NEURAL SITES OF THE HUMAN COLON COLOCALIZE NITRIC-OXIDE SYNTHASE-RELATED NADPH DIAPHORASE ACTIVITY AND NEUROPEPTIDE-Y

Background/Aims: Nitric oxide and neuropeptide Y (NPY) exert similar b iological actions in the mammalian intestine including modulation of f ood intake, blood flow, motility, and secretion. In addition, these su bstances coexist in submucosal secretomotor neurons of the rodent inte stine. The aim of this study was to determine the relative disposition of elements displaying NPY immunoreactivity and NO synthase-related n icotinamide adenine dinucleotide phosphate (NADPH) diaphorase activity in the nerve networks of the human infant colon. Methods: Transverse and longitudinal sections, treated for immunohistofluorescent detectio n of NPY and then processed for NO synthase-related NADPH diaphorase h istochemistry, were examined. Results: Neural elements containing NPY immunoreactivity and NO synthase-related activity were identified in t he external muscle layers, myenteric plexus, and all nerve layers of t he submucosa, including Henle's plexus, the intermediate nerve layer, and Meissner's plexus. Perivascular NPY-immunoreactive nerve fibers di d not contain NO synthase activity. There were no nitrergic perivascul ar nerve fibers. NPY-immunoreactive endocrine cells in the mucosa did not display NO synthase-related activity. Conclusions: These findings provide anatomical data indicating that NPY immunoreactivity and NO sy nthase-related activity are extensively colocalized in all layers of t he human infant gut wall.