The Effects of Transcranial Magnetic Stimulation on Tryptophan Metabolism and Depressive-Like Behavior in Mice

This research seeks to explore the effects of repetitive transcranial magnetic stimulation (rTMS) as an intervention on a depression mouse model and its impact on blood tryptophan metabolism.

In this study, 24 mice were randomly divided into three groups: Sham, CUMS, and CUMS + rTMS, with each group comprising eight mice. The depression model was established using the chronic unpredictable mild stress (CUMS) method. High-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was employed to measure the levels of tryptophan and its metabolites in the mice's blood. The CUMS + rTMS group received rTMS treatment in addition to CUMS. Depressive-like behaviors of mice in the CUMS group and the CUMS + rTMS group were evaluated and compared through the sucrose preference test, open field test, and tail suspension test.

Blood serotonin levels, a tryptophan metabolite, were notably lower in the CUMS group than in the Sham group. Conversely, the levels of 5-hydroxyindole-3-acetic acid, xanthurenate, and indole-3-acetaldehyde were significantly higher in the CUMS group than in the Sham group. Additionally, the sucrose preference rate was lower, and the duration of immobility during the tail suspension test was longer in the CUMS group than in the Sham group; all these differences were statistically significant (p < 0.05). Following rTMS treatment, the CUMS+ rTMS group showed significantly lower blood levels of 5-hydroxyindole-3-acetic acid, xanthurenate, and indole-3-acetaldehyde, while serotonin levels were significantly higher than those in the CUMS group. Compared with the CUMS group, mice in the CUMS + rTMS group showed higher sucrose preference and shorter immobility duration in the tail suspension test (p < 0.05).

rTMS can affect tryptophan metabolism in the blood of mice and reduce symptoms similar to depression, providing new insights into the antidepressant properties of rTMS.