
%0 Journal Article
%A Constandil, L 
%A Parraguez, VH 
%A Torrealba, F 
%A Valenzuela, G 
%A Seron-Ferre, M 
%T Day-night changes in c-fos expression in the fetal sheep suprachiasmatic nucleus at late gestation
%J Reproduction, Fertility and Development
%D 1995/06/01
%V 7
%N 3
%P 411-413
%K 
%R https://doi.org/10.1071/RD9950411
%U https://www.publish.csiro.au/paper/RD9950411 
%X 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. 
