title: Day-night changes in c-fos expression in the fetal sheep suprachiasmatic nucleus at late gestation.
abstract: The suprachiasmatic nucleus (SCN) is a circadian oscillator in mammals and shows day-night changes in metabolic activity. To investigate whether the fetal sheep SCN behaves as a circadian oscillator, day-night changes in c-fos expression, a marker of neuronal activity, were measured. Eight fetal sheep were sacrificed at 135 days gestation--four at day-time (1200 hours) and four at night-time (2400 hours). Fetal brains were fixed, removed and cut in 40-microns serial coronal sections. Alternate sections were incubated with anti-Fos antibody (1:500) and Fos expression was revealed with extra-avidin-peroxidase and 3,3'-diaminobenzidine or stained with cresyl violet. The number of Fos-immunoreactive (Fos-ir) neurons per mm2 in the rostral, intermediate and caudal regions of the fetal sheep SCN was counted. Fetuses sacrificed in the day-time showed a higher number of Fos-ir neurons per mm2 (mean +/- s.e.; 516.7 +/- 60.1) in the three regions of the SCN than fetuses sacrificed at night-time (140.5 +/- 21.8). In addition, at night-time Fos-ir neurons were mainly localized to the ventrolateral area of the SCN. These findings demonstrate day-night changes in molecular activity consistent with the presence of a circadian oscillator in the fetal sheep SCN.
authors.affiliation: Facultad de Ciencias Biológicas, Pontifícia Universidad Católica de Chile, Santiago, Chile.
authors.forename: L
authors.initials: L
authors.lastname: Constandil
authors.forename: V H
authors.initials: VH
authors.lastname: Parraguez
authors.forename: F
authors.initials: F
authors.lastname: Torrealba
authors.forename: G
authors.initials: G
authors.lastname: Valenzuela
authors.forename: M
authors.initials: M
authors.lastname: Serón-Ferré
mesh_terms: D000818:Animals; D002940:Circadian Rhythm; D005260:Female; D005865:Gestational Age; D007150:Immunohistochemistry; D009474:Neurons / Q000378:metabolism; D011247:Pregnancy; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism*; D012756:Sheep / Q000196:embryology*; D013493:Suprachiasmatic Nucleus / Q000196:embryology* / Q000378:metabolism
chemical_list: D016760:Proto-Oncogene Proteins c-fos