Occurrence and Distribution of Substance P- and CGRP-Containing Nerve Fibers in Gastric Mucosa: Species Differences

Abstract

The gastric mucosa is rich in acetylcholinesterase-positive nerve fibers (cf. Schofield, 1968: Yamaguchi et al., 1974; Lechago and Barajas, 1976) and in fibers storing neuropeptides (Schultzberg et al., 1980; Ekblad, 1985; Keast et al., 1985; Tsutsumi and Hara, 1989). In the mucosa of the rat stomach, fibers containing VIP and GRP/bombesin immunoreactivity are notably numerous (Dockray et al., 1979; Ekblad et al, 1985; Iwanaga et al., 1988), while fibers storing other neuropeptides such as substance P (SP), neuropeptide Y and enkephalin are less frequent (Schultzberg et al., 1980; Ekblad et al, 1985). Keast et al. (1985) noted marked species differences in the density of SP-containing nerve fibers in the gastric mucosa. Thus, such fibers were fairly numerous in man, moderate in number in rat and guinea pig and absent altogether from the mucosa of the dog stomach. Also the density of calcitonin gene-related peptide (CGRP)-containing fibers in the gastric mucosa varies greatly among species (own unpublished observations). In the muscle layers and the myenteric ganglia the density of fibers storing SP and CGRP displays less species variation.