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At least 721 records · Page 40Linked to original sources
PubMed1990

Smooth muscle cells, interstitial cells of Cajal and myenteric plexus interrelationships in the human colon.

The plane between longitudinal and circular muscle of human colon, as revealed on examination with light and electron microscopes, has no clear-cut border. Some groups of smooth muscle cells, obliquely oriented and with features similar to both circular and longitudinal ones--the connecting muscle bundles--run from one muscle layer to another. Other groups of smooth muscle cells, possessing their own specific ultrastructural features--the myenteric muscle sheaths--, make up envelopes of variable thickness around some myenteric ganglia and nerve strands, partially or completely embedding them in one or other muscle layer. Non-neuronal, non-muscular cells (interstitial cells of Cajal, covering cells, fibroblast-like and macrophage-like cells) complicate the texture of the myenteric muscle sheaths, creating an intricate, interconnected cellular network inside them, widespread among nerve bundles and smooth muscle cells; however, only interstitial cells have cell-to-cell junctions also with the smooth muscle cells and nerve endings. These data document the existence in this colonic area of two different types of muscle cell arrangements, one of which, the myenteric muscle sheath, only contains putative pacemaker cells.

Aged↗
PubMed1983

GABA, glutamic acid decarboxylase, and GABA transaminase levels in the myenteric plexus in the intestine of humans and other mammals.

Regional distribution of endogenous gamma-aminobutyric acid (GABA), its synthesizing enzyme, glutamic acid decarboxylase (GAD), and metabolic enzyme, GABA transaminase (GABA-T), were determined in the intestinal tract of guinea pigs and cats and the findings compared with the number of ganglion cells in Auerbach's plexus. There were positive correlations among the GABA contents and the numbers of neural cells of the plexus. The precise localization of GABA and GAD in individual layers (mucosa, circular and longitudinal muscles, and Auerbach's plexus) in the human and cat colon was also determined. The endogenous GABA contents and GAD activity were the highest in Auerbach's plexus in tissues of both species. These results indicate that GABA is synthesized and localized in Auerbach's plexus and probably plays a significant role in the enteric nervous system.

4-Aminobutyrate Transaminase↗
PubMed2006

Effect of aminoguanidine treatment on diabetes-induced changes in the myenteric plexus of rat ileum.

The aim of this study was to investigate the ability of aminoguanidine (AG) to prevent diabetes-induced changes in nitric oxide synthase- (nNOS), vasoactive intestinal polypeptide- (VIP) and noradrenaline- (NA) containing nerves of the rat ileum using immunohistochemical and biochemical techniques. Diabetes was induced in adult male Wistar rats by a single intraperitoneal injection of streptozotocin (65 mg/kg). AG was administered in the drinking water to control (1.8 g/l) and diabetic (0.9 g/l) rats over a period of 8 weeks. Diabetes caused a significant increase in the thickness of nNOS-containing nerve fibres (p<0.001) in the circular muscle, in nNOS activity (p<0.05) and in the size distribution of nNOS-containing myenteric neurons (p<0.001). The thickness of VIP-containing nerve fibres was significantly greater (p<0.01) and there was a significant increase in varicosity size (p<0.01) and proportion of VIP-positive myenteric neurons (p<0.01) in diabetes. NA levels were significantly reduced (p<0.01) and the size of varicosities containing tyrosine hydroxylase (TH) was significantly increased (p<0.001) in diabetes. AG treatment completely or partially prevented the diabetes-induced increase in nNOS activity, in VIP-containing varicosity size, and in fibre width of both VIP- and nNOS-containing fibres in the circular muscle but had no effect on the diabetes-induced increase in nNOS-containing neuronal size or proportion of VIP-containing myenteric neurons. In contrast to VIP, AG treatment had no effect on the increase in TH-containing varicosity size in diabetes and also failed to prevent the decrease in NA levels induced by diabetes. These results indicate that AG treatment for neuropathy is not equally effective for all autonomic nerves supplying the ileum and that diabetes-induced changes in NA-containing nerves are particularly difficult to treat.

Animals↗
PubMed1987

Noradrenergic innervation of serotoninergic neurons in the myenteric plexus.

