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At least 577 records · Page 32Linked to original sources
PubMed1987

Lymphatics and myenteric plexus in the muscular coat in the rat stomach: a scanning electron microscopic study of corrosion casts made by intra-arterial injection.

Intra-arterially injected low viscosity methacrylate filled the lymphatic system in the muscularis externa of the young rat. Scanning electron microscopy of the corrosion casts revealed that between the inner and outer muscular coat there was a lymphatic network made up of polygonal meshes. The initial lymphatics, about 15 micron diameter drained into the thicker lymphatics, about 20-80 micron diameter. These lymphatics ran along the muscular fibers of either inner or outer layers and formed polygonal (most often rectangular) meshes. The casts of the thicker lymphatics possessed notches indicative of valve locations. The myenteric nervous plexus was also replicated between the inner and outer muscular coats. The plexus consisted of flat astral structures with primary and secondary, and occasionally, tertiary, processes which interconnected with neighboring ones. It is suggested that the enteric neurons are confined in an interconnected channel system.

Animals↗
PubMed1999

The effects of hibernation on the myenteric plexus of the golden hamster small and large intestine.

We have examined the effects of hibernation on the neurochemical composition of myenteric neurones in the small and large intestine of the golden hamster using immunohistochemical and histochemical techniques. Hibernation was induced in golden hamsters by altering the photoperiod and external ambient temperature. Age-matched hamsters kept at room temperature and those kept at 5 degrees C but which failed to hibernate were used as controls. Cell counts were carried out to examine possible changes in the numbers of cell bodies immunoreactive to all of the markers examined. The results demonstrated a significant increase during hibernation in the number of neurones immunoreactive to vasoactive intestinal polypeptide, substance P and calcitonin gene-related peptide; cell bodies positive for tyrosine hydroxylase, which were largely absent in the control animals, were prominent in the hibernating animals. There was a significant decrease in the number of neurones immunoreactive to 5-hydroxytryptamine, and no significant changes in the numbers of neurones immunoreactive to protein gene-product and nitric oxide synthase. It is suggested that selective upregulation and downregulation of myenteric neurones containing certain neurotransmitters may occur as a protective mechanism during hibernation to maintain the integrity of the muscular and mucosal layers of the intestine in the absence of luminal contents.

Animals↗
PubMed1982

Muscarinic presynaptic inhibition of synaptic transmission in myenteric plexus of guinea-pig ileum.

1. The effect of oxotremorine (300 pM to 30 nM) on synaptic transmission in isolated myenteric ganglia of guinea-pig ileum was investigated with intracellular recording techniques. 2. These low concentrations of oxotremorine had no effect on the resting membrane potentials or on the membrane conductance. 3. Oxotremorine reduced the amplitude of the fast excitatory post-synaptic potential (e.p.s.p.) but did not reduce the amplitude of nicotinic responses to ionophoretic application of acetylcholine (ACh). This effect of oxotremorine on the fast e.p.s.p. was dose-dependent; the amplitude was reduced by about 45% by 30 nM-oxotremorine. 4. Non-cholinergic slow e.p.s.p.s evoked by repetitive presynaptic nerve stimulation were reduced in amplitude by oxotremorine. 5. Hyoscine or atropine (1 nM) completely antagonized both these effects of oxotremorine (30 nM). 6. Muscarinic antagonists alone increased the amplitude of second and subsequent fast e.p.s.p.s when these were evoked at intervals of 1 s, and increased the amplitude and duration of the slow e.p.s.p. evoked by repetitive presynaptic nerve stimulation. 7. The results indicate that muscarinic receptor activation inhibits the release of the transmitters which mediate both the fast and the slow e.p.s.p.s and that this can occur with physiologically released ACh during repetitive presynaptic nerve activity.

Acetylcholine↗
PubMed1995

Nerve cell loss in the myenteric plexus of the human esophagus in relation to age: a preliminary investigation.

