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PubMed1992

Effect of inflammation of enteric nerves. Cytokine-induced changes in neurotransmitter content and release.

The results of our previously published work provide evidence of inflammation-induced functional disturbances in the enteric nervous system. Data presented in this paper describe our preliminary results indicating that the altered function in enteric nerves in the nematode-infected rat model of intestinal inflammation is mediated by interleukin-1. This is based on the ability of the exogenous cytokine to mimic changes observed in the model, and on the ability of a specific IL-1 antagonist to attenuate these changes. In addition, we have identified mechanisms underlying the actions of IL-1 in the myenteric plexus. Our data are consistent with a direct interaction between the cytokine and neural membranes. In addition, the delayed effect of IL-1 beta on neurotransmitter release appears to be due to the release of endogenous IL-1, most likely from macrophage-like cells in the myenteric plexus (Fig. 3). If such cells possess receptors for neuropeptides, as has been found with macrophages elsewhere in the gut, a neuroimmune axis would exist in the myenteric plexus. Thus, the finding of a source of IL-1 in the plexus of the noninflamed intestine invites speculation on a neuromodulatory role of the cytokine within the enteric nervous system.

Animals↗

PubMed1993

PYY: a neuropeptide in the canine enteric nervous system.

This study re-examined the anatomical locations of PYY in the canine gastrointestinal tract. Immunohistochemical studies with two relatively selective PYY antisera demonstrated PYY-LI immunoreactivity in nerve cell bodies and nerve fibres in the intestinal and gastric myenteric plexus and the intestinal submucosal plexus and in nerve fibres of the intestinal deep muscular plexus. Immunoreactive PYY-LI was also present in ileal endocrine cells. All PYY-LI immunoreactivity was completely abolished by pre-incubation of the antibodies with synthetic PYY but was unaltered by pre-incubation with synthetic NPY. Individual synaptosomal preparations obtained from canine intestinal and gastric myenteric plexus, and intestinal deep muscular plexus and submucous plexus, contained considerable quantities of PYY-LI which, on reverse-phase HPLC, co-eluted with a synthetic canine/porcine PYY standard. In contrast, isolated myenteric ganglia from rat and guinea pig did not contain detectable amounts of PYY-LI. These studies demonstrate that PYY is not confined to distal intestinal endocrine cells in the dog but is also an enteric neuropeptide with maximal concentrations being present in the intestinal myenteric plexus.

Animals↗

PubMed1991

Familial enteric neuropathy with pseudoobstruction.

We report a case of autosomal dominant chronic intestinal pseudoobstruction secondary to a familial enteric neuropathy. Esophagogastrointestinal manometry studies in the index case showed decreased postprandial contractile frequency with normal amplitude of pressure activity in the stomach and small bowel. Pupillary function and autonomic reflexes were all normal, excluding an extrinsic autonomic neuropathy of the viscera. Histologic examination of the small intestine by hematoxylin and eosin stains revealed normal smooth muscles but a reduced number of neurons in the myenteric plexus without inflammatory cells or neuroNal intranuclear inclusions. Histologic examination of the myenteric plexus using the sections taken along the longitudinal axis of the intestine, stained with silver by the Smith technique, disclosed decreased numbers of argyrophilic neurons and degeneration of neurons and axons; however, there was no reactive increase in the number of glial cell nuclei. The patient's mother had suffered from chronic intestinal pseudoobstruction, which did not abate following extensive small bowel resection. This is the third family reported with an autosomal dominant enteric neuropathy unassociated with evidence of extrinsic autonomic or peripheral neuropathy. Subtotal resection of the small bowel was followed by recurrence of the pseudoobstruction syndrome in both affected members of the family.

Adult↗

PubMed1998

Morphological and immunohistochemical identification of neurons and their targets in the guinea-pig duodenum.

