Interstitial cells of Cajal (ICCs) were first described as primitive neurons found within organs innervated by autonomie nerves. In the gut, ICCs are juxtaposed among enteric nerve fibers and smooth muscle cells, suggesting they may modulate enteric neurotransmission and affect motility. The recent discovery of neurokinin-1 receptor (NKrl)-like immunoreactivity (ir) on ICCs has strengthened this hypothesis. This study compared the distribution of NKlr-ir to the staining patterns of other reported markers of ICCs including cholera toxin subunit b (CTB), neuron specific enolase (NSE), NADH diaphorase, NADPH diaphorase, nitric oxide synthase (NOS), and vimentin. Albino male rats were anesthetized and whole mount preparations of myenteric plexus-longitudinal muscle with attached circular muscle were dissected. ICCs were stained using multi-label techniques and cells were visualized with a Sarastro 2000 confocal laser scanning microscope equipped with Image Space software.

In the small intestine, ICCs associated with circular muscle, but not longitudinal muscle, expressed NKlr-ir.