The present study examines the alterations in anxiety-like behavior and the expressions of selected genes associated with the CRH system and HPA axis activity (CRH, CRHR1, CRHR2, glucocorticoid receptor (GR), and FKBP5) in the brain regions responsible for anxiety, fear processing, and the stress response, specifically the BNST, Amy, and PVN in a single prolonged stress (SPS) animal model of PTSD after acute intranasal application of Ucn2 or Ucn3. This evidence concerns the gene FKBP5 and Anxiety.