Nerve circuits within the proximal duodenum were investigated using a combination of immunohistochemistry for individual neuron markers and lesion of intrinsic nerve pathways to determine axon projections. Cell shapes and axonal projections were also studied in cells that had been injected with a marker substance. Several major neuron populations were identified. Calbindin immunoreactivity occurred in a population of myenteric nerve cells with Dogiel type II morphology. These had axons that projected to other myenteric ganglia, to the circular muscle and to the mucosa. All were immunoreactive for the synthesizing enzyme for acetylcholine, choline acetyltransferase, and some were also immunoreactive for calretinin. Myenteric neurons with nitric oxide synthase immunoreactivity projected anally to the circular muscle. These were also immunoreactive for vasoactive intestinal peptide, and proportions of them had enkephalin and/or neuropeptide Y immunoreactivity. It is suggested that they are inhibitory motor neurons to the circular muscle. A very few (about 2%) of nitric oxide synthase-immunoreactive neurons had choline acetyltransferase immunoreactivity. Tachykinin (substance P)-immunoreactive nerve cells were numerous in the myenteric plexus. Some of these projected orally to the circular muscle and are concluded to be excitatory motor neurons. Others projected to the tertiary plexus which innervates the longitudinal muscle and others provided terminals in the myenteric plexus. Two groups of descending interneurons were identified, one with somatostatin immunoreactivity and one with vasoactive intestinal peptide immunoreactivity. The two most common nerve cells in submucous ganglia were neuropeptide Y- and vasoactive intestinal peptide-immunoreactive nerve cells. Both provided innervation of the mucosa. There was also a population of calretinin-immunoreactive submucous neurons that innervated the mucosal glands, but not the villi. Comparison with the ileum reveals similarities in the chemistries and projections of neurons. Differences include the almost complete absence of nitric oxide synthase immunoreactivity from vasoactive intestinal peptide-immunoreactive interneurons in the duodenum, the projection of calbindin-immunoreactive Dogiel type II neurons to the circular muscle and the absence of tachykinin-immunoreactivity from these neurons.

Animals↗

PubMed1994

Survival of the population of NADPH-diaphorase stained myenteric neurons in the small intestine of aged rats.

NADPH-diaphorase staining was performed on wholemount preparations of the muscularis externa (which includes the myenteric plexus) of the rat small intestine taken from animals of 4, 24 and 30 months of age. A population of NADPH-diaphorase-stained neuron cell bodies was observed predominantly in the ganglia of the plexus. There were also many stained axons throughout the plexus and in the muscularis at all ages. The distribution of stained neurons around the circumference of the intestine was the same at all ages, being greater on the mesenteric than on the anti-mesenteric aspect. The numbers of NADPH-diaphorase-positive neurons in the myenteric plexus were counted by a systematic random sampling method. At 4 months there were 3716 +/- 219 stained neurons per cm2. There was no difference in the neuron numbers between the 24- and 30-month animals but they were decreased in number by 15.01% in comparison to the 4-month rats when growth in the length of the intestine was taken into account. This reduction in neuron numbers is markedly less than that previously recorded for the total numbers of myenteric neurons in the aged rat small intestine suggesting that the NADPH-diaphorase neurons are relatively spared in old age. The density of NADPH-diaphorase-positive varicose axons in the myenteric plexus and in the muscularis appeared to be slightly greater in the aged animals. These results provide evidence that the majority of the population of the myenteric NADPH-diaphorase-stained neurons, which may play a part in relaxation of the gut, survive in old age.

Aging↗

PubMed2001

Gene expression and localization of GABA(C) receptors in neurons of the rat gastrointestinal tract.

