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Effects of square-wave and simulated natural light-dark cycles on hamster circadian rhythmsCircadian rhythms of activity (Act) and body temperature (Tb) were recorded from male Syrian hamsters under square-wave (LDSq) and simulated natural (LDSN, with dawn and dusk transitions) light-dark cycles. Light intensity and data sampling were under the synchronized control of a laboratory computer. Changes in reactive and predictive onsets and offsets for the circadian rhythms of Act and Tb were examined in both lighting conditions. The reactive Act onset occurred 1.1 h earlier (P < 0.01) in LDSN than in LDSq and had a longer alpha-period (1.7 h; P < 0.05). The reactive Tb onset was 0.7 h earlier (P < 0.01) in LDSN. In LDSN, the predictive Act onset advanced by 0.3 h (P < 0.05), whereas the Tb predictive onset remained the same as in LDSq. The phase angle difference between Act and Tb predictive onsets decreased by 0.9 h (P < 0.05) in LDSN, but the offsets of both measures remained unchanged. In this study, animals exhibited different circadian entrainment characteristics under LDSq and LDSN, suggesting that gradual and abrupt transitions between light and dark may provide different temporal cues.
Document ID
20040142004
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Tang, I. H.
(University of California Davis, California 95616-8519, United States)
Murakami, D. M.
Fuller, C. A.
Date Acquired
August 22, 2013
Publication Date
April 1, 1999
Publication Information
Publication: The American journal of physiology
Volume: 276
Issue: 4 Pt 2
ISSN: 0002-9513
Subject Category
Life Sciences (General)
Distribution Limits
Public
Copyright
Other
Keywords
NASA Discipline Regulatory Physiology
Non-NASA Center

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