CHOLINE-ACETYLTRANSFERASE IMMUNOREACTIVITY IN THE HUMAN SMALL AND LARGE-INTESTINE

Background & Aims: Choline acetyltransferase, an enzyme involved in th e synthesis of acetylcholine, is a marker of cholinergic neurons. In t his study, the distribution of choline acetyltransferase immunoreactiv ity in human intestine is described. Methods: Frozen-section and whole -mount preparations of human small and large bowels were made and labe led with antiserum to choline acetyltransferase. Double labeling with antiserum to neuron-specific enolase enabled the proportion of all neu rons that were immunoreactive for choline acetyltransferase to be dete rmined. Results: Nerve fibers, immunoreactive for choline acetyltransf erase, were frequent in the circular and longitudinal muscle layers an d were widespread in the myenteric and submucous plexuses, but none wa s observed in the mucosa. Myenteric neurons, immunoreactive for cholin e acetyltransferase, showed various morphologies, the most common bein g unipolar and having an irregular outline with several short, lamella r processes. Sixty-four percent of all myenteric neurons were immunore active for choline acetyltransferase. Cholinergic submucous neurons we re homogeneous in appearance with oval, smooth cell bodies and filamen tous dendrites and accounted for 53% of all submucous neurons. A numbe r of cells resembling enteroendocrine cells in the epithelium of the s mall and large bowels had intense choline acetyltransferase immunoreac tivity. Conclusions: The majority of neurons in human small and large intestines are cholinergic.