The enteric nervous system consists of two major plexi, the submucous (Meissner’s) lying between the circular muscle and mucosal layers, and the myenteric (Auerbach’s) between the circular and longitudinal muscle. In recent years, it has become apparent that the chemical coding of the neurons in these two plexi differs significantly within a single species (1 ) and between species (2 ). The functional significance of the chemical coding of the enteric neurons is difficult to assess in vivo because of the absence of knowledge about the electrophysiological properties of the neurons and the regulation of neuropeptide/neurotransmitter release.
