The persistence of anxiety and the deficit in the extinction of fear memory are both phenomena related to the symptoms of disorders associated with stress, including post-traumatic stress disorder (PTSD). Recently, we have shown that acute restraint stress (2h) in rats induces both late anxiety-like behavior (observed 10 days after stress) and fear extinction impairment. In addition to these behavioral effects, the acute stress also promoted changes in the medial prefrontal cortex (mPFC) and in the basolateral amygdala complex (BLA) neuronal activities. In general, it is known that the mPFC projections to BLA are crucial for both fear memory formation and its extinction, and that the BLA projections to mPFC modulate the activity of the mPFC containing neurons, forming a self-modulated bidirectional circuit. It is not clear, however, whether the effects of stress on the extinction impairment are based on changes in the functionality of this circuit. In this project, therefore, we intend to investigate whether the late stress-induced fear extinction impairment is related to changes in the mPFC-BLA circuit, particularly, the modulatory projections of the BLA to mPFC.
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