title: The expression of Fos within the suprachiasmatic nucleus of the diurnal rodent Arvicanthis niloticus.
abstract: Rhythms in the expression of the nuclear phosphoprotein Fos, have been demonstrated in the suprachiasmatic nucleus (SCN) of nocturnal rodents. When rats are housed in a 12:12-h light/dark (LD) cycle the number of Fos-immunoreactive (-IR) cells within the SCN is higher during the day than at night [9,23]. In the two experiments reported here, Fos-IR was examined in the SCN of a diurnal murid rodent, Arvicanthis niloticus. First, thirty-six adult male A. niloticus housed in a 12:12-h LD cycle were perfused at six equally spaced time points beginning 1 h after lights on (n=6 per time point). Brains were sectioned and treated with immunohistochemical procedures for the identification of Fos. The number of Fos-IR cells in the SCN varied significantly as a function of time, and was highest 1 h after lights on and decreased thereafter. The distribution of Fos-IR within the SCN overlapped with that of arginine-vasopressin-IR (AVP-IR) and vasoactive intestinal peptide-IR (VIP-IR), but not with that of gastrin-releasing peptide-IR (GRP-IR). In the second study, double-labeling techniques revealed extensive Fos expression within SCN neurons containing AVP-IR, but not neurons containing GRP-IR. In conclusion, although the overall rhythm of Fos-IR in the SCN is similar in diurnal and nocturnal rodents, differences may exist with respect to the relative distribution of Fos-immunoreacte cells within different SCN cell populations.
authors.affiliation: Department of Psychology and Neuroscience Program, Michigan State University, East Lansing, MI 48824-1117, USA.
authors.forename: C
authors.initials: C
authors.lastname: Katona
authors.forename: S
authors.initials: S
authors.lastname: Rose
authors.forename: L
authors.initials: L
authors.lastname: Smale
mesh_terms: D000818:Animals; D001127:Arginine Vasopressin / Q000032:analysis; D002940:Circadian Rhythm / Q000502:physiology*; D019886:Gastrin-Releasing Peptide / Q000032:analysis; D007150:Immunohistochemistry; D008297:Male; D009115:Muridae / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000096:biosynthesis*; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis*; D013493:Suprachiasmatic Nucleus / Q000378:metabolism*
chemical_list: D009419:Nerve Tissue Proteins; D016760:Proto-Oncogene Proteins c-fos; D001127:Arginine Vasopressin; D019886:Gastrin-Releasing Peptide