BioAcyl Corp

The Microbiota-Gut-Brain Axis (A) Factors influencing the composition of the gut microbiota. The initial microbiota is acquired at birth and is shaped by a variety of intrinsic and environmental factors. Although microbiota stability peaks in adulthood, it maintains flexibility to adjust to environmental or dietary changes. (B) Evidence for the influence of the gut microbiota on brain physiology has surfaced mostly from studying germ-free animals, which show alterations in various aspects of neurophysiology. (C) The microbiota-gut-brain axis encompasses different routes of communication that, depending on their location and function, can be hijacked by specific species of the gut microbiota to influence brain and behavior. Gradients of pH, oxygen, antimicrobial peptides, and bile salts determine the density and diversity of microbial species along the GI tract. Metabolites produced by the gut microbiota can either activate enteroendocrine cells to release gut hormones or be absorbed across the epithelial cell layer to either be taken up by the bloodstream or to activate vagus nerve afferents to communicate with the brain. Different types of vagal afferents can be found within the GI tract that transmits different signals to the brain. Thus, a combination of the location of the microbiota within the GI tract and the chemicals produced is likely to determine where and how within the NTS the information is relayed, thereby provoking different behavioral responses.