Institution: Virginia Commonwealth University, Richmond, Virginia 23284
Over 50% of patients are resistant to current treatments for depression. With a lifetime prevalence of 20.6% among US adults, it is evident that the present understanding of major depressive disorder is limited, and current experimental methods are inadequate to decode the complex pathology of depression. This study used a novel animal model, Repeated Forced Social Defeat, to induce depressive-like symptoms in mice in order to add to the current literature on depression. The study sample comprised forty wild type male C57BL/6 inbred mice. The Tube Test was utilized to determine the established social rankings within each group of mice. This was followed by administration of the Tail Suspension Test and a second administration of the Tube Test. Repeated Forced Social Defeat was administered a week after the second round of Tube Test administration, followed by one last round of the Tail Suspension Test. Results indicate that the dominant mice did not display significantly greater immobility times than the subordinate mice in the Tail Suspension test prior to- and after administration of Repeated Forced Social Defeat. However, there was a non-significant trend towards the dominant mice displaying greater immobility times in comparison to the subordinate mice post social defeat. Evidently, while there were no significant differences, dominant mice seem to display less resilience following social defeat in comparison to subordinate mice. A possible explanation for a lack of significant differences is a small sample size and short period of administration. These findings demonstrate the potential of utilizing Repeated Forced Social Defeat as a means to induce depressive-like symptoms in mice, as well as the relevance of dominance hierarchies in predicting susceptibility to specific stressors. Further investigation of Repeated Forced Social Defeat is warranted.
Keywords: Depression; Animal Model; Social Stress; Social Hierarchy; Antidepressant