Effects of diet quality on vulnerability to mild subchronic social defeat stress in mice.

OBJECTIVES: The chronic social defeat stress (CSDS) mouse model is a potentially useful system for understanding stress responses to social environments. We previously developed a mouse model of subchronic and mild social defeat stress (sCSDS) that exhibits increased body weight gain and food intake following polydipsia-like features. sCSDS mice also show avoidance behavior in a social interaction test. In this study, we examined the effects of diet quality on susceptibility to sCSDS by feeding these mice semi- and non-purified diets.

METHODS: Male C57BL/6J (B6; n = 82) mice were exposed to sCSDS using male ICR mice. The B6 mice were divided into four test groups: semi-purified pellet diet + sCSDS, non-purified pellet diet + sCSDS, semi-purified diet + control (no sCSDS), and non-purified diet + control.

RESULTS: Although increased body weight, and food and water intake following sCSDS exposure were consistently observed in the groups that were fed semi- and non-purified diets, social avoidance behavior was influenced by food type (i.e., sCSDS mice fed semi-purified diet showed the greatest social avoidance behavior). In addition, the rates of stress susceptibility were estimated at 73.9 and 34.8% in sCSDS mice fed semi-purified and non-purified diets, respectively (P < 0.05). For comparison, the susceptible-like phenotype rates were estimated at 12.5 and 8.3% in healthy control mice fed semi-purified and non-purified diets, respectively.

DISCUSSION: These results suggest that diet quality affects the vulnerability of mice to social defeat stress.