Effect of adrenocorticotropic hormone on conditioned avoidance in rats interpreted as state-dependent learning.

Rats were given one training trial that was followed 2 days later by one test trial in a "step-out" passive avoidance task. Each rat was injected with either adrenocorticotropic hormone (ACTH) or placebo before training and before testing. Four groups of rats were used, representing the 4 possible training-testing injection combinations: placebo-placebo, placebo-ACTH, ACTH-placebo, and ACTH-ACTH. ACTH given in testing increased avoidance for subjects that had received ACTH in training and decreased avoidance for those that had received placebo in training.