Isolation stress during the third postnatal week alters radial arm maze performance and corticosterone levels in adulthood.

Stressful experiences during development cause long-lasting changes in neuroendocrine systems as well as lasting changes in behavior. The present study examines the long-term consequences of daily periods of social isolation during the third postnatal week on radial arm maze performance in adulthood. Male rat pups were either isolated for 6 h per day between postnatal days 15-21 or remained in the home cage. This manipulation caused a significant increase in plasma corticosterone during the isolation period. As adults, these animals were tested on a 12-arm radial arm maze. Rats that experienced social isolation during development made more working memory errors during initial acquisition but reached an asymptotic level of performance comparable to controls. The pattern of reference memory errors across testing was comparable to the pattern of working memory errors, though the difference between isolated and control animals was not significant. Blood samples taken in adulthood revealed that social isolation during development results in an long-term elevation in plasma corticosterone levels. These findings indicate that isolation stress during the third week of life leads to lasting impairments in cognition and HPA axis activity and suggest a potential alteration in hippocampal function.