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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 339 (1989), S. 409-414 
    ISSN: 1432-1912
    Keywords: Enteric nervous system ; 5-Hydroxytryptamine ; Electrolyte transport ; Small intestine ; Secretomotor neurons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Flat sheet preparations of the mucosa plus submucosa from the guinea-pig ileum were placed in Ussing chambers so that short circuit currrent (I sc), an index of electrolyte movement across the mucosa, could be measured. In these preparations, 5-hydroxytryptamine (5-HT) increasesI sc indirectly by stimulating both cholinergic and non-cholinergic secretomotor neurons. The 5-HT3 receptor antagonist, ICS 205–930 (10−13–10−5 M), substantially depressed the secretory response due to 5-HT (10−6 M), but not that produced by direct activation of muscarinic receptors on the mucosal epithelium with carbachol (10−6 M), or by stimulation of secretomotor neurons with substance P (10−8 M) or 1,1-dimethyl-4-phenylpiperazinium (10−5 M). The residual response to 5-HT, after the addition of a maximally effective concentration of ICS 205–930 (10−6 M), was further reduced by hyoscine (10−7M). When that part of the 5-HT response attributable to the release of acetylcholine was blocked by hyoscine (10−7M), ICS 205–930 did not further modify the response to 5-HT. The hyoscine-resistant component was, however, sustantially depressed by tetrodotoxin (3.5 × 10−7 M). The response remaining after ICS 205–930 and hyoscine was not affected by methysergide (2 × 10− 5 M) or cyproheptadine (10−7 M). We conclude that there are ICS 205–930 sensitive 5-HT receptors on cholinergic secretomotor neurons, and ICS 205–930, methysergide, and cyproheptadine insensitive 5-HT receptors on non-cholinergic secretomotor neurons.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 352 (1995), S. 538-544 
    ISSN: 1432-1912
    Keywords: Key words Pituitary adenylyl cyclase activating peptide (PACAP) ; Taenia caeci ; Electrophysiology ; Enteric nervous system ; Inhibitory neurotransmitter ; Smooth muscle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The actions of pituitary adenylyl cyclase activating peptide (PACAP) on membrane potential and conductance were investigated in the taenia of the guinea-pig caecum. The possible role of PACAP in inhibitory transmission was also investigated. Membrane potentials of smooth muscle cells were measured by intracellular microelectrodes, in the presence of hyoscine and nifidepine (both 10-6M). To determine conductance changes, current was passed from external plate electrodes using the technique of Abe and Tomita (1968). PACAP-27 caused a concentration dependent hyperpolarization of the muscle with a maximum of 12–15 mV at 10-6M. The hyperpolarization caused by PACAP was associated with a substantial increase in membrane conductance. The hyperpolarization was abolished by apamin (10-6M), a blocker of small conductance, calcium-dependent, potassium channels, and was reduced to about 50% by suramin (10-4M), which is an antagonist of P2 receptors for purines. The hyperpolarization was not reduced by tetrodotoxin (2×10-6M), suggesting PACAP acts directly on the muscle. With continued exposure to PACAP, the hyperpolarization decayed back to resting membrane potential after several minutes, possibly due to receptor desensitization. Inhibitory junction potentials (IJPs) were markedly reduced in amplitude in the period of presumed receptor desensitization to PACAP, were abolished by tetrodotoxin, but were not affected by suramin. Apamin abolished the IJP and revealed a small excitatory junction potential. This study implies that PACAP released from nerve fibres in the taeniacaeci hyperpolarizes the muscle via an opening of apamin-sensitive potassium channels. The action is probably through type I PACAP receptors.
