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  • 1990-1994  (7)
  • Colon  (3)
  • Vasoactive intestinal peptide  (2)
  • After-hyperpolarization  (1)
  • Chemical coding  (1)
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  • 1
    ISSN: 1432-2013
    Keywords: Potassium channels ; Enteric nervous system ; After-hyperpolarization ; Toxins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Myenteric neurons of guinea-pig ileum were studied with intracellular microelectrodes. The specific toxins charybdotoxin, iberiotoxin and apamin were used to characterize the prolonged after-hyperpolarizations of AH neurons in this preparation. Charybdotoxin and iberiotoxin blocked prolonged after-hyperpolarizations in 23 of 24 AH neurons, but apamin had no effect on 5 of 5 AH neurons. Abolition of the after-hyperpolarizations was accompanied by depolarization and increases in input resistances of those AH neurons affected, but the shapes of action potentials were unchanged. The excitability of the AH neurons was enhanced as shown by an increase in the number of action potentials evoked by a 500-ms depolarizing current pulse or by a train of 15 ms depolarizing current pulses (10Hz). The other class of myenteric neurons, S neurons, was also investigated. The 19 S neurons studied fired action potentials only at the start of a 500 ms depolarization, but the toxins had no effect on this behaviour or on their other properties. Intracellular injection of Neurobiotin into the neurons studied and subsequent immunohistochemical staining to localise the calcium-binding protein, calretinin, indicated that all major classes of S neurons were included in the sample. Thus, the prolonged after-hyperpolarizations in AH neurons may be due to opening of a large-conductance (BK) calcium-dependent potassium channel, but similar channels play little or no role in regulation of the excitability of S neurons.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0878
    Keywords: Enteric nervous system ; Caecum ; Neurochemistry ; Neuropeptides ; Nitric oxide synthase ; Chemical coding ; Guinea-pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The present work was undertaken to determine by immunocytochemical methods which of the putative enteric neurotransmitters are contained in axons supplying the guinea-pig taenia coli and what proportion of axons is accounted for by the presence of these substances. Numerous fibres displayed immunoreactivity for dynorphin (DYN), enkephalin (ENK), γ-aminobutyric acid (GABA), nitric oxide synthase (NOS), substance P (SP) and vasoactive intestinal peptide (VIP), but, in contrast to other gut regions, fibres showing immunoreactivity for gastrin-releasing peptide, galanin and neuropeptide Y were rare in the taenia. Fibres reactive for calbindin, calcitonin gene-related peptide, cholecystokinin, 5-hydroxytryptamine and somatostatin were also rare. Tyrosine hydroxylase-like immunoreactivity (TH-LI) was present in numerous fibres that disappeared after extrinsic denervation, a procedure that did not detectably affect any of the other major groups of fibres. Simultaneous staining of extrinsically denervated preparations revealed that SP-LI and VIP-LI were located in separate fibres, and ultrastructural studies showed these to be 58% and 33% of intrinsic fibres supplying the muscle. Immunoreactivity for the general marker, neuron-specific enolase, was located in 95–98% of axons. ENK-LI and DYN-LI were in the same axons, and similar proportions of the fibres with either SP-LI or VIP-LI, about 85%, contained immunoreactivity for ENK and DYN. All VIP-LI fibres, but no SP-LI fibres, were reactive for NOS. The results imply that the taenia of the guinea-pig caecum is innervated by two major groups of enteric neurons: (i) excitatory neurons that contain ACh, SP, other tachykinins, and, in most cases, DYN-LI and ENK-LI; and (ii) inhibitory neurons that contain NOS-LI, VIP-LI, in most cases, the two opioids and, quite probably, ATP as a transmitter. GABA-LI is contained in a smaller population of intrinsic axons. Even though the taenia represents one of the simplest tissues for examining transmission from enteric neurons to intestinal muscle, it shares some of the complexity of other regions, in that four major axon types supply the muscle and both the enteric excitatory and enteric inhibitory neurons contain multiple transmitters.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0878
    Keywords: Enteric nervous system ; Stomach ; Vasoactive intestinal peptide ; Galanin ; Gastrin-releasing peptide ; Substance P-Dog
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The distribution of nerve cell bodies and fibres in the canine stomach was investigated using antibodies to the general neuronal marker, neuron-specific enolase. Prominent ganglia containing many reactive nerve cells were found in the myenteric plexus of the gastric corpus and antrum. Nerve cells were absent from the submucosa of the corpus and were extremely rare in the antrum. Renoval of areas of longitudinal muscle and myenteric plexus from the corpus (myectomy), with 7 days allowed for axon degeneration, resulted in the loss of fibres reactive for galanin, gastrin-releasing peptide, substance P and vasoactive intestinal peptide from both the circular muscle and mucosa in the area covered by the lesion. Combined vagotomy and sympathetic denervation did not significantly affect these fibres, but did cause fibres reactive for calcitonin gene-related peptide to degenerate. It is concluded that the myenteric plexus of the gastric corpus, like the myenteric plexus of the small intestine and colon, is the source of nerve fibres innervating the circular muscle, but, in contrast to other regions of the gastrointestinal tract, myenteric ganglia, not submucous ganglia, are the major, or sole, source of the intrinsic innervation of the mucosa.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0878
