Vagal Pathways for Microbiome-Brain-Gut Axis Communication

Abstract

There is now strong evidence from animal studies that gut microorganism can activate the vagus nerve and that such activation plays a critical role in mediating effects on the brain and behaviour. The vagus appears to differentiate between non-pathogenic and potentially pathogenic bacteria even in the absence of overt inflammation and vagal pathways mediate signals that can induce both anxiogenic and anxiolytic effects, depending on the nature of the stimulus. Certain vagal signals from the gut can instigate an anti-inflammatory reflex with afferent signals to the brain activating an efferent response, releasing mediators including acetylcholine that, through an interaction with immune cells, attenuates inflammation. This immunomodulatory role of the vagus nerve may also have consequences for modulation of brain function and mood.What is currently lacking are relevant data on the electrophysiology of the system. Certainly, important advances in our understanding of the gut-brain and microbiome- gut-brain axis will come from studies of how distinct microbial and nutritional stimuli activate the vagus and the nature of the signals transmitted to the brain that lead to differential changes in the neurochemistry of the brain and behaviour.Understanding the induction and transmission of signals in the vagus nerve may have important implications for the development of microbial-or nutrition based therapeutic strategies for mood disorders.

The Effects of Vitamin B in Depression

“…Toxic chemicals, such as nitric oxide, quinolinic acid and kynurenic acid, can also be stimulated for release by vagal signaling. These chemicals cause decreased function of nerve cells [29,30]. In fact, the gut microbiome and intestinal permeability has mounting evidence linking it to brain development, function and behavior, through the immune, endocrine and neural pathways [31].…”

A dysbiotic subpopulation of alcohol-dependent subjects

“…The microbiota and the increase in permeability may also interact through the enteric tract with the vagus nerve. 29 It may affect the stress system. 30 Finally, it generates a mild form of chronic inflammation, related to the increased gut permeability, 31,32 that is currently considered an important factor for the development of depression.…”

Gut–Brain Axis Dysfunction May Be Associated With Psoriatic Arthritis: Comment on the Article by Scher et al

“…Bravo et al reported that gut microbial dysbiosis can influence the function of the gut-brain axis via the vagus nerve and metabolites (3,4). As a result, the brain may release mediators, causing further immune modulation dysfunction, and activate inflammation through interaction with immune cells (5).…”