IMPACT OF DIRECT AND VICARIOUS SOCIAL STRESS ON AVERSIVE MEMORY IN MICE IN LATE ADOLESCENCE

Adolescent stress is a major risk factor for long-term behavioral and physiological changes. This developmental stage features high neural plasticity and vulnerability, increasing sensitivity to stress-related disruptions in emotion and cognition. Stress can be experienced directly or indirectly through observation, potentially affecting brain function. This study aimed to examine the short-term effects of direct and indirect social defeat stress on depressive-like behavior and cognitive performance in late-adolescent mice. A total of 60 late-adolescent male OF1 mice at postnatal day 47 were randomly assigned to direct social defeat stress (DSR), vicarious social defeat stress (VSD), or control groups. Stress-exposed animals underwent four agonistic encounters following a standardized protocol, while controls experienced the procedure without an aggressor. Plasma corticosterone was measured after the first and fourth exposures to assess stress responses. Behavioral tests then evaluated locomotion, depressive-like behavior, and cognitive performance. No statistically significant differences were observed among groups in locomotor activity or depressive-like behavior, as assessed by the open field and tail suspension tests. However, in the passive avoidance task, both directly and indirectly stressed mice exhibited a reduced latency to enter the aversive compartment compared to control animals, indicating deficits in aversive memory retention.These findings suggest that exposure to social stress during late adolescence, even when experienced indirectly, can lead to early cognitive impairments without inducing overt depressive-like behaviors. Overall, the results highlight the heightened vulnerability of the adolescent brain to stress and its potential negative impact on cognitive functioning.