Posttraumatic stress disorder (PTSD) is one of the major mental disorders that undermine people’s health. Since effective treatment of PTSD is rare, the prevention of its formation is crucial. In the peritraumatic period, cognitive, emotional and behavioral changes occurred inside the body, which may predict the formation of PTSD. Thus, to investigate the relationship between peritraumatic response and PTSD symptoms may contribute to the prediction and prevention of PTSD. This study established PTSD model in rats by high strength footshock. Using hypervigilance in novel environment as an indicator of hyperarousal, the role of peritraumatic hyperarousal in the prediction of various PTSD symptoms is explored. Besides, the study examined the effect of peritraumatic period morphine injection on preventing the development of PTSD symptoms. The major research findings are as follows. Firstly, peritraumatic hyperarousal positively related with the strength of stress, and only high stress (1.5mA, 3.0mA) induced hyperarousal disturbance. The level of peritraumatic hyperarousal could predict the early stage (1 week) conditional fear response and avoidance to novel environment and the late stage (4 weeks) conditional fear response. Secondly, the peritraumatic hyperarousal caused by stress with different avoidable possibilities could predict the early stage (1 week) and late stage (4 weeks) avoidance to novel environment and the strange others, hypervigilance in novel environment and conditional fear response. Thirdly, three-day morphine injection during peritraumatic period showed no significant influence on the hypervigilance behaviors. However, both high dose (10mg/kg) and low dose (1mg/kg) morphine somehow reduced avoidance learning and the avoidance behavior of novel environment and another strange rat. The results indicate that peritraumatic hyperarousal predicts the re-experiencing symptoms of PTSD. Although morphine fails to affect peritraumatic hyperarousal, it attenuates avoidance symptoms of PTSD. In addition, the results suggest the imbalance of PTSD-symptom development, which indicates that these different symptoms may base on different neurobiological mechanisms.
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