title: c-Fos expression in the rat intergeniculate leaflet: photic regulation, co-localization with Fos-B, and cellular identification.
abstract: Ambient light alters the level of the transcriptional regulatory protein c-Fos in the suprachiasmatic nucleus, the site of an endogenous circadian clock in mammals, and in one other retino-recipient area, the intergeniculate leaflet of the lateral geniculate complex. Complementing previous work by ourselves and others on the photic and temporal regulation of c-Fos expression in the suprachiasmatic nucleus, the present studies investigated c-Fos regulation in the rat intergeniculate leaflet, revealing some important differences between the two brain regions. In the intergeniculate leaflet, the levels of c-fos mRNA (by in situ hybridization) and immunoreactive c-Fos protein (by immunohistochemistry) were elevated by light pulses administered either during the subjective day or subjective night. The regulation of immunoreactive Fos-B protein was similar to c-Fos, and 98% of Fos-B-expressing cells were also c-Fos-positive (by double-label immunofluorescence). By combining c-Fos immunofluorescence with stereotaxic injections of the retrograde tract tracer FluoroGold, we found photically-induced c-Fos in 15% of intergeniculate leaflet neurons projecting to the suprachiasmatic nucleus and in 34% of those projecting to the contralateral intergeniculate leaflet. Intergeniculate leaflet cells that express c-Fos after photic stimulation appear to represent a functionally-defined population that does not correspond to anatomically-defined categories based on connectivity or peptidergic phenotype.
authors.affiliation: Department of Neurology, University of Massachusetts Medical School, Worcester 01655, USA.
authors.forename: R V
authors.initials: RV
authors.lastname: Peters
authors.forename: N
authors.initials: N
authors.lastname: Aronin
authors.forename: W J
authors.initials: WJ
authors.lastname: Schwartz
mesh_terms: D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology*; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008297:Male; D010775:Photic Stimulation; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013493:Suprachiasmatic Nucleus / Q000378:metabolism*; D014796:Visual Perception / Q000502:physiology*
chemical_list: D016760:Proto-Oncogene Proteins c-fos