Neuropeptide-containing nerve fibers in the pharynx of the rabbit.

The distribution of peptide-containing nerve fibers in the pharyngeal region of rabbits was studied by immunocytochemistry. Neuropeptide Y (NPY)-containing fibers were numerous around blood vessels and moderate in number among bundles of striated muscle fibers. A few NPY-containing fibers were seen around seromucous glands and beneath the epithelium. Nerve fibers containing vasoactive intestinal peptide (VIP) were numerous around seromucous glands and moderate in number around blood vessels, bundles of muscle, and in the subepithelial layer. A few nerve fibers containing substance P (SP) were seen around blood vessels, seromucous glands, among bundles of muscle, and in the subepithelial layer. Nerve fibers containing calcitonin gene-related peptide (CGRP) were numerous. They were distributed close to blood vessels, among bundles of muscle, in the subepithelial layer, and within the epithelium. A conspicuous finding was the occurrence of CGRP within motor end plates of striated muscle.