    Type of Medium: Electronic Resource
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  • 3
    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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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 247 (1987), S. 377-384 
    ISSN: 1432-0878
    Keywords: Enkephalin ; Gastrin releasing peptide ; Neuropeptide Y ; Somatostatin ; Substance P ; Vasoactive intestinal peptide ; Enteric nervous system ; Intestine, small ; Dog
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The projections of nerve fibres with immunoreactivity for the peptides enkephalin (ENK), gastrin-releasing peptide (GRP), neuropeptide Y (NPY), somatostatin (SOM), substance P (SP) and vasoactive intestinal peptide (VIP) were studied in canine small intestine by analysing the consequences of lesions of intrinsic and extrinsic nerves. Of peptides present in fibres supplying myenteric ganglia, GRP, SOM and VIP were in anally directed nerve pathways, whereas ENK and NPY were in orally directed pathways. Pathways ran for up to about 30 mm. SP fibres ran for short distances in both directions in the myenteric plexus. The circular muscle was supplied with ENK, NPY, SP and VIP fibres arising from the myenteric ganglia, whereas most mucosal SP and VIP fibres were deduced to arise from submucous ganglia. There were projections of fibres reactive for ENK, GRP, SOM, SP and VIP from myenteric ganglia to submucous ganglia. Antibodies to tyrosine hydroxylase were used to locate noradrenaline nerve fibres supplying the intestine; these fibres all disappeared when extrinsic nerves running through the mesentery to the small intestine were cut. It is deduced that there is an ordered pattern of projections of peptide-containing fibres in the canine intestine.
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  • 5
    ISSN: 1432-0878
    Keywords: Galanin ; Enteric nervous system ; Intestine, small ; Neuropeptides ; Guinea-pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Galanin immunoreactivity was observed in nerve cell bodies and nerve fibres, but not in enteroendocrine cells, in the small intestine of the guinea-pig. Nerve terminals were found in the myenteric plexus, in the circular muscle, in submucous ganglia, around submucous arterioles, and in the mucosa. Lesion studies showed that all terminals were intrinsic to the intestine; those in myenteric ganglia arose from cell bodies in more orally placed ganglia. Myenteric nerve cells were also the source of terminals in the circular muscle. Galanin (GAL) was located in a population of submucous nerve cell bodies that also showed immunoreactivity for vasoactive intestinal peptide (VIP) and in a separate population that was immunoreactive for neuropeptide Y (NPY). Processes of the GAL/VIP neurons supplied submucous arterioles and the mucosal epithelium. Processes of GAL/NPY neurons ran to the mucosa. It is concluded that galanin immunoreactivity occurs in several functionally distinct classes of enteric neurons, amongst which are neurons controlling (i) motility, (ii) intestinal blood flow, and (iii) mucosal water and electrolyte transport.
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  • 6
    ISSN: 1432-0878
    Keywords: Calcium-binding protein ; Enteric nervous system ; Intestine ; Immunocytochemistry ; Guinea-pig ; Rat ; Man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Immunoreactivity for vitamin D-dependent calcium-binding protein (CaBP) has been localized in nerve cell bodies and nerve fibres in the gastrointestinal tracts of guinea-pig, rat and man. CaBP immunoreactivity was found in a high proportion of nerve cell bodies of the myenteric plexus, particularly in the small intestine. It was also found in submucous neurons of the small and large intestines. Immunoreactive nerve fibres were numerous in the myenteric ganglia, and were also common in the submucous ganglia and in the intestinal mucosa. Immunoreactive fibres were rare in the circular and longitudinal muscle coats. In the myenteric ganglia of the guinea-pig small intestine the immunoreactivity is restricted to one class of nerve cell bodies, type-II neurons of Dogiel, which display calcium action potentials in their cell bodies. These neurons were also immunoreactive with antibodies to spot 35 protein, a calcium-binding protein from the cerebellum. From the distribution of their terminals and the electrophysiological properties of these neurons it is suggested they might be sensory neurons, or perhaps interneurons. The discovery of CaBP in restricted sub-groups of enteric neurons may provide an important key for the analysis of their functions.
