Voluntary wheel running prevented the short-term behavioural effects of vicarious intermittent social defeat in female mice.

In a previous study, we observed that a Vicarious Intermittent Social Defeat (VISD) protocol induced anxiety- and depression-like symptoms in late adolescent female mice, and in some of them, enhanced sensitivity to cocaine reward in adulthood. Exposure to voluntary physical activity has been shown to mitigate the effects of different stress protocols in both male and female mice. Therefore, the aim of this study was to evaluate the efficacy of a voluntary wheel running (VWR) procedure in preventing the effects of the VISD in female mice. Four groups of female mice were used; (1) mice without exercise (control) nor stress (only exploration of an empty cage) (CONTROL + EXPL); (2) mice without exercise and exposed to VISD on PND 47, 50, 53 and 56 (CONTROL + VISD), (3) mice exposed to VWR (1 h, 3 days/week, from PND 21 to PND 46) without stress (VWR + EXPL); (4) mice exposed to both VWR and VISD (VWR + VISD). On PND 57-58, all female mice performed the Elevated Plus Maze, Hole-Board, Social Interaction, Splash and Object Recognition tests. Three weeks later, all female mice underwent a place conditioning procedure with cocaine. VWR exposure attenuated the VISD-induced reduction in the percentage of time spent in the open arms of the elevated plus maze and prevented the effects of the VISD in the hole-board, splash and object recognition tests. In addition, VWR facilitated the acquisition of the cocaine-induced conditioned place preference. Therefore, access to exercise during adolescence induced protective effects against the short-term negative consequences of social stress in female mice.