Witness Defeat: A Novel Animal Model Of Vicarious Stress-Induced Depression In Female C57bl/6 Mice

RM 217

Stress exposure is a prevailing risk factor for the development of mood-related illnesses, wherein women represent the greater majority of those who suffer from depression-, anxiety-, and posttraumatic stress- disorder. Despite the growing body of studies suggesting that affective disorders can arise after a traumatic event is vicariously experienced, this relationship remains to be examined in female subjects at the preclinical level. Thus, the objective of the current investigation is to examine whether the “witness defeat” paradigm – a model that dissociates emotional versus physical social stressors – induces a depression-like behavioral phenotype in female c57BL/6 mice. To do this, female mice witnessed the social defeat bout of a male conspecific, by a larger CD1 aggressor, for 10 consecutive days. Twenty-four hr after stress exposure, mice were tested in the social interaction, sucrose preference, tail suspension, forced swimming, and elevated plus-maze behavioral tests. As expected, the physically stressed male c57BL/6 mice displayed a depressive-like phenotype as inferred from decreases in social interaction, decreased sucrose preference, increased total immobility in the tail suspension and forced swim tests, along with increases in sensitivity to the anxiety-inducing environment of the elevated plus maze. Interestingly, when compared to non-stressed female controls, female mice exposed to witness defeat stress also displayed a depressive-like phenotype across the same behavioral assays. As such, our results indicate that exposing female c57BL/6 mice to the “witness defeat” paradigm may be used to examine the etiology of vicarious stress-induced mood-related disorders in female populations.