c-Fos expression in the brains of behaviorally "split" hamsters in constant light: calling attention to a dorsolateral region of the suprachiasmatic nucleus and the medial division of the lateral habenula

UMMS Affiliation

Department of Neurology

Publication Date


Document Type



Animals; Circadian Rhythm; Cricetinae; Darkness; *Habenula; *Light; Male; Mesocricetus; Motor Activity; Nuclear Proteins; Photoperiod; Proto-Oncogene Proteins c-fos; *Suprachiasmatic Nucleus


Life Sciences | Medicine and Health Sciences


"Splitting" of circadian activity rhythms in Syrian hamsters maintained in constant light appears to be the consequence of a reorganized SCN, with left and right halves oscillating in antiphase; in split hamsters, high mRNA levels characteristic of day and night are simultaneously expressed on opposite sides of the paired SCN. To visualize the splitting phenomenon at a cellular level, immunohistochemical c-Fos protein expression in the SCN and brains of split hamsters was analyzed. One side of the split SCN exhibited relatively high c-Fos levels, in a pattern resembling that seen in normal, unsplit hamsters during subjective day in constant darkness; the opposite side was labeled only within a central-dorsolateral area of the caudal SCN, in a region that likely coincides with a photo-responsive, glutamate receptor antagonist-insensitive, pERK-expressing cluster of cells previously identified by other laboratories. Outside the SCN, visual inspection revealed an obvious left-right asymmetry of c-Fos expression in the medial preoptic nucleus and subparaventricular zone of split hamsters killed during the inactive phase and in the medial division of the lateral habenula during the active phase (when the hamsters were running in their wheels). Roles for the dorsolateral SCN and the mediolateral habenula in circadian timekeeping are not yet understood.

DOI of Published Version



J Biol Rhythms. 2005 Oct;20(5):419-29. Link to article on publisher's site

Journal/Book/Conference Title

Journal of biological rhythms

Related Resources

Link to Article in PubMed

PubMed ID