Following behavioral testing, mice were returned to their home cages. After 2 h, mice were deeply anesthetized with isoflurane and sacrificed. The mouse skull was opened and whole brain was removed. Fresh tissues of BLA, vHIP and mPFC were isolated from the corresponding coronal sections under the stereomicroscope. Total proteins were extracted from BLA, vHIP or mPFC samples using RIPA buffer that contained protease inhibitors. The extracted proteins (50 g) were fractionated on 10% sodium dodecyl sulfate polyacrylamide gel, and then transferred onto polyvinylidene fluoride membranes. The membranes were blotted with anti-c-Fos (1:1000), anti-GAPDH (1:5000), and horseradish peroxidase-conjugated second antibodies (1:5000). Immunoreactive protein bands were visualized by enhanced chemiluminescence using the Bioanalytical imaging system (Azure Biosystems, INC, USA).