Timing is everything: Developmental differences in the effect of chronic corticosterone exposure on extinction retention.

Adolescence is noted as a time of "storm and stress." In this developmental stage both rodents and humans exhibit an impairment in the extinction of learned fear; however, this impairment can be alleviated, at least in rodents, by increasing the amount of extinction training given or by administering the partial NMDA receptor agonist D-Cycloserine. In the present study we explored whether the benefits of these treatments would be reduced by chronic exogenous corticosterone (a commonly studied stress-related hormone). In 2 experiments, adolescent rats were given pairings of a white noise and shock (acquisition) and then given extinction training (white noise presented alone). In Experiment 1, adolescents exhibited impaired extinction retention even after 2 days of extinction training if they had been exposed to corticosterone in adolescence but not if the exposure occurred when they were juveniles. In Experiment 2, exposure to exogenous corticosterone in adolescence, but not during the juvenile period, reduced the efficacy of the pharmacological adjunct D-Cycloserine at enhancing extinction retention after 1 day of extinction training. Taken together, the results support the idea that adolescence is a time of particular susceptibility to elevated levels of the stress hormone corticosterone. (PsycINFO Database Record (c) 2019 APA, all rights reserved).