Effects of β-Estradiol on Enhanced Conditioned Fear Induced by Single Prolonged Stress and Shock in Rats

Introduction:This study examined the effects of administration of subcutaneous β-estradiol on PTSD-like symptoms (the enhanced conditioned fear response, CFR) that induced by a single-prolonged stress (SPS) and shock in rats. Adult male Wistar rats were exposed to SPS procedure: restraint for 2 h, forced swim for 20 min, and ether anesthesia. Then the rats were placed in fear conditioning system and received 1 mA electric foot shock for 4 s. Following, stressed rats injected with β-estradiol (600 μg/kg) or sesame oil. For CFR testing, 24 h later animals were re-exposed to the shock chamber for 3-min without further shock application. Percent of freezing was scored. Following testing, the animals were anesthetized and their brains were removed for histological examination (cell count) of the hippocampus that stained with cresyl violet. Results: Our results indicated that rats who received electric shock after the SPS exhibited the CFR. β-estradiol significantly reduced the CFR in the SPS rats as compared with control rats. No significant differences were found in cell count in different regions of the hippocampus between experimental groups. Discussion: Our findings indicated that β-estradiol administration after SPS prevents the enhanced CFR in an animal model of PTSD, suggesting a possible role for β-estradiol in the prevention of PTSD Methods: