Three-dimensional demonstration of the interstitial cells of Cajal associated with the submucosal plexus in guinea-pig caecum.

The guinea-pig caecum was studied by using immunohistochemistry for Kit receptors and nerves to clarify whether interstitial cells of Cajal (ICC) were localized in association with the submucosal plexus (ICC-SP). A large area of the guinea-pig caecum was nearly devoid of longitudinal muscles, because they were concentrated into three bundles of the taenia caeci (coli) and this allowed clear observation of the myenteric and submucosal plexus as separate networks in whole-mount stretch preparations. The myenteric plexus was observed as a loose polygonal network consisting in elongated ganglia and long connecting nerve strands, whereas the submucosal plexus was identified as smaller ovoid ganglia connected to much thinner nerve strands in different tissue layers. Three-dimensional reconstruction of confocal images revealed multipolar-shaped ICC-SP located around the submucosal ganglion in a basket formation. Bipolar ICC-SP were also observed along the connecting nerve strands of the submucosal plexus. The functional involvement of ICC-SP in mucosal activity is discussed in relation to fluid transportation. This three-dimensional study of ICC-SP thus provides a candidate for the most suitable material available for functional experiments examining the physiological significance of ICC-SP.