Dissociation between behavioral and corticosterone responses on repeated exposures to cat odor.

Rats exposed for 5 min to a phobic stimulus (the odor of a cat) had plasma corticosterone concentrations significantly higher than those exposed to a neutral odor and than a group remaining undisturbed in the animal house. During the first exposure to cat odor the increased corticosterone was related to the avoidance behavior, measured as the time spent sheltering. After five exposures to cat odor the rats continued to avoid the odor cloth, but no longer responded with raised corticosterone levels. The results are discussed with reference to the two components of a phobic response (avoidance and disturbance), and it is suggested that the latter, reflected by changes in corticosterone, habituates more readily than the former.