The importance of the enteric nervous system for coordinating and programming the digestive modes of the gastrointestinal effecters is well recognized. Attention has been focused in the past on the involvement of intrinsic nerves in generating specific motility patterns of the smooth muscle effecters, with little regard for the influence of intrinsic nerves on mucosal transport processes. The advent of immunohistochemical techniques for identifying neuronal types and their projections has documented the intrinsic innervation of the mucosa and has renewed interest in the epithelium as a neuroeffector system. The first definitive evidence of the direct involvement of the enteric nervous system in the regulation of intestinal mucosal ion transport was provided by Hubel (1) who adapted conventional electrical field stimulation techniques that were used routinely to examine the neural regulation of smooth muscle contractile activity to whole-thickness sheets of intestine in Ussing chambers. This technique, with its subsequent modifications by Cooke et al. (2), has been the basis for current understanding of the involvement of the enteric nervous system in the regulation of mucosal transport function. Significant progress has been made over the last decade to develop the foundation on which to build a working model of neural mechanisms that influence the mucosa; however, physiologic experiments have not kept pace with the morphologic studies that have identified a multiplicity of putative neurotransmitters within submucosa neurons, and, therefore, the