title: NADPH-diaphorase-positive nerve fibers in smooth muscle layers of opossum esophagus: gradients in density.
abstract: Nitric-oxide-releasing nerves regulate esophageal smooth muscle function. The density of such nerve fibers may differ in the different functional parts of the esophagus. We used both inspection and gray-scale analysis of digitized images to seek differences in density of such nerve fibers, stained for reduced nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-diaphorase), between esophageal body and esophago-gastric sphincter and between smooth muscle layers in the opossum esophagus. Sections of Swiss roll preparations of the entire organ were stained for NADPH-diaphorase and for immunoreactivity to vasoactive intestinal polypeptide (VIP), calcitonin gene-related peptide (CGRP), galanin (GAL), substance P (SP) and constitutive nitric oxide synthase (cNOS). In the circular muscle layer, NADPH-diaphorase-positive fibers were most abundant at the cephalic end of the esophageal body with a significant decline toward and through the esophago-gastric sphincter. In the longitudinal muscle layer and the longitudinally-oriented muscularis mucosae, NADPH-diaphorase-positive nerve fibers were most abundant at the esophago-gastric sphincter with a significant decline toward and through the striated-smooth muscle junction. cNOS immunoreactivity co-localized with NADPH-diaphorase activity. Fibers stained for CGRP immunoreactivity were distributed like the NADPH-diaphorase-positive fibers. Fibers stained for immunoreactivity to the other peptides (VIP, GAL, SP) showed no clear differences in distribution along the esophagus in any of the muscle layers.
authors.affiliation: Department of Internal Medicine, College of Medicine, University of Iowa, Iowa City 52242, USA.
authors.forename: J
authors.initials: J
authors.lastname: Christensen
authors.forename: S
authors.initials: S
authors.lastname: Fang
authors.forename: G A
authors.initials: GA
authors.lastname: Rick
mesh_terms: D000594:Amino Acid Oxidoreductases / Q000378:metabolism; D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism; D004947:Esophagus / Q000201:enzymology* / Q000294:innervation*; D019004:Galanin; D005769:Gastrointestinal Motility / Q000502:physiology; D007150:Immunohistochemistry; D009130:Muscle, Smooth / Q000201:enzymology* / Q000294:innervation*; D009252:NADPH Dehydrogenase / Q000378:metabolism*; D009412:Nerve Fibers / Q000201:enzymology*; D009479:Neuropeptides / Q000378:metabolism; D019001:Nitric Oxide Synthase; D009893:Opossums / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism; D013373:Substance P / Q000378:metabolism; D014660:Vasoactive Intestinal Peptide / Q000378:metabolism
chemical_list: D009479:Neuropeptides; D010455:Peptides; D013373:Substance P; D014660:Vasoactive Intestinal Peptide; D019004:Galanin; D019001:Nitric Oxide Synthase; D000594:Amino Acid Oxidoreductases; D009252:NADPH Dehydrogenase; D015740:Calcitonin Gene-Related Peptide