Dopamine and the Gut Microbiota: Interactions Within the Microbiota–Gut–Brain Axis and Therapeutic Perspectives

The microbiota-gut-brain axis (MGBA) comprises a complex bidirectional communication network integrating neural, immune, metabolic, and endocrine pathways. Dopamine, traditionally viewed as a central neurotransmitter, also plays essential roles in the gastrointestinal (GI) tract, where it regulates motility, secretion, barrier homeostasis, and mucosal immunity. Growing evidence indicates that the gut microbiota significantly contributes to intestinal dopamine metabolism through specialized enzymatic pathways, particularly tyrosine decarboxylase in <i>Enterococcus</i> species and catechol dehydroxylase in <i>Eggerthella</i> species. These microbial reactions compete with host processes, alter dopaminergic tone, and degrade orally administered levodopa (L-DOPA), providing a mechanistic explanation for the variability in treatment response in Parkinson's disease (PD). Beyond PD, microbially mediated alterations in dopaminergic signaling have been implicated in mood disorders, neurodevelopmental conditions, metabolic dysfunction, and immune-mediated diseases. This review synthesizes current mechanistic and translational evidence on the dopamine-microbiota interface, outlines microbial pathways shaping dopaminergic activity, and highlights therapeutic opportunities including microbiota modulation, dietary strategies, fecal microbiota transplantation, and targeted inhibitors of microbial dopamine metabolism. Understanding this interface offers a foundation for developing personalized approaches in neurogastroenterology and neuromodulatory therapies.