The effects of GABA in the CNS are mediated by three different GABA receptors: GABA(A), GABA(B) and GABA(C) receptors. GABA(A) and GABA(B) receptors, but not yet GABA(C) receptors, have been demonstrated in the enteric nervous system, where GABA has been proposed to be a transmitter. The purpose of this study was to determine whether GABA(C) receptors are present and thus may play a role in mediating the effects of GABA in the myenteric plexus of the rat gastrointestinal tract. We examined the expression of the three known GABA(C) receptor subunits, rho1, rho2 and rho3, in the rat duodenum, ileum and colon using the reverse transcriptase-polymerase chain reaction. We determined the localization of GABA(C) receptors in the myenteric plexus of these regions using two different antisera directed against GABA(C) receptor subunits. The polymerase chain reaction revealed that all three subunits were expressed in the gastrointestinal tract. When the layers of the intestine were separated and the layer containing myenteric neurons was assayed, the rho3 subunit was found in the ileum and colon, whereas rho1 was expressed in the duodenum and weakly in the colon and rho2 was expressed in the ileum. Immunocytochemistry revealed numerous labeled neurons in the myenteric plexus of each region. Colocalization showed that a large proportion of calbindin plus calretinin immunoreactive neurons (intrinsic primary afferent neurons) were immunoreactive for the GABA(C) receptor, and that 56% of nitric oxide synthase immunoreactive neurons (inhibitory motor neurons) exhibited the receptor. These results indicate that GABA(C) receptors of differing subunit compositions are expressed by neurons in the rat gastrointestinal tract. The effects of GABA on intrinsic sensory and on inhibitory motor neurons are likely to be mediated in part through GABA(C) receptors.

Animals↗

PubMed1993

Cisapride treatment of constipation in Parkinson's disease.

Constipation, a frequent symptom in Parkinson's disease (PD), is probably caused by degeneration of the autonomic nervous system, particularly the myenteric plexus. Cisapride is a drug that causes increased release of acetylcholine in the myenteric plexus. In a pilot study, cisapride therapy was investigated in 20 PD patients, 10 women and 10 men, who suffered from delayed intestinal transit. In all cases, cisapride therapy was associated with a significant acceleration of colonic transit, as measured by radioopaque pellets viewed on radiographs. Pellet count fell from a mean of 53.8 pretreatment to 30.4 after cisapride treatment. No adverse reaction and no "overshoot affects," such as diarrhea, were seen. Our findings suggest that cisapride may alleviate the constipation associated with Parkinson's disease.

Acetylcholine↗

PubMed1997

Distribution of enkephalin-like immunoreactivity in the cat digestive tract.

Immunohistochemical investigations were carried out to determine the pattern of distribution of methionine- and leucine-enkephalin-like materials in the cat pylorus, duodenum, ileum and proximal and distal colon. The present results indicate that leucine-enkephalin-like materials are less densely distributed than methionine-enkephalin-like materials, but that the two patterns of distribution show some similarities. Considerable regional differences exist however in the distribution of these enkephalin-like materials in the muscular layers. In the duodenum, ileum and proximal colon, the immunoreactivity was mainly confined to the myenteric plexus and the circular muscle layer, where it was present in nerve cell bodies and in numerous fibres. In the longitudinal muscle and submucous layers, a few immunoreactive fibres were observed which sometimes surrounded blood vessels. In the pylorus and the distal colon, however, numerous immunoreactive fibres were observed in the longitudinal and circular muscle layers; the immunoreactivity was detected in the cell bodies of numerous myenteric plexus neurons but those of only a few submucous plexus neurons. In addition, the pylorus tissues contained immunoreactive plexi which were localized either within the longitudinal muscle or between the serosa and the longitudinal muscle layer. These plexi were connected to the myenteric plexus by immunoreactive nerve strands. In all the small intestinal segments studied, numerous immunoreactive varicosities were present in the deep muscular plexus, in the inner part of the circular muscle layer. Our results suggest that in cats, the nervous control of external muscular layers mediated by enkephalins shows regional differences. In the pylorus and the distal colon, it involves both the longitudinal and circular muscle layers, whereas in other intestinal segments, only the circular muscle layer is involved.

Animals↗

PubMed1983

Peptide-containing nerve fibres in the gut wall in Crohn's disease.

