title: Light-induced c-fos mRNA expression in the suprachiasmatic nucleus and the retina of C3H/HeN mice.
abstract: Light-induced expression of c-fos mRNA was studied over a circadian period (approximately 24 h) in C3H/HeN mice maintained in constant dark. This mouse strain expresses an rd mutation (retinal degeneration) which does not affect light-induced phase shifts of circadian rhythms. c-fos mRNA expression in the retina and the suprachiasmatic nucleus (SCN) after a light pulse (300 lux) was determined by in-situ hybridization autoradiography using a 35S-labeled c-fos riboprobe. Light induced the expression of c-fos mRNA in retino-recipient areas of the SCN. This response was dependent on the circadian time (CT) and was observed only during the subjective night (CT14-CT22) and early subjective day (CT2). However, the period of photosensitivity for c-fos induction extended 1 h over the period of photosensitivity for phase shifts in circadian behavior. In the retina of C3H/HeN mice, light-induced c-fos mRNA expression was observed in a small number of cells in the ganglion cell layer (approximately 0.2%) which may represent ganglion cells projecting to the SCN. A dependence of c-fos expression with the circadian time was observed in retinal ganglion cells, suggesting that retinal photosensitivity may also be controlled by a circadian oscillator. In conclusion, we demonstrated light-induced expression of the immediate early gene c-fos mRNA in both the retina and SCN of C3H/HeN mice expressing the rd mutation.
authors.affiliation: Department of Molecular Pharmacology and Biological Chemistry (S215), Northwestern University Medical School, Chicago, IL 60611, USA.
authors.forename: M I
authors.initials: MI
authors.lastname: Masana
authors.forename: S
authors.initials: S
authors.lastname: Benloucif
authors.forename: M L
authors.initials: ML
authors.lastname: Dubocovich
mesh_terms: D000818:Animals; D017403:In Situ Hybridization; D008027:Light; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D012160:Retina / Q000378:metabolism*; D013493:Suprachiasmatic Nucleus / Q000378:metabolism*
chemical_list: D016760:Proto-Oncogene Proteins c-fos; D012333:RNA, Messenger