Effects of pre-germinated brown rice on depression-like behavior in mice

We investigated the antidepressant-like effects of pre-germinated brown rice (PGBR) and polished rice (PR) pellets, respectively, in comparison with control (AIN-93G) pellets in the forced swimming test and the learned helplessness paradigm in mice. Mice were fed respective pellets for 30 days. The immobility time on the 2nd day of the forced swimming test was shorter in mice fed with PR or PGBR pellets than in mice fed with control pellets. In the learned helplessness paradigm, the number of escape failures in mice fed with PGBR pellets was significantly smaller than that in mice fed with control pellets. Compared to the control group, an increase in serotonin (5-HT) levels, but not in 5-hydroxyindoleacetic acid (5-HIAA) levels, and a decrease in the 5-HIAA/5-HT ratio were observed in the frontal cortex of the PGBR group. There were no differences among the three groups in terms of 5-HT and 5-HIAA levels and their ratios in the hippocampus and striatum. The levels of noradrenaline and 3-methoxy-4-hydroxyphenylglycol were not affected by the food pellets in all the brain regions tested. Additionally, we could not detect any differences in the expression of the 5-HT1A receptor and the 5-HT transporter in the frontal cortex of the three groups. These results suggest that the increase of 5-HT levels in the mouse frontal cortex contributes to the antidepressant-like effects of PGBR pellets.