Development of a fetal circadian rhythm after disruption of the maternal circadian system

The role of maternal circadian rhythms in the development of the fetal circadian system was investigated in the rat. Pregnant females were subjected to procedures known to disrupt circadian function, ablation of the maternal suprachiasmatic nuclei (SCN) or housing in constant illumination, on gestational day 10. Circadian function was assessed in fetuses at gestational day 22 by analysis of glucose utilization in hypothalamic slices in vitro using the 2-deoxyglucose method. Fetuses from control females exhibit a robust rhythm in glucose utilization in the SCN. In contrast, the SCN of fetuses from females with SCN lesions, or housed in constant illumination, show no significant day-night difference in glucose utilization. Analysis of individual brains indicates, however, that this apparent disruption in the development of circadian rhythmicity in metabolism in the fetal SCN is due to a desynchronization of individual fetuses resulting from the loss of maternal entraining influences. Thus, the fetal SCN is capable of developing a circadian rhythm in glucose utilization independent of the maternal circadian system.