Abstract

Animals respond to threatening situations by exhibiting a number of defensive behaviors, including avoidance, freezing, and risk assessment. An animal model with an ethological approach offers a deeper insight into the biological mechanisms underlying threat responses. This paper describes a methodology to measure defensive behaviors toward both innate and learned aversive stimuli in rats. Animals were individually exposed to predator odor in an inescapable chamber to elicit a measurable, sustained, defensive state. The experimental design involved placing a rat in a familiar chamber for 10 min followed by exposure to cat odor for another 10 min in the same context. The next day, the rats were