Fear extinction results in the suppression of the fear response once the conditional stimulus does not predict the threatening event anymore. Different anxiety disorders have typical deficits in both extinction memory formation and expression.
Given the particular role of the infralimbic medial prefrontal cortex (mPFC-IL) in extinction memory, we planned to define whether acute stress may impact on the synaptic structural remodeling in mPFC-IL in fear trained rats, and thus account for the changes in the dynamic of extinction memory induced by a single stress exposure.
Stressed animals were fear conditioned to context and later on trained in an extinction paradigm (context re-exposures without footshock). Animals were sacrificed for dendritic spines analysis (structural plasticity) either 1 day after fear conditioning (pre-extinction) or 1 day after the end of extinction training (post- extinction).
We observed that before extinction, stressed animals regardless of conditioning, presented a higher dendritic spine density, particularly mature spines, in comparison to non-stressed animals. On the other hand, after extinction training, conditioned animals independently of the stress exposure, presented a reduced density of dendritic spines in comparison to non-conditioned animals.
Thus, changes in the dynamic of the extinction fear memory might not be supported by synaptic structural remodeling in IL-mPFC.
