Enrichment Influences Social Preference Behavior In Older Female And Male Adolescent Rats

Rats engage in novelty-seeking behaviors in adolescence. Environmental enrichment (EE) allows rats to experience novelty through physical environments and interaction with conspecifics. The effects of EE on adolescent rats’ behavior during a social preference task was investigated along with EE’s effects on neural activation in the basolateral amygdala (BLA) and cornu ammonis 2 (CA2). Adolescent Long-Evans rats (n=12) experienced EE between postnatal days (pnd) 23 and 48; controls (n=18) were not enriched. On pnd 49, a two-trial social preference task occurred. Proportion of time spent and proportion of contact initiated with the novel rat was measured. After the task, brain tissue was processed to identify neural activity in the BLA and CA2. A significant interaction of EE and sex on proportion of time spent with the novel rat was found; no-EE males displayed a larger proportion than no-EE females (p = .007). A significant interaction of EE and sex on proportion of contact initiations was observed; EE males showed a larger proportion than EE females (p = .004). Histology indicated 60% less neural activation in the BLA and CA2 of EE rats (p = .001). Behavioral and neural data indicate that EE and maturity differences impacted rats’ responses to novelty.