Effects of housing on corticosterone rhythm and stress responses in female mice

Abstract

In a longitudinal study of grouping of virgin female mice, basal plasma corticosterone levels were significantly higher at 1 hour, 5 hours and 9 hours before lights off when the animals were grouped than when individually housed. There were no differences 3 hours, 7 hours and 11 hours after lights off. A week of daily vaginal smearing at the expected circadian peak elevated plasma corticosterone at that time of day but not at other times. A circadian rhythm of basal plasma corticosterone with highest values 1 hour before lights out was demonstrated, but there were no apparent differences in the rhythm phase in differentially housed mice. Group housed females, blood sampled and ether stressed, but not mice only ether stressed, had significantly higher plasma corticosterone levels than individually housed mice. There was no circadian rhythm in stress levels.