Exposure to various stressors alters preferences for natural odors in rats (Rattus norvegicus)

Male Sprague-Dawley rats (Rattus norvegicus) were given choice tests (Test 1) in a maze with the odors of clean bedding, citronella, an alpha colony (ACO), shocked conspecifies (SCO), or a predator cat (PCO). In Experiments 1-3, groups were exposed to no stress, defeat by a conspecific, or shocks. During subsequent tests (Test 2), nonstressed rats showed no change in odor preferences; defeated rats showed a nonsignificant reduction in preference for ACO; and shocked rats showed significant preference reductions for SCO and PCO and a significant increase in preference for ACO. In Experiment 4, odors of isolated, nonstressed conspecifics (CO) were preferred more than ACO, for rats given shock before Test 2. In Experiment 5, rats significantly preferred CO over ACO when exposed to a caged cat during Test 2. Because of exposure to stress, rats later avoided certain fear odors and showed strong preferences for the odors of nonstressed conspecifics.