A Potential Driving Force of Social Dominance in Mice: Wheel Running on BDNF and Orexin

By Jane Sullivan, Kristin Haes

Faculty mentor: Dr. Parrish Waters

Physical exercise has profound effects on both the brain and behavior, including decreased anxiety and depression, and the regulation of multiple hypothalamic peptides. This study explores the effects that physical exercise may have on social dominance in mice, which is determined by many of the behavioral and physiological traits that exercise influences. Namely, the hypothalamic peptides orexin and brain derived neurotrophic factor (BDNF) evoke structural and physiological changes in the brain that modulate behaviors associated with social dominance (e.g. cognition, aggression, fear, and motivation). While individual relationships have been established between these peptides, exercise, and specific behaviors, the link between physical exercise and social rank, resulting from changes in BDNF and orexin has not been demonstrated. This study examines the possibility that wheel running can drive social dominance by increasing levels of orexin and BDNF in specific brain areas. We allowed select mice living in social cages to access a running wheel for 28 days and tracked dominance related behaviors during over that time. Afterward, we collected brain and blood tissue to assess levels of orexin and BDNF (using qPCR), and corticosterone (using ELISA), all of which are known to influence social dominance behaviors in mice. Furthermore, we observed homecage behavior of the mice and conducted behavioral tests to determine dominance status and other behaviors in each homecage. Thus far, our results illustrate that access to a running wheel has no effect on social dominance in mice. We will continue to examine our tissue samples for possible effects of exercise on the physiology and behavior of the discrepancy between prior research and the results observed in this study.