The monoaminergic innervation of the guinea pig small intestine was investigated to determine if there is an anatomical basis for the hypothesis that serotoninergic and noradrenergic neurons physiologically interact in the enteric nervous system. Initial rates of uptake of tritiated 5-hydroxytryptamine (3H-5-HT) or norepinephrine (3H-NE) by segments of guinea pig small intestine were measured in order to estimate the regional density of the serotoninergic and noradrenergic innervation. No change was found in the uptake of 3H-5-HT as a function of distance between duodenum and ileum, whereas the relative uptake of 3H-NE declined. The pattern of serotoninergic elements demonstrated radioautographically was compared with that obtained by visualizing 5-HT immunoreactivity. Both methods revealed that a small number of serotoninergic neurons, located in 35.3% +/- 1.5% of myenteric ganglia, give rise to many fibers that form thick bundles in interganglionic connectives. Moreover, there was a pronounced heterogeneity in the serotoninergic innervation of individual myenteric neurons and ganglia. In material fixed with aldehydes and postfixed with NaMnO4, noradrenergic axon terminals were identified by their characteristic small dense-cored vesicles. Following incubation with 3H-NE only terminals with small dense-cored vesicles were radioautographically labeled, confirming that these terminals are noradrenergic. When 3H-5-HT was substituted for 3H-NE, noradrenergic terminals were not labeled, showing that nonspecific uptake of 3H-5-HT into noradrenergic axons did not occur in the presence of 5-hydroxydopamine. The combination of aldehyde-NaMnO4 fixation with the radioautographic localization of 3H-5-HT thus permitted the simultaneous identification of serotoninergic and noradrenergic neural elements. Serotoninergic varicosities were found to differ from noradrenergic varicosities in the size, appearance, and packing density of their synaptic vesicles. In addition, recognizable but rudimentary pre- and postsynaptic membrane specializations were associated with serotoninergic but not noradrenergic varicosities. Most serotoninergic neuronal cell bodies were contacted both by serotoninergic synapses and noradrenergic varicosities. Similar appositions of noradrenergic varicosities with nonserotoninergic neurons appeared to be rare. In view of earlier observations that sympathetic nerves affect the release of 5-HT from stimulated enteric serotoninergic neurons, it seems likely that the noradrenergic appositions with serotoninergic neurons are the anatomical substrate for this effect.(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenergic Fibers↗
PubMed1993

Myenteric plexus neurons have developmentally acquired differences in the medium molecular weight subunit of neurofilament protein.

We have previously shown that neurofilaments in enteric neurons are immunologically distinct from those found in the central nervous system. In particular, one monoclonal antibody to the medium molecular weight neurofilament subunit, called NN18, stained the perikarya of enteric neurons very weakly, if at all, although other medium molecular weight neurofilament subunit antibodies clearly showed the presence of significant amounts of medium molecular weight neurofilament subunit. We have since located the epitope for NN18 in a peptide sequence at the carboxy terminal tail of medium molecular weight neurofilament subunit and have now looked for further neurofilament antibodies that stain the same region. We found two monoclonal antibodies, RMO1 and RMO59, that recognize the same peptide. These antibodies also show much reduced staining in myenteric neurons compared to those in the central nervous system, suggesting that this region of the medium molecular weight neurofilament subunit is specifically modified in certain cells. In the developing enteric nervous system, we found that all the antibodies show strong staining of enteric neurons in the neonatal rat, but that with NN18, RMO1, and RMO59, the staining intensity decreases during further development, and by postnatal day 21 all three demonstrate decreased or absent staining identical to the adult. These results indicate that myenteric neurons, in contrast to the brain, have a developmentally regulated modification in a specific region of the medium molecular weight neurofilament subunit, which may reflect adaptation to structural stress by myenteric neurons.

Alkaline Phosphatase↗
PubMed1980

[Neuronal organization of the myenteric plexus (Auerbach) in the small intestine of the pig. I. Type I neurons].

Examinations were done in silver impregnated strips of the small intestine of the pig. As a result of these findings we can state: 1. The real type I-neurons (according to Dogiel) are an integrated part (besides four other neuron-types) of the neuronal organization of the plexus myentericus (Auerbach). 2. There are uniaxonal multidendritic (short-dendritic) neurons, organized in aggregates as a rule. They are mainly found in the peripheric and oral parts of ganglia. The higher portion of neurits runs orally. These neurits form a type specific ascending tract. 3. The hitherto existing ideas on the neuronal organization of the intestinal nervous system are seriously doubted.

Animals↗
PubMed1985

[Intestinal pseudo-obstruction and cytomegalovirus infection of myenteric plexuses].

