Neural sites of the human colon colocalize nitric oxide synthase-related NADPH diaphorase activity and neuropeptide Y

Abstract

Background/Aims: Nitric oxide and neuropeptide Y (NPY) exert similar biological actions in the mammalian intestine including modulation of food intake, blood flow, motility, and secretion. In addition, these substances coexist in submucosal secretomotor neurons of the rodent intestine. The aim of this study was to determine the relative disposition of elements displaying NPY immunoreactivity and NO synthase-related nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase activity in the nerve networks of the human infant colon. Methods: Transverse and longitudinal sections, treated for immunohistofluorescent detection of NPY and then processed for NO synthase-related NADPH diaphorase histochemistry, were examined. Results: Neural elements containing NPY immunoreactivity and NO synthase-related activity were identified in the external muscle layers, myenteric plexus, and all nerve layers of the submucosa, including Henle's plexus, the intermediate nerve layer, and Meissner's plexus. Perivascular NPY-immunoreactive nerve fibers did not contain NO synthase activity. There were no nitrergic perivascular 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 synthase-related activity are extensively colocalized in all layers of the human infant gut wall.