Development of melatonin rhythm in the pineal gland and eyes of chick embryo.
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.
Zeman
M
M
Institute of Animal Biochemistry and Genetics, SASci, Ivanka pro Dunaji, Czechoslovakia.
Gwinner
E
E
Somogyiová
E
E
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
D008550:Melatonin