Document Detail

Irradiance responsivity and unequivocal type-1 phase responsivity of rat circadian activity rhythms.
MedLine Citation:
PMID:  1443229     Owner:  NLM     Status:  MEDLINE    
Behavioral, neuropharmacological, and molecular studies of light-induced phase shifting of rodent circadian rhythms evaluate carefully the phase dependence of light responsivity. However, much less information is available regarding the dependence of such effects on the duration and irradiance of the photic stimulus used. In this study, very brief (5-min) white light pulses of 50 microW/cm2 (175 lux) administered to hooded rats elicited unequivocal type-1 phase responsivity, without significant changes in period, and with phase shift variability comparable to that in studies using longer, higher intensity pulses. Irradiance dependence was demonstrated in the phase-delay, phase-advance, and crossover portions of the phase-response curve, with minimal phase shifting seen during the dead zone even at very high irradiance. These results indicate that maximal phase-shifting magnitude may be achieved with shorter, less intense photic stimuli than are often used in studies of the neural mechanisms involved in light responsivity of rat circadian rhythms.
M S Bauer
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The American journal of physiology     Volume:  263     ISSN:  0002-9513     ISO Abbreviation:  Am. J. Physiol.     Publication Date:  1992 Nov 
Date Detail:
Created Date:  1992-12-22     Completed Date:  1992-12-22     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0370511     Medline TA:  Am J Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  R1110-4     Citation Subset:  IM    
Department of Veterans Affairs Medical Center, Providence, Rhode Island.
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MeSH Terms
Circadian Rhythm*
Dose-Response Relationship, Radiation
Photic Stimulation / methods
Rats, Inbred Strains
Time Factors
Grant Support

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