The authors report an intestinal pseudo-obstruction syndrome occurring in a 2 month-old boy, with acquired major and persistent abdominal distension, leading to total parenteral nutrition. Rectal biopsy revealed hypoganglionosis with thickening of nerve processes and intranuclear inclusions in some neurons. Suspected cytomegalovirus infection was confirmed by viruria and specific IgM and IgG antibodies.

Autonomic Nervous System Diseases↗
PubMed1987

Diprenorphine has agonist activity at opioid kappa-receptors in the myenteric plexus of the guinea-pig ileum.

The opioid agonist and antagonist activities of diprenorphine have been tested in four in vitro bioassay preparations. Diprenorphine is an antagonist at delta-receptors in the hamster vas deferens, at mu-receptors in the rat vas deferens and at kappa-receptors in the rabbit vas deferens. In the guinea-pig ileum it is an antagonist at mu-receptors and an agonist at kappa-receptors.

Animals↗
PubMed1996

Argyrophilia in the developing human myenteric plexus.

Silver staining is a useful means of demonstrating enteric neurons, and an absence of argyrophilic neurons has been proposed as a cause of functional intestinal obstruction in infants. No systematic data are available about the origin and development of argyrophilia, or of normal neuronal appearances. Specimens of colon from 48 infants and children (pre-term to 14 years) who had died of nongastrointestinal causes were studied by silver staining. Inter-sample variations in neuronal size, morphology and intensity of staining (strong, faint or absent) were seen: strong argyrophilia (n = 17), age range three days to eight years (median seven months); no argyrophilia (n = 19), pre-term to one year (median eight weeks); weak argyrophilia (n = 12) one day to 14 years (median eight weeks). Neurons in every preterm infant were argyrophobic, and argyrophilic neurons were always found in babies aged over one year. Where argyrophilic neurons were seen, argyrophobes outnumbered them (median ratio of 9:1). This study demonstrated considerable variability in the appearance and argyrophilia of colonic myenteric neurons in the first year of life. The data were consistent with the continuing post-natal development of the enteric nervous system in a manner analogous to the brain, and show the importance of age in the interpretation of silver-stained material from infants with pseudo-obstruction.

Adolescent↗
PubMed1984

Ultrastructural identification of substance P cells and processes in the rat myenteric plexus.

Substance P containing perikarya and processes were identified by electron microscopic immunocytochemistry in the rat small intestine. The labelled perikarya possessed a cytoplasm of high electron density rich in organelles most of which contained numerous 80 to 130 nm large granulated vesicles. Labelled processes were found in pre- and postsynaptic positions. The presynaptic terminals contained 80 to 130 nm granular vesicles and 30 to 40 nm clear vesicles. These findings provide a morphological basis for the assumption that the peptide substance P may act as a transmitter and exerts postsynaptic effect on other intrinsic neurons and that the labelled cell bodies are links to a local neuronal circuit in the small intestine.

Animals↗
PubMed1991

Histamine H3-receptor activation inhibits acetylcholine release from the guinea pig myenteric plexus.

The role of histamine H3-receptors in the control of acetylcholine release from peripheral cholinergic neurons was evaluated in the isolated guinea pig ileum, previously loaded with 3H-choline. When tested in the presence of H1- and H2-blockade, histamine (0.1-100 mumol/l) and (R) alpha-methylhistamine (0.01-1 mumol/l) dose-dependently reduced the electrically-evoked choline outflow, with (R) alpha-methylhistamine being a partial agonist. Selective H3-receptor blocking drugs, thioperamide (0.1 mumol/l) and impromidine (0.1 mumol/l) reversed the histamine-induced inhibitory effect. These data suggest that intestinal cholinergic nerves are endowed with histamine H3-receptors whose activation produces an inhibitory effect upon acetylcholine release. The practical implications of these findings are obvious.

Acetylcholine↗
PubMed1987

Analysis of enteric neurons, glia and their interactions using explant cultures of the myenteric plexus.

The enteric nervous system (ENS) of the gastrointestinal tract is the largest and most complicated division of the peripheral nervous system. The ENS possesses reflex pathways composed of motor neurons, interneurons and sensory neurons which act in an integrated fashion together with input from the central nervous system to control gut function. The neurons, morphologically and electrophysiologically a very heterogeneous group containing a large number of different proven and putative neurotransmitters, are intimately associated with enteric glia, which both at the morphological and molecular level resemble astrocytes. In this review we describe how explant cultures from the ENS have been used to investigate the neurochemical, molecular and electrophysiological characteristics of ENS neurons, the molecular properties of enteric glia and their interactions with one another.

Animals↗