• enteric nervous system;
  • excitatory and inhibitory motor neurons;
  • interstitial cells of Cajal;
  • PDGFRα+ cells


Background  Morphological studies have revealed a close anatomical relationship between enteric nerve terminals and intramuscular ICC (ICC-IM) which supports a role for ICC-IM as intermediaries in enteric motor neurotransmission. Recently, a second type of interstitial cell previously described as ‘fibroblast-like’ but can now be identified by platelet-derived growth factor receptor-α expression, has also been implicated in enteric neurotransmission in rodents. The present study was performed to determine if enteric nerve fibers form close anatomical relationships with ICC and PDGFRα+ cells throughout the primate GI tract.

Methods  Immunohistochemical experiments and confocal microscopy were performed to examine the relationship between excitatory and inhibitory motor neurons, ICC and PDGFRα+ cells throughout the monkey GI tract.

Key Results  The pan neuronal marker. Protein gene product 9.5 (PGP9.5) was used to label all enteric neurons and substance-P (sub-P) and neuronal nitric oxide synthase (nNOS) to label excitatory and inhibitory neurons, respectively. Double labeling with Kit revealed that both classes of nerve fibers were closely apposed with ICC-IM in the stomach, small intestine and colon (taenia and inter-taenia regions), but not with ICC at the level of the myenteric plexus (ICC-MY). Varicose enteric nerve fibers were closely associated with ICC-IM for distances up to 250 μm. Both excitatory and inhibitory nerve fibers were also closely apposed to PDGFRα+ cells throughout the primate GI tract.

Conclusions & Inferences  The close anatomical relationship between enteric nerve fibers and ICC-IM and PDGFRα+ cells throughout the GI tract of the Cynomolgus monkey provides morphological evidence that these two classes of interstitial cells may provide a similar physiological function in primates as has been attributed in rodent animal models.