Predator odor as an unconditioned fear stimulus in rats: Elicitation of freezing by trimethylthiazoline, a component of fox feces

Four experiments tested whether an odor from a rat predator can uncondition ally elicit a fear response in mts. In a large chamber, rats displayed fear -related behaviors to trimethylthiazoline (TMT, a volatile compound isolate d from fox feces), including avoidance and immobility, while showing Less e xploratory behavior. In a smaller chamber, TMT induced a species-typical fe ar response, freezing, whereas other odors did not. In addition, TMT system atically elicited more freezing as the amount of TMT increased. Moreover, t here was no within-sessions or between-sessions habituation of freezing to TMT, nor did TMT promote contextual conditioning. The results indicate that the predator odor, TMT, can induce a fear-related behavioral response in r ats that is controllable and quantifiable, suggesting that TMT-induced free zing may be a useful paradigm for a neurobehavioral system analysis of ecol ogically relevant, unconditioned fear.