The present investigation assessed whether increased congruency between
ACTH state present shortly after training and that at testing contributed to memory recovery. If recovery were related to an increased correspondence between internal state present after training and that at testing, then suppressing
ACTH release should block memory recovery. This was the hypothesis that was examined in the present investigation. Specifically, animals were trained on a passive avoidance task, administered
hypothermia (the amnestic agent) and, shortly prior to testing, given treatments known to be effective in reversing
memory loss induced by
hypothermia. Before training (Experiment 1) or testing (Experiment 2) animals were injected with either
dexamethasone (an agent that suppresses
ACTH release) or saline. Results, in general, indicated that when
ACTH release was suppressed, a blunted recovery effect was obtained. This reduction in the extent of memory recovery was observed when
ACTH was suppressed either at training or at testing. These data are interpreted as providing support for an
ACTH-related, state-dependent retention mechanism contributing to recovery from
hypothermia-induced retrograde amnesia in rats.