The predator odor, TMT, displays a unique, stress-like pattern of dopaminergic and endocrinological activation in the rat.

Predator odors may provide a species relevant aversive stimuli to study the central effects of stress in rats and may have several benefits over currently applied models. Here, we examined one such odor, TMT, isolated from the fox, a predator of the rat, on fear-induced behaviors, serum corticosterone, and central dopamine metabolism. Habituated rats were exposed to TMT, or a control odor, butyric acid, in an open field. For comparison, other rats were subjected to a model of conditioned fear - a traditional fear model. Several similarities between the two stresses were observed including increased serum corticosterone and increased dopamine metabolism in the medial prefrontal cortex. Differences were also observed. TMT, but not conditioned fear, activated dopamine metabolism in the amygdala, but not the nucleus accumbens core and shell. Rats exposed to conditioned fear, but not TMT odor, demonstrated altered behaviors associated with fear, including locomotion, grooming and immobility. Finally, rats reexposed to TMT after a 24-h delay did not demonstrate any of the changes observed with acute exposure to TMT. These data indicate acute exposure to a predator odor, TMT, can result in a unique pattern of biochemical activation that is similar, but not identical, to conditioned fear. The differences may indicate unique features of a central 'fear arousal' pathway that responds to innate, unlearned stressful stimuli, such as predator odors.