Certain gut microbes’ chemicals in the small intestine influence nerve signals to the brain through specific receptors

Mice reared germ-free exhibit decreased vagal tone, which is reversed by microbiota restoration.

• Germ-free mice show lower vagal activity compared to those with a normal gut microbiome.
• Administration of antibiotics reduces vagal activity in conventional mice but not in germ-free mice.
• Restoration of vagal activity occurs when conventional intestinal filtrates are reintroduced to antibiotic-treated mice.
• Specific metabolites produced by the microbiome, such as short-chain fatty acids and bile acids, stimulate vagal activity through receptors.
• Different classes of metabolites activate various neuronal subsets, influencing the speed and nature of the response.
• Increases in vagal activity from metabolite stimulation correspond with activation of brainstem neurons.

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