Parameter-Specific Effects of Low-Intensity Transcranial Focused Ultrasound Stimulation on Depression-Like Behaviors...

Depression is a multifactorial disorder involving neurotransmitter dysregulation, gut microbiota imbalance, and metabolic disturbances. Low-intensity transcranial focused ultrasound stimulation (LIFUS) holds promise for treating depression. However, the effects of different LIFUS parameter settings on depression-like behaviors, and their potential associations with gut microbiota and fecal metabolite changes, remain largely unexplored. This study aims to investigate the parameter-specific effects of LIFUS on depression-like behaviors in a chronic unpredictable mild stress (CUMS) mouse model, and to explore potential associations with changes in gut microbiota and fecal metabolites.

To establish a depression model, C57BL/6 mice were subjected to CUMS, while a separate cohort was kept as a control (CON) group. The CUMS-exposed mice were then randomly divided into four groups: CUMSpo, LIFUS1, LIFUS2 and SHAM. Depressive-like behaviors were evaluated using the sucrose preference test (SPT) and forced swim test (FST). The levels of neurotransmitters and Fecal concentrations of metabolites were quantified using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Gut microbiota composition was analyzed by metagenomic sequencing, and α-diversity was assessed using the ACE, Chao1, and Shannon indices. Histopathology was assessed via HE staining.

LIFUS at 1.5 kHz PRF, but not 300 Hz, significantly attenuated CUMS-induced depressive-like behaviors, evidenced by increased sucrose preference and reduced immobility time, without affecting locomotor activity. This behavioral effect was accompanied by a significant increase in cortical glutamate. LIFUS2 protocol was associated with a significant increase in tryptamine, alongside a concurrent trend towards restoring the abundance of Clostridia and enhancing gut microbiota α-diversity. HE staining confirmed protocol safety.

The antidepressant-like effects of LIFUS appear to be associated with multi-systemic alterations, including changes in cortical glutamate, modulation of the gut microbiota, and specific changes in tryptophan metabolism.