Consolidated memories may result into a labile one after retrieval, requiring a re-stabilization process, defined as reconsolidation, which is dependent on protein synthesis. The functional significance of this process remains unknown; one hypothesis proposes that this phase is essential to incorporate new environmental experiences to the original memory, a process defined as memory updating. Adult male Wistar rats were subjected to a contextual fear conditioning paradigm using a single footshock (weak training session). One day after training, rats were subjected to a stressful situation (restraint for 30 min.) and another group remained in their home cage without manipulation. Half of the rats were re-exposed to the original context of conditioning (test 1) for 3 minutes one day after the stress. There was an increase of freezing only in those animals re-exposed to the associated context, which was maintained for 10 days during the re-exposure to the training context (test 2). Pharmacological manipulations (benzodiazepines and NMDA antagonists) that attenuates the stress consequence or prevents the fear memory reconsolidation, as well as very short period of re-exposure to the associated context, prevented stress-induced increase in freezing. We conclude that the reactivation session allows the updating of new environmental information corresponding to a traumatic event (inescapable stress) into an already consolidated fear memory.
