Moderate Stress Enhances Memory Persistence: Are Adrenergic Mechanisms Involved?

Memory persistence in the inhibitory avoidance (IA) task has been recently shown to require a new event of consolidation 12 hr after acquisition. The immobilization stress (IS) model is largely used to study the effects of stress on memory. In this study we investigated the interactions between stress by immobilization and its effect on the persistence of memory, and also a possible effect mediated by beta-adrenergic modulation of stress on memory persistence. An enhancement of long-term memory (LTM) persistence caused by stress through immobilization applied 12 hr after IA training was observed when the animals were submitted to 15 min or I hr of IS, but not to 3 hr. The reversal of this memory enhancement caused by IS was observed when the beta-adrenergic antagonist propranolol was infused intraperitoneally prior to stress, which implies that beta-adrenergic receptors are involved in stress enhancement of LTM persistence.