Benton, D., Brain, P. F., Goldsmith, J. F. 1979. Effects of prior housing on endocrine responses to differential caging in male TO-strain mice. Physiological Psychology 7, 89-92.

The results support the suggestion that changing the housing condition of mice [e.g., from single-housing to pair-housing and vice versa] is stressful as measured in elevated corticosterone levels.... The influence of re-housing was sufficient to produce higher basal corticosteroide titers 32 days afterwards. Of undisturbed pairs dominants had significantly lower basal corticosteroide levels than either isolates or subordinates. It must be emphasized that mice were not paired with their initial cagemates but with strangers; they were tested 32 days after pair formation.