Increasing experimental evidence indicates that fear memory reactivationinduces a transient plastic state that presumably activates the neuronalcircuit involved in the encoding of the long term fear memory. Under certaincircumstances, such reactivation allows the incorporation and integration ofnew information to the original memory trace.

Here, we evaluated whether fear memory reactivation impacts on thedendritic spines remodeling in CA1 region of the dorsal hippocampus associatedwith the formation of the contextual fear memory. In the same way, we testedwhether stress exposure affects such dendritic spine remodeling. Thus, stressedand control animals were fear conditioned and sacrificed 24hs post conditioning(pre retrieval), 60min post retrieval or 24hs post retrieval.
A higher dendritic spines density, particularly mature ones, were observedafter fear encoding and later reduced to basal levels 60min after fearreactivation, returning to higher levels 24hs post retrieval. This temporaldynamic structural plasticity was prevented by pharmacologically blocking thedestabilization/reconsolidation process in the basolateral amygdala complex orby a single stress exposure just before fear memory conditioning.

Thus, the destabilization/reconsolidation process was evidenced by achange in the hippocampal structural plasticity immediately followingreactivation, a plausible necessary step for the integration of newinformation.