Comparative Study of Interstitial Cells of Cajal

The cells present in the alimentary canal, contacting both nerve endings and smooth muscle cells and named interstitial cells of Cajal, show different ultrastructural features. A comparative study has been performed in order to see if these differences can be related to the animal species studied or to the interstitial cell localizations inside the muscle wall of the various levels of the alimentary canal or to their contacts with other cells. Only mammals were considered, and rat, mouse, hedgehog and man have been studied. All the localizations where interstitial cells of Cajal have usually been found were considered: esophagus (body and lower sphincter), stomach (gastric extent of the lower esophageal sphincter, fundus and corpus), small intestine and colon. From this comparison a correlation was found between the morphology and the location of interstitial cells. On the contrary, the morphological differences existing between animal species do not seem to be that consistent. Moreover, the number of contacts between interstitial cells and between these and smooth muscle cells and nerve endings varies according to the interstitial cell location and morphology. It is concluded that the chain nerve endings----interstitial cells of Cajal----smooth muscle cells is not morphologically identical at each gastrointestinal level, and this finding is considered very important in interpreting the role played by the interstitial cells of Cajal in gastrointestinal motility.