NEW DEVELOPMENTS IN THE ENTERIC NERVOUS-SYSTEM

Research on the enteric nervous system is important because the mechan ism by which the motility of the bowel is locally controlled is still not understood and because this research is critical in developing eff ective therapies for functional bowel disease. Although the behaviors regulated by the enteric nervous system cannot yet be explained in ter ms of the activity of single cells, it should soon be possible to do s o. Considerable progress has been made in determining the function of particular types of enteric neurons, including sensory neurons of the submucosal plexus, motor neurons, and interneurons of the myenteric pl exus. Uncertainty persists as to the nature of the myenteric neuron cl assified electrophysiologically as type 2/AH and morphologically as Do giel type II. These cells may act as sensory neurons, as interneurons, or both. Nitric oxide has clearly been established to play a critical role as an intrinsic inhibitory neurotransmitter, as has ATP and vaso active intestinal peptide, although neurons, smooth muscle, and inters titial cells of Cajal may each be both sources nitric oxide and the ta rgets of its action. Interstitial cells appear to play roles as both a s pacemaker cells for the circular muscle and in transmitting neural s ignals to smooth muscle cells. Although one cannot yet map the compone nts of an enteric microcircuit, it should soon be possible to do so.