Some characteristics of the muscularis mucosae of the cat lower esophageal sphincter

Localization of substance P (SP)-immunoreactivity in the myenteric plexus of the rat esophagus

The present immunohistochemical study was performed to examine the number, distribution, and chemical coding of intrinsic substance P (SP) neurons and nerve fibers within the esophagus and discuss their functional roles. Many SP neurons and nerve fibers were found in the myenteric plexus, and the SP neurons gradually decreased from the oral side toward the aboral side of the esophagus. Double-immunolabeling showed that most SP neurons were cholinergic (positive for choline acetyltransferase), and few were nitrergic (positive for nitric oxide synthase). Some cholinergic SP nerve terminals surrounded cell bodies of several myenteric neurons. In the muscularis mucosa and lower esophageal sphincter, and around blood vessels, numerous SP nerve endings were present, and many of them were cholinergic. Also, SP nerve endings were found on only a few motor endplates of the striated muscles, and most of them were calcitonin gene-related peptide (CGRP)-positive. Retrograde tracing using Fast Blue (FB) showed that numerous sensory neurons in the dorsal root ganglia (DRGs) and nodose ganglion (NG) projected to the esophagus, and most FB-labeled SP neurons were CGRP-positive. These results suggest that the intrinsic SP neurons in the rat esophagus may play roles as, at least, motor neurons, interneurons, and vasomotor neurons, which are involved in local regulation of smooth muscle motility, neuronal transmission, and blood circulation, respectively. Moreover, SP nerve endings on only a minority of motor endplates may be extrinsic, derived from DRGs or NG, and possibly detect chemical circumstances within motor endplates to modulate esophageal motility.

Effects of chronic ethanol consumption on rat upper gastrointestinal system: functional and histologic findings

The purpose of the present study was to determine the effect of chronic alcohol consumption on reactivity of esophageal tunica muscularis mucosae (TMM) and lower esophageal sphincter (LES) smooth muscle. Six male rats in alcohol-fed group received ethanol (7.2% v/v) in a modified liquid diet for 4 weeks. Two control groups were used; six rats in the standard diet-fed group received rat chow and water for 4 weeks. Six rats in sucrose-fed group were given sucrose and received a liquid diet. The smooth muscle reactivity of TMM and LES strips from ethanol-fed and control animals was evaluated in organ chambers. Also histologic study was undertaken to show effects of chronic alcohol consumption. Maximum contractile responses of TMM to KCl and carbachol were decreased in the ethanol-fed group compared to the control groups. Relaxant responses to serotonin were decreased in the ethanol-fed group compared to the control groups. In TMM, isoproterenol- and papaverine-induced relaxant responses were similar in the ethanol-fed and control groups. In LES smooth muscle, relaxant responses to papaverine or isoproterenol were similar in the control groups and the ethanol-fed group. There was no change in agonist potency among the groups. The relaxation response elicited by nicotine and sodium nitroprusside (SNP) or contractile response elicited by carbachol and 80 mM KCl was decreased with maximum responses and pD(2) values, in the ethanol-fed group compared to that of the control groups in LES. Decreased nNOS immunoreactivity in myenteric plexus was found in alcohol-exposed group compared to control groups. Our findings suggest that chronic alcohol consumption impairs relaxant and contractile responses of both TMM and LES smooth muscle and it may contribute to gastroesophageal reflux commonly seen after alcohol binges.

Mucosa of the guinea pig gastric corpus is innervated by myenteric neurones with specific neurochemical coding and projection preferences

The present study identified and characterised myenteric neurones involved in the innervation of the gastric mucosa. We applied retrograde neuronal tracing methods by using the dye DiI (1,1'-didodecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorat) in combination with the immunohistochemical demonstration of choline acetyltransferase (ChAT), enkephalin (ENK), neuropeptide Y (NPY), nitric oxide synthase (NOS), substance P (SP), and vasoactive intestinal peptide (VIP). This method showed distinct neurochemical coding of DiI-labelled neurones with projections to the mucosa (mucosa neurones): ChAT/- (indicating the presence of ChAT only, 32%), ChAT/NPY/ +/- VIP (22%), NOS/NPY/ +/- VIP (19%), ChAT/SP/ +/- ENK (12%), NOS/- (indicating the presence of NOS only, 8%), or ChAT/ENK (4.6%). DiI-labelled mucosa neurones did not contain calretinin, serotonin, or somatostatin. All ChAT population had primarily ascending projections, whereas the NOS populations had mainly descending projections. Both were further classified as longitudinally and circumferentially projecting neurones, the latter having projection preferences towards the lesser or greater curvature. All subpopulations exhibited projection preferences. Nitrergic projections primarily arose from cell bodies located at the lesser curvature. ChAT/- projections, which dominated the cholinergic pathway, mainly arose from cell bodies located at the greater curvature. The other major cholinergic pathway with the code ChAT/NPY/ +/- VIP consisted of neurones located mainly at the lesser curvature. The results suggest specific coding of gastric myenteric neurones with projections to the mucosa. Polarised projections consisted of ascending cholinergic and descending nitrergic neurones; the additional presence of NPY/VIP was a prominent feature in both pathways. Chemical coding, polarity, and projection preferences of enteric pathways to the gastric mucosa are remarkably different from those of other regions in the gut.