Morphometric measurements have been carried out on the human myenteric esophageal neurons at the ages of 20-40 and more than 70 years. The number of neurons decreases after 70 years of age, which is accompanied by an increase in the sizes of the neurons. In percentage terms the decrease in the number of neurons in the aged varied from 22 to 62% along the esophagus being most pronounced in its superior third at the junction with the pharynx.

Adult↗
PubMed1994

Enterotoxin Escherichia coli STa activates a nitric oxide-dependent myenteric plexus secretory reflex in the rat ileum.

1. Mucosally added enterotoxin Escherichia coli STa increased the electrogenic Cl- secretion measured as the short-circuit current (Isc) across isolated muscle-stripped and muscle-unstripped rat mid-ilea incubated in vitro. 2. Pretreatment with serosal L-NAME (N omega-nitro-L-arginine methyl ester) or tetrodotoxin (TTX) significantly reduced the maximum Isc and the duration of action of STa in the unstripped but not stripped ilea. D-NAME (serosal), indomethacin or 5-hydroxy-tryptamine-desensitization was ineffective on STa-induced Isc in either stripped or unstripped ilea. 3. Serosal capsaicin reduced the maximum Isc of STa and its duration of action in unstripped ilea. 4. L-Arginine induced a significantly larger increase in the Isc across unstripped ilea than across stripped ilea; this could be significantly reduced by serosal L-NAME or TTX, although these were ineffective in stripped ilea. 5. Pretreatment of anaesthetized rats with I.P. L-NAME suppressed the fluid secretion induced by luminal STa in ilea in vivo but had no effect on that induced by luminal carbachol. 6. Mucosal STa increased electrogenic Cl- secretion across intact rat ileum in vitro by activating a capsaicin-sensitive, nitric oxide-dependent myenteric plexus-mediated secretory reflex. The suppression by L-NAME of STa induced ileal fluid secretion in vivo probably involves the inhibition of this reflex.

Animals↗
PubMed1995

Bombesin-mediated calcium fluxes in myenteric plexus neurons.

Dual excitation microfluorimetry (Fura-2) was used to measure changes in intracellular calcium ([Ca2+]i) in individual cultured guinea pig myenteric neurons. Bombesin (5-500 nM) induced concentration-dependent increases in [Ca2+]i responses, with a maximal effect at 500 nM (56% of neurons responding, mean peak Ca2+ response 244 +/- 25 nM vs. basal 65 +/- 7 nM). Removal of Ca2+ from the median did not affect the initial [Ca2+]i peak but eliminated the subsequent plateau phase. The [Ca2+]i responses to bombesin was abolished by preincubation with thapsigargin (1 microM), a Ca(2+)-ATPase inhibitor (91 +/- 7% inhibition). [Ca2+]i responses to bombesin were inhibited by U73122 (1 microM), an inhibitor of phospholipase C (84 +/- 6% inhibition).

Animals↗
PubMed1983

Ontogenesis of the myenteric plexus in the cat gastro-intestinal sphincters. I. Development of the neuronal perikarya and dendrites.

The pre- and postnatal development of the myenteric nerve perikarya and processes in gastro-intestinal sphincters was studied by means of light and electron microscopes. In the early fetal period, when migrate neuroblats were still seen, the myenteric ganglia were not formed. A peculiarity of each period of development was the presence of relative proportions of immature, transitional and mature nerve cells. With the progress of development the number of the immature neurons decreased, although single undifferentiated neurons were observed in adult cats. Multi-, bi- and pseudounipolar cells were distinguished in the late fetal period. On the electron microscope different myenteric neuronal types were differentiated in this period too. At birth and during the first postnatal weeks the impregnation showed an intensive dendritic branching and the Dogiel nerve types were well distinguished. To that corresponded a great variety in the fine structure of the dendrites. The nerve perikarya displayed a larger size and a richer content of organelles. Special attention was directed to the differences in the impregnation and fine structural features of the myenteric perikarya and dendrites the sphincters studied during the development.

Aging↗