Abstract
We have developed a novel stress model with high ecological validity using a chasing robot. To emulate predatory threat, rats were repeatedly chased by a fast-approaching robot in an inescapable, donut-shaped circular maze. In Exp. 1, validity of the chasing stress model was tested by measuring the plasma corticosterone(CORT) level and freezing and ultrasonic vocalization (USV). In Exp. 2, rats were tested for the memory of the chasing stress and sensitivity to another aversive situation, three weeks later. The results demonstrated that a distinctive pattern of stress responses and long-term sensitization of defensive response in subsequent aversive events could emerge following chasing stress by a fast-approaching artificial object that emulates an attacking predator. The new stress paradigm would open up a new possibility to investigate how an evolutionarily preserved defensive system mediates stress response and related psychopathology.
