Influence of the Microbiota on the Development and Function of the "Second Brain"-The Enteric Nervous System

The enteric nervous system (ENS) is the intrinsic nervous system of the gut, made up of an extensive network of neurons that lines the walls of the gastrointestinal (GI) tract. The framework of the ENS is laid during the first gestational trimester, but the network continues to undergo modifications throughout the prenatal period and into postnatal life. Colonization of the GI tract by trillions of microorganisms during the early postnatal period represents a significant change from the prenatal condition that undoubtedly affects the developing ENS. The specific changes to the ENS brought about by microbial colonization of the gut are only beginning to be uncovered. In this chapter we highlight the preliminary evidence from our laboratory and others supporting a role for the early intestinal microbiota in shaping the developing ENS. We also review the potential clinical implications of this relationship, including the role for probiotics as a means of targeting the developing ENS.