It is indicated that the intestinal environment affects the brain, which is known as the gut-brain axis. In fact, improvement of intestinal environment is reported to suppress anxiety-like behavior in mice model of depression and schizophrenia. However, its detailed mechanisms remain unclear, particularly in context of intestinal environment effects on emotion in non-disease mice. The object of this experiment is therefore to verify the effect of intestinal environment on anxiety-like behavior and its detailed physiological mechanisms.
We previously found that cellulose rich food (AIN-93M) suppresses the production of short-chain fatty acid and exacerbate the intestinal condition. In the present study, we fed mice with AIN-93M to modify the intestinal environment, or the mouse chow that can maintain a favorable intestinal environment (MF). After 8-weeks feeding, AIN-93M-fed animals displayed the significant increase of marble-burying behavior compared to MF-fed group, suggesting that dysfunction of intestine lead by AIN-93M enhanced anxiety-like behavior. Furthermore, dopamine release as well as dopamine receptor expression has been increased in amygdala of AIN-93M fed mice but not in MF animals, indicating that enhanced anxiety-like behavior in AIN-93M animals is due to such modification of amygdalar dopaminergic system. 
These results suggest that cellulose rich food may exacerbate intestinal environment, which may enhance the anxiety-like behavior and overactivation of dopaminergic system.