Background/aims: The chemical coding of enteric neurons differs significantly among species. In the present study, the innervation of normal human ileum was characterized with respect to its chemical coding.
Methods: The submucosa was subdivided into zones 1-3 based on its thickness and distribution of ganglia. The neuropeptides, calbindin D28k, and protein gene product 9.5 were identified by immunocytochemistry. Nitric oxide production was identified by nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase histochemistry.
Results: Protein gene product 9.5 staining indicated that cell bodies of the submucosa could be subdivided into zones 1-3. Two major groups of submucosal cell bodies contained either substance P/somatostatin/calcitonin gene-related peptide or vasoactive intestinal peptide/neuropeptide Y/calbindin D28k. Gastrin-releasing peptide-containing cell bodies also colocalized with a subgroup of somatostatin cell bodies. No galanin, met-enkephalin, or NADPH diaphorase-positive cell bodies were present. In the myenteric plexus, the two major groups of cell bodies contained either calbindin or NADPH diaphorase. A proportion of the latter group costained with vasoactive intestinal peptide and met-enkephalin. Cell bodies containing substance P, somatostatin, and calcitonin gene-related peptide were present, forming three different subgroups.
Conclusions: Of the species investigated to date, the chemical coding of human ileal cell bodies most closely resembles that of the rat.