Calcitonin gene-related peptide-alpha receptor binding sites in the gastrointestinal tract.

Calcitonin gene-related peptide-alpha (CGRP alpha) is a putative neurotransmitter in the brain and in peripheral tissues. Quantitative receptor autoradiography was used to localize and quantify the distribution of specific binding sites for radiolabeled human CGRP alpha in the canine gastrointestinal tract. The canine gastrointestinal tract was chosen as a model since it is similar in both size and structure to the human gastrointestinal tract. In the stomach CGRP alpha binding sites were localized to smooth muscle cells in the muscularis mucosa and muscularis externa, the smooth muscle and endothelium of medium and small arteries, neurons in the myenteric plexus, mucosal epithelial cells and the germinal centers of lymph nodules. In the intestines, the prominent cells types expressing CGRP alpha receptors were myenteric neurons and the germinal centers of lymph nodules. Since previous studies have demonstrated that CGRP-containing sensory neurons innervate the muscularis externa in the stomach and since CGRP alpha receptors are expressed by smooth muscle cells in the muscularis externa, these results suggest that sensory neurons may directly regulate gastric motility by releasing CGRP. In correlation with previous physiological data, the present study suggests that CGRP is involved in the regulation of a variety of gastrointestinal functions including gastric motility, mucosal ion transport, hemodynamics, digestive enzyme secretion, neuronal excitability, and the inflammatory and immune response.

Vasoactive intestinal polypeptide receptor binding sites in the human gastrointestinal tract: localization by autoradiography.

Vasoactive intestinal polypeptide (VIP) is a putative neurotransmitter in both the brain and peripheral tissues. To define possible target tissues of VIP we have used quantitative receptor autoradiography to localize and quantify the distribution of [125I]VIP receptor binding sites in histologically normal human surgical specimens. While the distribution of VIP binding sites was different for each gastrointestinal segment examined, specific vasoactive intestinal polypeptide binding sites were localized to the mucosa, the muscularis mucosa, the smooth muscle of submucosal arterioles, the circular and longitudinal smooth muscle of the muscularis externa, the myenteric plexus, and lymph nodules. In most segments, the mucosal layer expressed the highest concentration of VIP binding sites, with the duodenal and jejunal mucosa showing the highest density of receptors. These results identify putative VIP target tissues in the human gastrointestinal tract. In correlation with physiological data, VIP binding sites appear to be involved in the regulation of a variety of gastrointestinal functions including mucosal ion transport, gastric secretion, hemodynamic regulation, gastric and intestinal motility, neuronal excitability, and modulation of the immune system.

Epidermal growth factor receptors in the canine antrum.

In this study we localized receptor binding sites for 125I-human epidermal growth factor (hEGF) in the antrum of the adult canine stomach. High levels of specific 125I-hEGF binding sites were observed over the mucosa and muscularis mucosa, whereas specific binding sites were not detectable over the submucosa, external circular and longitudinal muscle or myenteric neurons. These results are in agreement with previous studies which indicated that EGF stimulates the proliferation of cultured epithelial cells and inhibits gastric acid secretion. This suggests that EGF may be a useful therapeutic agent in the healing of gastric ulcers.

Substance P and substance K receptor binding sites in the human gastrointestinal tract: localization by autoradiography.

Quantitative receptor autoradiography was used to localize and quantify the distribution of binding sites for 125I-radiolabeled substance P (SP), substance K (SK) and neuromedin K (NK) in the human GI tract using histologically normal tissue obtained from uninvolved margins of resections for carcinoma. The distribution of SP and SK binding sites is different for each gastrointestinal (GI) segment examined. Specific SP binding sites are expressed by arterioles and venules, myenteric plexus, external circular muscle, external longitudinal muscle, muscularis mucosa, epithelial cells of the mucosa, and the germinal centers of lymph nodules. SK binding sites are distributed in a pattern distinct from SP binding sites and are localized to the external circular muscle, external longitudinal muscle, and the muscularis mucosa. Binding sites for NK were not detected in any part of the human GI tract. These results demonstrate that: 1) surgical specimens from the human GI tract can be effectively processed for quantitative receptor autoradiography; 2) of the three mammalian tachykinins tested, SP and SK, but not NK binding sites are expressed in detectable levels in the human GI tract; 3) whereas SK receptor binding sites are expressed almost exclusively by smooth muscle, SP binding sites are expressed by smooth muscle cells, arterioles, venules, epithelial cells of the mucosa and cells associated with lymph nodules; and 4) both SP and SK binding sites expressed by smooth muscle are more stable than SP binding sites expressed by blood vessels, lymph nodules, and mucosal cells.

