Abstract

Stressors are perceptual stimuli that activate both the Sympathetic-Adrenal Medullary System and the Hypothalamic-Pituitary-Adrenal (HPA) Axis. The release of hormones specific to the HPA axis interferes with multiple types of recognition memory. The goal of this study was to examine how the HPA axis interacts with brain pathways that are responsible for either neutral object or social olfactory recognition memory. Twenty young adult male Long Evans rats (10/group) were exposed to either visual or olfactory stimuli presented in the delayed nonmatch to sample (DNMS) task. Performance in the DNMS task was compared between trials and groups. Five rats from each group swam for 15 minutes in the Porsolt Swim Arena prior to the last trial. In the object recognition task, investigation time was significantly diminished as a result of the swim (p=0.4), but memory performance was not significantly impaired; both groups investigated the novel object (p=0.003). In the olfactory recognition task, there was no significant effect of the swim on investigation time or memory performance. The swim task caused decreased investigation of neutral object stimuli, but not investigation of social scent stimuli. Memory overall was not impaired in either task. Acute stress has a different effect on neutral object recognition memory compared to social olfactory recognition memory, which suggests that olfactory recognition memory is more necessary than object recognition memory for rats to survive.