Topographical distribution of neuropeptide-containing nerve fibers in the rat stomach: A quantitative analysis using antibodies against protein gene product 9.5 and gastric mucins

In the rat cardia, corpus, and pyloric antrum identified with antibodies against the gastric mucins (RGM 25, RGM 26), the density of eight neuropeptides, substance P (SP), calcitonin gene-related peptide (CGRP), vasoactive intestinal polypeptide (VIP), neuropeptide Y (NPY), galanin (GAL), somatostatin (SOM), leucine-enkephalin, and methionine-enkephalin (1-ENK and m-ENK) containing nerve fibers was expressed as the percentage of the total nerve fibers demonstrated by protein gene product (PGP) 9.5 immunoreactivity for a quantitative representation of these peptidergic fibers. In the lamina propria and the submucosa of the cardia, corpus, and pyloric antrum, VIP and CGRP fibers were more numerous than the other neuropeptides. In the smooth muscle layer of the corpus and antrum, VIP, NPY, and GAL fibers were numerous, and VIP, NPY and GAL immunoreactive ganglion cells were also found in the myenteric plexus. The density of VIP fibers in the lamina propria of the cardia, corpus, and antrum was 67.8+/-18.7%, 88.9+/-17.3%, and 91.8+/- 16.7%, respectively, and that of CGRP fibers was 40.3 +/-6.2%, 58.7 +/- 11.3%, and 66.3 +/- 14.3%, respectively. The density of SP, NPY, and GAL fibers in the lamina propria of the cardia, corpus, and antrum was below 20%. In the submucosus layer, the density of VIP fibers was 53.5+/-17.2%, 52.8+/-12.7%, and 52.6+/-7.2%, respectively, and that of CGRP fibers was 50. 8+/-10.1%, 50.3+/-9.6%, and 49.3+/-8.0%, respectively. In the smooth muscle layer, the density of VIP, NPY, and GAL fibers in the corpus was 87.2+/-12.7%, 80.5+/-15.8%, and 72.8+/-11.9%, respectively, and that in the antrum was 95.5+/-12.3%, 83.2+/-9.8%, and 87.3+/-12.2%, respectively. The density of SP and CGRP fibers in the corpus and antrum was below 20%. SOM, 1-ENK, and m-ENK fibers were scarce (<10%) in the smooth muscle layer. The present quantitative examination made it possible to perform a numerical analysis of peptidergic fibers in the different areas of the rat stomach, and could be an indication of topographic difference in the gastric functions.