    Keywords: Calretinin ; Enteric nervous system ; Calcium-binding protein ; Colon ; Guinea-pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The distribution of nerve cells and fibres with immunoreactivity for the calcium-binding protein, calretinin, was studied in the distal colon of the guinea-pig. The projections of the neurons were determined by examining the consequences of lesioning the myenteric plexus. Calretinin-immunoreactive neurons comprised 17% of myenteric nerve cells and 6% of submucous nerve cells. Numerous calretinin-immunoreactive nerve fibres were located in the longitudinal and circular muscle, and within the ganglia of the myenteric and submucous plexuses. Occasional fibres were found in the muscularis mucosae, but they were very rare in the lamina propria of the mucosa. Lesion studies revealed that myenteric neurons innervated the underlying circular muscle and provided both ascending and descending processes that gave rise to varicose branches in myenteric ganglia. Calretinin-immunoreactive fibres also projected to the tertiary component of the myenteric plexus, and are therefore likely to be motor neurons to the longitudinal muscle. Varicose fibres that supplied the submucous ganglia appear to arise from submucous nerve cells. Arterioles of the submucous plexus were sparsely innervated by calretinin-immunoreactive fibres. The submucous plexus was the principal source of immunoreactive nerve fibres in the muscularis mucosae. This work shows that calretinin-IR reveals different neuronal populations in the large intestine to those previously reported in the small intestine.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 278 (1994), S. 379-387 
    ISSN: 1432-0878
    Keywords: Key words: Enteric nervous system ; Immunohistochemistry ; 5-Hydroxytryptamine ; Colon ; Guinea-pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The presence of 5-hydroxytryptamine in enteric neurons of the guinea-pig distal colon was demonstrated by immunohistochemistry and the projections of the neurons were determined. 5-Hydroxytryptamine-containing nerve cells were observed in the myenteric plexus but no reactive nerve cells were found in submucous ganglia. Varicose reactive nerve fibres were numerous in the ganglia of both the myenteric and submucous plexuses, but were infrequent in the longitudinal muscle, circular muscle, muscularis mucosae and mucosa. Reactivity also occurred in enterochromaffin cells. Lesion studies showed that the axons of myenteric neurons projected anally to provide innervation to the circular muscle and submucosa and to other more anally located myenteric ganglia. The results suggest that a major population of 5- hydroxytryptamine neurons in the colon is descending interneurons, most of which extend for 10 to 15 mm in the myenteric plexus and innervate both 5-hydroxytryptamine and non-5-hydroxytryptamine neurons.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 269 (1992), S. 119-132 
    ISSN: 1432-0878
    Keywords: Enteric nervous system ; Coeliac ganglion ; Retrograde tracing ; Calbindin ; Vasoactive intestinal peptide ; Guinea-pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The digestive tract of the guinea-pig, from the esophagus to the rectum, was examined in detail to determine the distribution and relative abundances of neurons in these organs that project to the coeliac ganglion and the routes by which their axons reach the ganglion. A retrogradely transported neuronal marker, Fast Blue, was injected into the coeliac ganglion. The esophagus, stomach, gallbladder, pancreas, duodenum, small intestine, caecum, proximal colon, distal colon and rectum were analysed for labelled neurons. Retrogradely labelled neurons were found only in the myenteric plexus of these organs, and in the pancreas. No labelled neurons were found in the gallbladder or the fundus of the stomach, or in the submucous plexus of any region. A small number of labelled neurons was found in the gastric antrum. An increasing density of labelled neurons was found along the duodenum. Similarly, an increasing density of labelled neurons was found from proximal to distal along the jejuno-ileum. However, the greates densities of labelled neurons were in the large intestine. many labelled neurons were found in the caecum, including a high density underneath its taeniae. An increasing density of labelled neurons was found along the length of the proximal colon, and labelled neurons were found in the distal colon and rectum. In total, more labelled cell bodies occurred in the large intestine than in the small intestine. The routes taken by the axons of viscerofugal neurons were ascertained by lesioning the nerve bundles which accompany vessels supplying regions of the digestive tract. Viscerofugal neurons of the caecum project to the coeliac ganglion via the ileocaeco-colic nerves; neurons in the proximal colon project to the ganglion via the right colic nerves, and neurons in the distal colon project to the ganglion via the mid colic and intermesenteric nerves. Neurons in the rectum project to the coeliac ganglion via the intermesenteric nerves. These nerves (except for the intermesenterics) all join nerve bundles from the small intestine that follow the superior mesenteric artery. All viscerofugal neurons of the caecum were calbindin-immunoreactive (calb-IR) and 94% were immunoreactive for vasoactive intestinal peptide (VIP-IR). In the proximal colon, 49% of labelled neurons were calb-IR and 85% were VIP-IR. In the distal colon, 80% of labelled neurons were calb-IR and 71% were VIP-IR.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 278 (1994), S. 379-387 
    ISSN: 1432-0878
    Keywords: Enteric nervous system ; Immunohistochemistry ; 5-Hydroxytryptamine ; Colon ; Guinea-pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The presence of 5-hydroxytryptamine in enteric neurons of the guinea-pig distal colon was demonstrated by immunohistochemistry and the projections of the neurons were determined. 5-Hydroxytryptamine-containing nerve cells were observed in the myenteric plexus but no reactive nerve cells were found in submucous ganglia. Varicose reactive nerve fibres were numerous in the ganglia of both the myenteric and submucous plexuses, but were infrequent in the longitudinal muscle, circular muscle, muscularis mucosae and mucosa. Reactivity also occurred in enterochromaffin cells. Lesion studies showed that the axons of myenteric neurons projected anally to provide innervation to the circular muscle and submucosa and to other more anally located myenteric ganglia. The results suggest that a major population of 5-hydroxytryptamine neurons in the colon is descending interneurons, most of which extend for 10 to 15 mm in the myenteric plexus and innervate both 5-hydroxytryptamine and non-5-hydroxytryptamine neurons.
    Type of Medium: Electronic Resource
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