Synergistic antidepressant effects of gastrodin combined with repetitive transcranial magnetic stimulation: Mediation by the gut-brain axis and endocannabinoid system.

This study investigates the synergistic antidepressant mechanisms of gastrodin (GAS) combined with repetitive transcranial magnetic stimulation (r-TMS) through the gut-brain axis and the endocannabinoid system. A depression model was established in male C57BL/6J mice using Chronic Unpredictable Mild Stress (CUMS). Following four weeks of modeling, animals were divided into five groups and received respective treatments for two weeks. A multi-modal approach was employed, encompassing behavioral tests, hematoxylin and eosin (HE) staining, 16S rRNA sequencing, liquid chromatography-mass spectrometry (LC-MS) metabolomics, Western blot analysis, and mediation analysis. Results demonstrated that the combined therapy significantly ameliorated depressive-like behaviors and cognitive deficits in CUMS mice, exhibiting superior efficacy compared to monotherapies. The treatment repaired hippocampal neuronal architecture and colonic mucosal integrity, upregulated the tight junction protein ZO-1, and reshaped the serum metabolic profile. Western blot analysis confirmed the activation of key proteins within the target pathway. Mediation analysis established a credible microbiota-metabolite-behavioral association, indicating that specific gut microbiota influence behavioral outcomes by modulating differential metabolites, with this relationship mediated through the endocannabinoid system. This study confirms that the combination of GAS and r-TMS exerts synergistic antidepressant effects by regulating gut-brain axis homeostasis and activating the target signaling pathway, providing a novel mechanistic foundation for combined depression treatment strategies.