ULTRASTRUCTURE OF INTERSTITIAL-CELLS OF CAJAL IN THE CANINE DISTAL ESOPHAGUS

The ultrastructure of canine distal esophagus was studied focusing on interstitial cells of Cajal (ICC) and their relationships to nerves an d muscle. The distal esophagus consisted of two muscle layers composed of intertwining skeletal and smooth muscle bundles. The ICC formed an interconnecting network and were an integral part of these structures . The ICC communicated with one another and with adjacent smooth muscl e cells through numerous gap junctions. The morphology of individual I CC resembled that observed in other gut regions. All interstitial cell s were densely innervated. The highest density of ICC, just proximal t o the lower esophageal sphincter, coincided with the previously report ed highest incidence of occurrence of electrical slow wave type action potentials. Examination of a large number of structural associations of ICC led us to conclude that in the distal esophagus, two networks o f ICC and nerves exist, one associated with the inner muscle layer, an other associated with the outer muscle layer. These networks are not s heet-like structures, such as the network of ICC in the myenteric plex us or deep muscular plexus of the small intestine, but are three dimen sional and are interspersed throughout both muscle layers. The network s do not extend into Auerbach's plexus. The main branches of the netwo rks run along the long axis of the esophagus and seem ideally suited t o facilitate communication in this direction. These observations sugge st that esophageal interstitial cells are structurally organized in su ch a manner that they may play a role in pacemaking and neural control of esophageal motility.