A vagus-dependent gut microbiota–metabolite axis drives chronic inflammatory pain and working-memory deficits in mice

Chronic inflammatory pain (CIP) has been increasingly linked to gut microbiota (GM)-brain interactions, yet whether these effects rely on vagal signaling remains unclear. Here, we investigated whether GM from CIP mice is sufficient to transfer pain-like behaviors to healthy recipients and whether this process depends on the vagus nerve. Fecal microbiota transplantation (FMT) from mice treated with complete Freund's adjuvant induced mechanical and thermal hypersensitivity and impaired working memory in recipients, accompanied by hippocampal neuroinflammation and GM dysbiosis. Subdiaphragmatic vagotomy (SDV) performed prior to FMT attenuated these behavioral and neuroinflammatory alterations and partially normalized microbial community structure. Plasma metabolomics further showed that SDV restored phosphatidylcholines while reducing pro-inflammatory lipid classes, with several metabolites and bacterial taxa correlating significantly with pain sensitivity and hippocampal cytokine levels. Collectively, these findings demonstrate that a vagus-dependent GM-metabolite-brain axis contributes to CIP-like behaviors and neuroinflammation. Targeting vagal pathways and GM-regulated lipid metabolism may offer therapeutic strategies and pharmacodynamic biomarkers for inflammatory pain.