Neuronal markers in Hirschsprung's disease with special reference to neuropeptides

Hirschsprung's disease (Megacolon congenitum) is characterized by a sustained contraction of a segment of the large intestine and a consequent enlargement of the preceding gut segment. Morphologically, Hirschsprung's disease is characterized by an absence of neuronal cell bodies in the intramural ganglia of the contracted segment. An additional characteristic finding is the presence of enlarged nerve trunks in the submucosa and in the layer separating the circular and longitudinal muscle layers. These nerve trunks contain abundant acetylcholine esterase (AChE)-positive nerve fibers. The nerve fiber hyperplasia together with an increased amount of acetylcholine as well as AChE activity in the aganglionic segment suggests a cholinergic hyperinnervation. There are other reports claiming an adrenergic hyperinnervation in the aganglionic segment. Recent studies on the peptidergic innervation of the afflicted intestinal segment have demonstrated marked reduction in the density of nerve fibers storing vasoactive intestinal peptide (VIP), substance P (SP), enkephalin and gastrin releasing peptide (GRP). The frequency of nerve fibers storing calcitonin gene-related peptide (CGRP) and galanin seems less affected. Interestingly, nerve fibers storing neuropeptide Y (NPY) are more frequent than normally in the aganglionic segment, the circular muscle being penetrated by numerous NPY-containing nerve fibers. Thus, neuropeptides have turned out to be interesting and promising new markers in the histochemical diagnosis of Hirschsprung's disease. Other possibilities for the histochemical diagnosis includes the immunocytochemical demonstration of general neuronal markers such as neurospecific enolase (NEC), neurofilament and chromogranins. Techniques demonstrating the cholinergic and adrenergic hyperinnervation in the aganglionic intestine such as AChE staining and staining for adrenergic nerves are also of interest for the diagnosis.