ESCAPABLE STRESS MODULATES RETENTION OF SPATIAL-LEARNING IN RATS - PRELIMINARY EVIDENCE FOR INVOLVEMENT OF NEUROSTEROIDS

The ability to escape stress has been shown to protect an organism fro m many of the deleterious effects of stress exposure. It has been sugg ested that this amelioration could be mediated by the release of an en dogenous benzodiazepine-like substance in the brain demonstrated 2 h p oststress. Since benzodiazepines possess amnestic as well as antianxie ty actions, the possibility of memory alterations in coping subjects w as evaluated. Animals were randomly assigned to three groups: escapabl e shock, yoked inescapable shock, and no shock. Immediately poststress , all subjects were trained in a circular water maze. Acquisition and retention data were obtained in a between-subjects design at three dif ferent retention intervals (2 h, 4 h, and 24 h postshock). Results rev ealed no significant group differences in acquisition of the spatial l earning task between groups. However, subjects in the escapable stress group had enhanced retention at 2 h postshock but were significantly impaired 24 h postshock relative to yoked-inescapable-shock and nonsho ck controls. Blockade of the synthesis of neuroactive GABAA positive s teroids by 4-MA, a 5-alpha reductase enzyme inhibitor, blocked this ef fect. Thus, neuroactive steroid metabolites may play a critical role i n the escapable-stress-induced retention deficit seen at 24 h poststre ss. These observations suggest that altered memory in the escapable-sh ock subjects may impart stress resiliency by reducing proactive interf erence of prior stress on subsequent learning and physiology.