TNF and major depressive disorder: Previous studies have shown (34) that taVNS can ameliorate depression-like behaviors in a lipopolysaccharide (LPS)-induced rat model of inflammatory depression, regulate peripheral pro-inflammatory factors (e.g., IL-1β, TNF-α) and anti-inflammatory factors (e.g., IL-4, IL-10), and inhibit activation of the NF-κB pathway in the prefrontal cortex, thereby playing a key role in modulating the peripheral-central inflammatory network.