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  • Title: Systemic administrations of β-estradiol alleviate both conditioned and sensitized fear responses in an ovariectomized rat model of post-traumatic stress disorder.
    Author: Mirshekar M, Abrari K, Goudarzi I, Rashidy-Pour A.
    Journal: Neurobiol Learn Mem; 2013 May; 102():12-9. PubMed ID: 23474020.
    Abstract:
    Although no single widely accepted animal model of PTSD has been established to date, the single prolonged stress (SPS) animal model has been partially validated as a model for PTSD. SPS rats mimic the pathophysiological abnormalities and behavioral characteristics of PTSD, such as enhanced fear response to the traumatic cue (conditioned fear response) and hyper arousal (the sensitized fear response). In the present study we are looking at PTSD-like symptoms in rats. We examined whether Systemic administrations of β-estradiol could alleviate PTSD-like symptoms that are induced by SPS model. In this study, electric foot shocks (two 4s, 1mA with an interval of 30s) were given to Adult ovariectomized rats 1day after SPS procedures. Additionally, β-estradiol (45, 90, and 180μg/kg) or sesame oil (vehicle) were injected immediately after foot shock and before Tests 2 and 3. After different incubation times, one (Test 1), two (Test 2), and three (Test 3) weeks later, the conditioned or sensitized fear responses were measured (Percent of freezing during test) by re-exposing the stressed rats to the shock chamber or a neutral tone in a novel environment. Three other groups were shock, control and sham groups. Ovariectomized rats of Shock group received shocks conducted through the procedure described below on. Animals in control (Ovariectomized rats) and Sham groups (Only submitted to surgery without removal of the ovaries), neither were exposed to the SPS procedure nor received an electrical shock. Also, these three groups were tested for fear responses three times. Findings indicated that rats who received electric shock the day after SPS exhibited both enhanced conditioned and sensitized fear responses in comparison to the control group. β-estradiol in 45μg/kg dose could reduce both types of fear responses. β-estradiol exert an inhibitory influence on contextual fear conditioning (hippocampal-dependent) and on sensitized fear conditioning (amygdala-dependent). Single injection of this dose is enough for CFR alleviation but at least twice injections are necessary to reduce sensitized fear response. Overall our data demonstrate that multiple injections of β-estradiol, dose dependently, could alleviate both SPS induced conditioned and sensitized fear responses, as signs of PTSD.
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