Post-weaning social environment shapes reward learning, social hierarchy, and pCREB signaling in adult male rats exposed to early-life adversity.

Adverse experiences during early life are known to disrupt neuronal development and maturation of reward circuits, affecting both social behavior and responses to reward-predicting stimuli. We have previously demonstrated that rats exposed during early life to denial of expected reward in the form of maternal contact (DER, animal model of maternal neglect) develop anhedonia, increased aggressive play-fighting behavior, aberrant prefrontal structure, reward system overactivation, deficient adult learning, and disturbed social dynamics during a group-based food anticipation (FA) learning task. Although these findings point to potential within-group destabilizing factors, the influence of post-weaning social composition on the DER phenotype has not yet been explored. Thus, using the previously described FA task, we investigated the behavior and the levels of pCREB in reward-related brain areas of adult male rats housed after weaning in triads comprising mixed groups of DER and control (CTR) animals. Mixed social composition exerted differential effects on social dynamics, reward learning, and pCREB levels: Rearing of DER rats with CTRs improved their reward-association behavior, whereas rearing of one CTR rat with two DER animals induced behavioral alterations in the CTR rat. Furthermore, mixed rearing was associated with more stable social hierarchy formation and normalized pCREB levels in vPFC and nucleus accumbens. Collectively, our findings indicate that post-weaning rearing of DER with CTR animals mitigates several long-term consequences of the DER experience. These results suggest the presence of reciprocal influences between co-housed DER and control animals and point to the ELS-ameliorating potential of a stable environment during later developmental stages.