SIGNALLING THROUGH THE MICROBIOTA-GUT-BRAIN TRIADE

Gut microbiota is well known for its role in regulation of intestinal function. However, intriguing evidence indicates that gut microbes can also modulate the development and activity of the nervous system through a bidirectional communication pathway, so called the microbiota-gut-brain axis. One of the ways through commensal microbial strains in intestinal lumen could signal to the brain, is by producing similar neurotransmitters with those found in mammalian organisms, such as GABA, serotonin, catecholamines and histamine. Given the fact that mental disorders relate to the imbalance of neuroactive compounds, and several gut microorganisms could alter neurotransmitters levels, it was assumed that gut microbiota could influence mood, stress and behaviours and be also a determinant factor for the onset or evolution of neurological and psychiatric pathologies. This review aims to assess the relationship between the intestinal microbiome and the brain, by focusing on the main neurotransmitters secreted by the gut microbes.