Neurones containing VIP, substance P, or enkephalin were studied by immunocytochemistry in intestinal specimens from 27 patients with Crohn's disease. Also several endocrine cell systems in the gut were examined. The results were compared with those from a control group of 26 patients. The relative frequency of various endocrine cells did not differ overtly from that in controls. Vasoactive intestinal polypeptide and substance P nerve fibres were distributed in all layers of the gut wall, including the submucosal and myenteric plexuses, whereas enkephalin fibres were restricted to the smooth muscle layer and the myenteric plexus. The distribution and frequency of the peptide-containing nerve fibres were the same in Crohn's disease patients as in control patients. A proportion of these nerve fibres, however, were notably coarse in the Crohn's disease patients. This was particularly apparent in the afflicted parts of the intestine although it was noted also in non-afflicted parts. The concentration of VIP and substance P (expressed as pmol/g wet weight) did not, however, exceed that of the control group.

Adolescent↗

PubMed1972

Ultrastructural and histochemical studies of murine megacolon.

The myenteric plexus of the colon was studied ultrastructurally in a colony of an Ls Ls strain of mice manifesting a piebald coat color mutation associated with a high incidence of genetically determined aganglionic megacolon. Ultrastructural studies were histochemically supplemented by the Maillet technic and stains for acetylcholinesterase and catecholamines. The development of megacolon did not appear to require total aganglionosis, since ostensibly aganglionic areas contained rare ganglion cells. In the distal narrowed segment, both cholinergic and adrenergic fibers in the muscularis, submucosa and mucosa were somewhat reduced. In the mouse, the dilated portion showed an abrupt increase in adrenergic fibers. These findings are related to the pathophysiology of the disorder. The increasing degenerative changes seen in myenteric plexus structures from the fetus to adult suggest that aganglionic megacolon may be an abiotrophy, wherein the congenitally deficient myenteric plexus may be unusually predisposed to postnatal injury and degeneration.

Acetylcholinesterase↗

PubMed1997

The mechanism of altered neural function in a rat model of acute colitis.

BACKGROUND & AIMS: Distal colitis induced in rats by trinitrobenzene sulfonic acid (TNBS) causes a suppression of [3H]noradrenaline release from the myenteric plexus, of inflamed distal colon, as well as in noninflamed regions of colon and ileum. The aim of this study was to explore the mechanisms underlying these neural changes in TNBS colitis. METHODS: Colitis was induced by intrarectal administration of TNBS, and the animals were killed on day 5. Inflammation was assessed by measuring myeloperoxidase (MPO) activity, and noradrenaline release was measured as 3H release from rats myenteric plexus preparations preloaded with [3H]noradrenaline. These end points were examined: (1) after administration of the locally active steroid budesonide; (2) in congenitally athymic rats; and (3) in rats treated with the interleukin 1 receptor antagonist (IL-1ra) to interleukin 1 beta. RESULTS: In colitis, both topical budesonide and systemic IL-1ra treatments attenuated the suppression of KCl-evoked 3H release from longitudinal muscle myenteric plexus in both inflamed and noninflamed segments. However, neither of these treatments altered MPO activity. A similar suppression of [3H]noradrenaline release was observed in athymic rats after TNBS, although there was a substantially greater increase in MPO activity compared with euthymic rats with colitis. CONCLUSIONS: TNBS-induced colitis alters myenteric nerve function at inflamed and noninflamed sites via a steroid-sensitive and interleukin 1-mediated process that does not require T lymphocytes.

Acute Disease↗

PubMed1990

Innervation of the pancreas by neurons in the gut.

