Vulnerability to chronic subordination stress-induced depression-like disorders in adult 129SvEv male mice

Exposure to stressful life events is intimately linked with vulnerability to neuropsychiatric disorders such as major depression. Pre-clinical animal models offer an effective tool to disentangle the underlying molecular mechanisms. In particular, the 129SvEv strain is often used to develop transgenic mouse models but poorly characterized as far as behavior and neuroendocrine functions are concerned. Here we present a comprehensive characterization of 129SvEv male mice's vulnerability to social stress-induced depression-like disorders and physiological comorbidities. We employed a well characterized mouse model of chronic social stress based on social defeat and subordination. Subordinate 129SvEv mice showed body weight gain, hyperphagia, increased adipose fat pads weight and basal plasma corticosterone. Home cage phenotyping revealed a suppression of spontaneous locomotor activity and transient hyperthermia. Subordinate 129SvEv mice also showed marked fearfulness, anhedonic-like response toward a novel but palatable food, increased anxiety in the elevated plus maze and social avoidance of an unfamiliar male mouse. A direct measured effect of the stressfulness of the living environment, i.e. the amount of daily aggression received, predicted the degree of corticosterone level and locomotor activity but not of the other parameters. This is the first study validating a chronic subordination stress paradigm in 129SvEv male mice. Results demonstrated remarkable stress vulnerability and establish the validity to use this mouse strain as a model for depression-like disorders.