Aging-related changes in retrograde amnesia for mice.

Aging mice showed a retrograde amnesia for passive avoidance behavior when a single electroconvulsive shock (ECS) was given at post-training intervals up to 1 h, whereas adult mice showed no significant amnesia when ECS was given 10 min or more after training. Catecholamines (norepinephrine and dopamine), but not serotonin (5-HT) changed with aging in the several brain regions, but only 5-HT was significantly changed (elevated) by ECS. Protein synthesis was significantly inhibited by ECS, notably in limbic structures. The increased susceptibility of aging mice to the amnesic effect of ECS could be related to aging-related changes in the rate of memory consolidation or to the duration of neural chemical changes that disrupt processes such as consolidation, storage, and/or retrieval of the memory trace.