Aim: Posttraumatic nightmares are a prevalent and distressing symptom of posttraumatic stress disorder (PTSD).In this study, we found some rats wake up with a start after traumatic stress and investigated the underlying neuroanatomical pathway of this behavior.Methods: Female SD rats exposed to inescapable footshock in proestrous.Twenty-one days after the shock, rats were used for observing whether wake up with a start by using infrared camera and recording EEG/EMG simultaneously.