Marjan Nikbakhtzadeh - Department of Physiology, School of Medicine, Tehran University of Medical Science, Tehran, Iran
Vahid Sheibani - Kerman Neuroscience Research Center, Neuropharmacology Institute, Kerman, Iran
Kadijeh Moradbeygi - Department of Physiology, School of Medicine, Tehran University of Medical Science, Abadan Faculty of Medical Sciences, Abadan, Iran Tehran, Iran
Elham Zahedi - Department of Physiology, School of Medicine, Tehran University of Medical Science, Tehran, Iran

Background and Aim : Post-traumatic stress disorder (PTSD) symptoms and the associated pain can be appeared repeatedly following traumatic events. In acute stress condition, pain perception significantly covered by HPA axis activity. Studies have a controversy about changes in pain perception in PTSD stress condition. In the present study, changes of facial acute pain and allodynia have been evaluated in an animal model of PTSD.Methods : 80 Male wistar rats were divided in to two groups as following: control and stress. PTSD was induced by single prolong stress (SPS) method and confirmed by elevated plus maze (EPM) and rats plasma corticosterone levels. The facial pain is evaluated by the eye wiping test and von Frey test in separated groups.Results : SPS rats spent less time in EPM and had a fewer entries into open arms of EPM (P<0.05). The corticosterone level significantly have reduced in SPS group in comparison to control (p<0.05). The number of eye-wiping significantly decreased in SPS rats in comparison to control (p<0.001). The response threshold of von Frey filament application in face of SPS rats significantly augmented in comparison to control (p<0.001).Conclusion : This study showed that acute pain perception and allodynia reduced in SPS condition. Increased endogenous opioids in PTSD condition may lead to reduction of facial pain perception.

PTSD; pain; Allodynia; Eye-wiping; Facial