Predator odor exposure facilitates acquisition of a leverpress avoidance response in rats

Francis X Brennan^1,2, Kevin D Beck^3,4, Richard J Servatius^3,4

¹Medical Research (151), VA Medical Center, Philadelphia, PA, USA; ²Department of Psychiatry, University of Pennsylvania School of Medicine, Philadelphia, PA, USA; ³Neurobehavioral Research Laboratory, VA Medical Center, East Orange, NJ, USA; ⁴Department of Neuroscience, New Jersey Medical School, Newark, NJ, USA

Abstract: We have previously reported that prior exposure to inescapable tailshock stress increased avoidance responding 24 hours later. We argued previously that this might model the avoidance behavior characteristic of post-traumatic stress disorder (PTSD). The current experiment was conducted to determine whether a more ethologically relevant stressor would produce similar effects on avoidance responding. Therefore, rats were restrained for 2 hours and exposed to trimethylthiazoline (TMT), a component of fox feces, restrained only, or served as home cage controls. Twenty-four hours later, subjects received a 4-hour escape–avoidance session. Animals exposed to TMT made more escape responses overall, and made more avoidance responses than the other two groups by the 4th hour of the session. Differences between the TMT-exposed animals and restraint alone could not be explained by differences in corticosterone (CORT) levels. Results are discussed in terms of the possible neural changes induced by TMT exposure and the relationship to the behavioral aspects of PTSD or acute stress.

Keywords: stress, escape–avoidance, coping, trimethylthiazoline, learning