A Standardized Protocol for Early-life Stress-induced Social Defeat in Mice

Neuropsychiatric diseases, like depression, have a considerable and persistent impact on human health; however, little is known about their underlying pathogenesis. Social defeat is a model for stress-induced psychopathologies that could present with behaviors resembling those observed in humans with depression. However, previous animal models of social defeat mainly focus on adults. Here, we re-design the protocol of early-life stress-induced social defeat paradigm, which is based on a classic resident-intruder model. Briefly, each two-week-old experimental mouse of C57BL/6 strain is introduced into the home cage of an unfamiliar CD1 aggressor mouse for 30 min per day for 10 consecutive days. Later, all experimental mice are raised individually for another month. Finally, the mice are identified as defeated through social interaction and open field tests. This model has been shown to be etiological and predictive and provide high validity and could be a powerful tool to investigate the underlying pathogenesis of early onset depression.