An animal model of posttraumatic stress disorder and its validity: effect of paroxetine on a PTSD model in rats]

To better understand neuroscientific aspects of posttraumatic stress disorder (PTSD), it is necessary to establish an animal model of PTSD in which behavioral changes persist after initial traumatization. We administered inescapable footshock (IS) to male Wistar rats in a shuttle-box (inescapable stress session), and after 2 weeks we performed an avoidance/escape task session in the shuttle-box using signal lights as anxiogenic external stimuli. Rats exposed to IS beforehand exhibited PTSD-like bi-directional behavioral changes, that is, "avoidance/numbing" (e.g. decreased activity, reactivity, and interest in surroundings) and "hyperarousal" (e.g. irritability and exaggerated responsiveness to external stimuli). Concretely speaking, in a relatively calm situation, spontaneous locomotion decreased during a 5-min adaptation period just before the avoidance/escape task session. On the other hand, in a stressful situation after starting the task session, not only avoidance responses to external stimuli (signal lights) but also gate-crossings during inter-trial interval increased. Accordingly, the paradigm used here could serve as a useful model of PTSD. We administered paroxetine (PRX) to rats just after IS for 2 weeks to examine its chronic effect on our animal model. Two weeks of PRX treatment significantly reduced hyperarousal-like behaviors, but no effect on avoidance/numbing-like ones was manifested.