Experiments were done in order to test the hypothesis that neurons in the bowel send axonal projections to the pancreas and can modify pancreatic activity. pancreatic injections of the retrograde tracer, Fluoro-Gold, labeled neurons in the myenteric plexus of the antrum of the stomach and in the first 6 cm of the duodenum. this labeling was not due to the diffusion of Fluoro-Gold from the pancreas, because the injections did not label longitudinal muscle cells overlying labeled ganglia in the bowel or neurons in the phrenic nerve nucleus or nucleus ambiguous; nor were enteric neurons labeled if insufficient time was allotted for retrograde transport. More Fluoro-Gold labeled neurons were found in the stomach (9.2 +/- 0.9/ganglion) than in the duodenum (3.8 +/- 0.3/ganglion; p less than 0.001). Neurons were found in myenteric ganglia of both duodenum and stomach that were doubly labeled by retrograde transport of Fluoro-Gold and anti-serotonin (5-HT) sera. In addition, thick bundles of 5-HT immunoreactive nerve trunks were found to run between the duodenum and the pancreas. Most 5-HT immunoreactive axons in the pancreas terminated in ganglia, although some fibers were also observed near acini, ducts, vessels, and islet cells. The B subunit of cholera toxin (B-CT) was microinjected into single myenteric ganglia in order to determine if axon terminals in the pancreas would become labeled by anterograde transport in the pancreas. B-CT labeled bundles of axons in the pancreatic stroma. Branches of these bundles entered the pancreatic parenchyma and varicose B-CT labeled terminal axons were found in pancreatic ganglia and in proximity to acinar and insulin immunoreactive cells. The intercalating fluorochrome 1, 1', dioctadecyl-3,3,3',3'-tetramethylcarbocyanine perchlorate (Dil), which moves by lateral diffusion to outline entire cells, was introduced by microinjection into individual myenteric ganglia of fixed preparations. Fluorescence was seen in sequential observations to move away from the injected ganglion along connectives of the myenteric plexus. After about a month, neurons in ganglia at some distance from the injection site displayed Dil fluorescence as did nerve bundles that exited from the myenteric plexus and pierced the longitudinal muscle in the direction of the pancreas. Varicose Dil fluorescent terminal varicosities were also observed int he pancreas. These observations indicate that there is an extensive entero-pancreatic innervation.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1998

Regional differences in the nitrergic innervation between the proximal and the distal colon in rats.

BACKGROUND & AIMS: Functional differences in the inhibitory neural pathway between the proximal and the distal colon are unknown. METHODS: We investigated the nonadrenergic, noncholinergic (NANC) relaxation, nitric oxide synthase (NOS) synthesis, and NOS messenger RNA (mRNA) expression of the myenteric plexus in the proximal and the distal colon in rats. RESULTS: Transmural nerve stimulation of the neuromuscular preparations from the proximal colon showed greater NANC relaxations than those from the distal colon. NANC relaxations were abolished by the NO biosynthesis inhibitor (NG-nitro-L-arginine methyl ester) in the proximal and the distal colon, suggesting mediation by NO released from the myenteric plexus. The average number of NOS-immunoreactive cells was significantly higher in the tissue from the proximal colon than in the tissue from the distal colon. Western and Northern blot analyses showed a higher density of the immunoreactive NOS band and the NOS mRNA band in the tissue from the proximal colon than in that from the distal colon. CONCLUSIONS: These observations indicate that the number of NOS-containing neurons and the NOS activity are increased in the myenteric plexus of the proximal colon compared with the distal colon, resulting in greater NANC relaxation in the proximal colon. These findings may explain the physiological role of the proximal colon as an organ for fecal storage and absorption of excess fluid.

Animals↗

PubMed1988

Diarrhea associated with myenteric ganglionitis in a dog.

Diarrhea in a Border Terrier was associated with inflammatory lesions of the myenteric plexus. This lesion has been documented rarely in dogs. It is speculated that the myenteric plexus lesions were responsible for an autonomic nervous system dysfunction, which resulted in extreme intestinal hypermotility and subsequent diarrhea. Suggested tests for dogs suspected to have autonomic dysfunction are given.

Animals↗

PubMed1995

Distribution of galanin-immunoreactive nerves in the canine gastrointestinal tract.

The distribution of nerves containing galanin immunoreactivity (GAL-IR) in the canine gastrointestinal tract was determined by immunohistochemistry. GAL-IR was observed in nerve cell bodies and nerve fibers in all layers of the lower esophagus, gastric antrum, pylorus, ileum, and colon, and in the sphincters of lower esophagus and pylorus. There were numerous GAL-IR-containing nerve cell bodies in the myenteric plexus of gastric antrum. GAL-IR nerve somata were also common in the myenteric plexus of lower esophagus, ileum, pylorus, and colon, and in the submucous plexus of stomach, ileum, and colon. GAL-IR-positive nerve fibers were also observed around submucous blood vessels of the stomach. GAL-IR nerves are distributed more widely in the canine enteric nervous system than previously recognized.

