Age and adolescent social stress effects on fear extinction in female rats

We previously observed that social instability stress (SS: daily 1 h isolation and change of cage partners for 16 days) in adolescence, but not in adulthood, decreased context and cue memory after fear conditioning in male rats. Effects of stress are typically sex-specific, and so here we investigated adolescent and adult SS effects in females on the strength of acquired contextual and cued fear conditioning, as well as extinction learning, beginning either the day after the stress procedure or four weeks later. For SS in adolescence, SS females spent more time freezing (fear measure) during extinction than did controls, whereas SS in adulthood had no effect on any measure of fear conditioning. The results also indicated an effect of age: females in late adolescence show more rapid extinction of cue and better memory of extinction of context compared to adult females, which may indicate resilience to acute footshock in adolescence. Thus fear circuitry continues to mature into late adolescence, which may underlie the heightened plasticity in response to chronic stressors of adolescents compared to adults.