Effect of chronic social defeat stress on behaviors and dopamine receptor in adult mice

Victims of bullying often undergo depression, low self-esteem, high anxiety and post-traumatic stress disorder symptoms. The social defeat model has become widely accepted for studying experimental animal behavior changes associated with bullying; however, differences in the effects in susceptible and unsusceptible individuals have not been well studied. The present study investigated the effects of social defeat stress on behavior and the expression of dopamine receptors D1 and D2 in the brains of adult mice. Adult mice were divided into susceptible and unsusceptible groups after 10 days of social defeat stress. Behavioral tests were conducted, and protein levels in the brains were assessed by Western blotting. The results indicate that all mice undergo decreased locomotion and increased anxiety behavior. However, decreased social interaction and impaired memory performance were only observed in susceptible mice. A significantly decreased expression of D1 was observed in the prefrontal cortex and amygdala of susceptible mice only. No significant differences in D2 expression were shown between control and defeated mice in any area studied. These data indicate that depression-like behavior and cognition impairment caused by social defeat stress in susceptible mice may be related to changes in the dopamine receptor D1. (C) 2015 Elsevier Inc. All rights reserved.