Effects of Partial Isolation on Mice Behavior
Background: The effects of an isolated human environment with little societal contact are a topic of interest in clinical psychiatry. Studies using animal models are important for investigating the effects of such an environment. Considering that the modern human environment that allows partial and limited communication even for those who are isolated from the society, raising mice in social isolation, a method that has been conventionally adopted with mice, is not an accurate simulation. Method: Therefore, in our experiment, to better simulate the partial isolation that is often observed in humans, we devised a method of dividing the breeding cage into two compartments using a transparent sheet, raising four mice in one section and a single mouse in the other (we defined it as physical isolation). We then compared the behavioral patterns of group-reared, conventionally socially isolated, and physically isolated mice to determine the effects of limited communication restrictions on individual mice. Result: When the new rearing method of physical isolation was adopted, there was no significant difference in the time spent around cages with and without familiar mice, or around cages with strange mice and cages with familiar mice, as observed in group rearing, confirming that social behavior is suppressed in the same way as in social isolation. However, there was no significant increase in immobility time on the forced swim test or tail suspension test, as observed in social isolation, suggesting no increase in anxiety or depression. In the cotton bud biting test, the number of attacks was significantly lower than the other two rearing methods, confirming a decrease in aggression. Conclusion: Our findings, which show that mice placed in such an environment may experience less stress than when being raised in groups, despite suffering problems with their development of sociability, are of considerable interest.