Wheel-running activity increases with social stress in male DBA mice.

Social affiliation-avoidance behaviors are essential indices of sociality. We examined changes in social affiliation-avoidance behaviors in an open-field apparatus while simultaneously measuring wheel-running activity. Recent studies suggest that mice increase wheel-running activity in stressful situations; thus, we hypothesized that wheel-running activity would reflect a state of social stress and avoidance. Mean duration of wheel-running increased significantly when mice were confronted with unfamiliar mice compared to cage mates. There were negative correlations between the amount of wheel-running and social affiliation indices. We also examined the effect of social defeat on wheel-running activity. Mice that had experienced social defeat significantly increased their wheel-running when an aggressor mouse was present. This social defeat-induced wheel-running activity was ameliorated by the administration of diazepam. Our results indicate that wheel-running activity is relevant to social affiliation-avoidance behaviors and may be a reliable index of anxiety induced by social stress.