm in the pineal gland and eyes of chick embryo.
abstract: A melatonin rhythm was observed in the pineals of 18-day-old chick embryos incubated under a light-dark regime of 18: 6 h. A low pineal melatonin content was found during the light phase of the day. Concentrations started to increase 2 h after dark onset and reached maximum levels after 4 h of darkness. The amplitude of the pineal melatonin rhythm increased considerably after 2 days and night-time concentrations in 20-day-old embryos were more than 5 times higher than in 18-day-old ones. Significant day/night differences in melatonin production were found both in pineals and eyes. Exposure of eggs to 1 h of light during the dark period decreased the high melatonin concentrations in the eyes but not in the pineals of the 20-day-old chick embryo. The results suggest that in this precocial bird at least part of the circadian system may already operate during embryonic life.
authors.affiliation: Institute of Animal Biochemistry and Genetics, SASci, Ivanka pro Dunaji, Czechoslovakia.
authors.forename: M
authors.initials: M
authors.lastname: Zeman
authors.forename: E
authors.initials: E
authors.lastname: Gwinner
authors.forename: E
authors.initials: E
authors.lastname: Somogyiová
mesh_terms: D000818:Animals; D002642:Chick Embryo; D002940:Circadian Rhythm; D005123:Eye / Q000196:embryology; D008027:Light; D008550:Melatonin / Q000502:physiology*; D009799:Ocular Physiological Phenomena; D010870:Pineal Gland / Q000196:embryology* / Q000502:physiology
chemical_list: D008550:Melatonin