Abstract:
:Several authors have suggested that the transcriptional regulatory protein c-Fos might be part of the mechanism for photic entrainment of the circadian pacemaker in the suprachiasmatic nucleus (SCN) to environmental light:dark cycles. This hypothesis has been based on evidence gathered using single light pulses administered acutely to animals free-running in constant darkness. In order to begin to analyze SCN c-fos gene expression in animals during steady-state entrainment to photic cycles, we exposed male BALB/c mice to a skeleton photoperiod consisting of two 1-h light pulses separating a long (14 h) and a short (8 h) dark interval. The cycle was designed so that stable entrainment could be achieved in either one of two patterns (with rhythmic locomotor activity occurring during either the long or the short dark interval); SCN c-fos mRNA levels could then be measured during entrainment to light pulses at different phases of the circadian cycle, while controlling for the duration of preceding darkness. We found that c-fos was induced equally well by a light pulse that represented ZT 12 or ZT 3. The ZT 12 pulse functioned as an entraining pulse, because animals free-ran after it was removed from the lighting regimen, whereas removing the ZT 3 pulse caused little or no phase shift of activity onset. The data confirm that the expression of SCN c-Fos is not itself sufficient to reset rhythm phase, and they indicate that the role of this gene in the mechanism of photic entrainment is not yet fully understood.
journal_name
J Biol Rhythmsjournal_title
Journal of biological rhythmsauthors
Schwartz WJ,Peters RV,Aronin N,Bennett MRdoi
10.1177/074873049601100104subject
Has Abstractpub_date
1996-03-01 00:00:00pages
35-44issue
1eissn
0748-7304issn
1552-4531journal_volume
11pub_type
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