INTERSTITIAL-CELLS OF CAJAL AND AUERBACH PLEXUS - A SCANNING ELECTRON-MICROSCOPIC STUDY OF GUINEA-PIG SMALL-INTESTINE

Interstitial cells of Cajal (ICC) appear to be involved in the regulation of intestinal motility, probably as pacemaker cells. We investigated the complex organisation of ICC associated with Auerbach's plexus of guinea-pig small intestine in the scanning electron microscope. The plexus was exposed by microdissection of zinc iodide/osmic acid stained tissue. After separation of the muscle layers by microdissection alone, the exposed Auerbach's plexus was seen to be covered by a smooth mat of reticular fibrils, thin enough to allow the detailed examination of the intact nerve plexus and interstitial tissue. ICC were distinguished as small, ovoid cell bodies from which 2-5 long, branching, roughly cylindrical processes emerge, associating to form a complex network. Characteristically, ICC processes participated in the formation of small bundles along their course, individual processes passing from one bundle to another. Cell bodies and processes of ICC were intimately associated with tertiary nerves of Auerbach's plexus. Axons were identified and distinguished from ICC processes by their varicose structure and by their smaller diameters as compared with ICC processes. We found no single axons in our material. The characteristic morphology of ICC clearly distinguished these as a separate cell population different from neurons, glial cells, fibroblasts, and smooth muscle cells. After removal of the mat of reticular fibrils by chemical digestion the detailed organization of the interstitial tissue was preserved. Macrophage-like cells were previously demonstrated by other techniques to constitute a constant and rather dense population of cells in the studied location. As an indication that we preserve the full complement of interstitial cells by our technique, these macrophage-like cells were for the first time identified in material processed for scanning electron microscopy. The cells had characteristically irregular cell surfaces with short, veil-like, folded extensions intertwined between the other cells in the interstices. Our study establishes an improved correlation between results obtained by the application of scanning electron microscopy to dissected tissue and results from light and transmission electron microscopy of the intact tissue.