ISSN:
1420-9071
Keywords:
Melatonin
;
circadian rhythm
;
embryo
;
ontogeny
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
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.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02124299
