Behavioral changes over time in post-traumatic stress disorder: Insights from a rat model of single prolonged stress

•SPS exposure induced significant depressive behavior in rats on days 1 and 7.•SPS exposure induced constantly significant anxiety-like behavior for over two weeks.•SPS exposure had a small effect on the physical activity of animals which decreased gradually, but was most significantly on day 7.•By day 14, the effect of SPS was diminished.•For chronic (pharmacological) studies longer than 7 days, a prolonged PTSD animal model should be developed, perhaps using enhanced stimulation.

Post-traumatic stress disorder (PTSD) is manifested as a persistent mental and emotional condition after potentially life-threatening events. Different animal models of PTSD have been developed for neuro-pathophysiology and pharmacological evaluations. A single prolonged stress (SPS) induced animal model has demonstrated to result in specific neuro-endocrinological dysregulation, and behavior abnormalities observed in PTSD. However, animal studies of PTSD have mostly been performed at one time point after SPS exposure. To better understand the development of PTSD-like behaviors in the SPS animal model, and to identify an optimal period of study, we examined depressive behavior, anxiety-like behavior, physical activity and body weight in SPS model rats for two weeks. Our results confirmed the SPS-induced PTSD-like behavior and physical activity observed in previous studies, and indicated that the most pronounced symptomatic behavior changes were observed on day 1 and 7 after SPS exposure, which may involve stress-induced acute hormone changes and unclear secondary neurobiological changes, respectively. These results provide a solid basis for further investigation into the neuro-pathophysiology of or neuropharmacology for PTSD using the SPS rat model. However, for chronic (pharmacological) studies longer than 7 days, a prolonged PTSD animal model should be developed, perhaps using enhanced stimulation.