The distribution of galanin-immunoreactive nerve fibers in the rat pharynx

Galanin (GAL) consists of a chain of 29/30 amino acids which is widely distributed in the central and peripheral nervous systems. In this study, the distribution of GAL-immunoreactive (-IR) nerve fibers was examined in the rat pharynx and its adjacent regions. GAL-IR nerve fibers were located beneath the epithelium and taste bud-like structure of the pharynx, epiglottis, soft palate and larynx. These nerve fibers were abundant in the laryngeal part of the pharynx, and were rare in other regions. Mucous glands were mostly devoid of GAL-IR nerve fibers. In the musculature of pharyngeal constrictor muscles, many GAL-IR nerve fibers were also located around small blood vessels. However, intrinsic laryngeal muscles contained only a few GAL-IR nerve fibers. The double immunofluorescence method demonstrated that the distribution pattern of GAL-IR nerve fibers was partly similar to that of calcitonin gene-related peptide-IR nerve fibers in the pharyngeal mucosa and muscles. The present findings suggest that the pharynx is one of main targets of GAL-containing nerves in the upper digestive and respiratory systems. These nerves may have sensory and autonomic origins.