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PubMed1978

[Neuronal activity of the submucous plexus of the pyloric and ileocecal sphincters].

In plexus of isolated segments of pyloric and ileo-caecal sphincters of the cat, three types of spontaneously active cells were revealed: 1) with single, 2) with fast, and 3) with slow burst type of discharges, as well as a group of silent neurons only responding to mechanical stimulation with electrode or application of acetylcholine. The data obtained indicated the qualitative unity of neuronal organization of submucous plexus along the alimentary canal, the neurons of the sphincters' plexus included. However, an increasing number of the silent cells and neurons with the single burst activity were revealed in the vicinity of mesenteric border and in the central belt of the segment which, probably, reflected the functional specifics of sphincters.

Acetylcholine↗
PubMed2005

Serotonin excites neurons in the human submucous plexus via 5-HT3 receptors.

BACKGROUND & AIMS: Serotonin (5-hydroxytryptamine [5-HT]) is a key signaling molecule in the gut. Recently, the neural 5-HT3 receptor received a lot of attention as a possible target in functional bowel diseases. Yet, the 5-HT3 receptor-mediated changes in properties of human enteric neurons is unknown. METHODS: We used a fast imaging technique in combination with the potentiometric dye 1-(3-sulfonatopropyl)-4-[beta[2-(di-n-octylamino)-6-naphthyl]vinyl]pyridinium betaine to monitor directly the membrane potential changes in neurons of human submucous plexus from surgical specimens of 21 patients. An Ussing chamber technique was used to study 5-HT3 receptor involvement in chloride secretion. RESULTS: Local microejection of 5-HT directly onto ganglion cells resulted in a transient excitation of enteric neurons characterized by increased spike discharge. This response was mimicked by the 5-HT3 receptor agonist, 2-methyl-5-HT, and blocked by the 5-HT3 receptor antagonist, tropisetron. The proportions of 5-HT-responsive nerve cells per ganglion ranged from 25.5% +/- 18.4% in the duodenum to 54.2% +/- 46.9% in the colon. Interestingly, 2-methyl-5-HT did not evoke chloride secretion in the human intestine but it did in the guinea-pig intestine. Specific 5-HT3A and 5-HT3B receptor subunit immunoreactivity as well as 5-HT3A and 5-HT3B receptor-specific messenger RNA were detected in the tissue samples. Based on co-labeling with the pan-neuronal marker HuC/D we conclude that submucous nerve cells potentially express heteromeric 5-HT3A/B receptors. CONCLUSIONS: We show that 5-HT excited human enteric neurons via 5-HT3 receptors, which may comprise both 5-HT3A and 5-HT3B receptor subunits.

Action Potentials↗
PubMed1994

Neuroimmune communication in the submucous plexus of guinea pig colon after sensitization to milk antigen.

We investigated electrical and synaptic behavior of neurons in the colonic submucous plexus during exposure to beta-lactoglobulin in guinea pigs sensitized by ingestion of milk. Microelectrodes were used to record electrical and synaptic behavior in neurons from milk-sensitized and nonsensitized age-matched animals during exposure to beta-lactoglobulin. Neurons in sensitized animals were hyperexcitable. Application of the histamine H2 antagonist cimetidine reversed the hyperexcitability, suggesting endogenously released histamine as one of the responsible factors. Antigenic exposure suppressed stimulus-evoked nicotinic cholinergic fast excitatory postsynaptic potentials (EPSPs). This was blocked by the selective histamine H3 antagonist burimamide. Suppression of the EPSPs resulted from presynaptic inhibition of acetylcholine release. Increased neuronal excitability and suppression of synaptic transmission was only found in milk-sensitized intestine, not in the intestine from age-matched nonsensitized animals. We concluded that signaling from mucosal mast cells to the enteric nervous system is important in colonic defense against antigenic threats. Histamine is a paracrine messenger in the communication network.

Acetylcholine↗
PubMed2001

Neurotransmitter coding of enteric neurones in the submucous plexus is changed in non-inflamed rectum of patients with Crohn's disease.

Knowledge of the neurochemical coding of submucosal neurones in the human gut is important to assess neuronal changes under pathological conditions. We therefore investigated transmitter colocalization patterns in rectal submucosal neurones in normal tissue (n=11) and in noninflamed tissue of Crohn's disease (CD) patients (n=17). Neurone-specific enolase (NSE), choline acetyltransferase (ChAT), vasoactive intestinal polypeptide (VIP), substance P (SP), nitric oxide synthase (NOS) and calcitonin gene-related peptide (CGRP) were detected immunohistochemically in whole-mount preparations from rectal biopsies. The neuronal marker NSE revealed no differences in the number of cells per ganglion (controls 5.0; CD 5.1). Four cell populations with distinct neurochemical codes were identified. The sizes of the populations ChAT/VIP (58% vs. 55%), ChAT/SP (8% vs. 8%), and ChAT/- (22% vs. 22%) were similar in control and CD. The population VIP/- was significantly increased in CD (12% vs. 2% in controls). Unlike in controls, all NOS neurones colocalized ChAT in CD. Thickened CGRP-fibres occurred in CD. We identified neurochemically distinct populations in the human submucous plexus. The increase in the VIP/- population, extensive colocalization of ChAT and NOS and hypertrophied CGRP fibres indicated adaptive changes in the enteric nervous system in noninflamed rectum of CD patients.

Adolescent↗
PubMed1991

Neurofilament M and calbindin D28k are present in mutually exclusive subpopulations of enteric neurons in the rat submucous plexus.

