Prosocial support in adolescence regulates behavior and corticosterone responses following early life adversity in male rats

Experiencing early life adversity (ELA) increases risk for developing psychiatric disorders later in life. Social environments during adolescence can influence hormonal and behavioral outcomes. Maternal separation (MS), a well-validated model of ELA, generally increases anxiety-and-depression-related behaviors and corticosterone (CORT) responses in rats, especially in males. Prosocial support encompasses receiving active and motivated help, often while experiencing distress. How and if receiving prosocial support in adolescence mitigates such negative impacts of ELA is unknown. In this study, male rats were reared under MS or control (CON) conditions. In adolescence, all rats experienced one week of restraint stress and were either freed (received prosocial support) or not freed from the restrainer by another rat. Blood samples were collected throughout restrainer testing to measure CORT, and several behavioral assays examining anxiety-like and depressive-like behaviors were carried out in adolescence and adulthood. MS rats demonstrated greater anxiety-like behavior at baseline compared to CON rats. After restraint stress, all rats who did not receive prosocial support demonstrated greater anxiety-like behavior, increased motivation for reward, and disrupted social behavior in adolescence compared to their supported counterparts, regardless of rearing condition. MS-induced blunting in adolescent baseline CORT was also rescued following prosocial support, while repeated stress exposure, without prosocial support, sensitized CORT stress responses in MS, but not CON animals. In adulthood, rats who did not receive prosocial support showed greater anxiety-like behavior and decreased food-seeking behavior in an anxiogenic context. Together, these results suggest that receiving prosocial support in adolescence shifts behavioral and hormonal outcomes following ELA.