Document Detail

Morphine-induced activity attenuates phase shifts to light in C57BL/6J mice.
MedLine Citation:
PMID:  10350536     Owner:  NLM     Status:  MEDLINE    
Circadian rhythms can be phase shifted and entrained by daily schedules of light and by non-photic stimuli such as locomotor activity. Relatively little is known of how photic and non-photic stimuli interact to regulate circadian phase. Morphine injections were used to examine the effects of locomotor activity on phase shifts to light pulses in mice free-running in constant dark. Morphine injections scheduled early or late in the active period (subjective night) induced hyperactivity, but did not induce phase shifts. Light pulses late in the subjective night induced phase advance shifts that were significantly attenuated (63% smaller, p<0. 01) by pretreatment with morphine. This inhibitory effect of morphine on light-induced phase advances was blocked by preventing mice from running for 6 h after the injections. Light pulses early in the subjective night induced phase delay shifts that were only weakly attenuated (15% smaller, p=0.06) by morphine. These results demonstrate behavioral inhibition of light-induced phase resetting of circadian rhythms in mice, and suggest that the strength of this effect may be phase dependent, although other interpretations are possible.
R E Mistlberger; M M Holmes
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Brain research     Volume:  829     ISSN:  0006-8993     ISO Abbreviation:  Brain Res.     Publication Date:  1999 May 
Date Detail:
Created Date:  1999-08-02     Completed Date:  1999-08-02     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0045503     Medline TA:  Brain Res     Country:  NETHERLANDS    
Other Details:
Languages:  eng     Pagination:  113-9     Citation Subset:  IM    
Copyright Information:
Copyright 1999 Elsevier Science B.V.
Department of Psychology, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada.
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MeSH Terms
Circadian Rhythm / drug effects*
Mice, Inbred C57BL
Morphine / pharmacology*
Motor Activity / drug effects*,  radiation effects
Sodium Chloride / pharmacology
Reg. No./Substance:
57-27-2/Morphine; 7647-14-5/Sodium Chloride

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