Vasoactive intestinal peptide (VIP) receptors in the canine gastrointestinal tract.

Vasoactive intestinal peptide (VIP) is a putative neurotransmitter in both the brain and peripheral tissues. To define possible target tissues of VIP we have used quantitative receptor autoradiography to localize and quantify the distribution of 125I-VIP receptor binding sites in the canine gastrointestinal tract. While the distribution of VIP binding sites was different for each segment examined, specific VIP binding sites were localized to the mucosa, the muscularis mucosa, the smooth muscle of submucosal arterioles, lymph nodules, and the circular and longitudinal smooth muscle of the muscularis externa. These results identify putative target tissues of VIP action in the canine gastrointestinal tract. In correlation with physiological data, VIP sites appear to be involved in the regulation of a variety of gastrointestinal functions including epithelial ion transport, gastric secretion, hemodynamic regulation, immune response, esophageal, gastric and intestinal motility.

Immunocytochemical localization of glycine in a subset of cartwheel cells of the dorsal cochlear nucleus in rats.

Glycine is an inhibitory neurotransmitter and a glutamate cofactor for N-methyl-D-aspartate (NMDA) receptors in the central nervous system. The distribution of glycine in the auditory system will therefore provide clues as to synaptic mechanisms underlying auditory signal processing. Previous studies have reported the immunocytochemical presence of glycine in the dorsal cochlear nucleus of a variety of mammals, but the specificity with respect to particular cell types has proven elusive at the light microscopic level. We sought to identify cell types in the superficial regions of the dorsal cochlear nucleus that were immunoreactive to glycine using light and electron microscopy in the rat. At the light microscopic level, glycine immunoreactivity was present in some but not all medium-sized cells in layers I and II. The somata of pyramidal and granule cells were not stained. At the electron microscopic level, using previously published ultrastructural criteria, we examined the glycine-labeled cells and determined that many but not all cartwheel cells were labeled. We also observed unlabeled unipolar brush cells, Golgi cells, and stellate cells. As some of the labeled cells could not be identified, we could not determine whether unipolar brush cells, Golgi cells or stellate cells had both labeled and unlabeled subpopulations. Our observations indicate that within the population of cartwheel cells, only a subset are glycine-immunoreactive.

Receptor binding sites for substance P, but not substance K or neuromedin K, are expressed in high concentrations by arterioles, venules, and lymph nodules in surgical specimens obtained from patients with ulcerative colitis and Crohn disease.

Several lines of evidence indicate that tachykinin neuropeptides [substance P (SP), substance K (SK), and neuromedin K (NK)] play a role in regulating the inflammatory and immune responses. To test this hypothesis in a human inflammatory disease, quantitative receptor autoradiography was used to examine possible abnormalities in tachykinin binding sites in surgical specimens from patients with inflammatory bowel disease. Surgical specimens of colon were obtained from patients with ulcerative colitis (n = 4) and Crohn disease (n = 4). Normal tissue was obtained from uninvolved areas of extensive resections for carcinoma (n = 6). In all cases, specimens were obtained less than 5 min after removal to minimize influences associated with degradation artifacts and were processed for quantitative receptor autoradiography by using 125I-labeled Bolton-Hunter conjugates of NK, SK, and SP. In the normal colon a low concentration of SP receptor binding sites is expressed by submucosal arterioles and venules and a moderate concentration is expressed by the external circular muscle, whereas SK receptor binding sites are expressed in low concentrations by the external circular and longitudinal muscle. In contrast, specific NK binding sites were not observed in any area of the human colon. In colon tissue obtained from ulcerative colitis and Crohn disease patients, however, very high concentrations of SP receptor binding sites are expressed by arterioles and venules located in the submucosa, muscularis mucosa, external circular muscle, external longitudinal muscle, and serosa. In addition, very high concentrations of SP receptor binding sites are expressed within the germinal center of lymph nodules, whereas the concentrations of SP and SK binding sites expressed by the external muscle layers are not altered significantly. These results demonstrate that receptor binding sites for SP, but not SK or NK, are ectopically expressed in high concentrations (1000-2000 times normal) by cells involved in mediating inflammatory and immune responses. These data suggest that SP may be involved in the pathophysiology of inflammatory bowel disease and might provide some insight into the interaction between the nervous system and the regulation of inflammation and the immune response in human inflammatory disease.