Effects of social defeat stress using different adjacent cages in mice

Developing animal models to investigate depression is a major challenge in psychiatric research. Although social defeat stress (SDS) is a well-established method, conventional protocols often involve shared housing that may not fully represent human social stress where physical harm is not constant. This study investigated whether mice exhibit chronic psychological stress when housed in separate, adjacent cages rather than shared cages. Subject and attacker mice were housed in adjacent transparent cages for three weeks, with a 10-minute social defeat task conducted daily. Subsequently, mouse-specific depressive behavior and serum corticosterone levels were measured. Our results showed that SDS without using a shared cage significantly increased depressive behavior and elevated stress hormone corticosterone levels in mice. These results indicate that SDS without using the same cage effectively induces behavioral changes similar to traditional SDS. This suggests that a breeding environment where neighboring cages can be observed is sufficiently stressful for mice, opening new possibilities for SDS research mediated through visual and other sensory information.