Modulating the Inflammatory Reflex in Rats Using Low-Intensity Focused Ultrasound Stimulation of the Vagus Nerve

Tumor necrosis factor α (TNF-α) is linked to several chronic inflammatory diseases. Electrical vagus nerve stimulation reduces serum TNF-α levels but may cause chronic nerve damage and requires surgery. Alternatively, we proposed focused ultrasound stimulation of the vagus nerve (uVNS), which can be applied non-invasively. In this study, we induced an inflammatory response in rats using lipopolysaccharides (LPS) and collected blood to analyze the effects of uVNS on cytokine concentrations. We applied one or three 5-min pulsed focused ultrasound stimulation treatments to the vagus nerve (250 kHz, I_SPPA = 3 W/cm²). Animals receiving a single ultrasound application had an average reduction in TNF-α levels of 19%, similar to the 16% reduction observed in electrically stimulated animals. With multiple applications, uVNS therapy statistically reduced serum TNF-α levels by 73% compared with control animals without any observed damage to the nerve. These findings suggest that uVNS is a suitable way to attenuate TNF-α levels.