Age-related decline in social interaction is associated with decreased induction in select brain regions independent of oxytocin receptor expression profiles.

Social behavior decreases with aging, and we have previously found a substantial decline in social investigative behavior of old female rats. In this study we examined the neural activation pattern ( mRNA) of young (3 month) and old (18 month) female rats after brief 10 min exposure to a novel female rat in order to identify forebrain regions that show selective age-related alterations in their neural response to social investigation. We also measured relative oxytocin receptor expression ( mRNA) as a possible factor in age-related declines in induction after social interaction. Young rats exposed to a social partner had a greater mRNA response than those exposed to novel context alone in the lateral septum and septohypothalamic area, with blunted increases evident in old rats. In addition, mRNA levels in the lateral septum were positively correlated with social investigative behavior. Interestingly, age-related differences in gene induction were unrelated to the local amount of expression within specific brain regions, although we found an age-related decline in expression in the ventromedial hypothalamus. This functional neuroanatomical characterization may point to certain brain regions that are especially sensitive to age-related declines associated with social interaction behavior.