Opposite Sex Contact and Isolation: A Novel Depression/Anxiety Model

To mimic human mood disorders, traditional chronic stresses and social defeat stress have been developed and widely applied. However, these active stresses do not mimic the emotional flaws induced by stresses, and their input levels vary greatly. Also, emotional stresses resulting from social unobtainability remain largely elusive due to the lack of useful animal models. In this study, we developed a mouse model named "opposite sex contact and isolation" (OSCI) and found that OSCI induced significant social avoidance, anhedonia, and anxiety. These behavioral defects developed differently after 7 days of OSCI. The social avoidance behavior was self-curable while anxiety gradually worsened but was alleviated by re-pairing with the same female partner. Corresponding to the behavior changes, the plasma corticosterone and phosphorylated cAMP response element binding protein levels were decreased in the nucleus accumbens of the mice that experienced isolation. Together, this study has developed a novel strategy for depression/anxiety modeling and shows that OSCI may be a useful tool for studying the lovelorn/lovesick type of depression.