Rearing in social isolation has profound effects on several aspects of behavior in adult rodents. However, little is known about effects of social stress on social behavior in these animals. In the present study, we examined social recognition in mice of both sexes that were individually housed from 30 days of age until testing at approximately 80 days of age, individually housed from day 30 until day 60, followed by group housing from day 60 until testing at around 80 days of age and in control mice that were group housed throughout experiment. A standard social recognition test was performed with ovariectomized female conspecifics introduced into the home cage of tested mice for 1 min, eight consecutive times with 9 min breaks between tests, and in the ninth test, new, unfamiliar females were introduced. The time spent investigating stimulus mice during each of the nine tests was recorded. Group housed male and female mice showed strong pattern of social learning, whereas mice reared in isolation from day 30 until testing did not show evidence of social recognition. Interestingly, mice reared in isolation from 30 until 60 days of age and then group housed again, also showed reduced ability for social learning in comparison to the controls housed in groups through the entire period. These results therefore show that social isolation has a profound effect on social behavior in mice, and that even isolation for a limited period can produce lasting behavioral deficits.
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