Quantitative Estimation and Chemical Coding of Spiny Type I Neurons in Human Intestines

Previous studies have shown that most human myenteric neurons co-staining for vasoactive intestinal peptide (VIP), neuronal nitric oxide synthase (nNOS) and neurofilaments (NF) display the morphology of spiny type I neurons displaying a descending projection pattern. Here, we estimated the proportions of spiny neurons in human intestines, the amount of congruence of VIP/nNOS-immunoreactive with spiny neurons and whether galanin (GAL) is co-localized with VIP. Three sets of colchicine-pretreated and fixed whole mounts of 21 patients or body donors (median age 65 years; 10 female, 11 male) were stained for VIP, nNOS and NF, for VIP, nNOS and the human neuronal protein Hu C/D (HU) as well as for VIP, nNOS and GAL. The majority of VIP/nNOS-co-reactive neurons were spiny neurons (79/80% in small/large intestine, respectively) and the majority of spiny neurons costained for VIP and nNOS (82/69%). Neurons co-immunoreactive for VIP/nNOS/HU amounted to 7 and 4%, respectively. GAL/VIP-co-immunoreactivity was demonstrated in 69 and 27% of spiny neurons, respectively. We conclude that the number of neurons displaying co-reactivity for VIP and nNOS is a quantitative indicator of spiny neurons in both small and large intestine and that the proportion of spiny neurons is about 7% in small and 4% in large intestines. Since nerve fibres co-staining for NF/VIP/nNOS were found mainly in the circular muscle layer but not the surrounding perikarya of spiny neurons, we suggest that they may represent inhibitory motor neurons rather than descending interneurons. Copyright (C) 2010 S. Karger AG, Basel