THE ENTERIC NERVOUS SYSTEM: NEW DEVELOPMENTS AND EMERGING CONCEPTS

Abstract

The enteric nervous system (ENS) is an integrative neuronal network, organized in two ganglionated plexuses, myenteric and submucosal, composed of neurons and enteric glial cells, controlling the activity of the smooth muscle of the gut, mucosal secretion and blood flow. The ENS contains as many neurons as the spinal cord, and the functional and chemical diversity of enteric neurons closely resembles that of the central nervous system. This highly integrated neural system is also referred to as the ‘brain-in-the-gut’, because of its capability to function in the absence of nerve inputs from the central nervous system. The ENS controls gut motility and secretion via local reflexes that are triggered by local distension of the intestinal wall, distortion of the mucosa, and chemical contents in the lumen. This neuronal regulation of GI functions is due to the liberation of specific neuromediators synthesized by functionally defined enteric neurons. In addition, ENS is involved in the control of immune and inflammatory processes throughout the gut. Thus, it is not surprising that any damage to ENS circuitries and in the neurotransmitters systems results in a wide array of gut disorders, including motor impairments, which are characterized by high morbidity. In the future challenges are to properly understand the molecular and cellular changes that underlie enteric neuropathies, to utilize knowledge of the normal neurochemistry, pharmacology and physiology of the ENS to devise strategies to treat disorders of motility and to develop effective therapeutic compounds.