Document Detail

Phase shifting the hamster circadian clock by 15-minute dark pulses.
MedLine Citation:
PMID:  12054195     Owner:  NLM     Status:  MEDLINE    
The mammalian circadian pacemaker can be phase shifted by exposure to a period of darkness interrupting otherwise continuous light. Circadian phase shifting by dark pulses was interpreted originally as reflecting a photic mirror-image mechanism, but more recent observations suggest that dark pulse-induced phase shifting may be mediated by a nonphotic, behavioral state-dependent mechanism. The authors recently presented evidence indicating that the dark-pulse phase response curve (PRC) is in fact a complex function, reflecting both photic mirror image and nonphotic mechanisms at different phases of the circadian cycle. Previous studies of dark pulse-induced phase shifting have universally employed relatively long (2 to 6 h) pulses, which complicates PRC analysis due to the extended segment of the underlying PRC spanned by such a long pulse. The present study was therefore designed to examine the phase-shifting effects of brief 15-min dark pulses presented at both mid-subjective day and subjective dusk, and to explore the possible activity dependence of these effects by using physical restraint to prevent evoked locomotor activity. The results indicate that 15-min dark pulses are effective phase-shifting stimuli at both midday and dusk. Furthermore, as with longer dark pulses, phase shifting by 15-min dark pulses is completely blocked by physical restraint during subjective day but combines in a simple additive manner with the independent phase-shifting effect of restraint at subjective dusk.
Alan M Rosenwasser; Suzanne M Dwyer
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Journal of biological rhythms     Volume:  17     ISSN:  0748-7304     ISO Abbreviation:  J. Biol. Rhythms     Publication Date:  2002 Jun 
Date Detail:
Created Date:  2002-06-10     Completed Date:  2002-11-13     Revised Date:  2005-11-17    
Medline Journal Info:
Nlm Unique ID:  8700115     Medline TA:  J Biol Rhythms     Country:  United States    
Other Details:
Languages:  eng     Pagination:  238-47     Citation Subset:  IM    
Department of Psychology, University of Maine, Orono 04469-5742, USA.
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MeSH Terms
Biological Clocks / physiology*
Circadian Rhythm / physiology*
Cricetinae / physiology*
Photic Stimulation
Restraint, Physical
Time Factors

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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