Animals↗

PubMed2006

Prokineticin 1 inhibits spontaneous giant contractions in the murine proximal colon through nitric oxide release.

Prokineticins are novel peptides with reported effects on gastrointestinal contractility. Prokineticin actions are mediated by distinct prokineticin receptors (PKR1 and PKR2). This study investigated the role of prokineticin 1 in colonic contractility as well as sites of expression of its receptor in the mouse proximal colon by immunohistochemistry and confocal microscopy. Prokineticin 1 suppressed giant contractions in circular muscle. The inhibitory effect of prokineticin 1 on giant contractions was blocked by the nitric oxide synthase (NOS) inhibitor Nomega-nitro-L-arginine methyl ester (L-NAME). In vitro, prokineticin 1 stimulated nitric oxide release from longitudinal muscle-myenteric plexus cultures. This effect was blocked by L-NAME. PKR1 is expressed on myenteric plexus neurons and colocalizes with a small subset of nNOS expressing neurons. This study suggests that PKR1 mediates an inhibitory effect in vitro, most likely through direct or indirect stimulation of nitric oxide release. PKR1 and its natural ligand, prokineticin 1 may be important for modulation of colonic motility.

Animals↗

PubMed1994

Sulfate esters of hydroxy amino acids as stereospecific glutamate receptor agonists.

Enantiomerically pure sulfate esters of the hydroxy amino acids homoserine, hydroxyproline and 4-hydroxypipecolic acid were synthesized and tested on alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) and N-methyl-D-aspartate (NMDA) receptors present in the mice cortical wedge preparation and on NMDA receptors present in the myenteric plexus of the guinea pig with the aim of finding new possible endogenous ligands (either agonists or antagonists) for excitatory amino acid receptors. The linear and flexible compound S-homoserine sulfate caused a depolarization of both AMPA and NMDA receptors. In the cortex its agonist action had an EC50 of 150 microM for NMDA and 300 microM for AMPA receptors and in the myenteric plexus its EC50 was 600 microM. The stereoisomer R-homoserine sulfate did not depolarize the cortical wedges and failed to cause ileal contraction up to a concentration of 500 microM. Among the four possible stereoisomers of 4-hydroxyproline sulfate, which are rigid structures and may be regarded as cyclization forms of homoserine sulfate, t-S-hydroxyproline sulfate was a selective AMPA receptor agonist with an EC50 of 70 microM in the cortex. The other three isomers were not active as agonists up to 500 microM and none of them had antagonist activity. Finally, t-4-hydroxy-S-pipecolic acid-4-sulfate, a superior homologue of t-S-hydroxyproline sulfate, was found to be one of the most potent and selective NMDA receptor agonists so far described with an EC50 of 0.7 microM in the cortex and 250 microM in the myenteric plexus.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗

PubMed2006

Distribution and biological activity of obestatin in the rat.

Obestatin, a 23 amino acid peptide recently isolated from the rat stomach, is encoded by the same gene that encodes ghrelin. With the use of an antiserum directed against the mouse/rat obestatin, obestatin immunoreactivity (irOBS) was detected in cells of the gastric mucosa, myenteric plexus, and in Leydig cells of the testis in Sprague-Dawley rats. Double labeling the myenteric plexus with obestatin antiserum and choline acetyltransferase (ChAT) antiserum revealed that nearly all irOBS neurons were ChAT positive and vice versa. For comparative purposes, myenteric ganglion cells, cells in the gastric mucosa, and Leydig cells of the testis were shown to be immunoreactive to preproghrelin. The biological activity of obestatin on rat central neurons was assessed by the calcium microfluorimetric Fura-2 method. Obestatin (100 nM) administered to dissociated and cultured rat cerebral cortical neurons elevated cytosolic calcium concentrations [Ca2+]i in a population of cortical neurons. The result provides the first immunohistochemical evidence that obestatin is expressed in cells of the gastric mucosa and myenteric ganglion cells, and also in Leydig cells of the testis; the peptide is biologically active on central neurons.

Animals↗