title: Circadian rhythms of C-FOS expression in the suprachiasmatic nuclei of the common vole (Microtus arvalis).
abstract: The suprachiasmatic nuclei of the hypothalamus (SCN) are the master circadian clock in mammals. Transcriptional activity in this master clock has a marker in the immediate-early gene c-Fos. Within the SCN, distinct differences in c-Fos in the ventrolateral and the dorsomedial SCN have been reported for rodent species such as rats, mice, and hamsters. We studied C-FOS expression in the common vole (Microtus arvalis) SCN under LD 12:12 h and under constant dim light conditions. In the vole dorsomedial SCN, rhythmic C-FOS expression was seen in LD with a clear peak in the middle of the light period. Under constant dim light, we report constitutive, non-rhythmic expression of C-FOS in the dorsomedial SCN. This pattern is consistent with the circadian organization of behavioral activity, which is weak in voles and may be lost under constant dim-light conditions. In the ventrolateral SCN, we observed a rise in C-FOS expression under LD conditions prior to lights-on, followed by peak expression at lights-on. Another peak was seen at lights-off. In an additional experiment, we subjected animals to LD 16:8 to test the hypothesis that the dawn and dusk peaks in ventrolateral C-FOS expression change phase along with the photoperiod. The peak in C-FOS expression did not shift with the time of lights on, but remained at the same external time 6. The results are consistent with the interpretation that in the vole, c-Fos expression reports transcriptional activity associated more likely with an internal, gating process than with an external effect of light.
authors.affiliation: Department of Chronobiology, University of Groningen, Haren, The Netherlands. d.veen@surrey.ac.uk
authors.forename: Daan R
authors.initials: DR
authors.lastname: van der Veen
authors.forename: Margriet M Th
authors.initials: MM
authors.lastname: van der Pol-Meijer
authors.forename: Koen
authors.initials: K
authors.lastname: Jansen
authors.forename: Maarten
authors.initials: M
authors.lastname: Smeets
authors.forename: Eddy A
authors.initials: EA
authors.lastname: van der Zee
authors.forename: Menno P
authors.initials: MP
authors.lastname: Gerkema
mesh_terms: D000818:Animals; D003411:Arvicolinae; D001683:Biological Clocks; D002940:Circadian Rhythm; D005786:Gene Expression Regulation; D007150:Immunohistochemistry / Q000379:methods; D008027:Light; D051379:Mice; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis*; D051381:Rats; D013493:Suprachiasmatic Nucleus / Q000378:metabolism*; D013997:Time Factors; D014158:Transcription, Genetic
chemical_list: D016760:Proto-Oncogene Proteins c-fos