Virchows Arch. A Path. Anat. and Histol. 362, 41--50 (1974) 9 by Springer-Verlag 1974 An Electron Microscope Study of the Auerbach's Plexus and Determination of Substance P of the Colon in Hirschsprung's Disease W. L. Tafuri, T. A. Maria, J. E. H. Pittella, and L. Bogliolo Departamento de Anatomia Patol6gica e Medicina Legal e Centro de Mieroseopia Eletr6nica, Faculdade de Medicina da UFMG., Belo Horizonte, Brasil W. HiM and C. 1%. Diniz Departamento de Bioqulmica e Imunologia do Instituto de Ci~,neias Bioldgieas da UFMG, Belo I-Iorizonte,Brasil Received August 9, 1973 Summary. The AA present a study of 3 cases of Hirsehsprung's disease performed under electron microscopy and whose data seen to suggest that substance P, which is always found in larger amounts in the ganglionic portion of the colon (than in the aganglionic one), may be related with the granular vesicles of Auerbach's plexus. Hirschsprung's disease (congenital megacolon, hypoganglionosis or agangli- onosis of the colon), although clinically and morphologically well known has not yet been thoroughly understood as its etiology, pathogenesis and physiopathology. Ehrenpreis and Pernow (1953) demonstrated that, in the disease, there can be observed small concetrations of substance P in the aganglionic segment of the colon, whereas large ones may be seen in the ganglionic portion. Gadun (1959) reported that such substance must be related to Meissner's plexus. Tafuri (1964) suggested its probable relation to the vesicular component of the intestinal plexuses. In human trypanosomiasis cruzi, where intense hypoganglionosis is present, especially in Auerbach's plexus, quantitative and volumetric alterations of the granular vesicles can be observed in the megaesophagus and megacolon, which could partially account for the peristaltic disturbances oceuring in that disease, ttial and Cols (1973) conducted a quantitative study of substance P in the megaesophagns and megacolon and, based on Tafuri and Cols' work (1971) suggested that such substance might be related with the neurons still at work in the organs. This paper presents, from 3 surgical eases of tiirschsprung's disease, a quanti- tative determination of substance P in the stratum of the muscle layer of both narrowed and dilated zones of the colon, as well as a study of the alterations de- veloped in the ultrastructures of Auerbach's plexus, in the dilated segment of the colon and in the inner nerve fibers of the narrowed zones. Material and Methods The material for this study consisted of snips from 3 surgical cases of congenital megacolon, collected in the surgery room. The procedure was as follows: