Document Detail

Asymmetric control of short day response in European hamsters.
MedLine Citation:
PMID:  16864649     Owner:  NLM     Status:  MEDLINE    
The European hamster (Cricetus cricetus) is a circannual species in which the synchronization of the circannual cycle to the natural year occurs during 2 annual phases of sensitivity. Around the summer solstice, the animals are sensitive to a shortening of photoperiod. During this sensitive phase, pronounced changes in circadian output parameters are observed, indicating a different functional state of the circadian system. This special state is assumed to be necessary to develop the extreme sensitivity to short day length in European hamsters during this phase. In natural conditions, the animals are able to recognize the shortening of photoperiod already in mid-July, when the photoperiod is reduced only by 30 min. To investigate the short-day response in sensitive European hamsters on the basis of the 2-coupled oscillator model of Pittendrigh and Daan (1976), daily activity and the reproductive state of European hamsters were recorded after an asymmetrical reduction of photoperiod from long (LD 16:08) to short (LD 08:16) photoperiods. The activity pattern of the animals showed an immediate response to the short photoperiod at the day of transfer when the night was extended only into the evening, but there was a significant delay in the response time when the night was extended into the morning. Thus, the evening oscillator E is more important in inducing the photoperiodic response than the morning oscillator M. Moreover, the broad intragroup variation in the latter conditions strongly suggests that the changes in the activity pattern were endogenously induced and that the animals were not able to recognize a lengthening of the night into the morning. Gonadal regression started in both groups 3 weeks after the change in the activity pattern, indicating that this process is initiated when the circadian system has received the short-day signal either through changes in photoperiod or through the circannual clock.
Stefanie Monecke; André Malan; Franziska Wollnik
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of biological rhythms     Volume:  21     ISSN:  0748-7304     ISO Abbreviation:  J. Biol. Rhythms     Publication Date:  2006 Aug 
Date Detail:
Created Date:  2006-07-25     Completed Date:  2007-01-16     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8700115     Medline TA:  J Biol Rhythms     Country:  United States    
Other Details:
Languages:  eng     Pagination:  290-300     Citation Subset:  IM    
Biological Institute, Department of Animal Physiology, University of Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart, Germany.
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MeSH Terms
Biological Clocks / physiology*
Circadian Rhythm / physiology*
Cricetinae / physiology*
Gonads / physiology
Motor Activity / physiology
Regression Analysis

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