Social experience alters the response to social stress in mice.

Individual differences in the response to stressful stimuli have been documented in humans and in a variety of animal species. Recently, we demonstrated that social stress induced a state of glucocorticoid (GC) resistance in mouse splenocytes, however this response was highly variable among cage mates. Since these studies were conducted using inbred mice (C57BL/6), it was suggested that environmental factors were the source of this variability. The following study examined possible factors that may have contributed to the development of individual differences in the susceptibility of mice to social stress. First, the effect of rearing conditions was studied by comparing the development of GC resistance in mice reared in isolation or in groups. In addition, the effect of previous social experiences was studied in mice that were re-housed to facilitate the formation of new social hierarchies in the cages. The results indicated that isolation altered the behavior of the mice during the social stress, but did not affect the development of GC resistance in response to the stress. Re-housing and the resulting loss of social status increased the susceptibility of mice to the development of GC resistance following social stress. Together, these findings indicate that environmental factors, such as previous social experiences, may alter the susceptibility to the effects of future social stress in inbred mice.