    Type of Medium: Electronic Resource
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  • 7
    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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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 284 (1996), S. 367-372 
    ISSN: 1432-0878
    Keywords: Key words: Calretinin ; Calcium-binding protein ; Enteric nervous system ; Distal colon ; Taenia coli ; Vasoactive intestinal peptide (VIP) ; Substance P ; γ-Aminobutyric acid (GABA) ; Guinea-pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Calretinin is a calcium-binding protein which occurs in neurons and endocrine cells, including neurons throughout the gastrointestinal tract. Calretinin-immunoreactive (IR) neurons innervate the circular muscle in the guinea-pig distal colon and have descending as well as ascending projections. This suggests that calretinin-IR is in motor neurons, but whether it might be in excitatory or inhibitory motor neurons or both was previously undetermined. The presence of calretinin-IR in neurons innervating the taenia coli has not been previously reported. Numerous fibres in the circular muscle of the distal colon and in the taenia coli displayed immunoreactivity for calretinin. Tachykinin (TK), vasoactive intestinal peptide (VIP), calretinin, and γ-aminobutyric acid (GABA) immunoreactivity was also in fibres innervating these targets. The abundances of these fibres was estimated to be TK〉VIP〉calretinin〉GABA. Double label immunohistochemistry revealed the presence in both tissues of populations of calretinin-IR fibres which were also TK-IR, and fibres with calretinin and GABA-IR in the colon, but calretinin-IR fibres were never VIP-IR. TK- and VIP-IR were in separate populations of nerve fibres as were GABA- and TK-IR. It is concluded that calretinin-IR does not provide a definitive labelling of a physiologically known subgroup of motor neurons, either in the distal colon or in the taenia coli, but that calretinin is most likely to be in excitatory motor neurons.
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  • 9
    ISSN: 1432-0878
    Keywords: Key words Choline acetyltransferase ; Vesicular acetylcholine transporter ; Enteric nervous system ; Sensory neurons ; Guinea-pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Antibodies against choline acetyltransferase (ChAT) and the vesicular acetylcholine transporter (VAChT) were used to determine whether neurons that have previously been identified as intrinsic primary afferent neurons in the guinea-pig small intestine have a cholinergic phenotype. Cell bodies of primary afferent neurons in the myenteric plexus were identified by their calbindin immunoreactivity and those in the submucous plexus by immunoreactivity for substance P. High proportions of both were immunoreactive for ChAT, viz. 98% of myenteric calbindin neurons and 99% of submucosal substance P neurons. ChAT immunoreactivity also occurred in all nerve cell bodies immunoreactive for calretinin and substance P in the myenteric plexus, but in only 16% of nerve cells immunoreactive for nitric oxide synthase. VAChT immunoreactivity was in the majority of calbindin-immunoreactive varicosities in the myenteric ganglia, submucous ganglia and mucosa and also in the majority of the varicosities of neurons that were immunoreactive for calretinin and somatostatin and that had been previously established as being cholinergic. We conclude that the intrinsic primary afferent neurons are cholinergic and that they may release transmitter from their sensory endings in the mucosa.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-0878
    Keywords: Enteric nervous system ; Intestine ; Noradrenergic nerves ; Pancreatic polypeptide ; Neuropeptide Y ; Neuropeptides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Pancreatic polypeptide-like immunoreactivity (PPLI) has been localized in nerves of the guinea-pig stomach and intestine with the use of antibodies raised against avian, bovine and human pancreatic polypeptide (PP), the C-terminal hexapeptide of mammalian PP, and against the related peptide, NPY. Each of the antibodies revealed the same population of neurones. Reactive cell bodies were found in both myenteric (5% of all neurones) and submucous ganglia (26% of all neurones) of the small intestine, and varicose processes were observed in the myenteric plexus, circular muscle, mucosa and around arterioles. The nerves were unaffected by bilateral subdiaphragmatic truncal vagotomy, but the staining of the periarterial nerves disappeared after treatment of animals with reserpine or 6-hydroxydopamine and was also absent after mesenteric nerves had been cut and allowed to degenerate. Vascular nerves showing immunoreactivity for dopamine it-hydroxylase and PPLI had the same distribution. It is concluded that PPLI is located in periarterial noradrenergic nerves. However, other noradrenergic nerves in the intestine do not show PPLI, and PPLI also occurs in nerves that are not noradrenergic. Analysis of changes in the distribution of terminals after microsurgical lesions of pathways in the small intestine showed that processes of myenteric PP-nerve cells provide terminals in the underlying circular muscle and in myenteric ganglia up to about 2 mm more anal. Submucous PP-cell bodies provide terminals to the mucosa.
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