125I-labeled galanin binding sites in congenital innervation defects of the distal colon

Abstract

Neuropeptides have turned out to be promising new parameters, in addition to the routinely performed histochemical diagnosis, of Hirschsprung's disease (HD). Studies of the peptidergic innervation of the affected intestinal segment of patients with HD have demonstrated a marked reduction in the density of several neuropeptide-containing nerve fibers. The frequency of nerve fibers storing the neuropeptide galanin (GAL) was found to be unchanged or slightly reduced in HD, but nothing is known about the occurrence of GAL receptors. In this study, in vitro receptor autoradiography using (125)I-labeled GAL and GAL immunofluorescence have been performed on frozen tissue sections from colon biopsies of 10 patients diagnosed with HD, 8 patients with intestinal neuronal dysplasia (IND B) and 20 patients with chronic obstruction but normal innervation. Binding sites were mainly detected in the mucosal and muscular layer, in acetylcholinesterase-positive nerve fiber bundles and ganglia within the submucosal layer and in close association to blood vessels. An increased population of GAL receptor positive, parasympathetic nerve fibers was seen in the aganglionic segment of HD as compared to controls and IND B. In contrast, GAL immunostaining which was unchanged in HD revealed a significant lack of GAL-positive structures in IND B colon biopsies. Colocalization of GAL and GAL binding sites was only observed in thick nerve fibers in the submucosa. The presence of GAL binding sites in different cellular structures suggests an involvement of GAL in various physiological functions of the gastrointestinal tract.