Differential long-term neuroendocrine and behavioral impact of controllable and uncontrollable foot-shock exposure during adolescence in male rats.

There is substantial evidence that control over stress affects both its short- and long-term consequences. However, much remains unknown about the impact of controllability, particularly during adolescence. In the present study, we examined in adolescent male rats the long-term effects of repeated exposure to controllable footshocks in a two-way active avoidance (TWAA) task (master group) versus exposure to identical but uncontrollable footshocks (yoked group). Neither the master nor the yoked procedure affected adult basal levels of ACTH and corticosterone. No evidence of altered anxiety-like behavior in the elevated plus-maze was found in either the master or the yoked groups compared with stress-naïve animals, whereas active social interaction was reduced in yoked but not master rats. As expected, prior adolescent experience of control over the TWAA task improved performance in an adult TWAA session. However, a significant, although less marked, improvement in performance was also found in rats previously assigned to the adolescent yoked condition. Improved performance in master and yoked versus stress-naïve rats were observed despite behavioral and endocrine (ACTH and corticosterone) evidence of shuttle-box context conditioning. Improved TWAA performance was paralleled by reduced ACTH response to the task. Finally, adolescent yoked rats showed a greater freezing response to the shuttle-box context of the shuttle after the adult sessions, suggesting long-lasting fear potentiation. These results confirm that stress during adolescence has long-term behavioral consequences, controllability over stress mitigating some of its effects.