A modified single-prolonged stress model for post-traumatic stress disorder.

In the rat, single-prolonged stress (SPS) model produces a core symptom of post-traumatic stress disorder (PTSD), the enhanced fear response to the traumatic cue (conditioned fear response). This investigative tool is typically used for PTSD studies. However, whether SPS can produce another core symptom of PTSD, hyperarousal (the sensitized fear response in animal models), has not been evaluated. It is also not clear whether SPS can enhance both conditioned and sensitized fear responses after different incubation times. In this study, a single inescapable electric foot shock was given to rats immediately after SPS procedures (SPS&S). After different incubation times (1, 7 or 14 days), the conditioned or sensitized fear response was measured by re-exposing the stressed rats to the shock context or a neutral tone in a novel environment. Additionally, paroxetine, a selective serotonin reuptake inhibitor (SSRI) was administered after SPS&S for 14 days to test its potential preventive effect on PTSD-like symptoms. We observed that conditioned fear persisted and sensitized fear increased with ongoing incubation times after SPS&S. Early rapid intervention with paroxetine after SPS&S ameliorated PTSD-like symptoms in both fear responses and anxiety behaviors. Our data suggests that this modified SPS&S model may be both novel and predictably mimic the clinical characteristics of PTSD better than other investigative paradigms.