Acute facial pain and allodynia in rat model of post-traumatic stress disorder

Post-traumatic stress disorder (PTSD) symptoms and pain can be appeared repeatedly following traumatic events. Although in acute stress condition, pain perception significantly covered by stress, few studies have discussed the changes in pain perception in a PTSD stress conditioning. In the present study, changes of facial acute pain and allodynia have been investigated in an animal model of PTSD.

Male Wistar rats were divided to two groups as control and under stress. PTSD was induced by single prolonged stress (SPS) method and confirmed by elevated plus maze (EPM) and rats plasma corticostrone levels. Acute facial pain and allodynia were evaluated by the eye wiping test and von frey test in the experimental groups.

SPS rats spent less time and made a fewer entries into the open arms of EPM (p < 0.05). The corticostrone level was significantly decreased in Stress + DEXA group compared to the Control + DEXA (p < 0.05). The number of eye wiping was significantly decreased in SPS-induced rats compared to the control (p < 0.001). The response threshold of applying von frey filament in face of SPS-induced rats was significantly increased compared to the control (p < 0.001).

Acute pain perception and allodynia of face area of rats was reduced in SPS-induced animals. Increased endogenous opioids in PTSD condition may lead to this observation.