Distribution and coexistence of peptides in nerve fibers of the external muscle of the human gastrointestinal tract

Abstract

The nerve fibers that supply the external muscle of the human gastrointestinal tract were examined for their immunoreactivity to the neuropeptides enkephalin, neuropeptide Y, somatostatin, substance P, and vasoactive intestinal peptide, for tyrosine hydroxylase (a catecholamine-synthesizing enzyme), and for coexistence between immunoreactivities in nerve fibers. Studies on coexistence revealed that the majority of reactive nerve fibers could be placed in one of two classes: (a) those fibers with reactivity to enkephalin or substance P, or both, and (b) fibers containing one or both of the peptides neuropeptide Y and vasoactive intestinal peptide. Many fibers immunoreactive for vasoactive int..