Immunocytochemical methods have been used to examine the localisation of 3 neurofilament proteins and the calcium binding protein, calbindin D28k, in whole mount preparations of the submucous plexus in the Wistar rat. Neurofilament-M (160 kDA protein) was present in 40% of the submucosal neurons, staining fine filaments in the soma and the axonal processes. Calbindin D28k was present in 40% of the submucosal neurons staining both the soma and nerves within the plexus. The neurofilament proteins and calbindin D28k were never observed within the same neurons. Neurofilament-M was co-localised with substance P and calcitonin gene-related peptide but not somatostatin or the other neuropeptides investigated. Calbindin D28k was co-localised with vasoactive intestinal polypeptide and neuropeptide Y. Galanin- and somatostatin-immunoreactive neurons did not contain either the neurofilament proteins or calbindin D28k. The results demonstrate the presence of subsets of submucosal neurons that can be distinguished by the presence of neurofilament-M or calbindin D28k.

Animals↗
PubMed1981

The fine structure of the submucous plexus of the guinea-pig ileum. II. Description and analysis of vesiculated nerve profiles.

A fine structural study has been made of the vesiculated nerve profiles of the submucous plexus of both normally innervated and extrinsically denervated segments of guinea-pig ileum. Two types of nerve profiles could be readily distinguished by their vesicular content after conventional fixation. The first type, comprising 5% of all intrinsic profiles, consisted of predominantly small vesicles containing electron dense material which usually formed a ring around the inner face of the vesicular membrane but sometimes partially or completely filled the vesicle. These profiles, termed ring-vesicle-containing profiles, remained after extrinsic denervation, and their vesicular content did not change following injection of reserpine or 5-hydroxydopamine. Thus ring-vesicle-containing profiles are not adrenergic. Profiles which were positive for the uranaffin method were similar in morphology and frequency of occurrence to ring-vesicle-containing profiles, although it is not possible to say that they are the same. The second type of profile, comprising 95% of all intrinsic profiles, contained varying proportions of large granular and small clear vesicles. These heterogeneous profiles were present in both normally innervated and extrinsically denervated tissue. Their vesicular content did not change following injection of reserpine, however, some profiles of this type in normally innervated, but not in extrinsically denervated, intestine contained electron dense deposits after injection of 5-hydroxydopamine. This means that noradrenergic profiles are a subpopulation of the heterogeneous profiles in normally innervated tissue. Analysis of intrinsic heterogeneous profiles showed that the proportion and packing density of large granular vesicles formed continuous distributions which did not provide any basis for further subdivision of this type of profile. Ring-vesicle-containing and heterogeneous profiles often formed synapses with neuronal cell bodies and processes. Two rarer types of profiles were also seen. The first type contained mainly small flattened vesicles which took up 5-hydroxydopamine and was not present in extrinsically denervated tissue. This type, like the group described above, is considered to be noradrenergic. The second rare type contained large numbers of lysosome-like dense bodies and vesicles of different sizes and content and was seen in both normally innervated and denervated tissue. This type probably represents spontaneously degenerating nerve profiles.

Animals↗
PubMed1994

Neuroimmune communication in the submucous plexus of guinea pig colon after infection with Trichinella spiralis.

BACKGROUND/AIMS: Enteric neuroimmune communication in gastrointestinal hypersensitivity responses includes antigen detection by mast cells and release of chemical messages to the enteric nervous system. The aim of this study was to analyze the electrical and synaptic behavior of neurons in the colonic submucous plexus during exposure to Trichinella spiralis antigen in animals infected earlier with the parasite. METHODS: Microelectrodes were used to record in submucous neurons of guinea pig distal colon during application of Trichinella antigen. RESULTS: Neurons in sensitized animals were more excitable than in controls. Hyperexcitability was seen as a greater probability of spontaneous action potential discharge and repetitive firing to depolarizing current or exposure to acetylcholine. Application of histaminergic antagonists reversed the augmented excitability, suggesting endogenously released histamine as a responsible factor. Antigenic exposure increased neuronal excitability and suppressed nicotinic transmission at fast cholinergic synapses only in sensitized animals. Effects on excitability, but not presynaptic inhibitory effects, were blocked by cimetidine. CONCLUSIONS: Signaling between mucosal mast cells and the enteric nervous system is involved in colonic anaphylactic responses to sensitizing antigens. Histamine is a paracrine signal in the communication pathway.

Action Potentials↗
PubMed1988

Localization of substance P binding sites in submucous plexus of guinea pig ileum, using whole-mount autoradiography.

Whole mounts of guinea pig ileum submucosa were incubated with radiolabeled tachykinins, and binding sites were visualized using autoradiography. Very dense specific binding for [125I]-Bolton-Hunter substance P (BHSP) was observed over ganglia of the submucous plexus, with weaker binding over internodal strands. Dense specific binding was also seen over occasional strands of circular muscle, with weak binding over clumps of mucosa. Although very weak binding was seen over some large blood vessels, no binding was associated with smaller blood vessels. Localization of binding was absent in whole-mounts coincubated with 1 microM substance P, used to define nonspecific binding. Localization of BHSP-specific binding was also abolished in whole-mounts coincubated with 1 nM substance P, but not with 1 nM neurokinin B, suggesting that binding was probably to an NK-1 tachykinin receptor. In whole-mounts incubated in [125I]-iodohistidyl neurokinin A (INKA) or [125I]-Bolton-Hunter neurokinin B (BHNKB), no specific binding over ganglia was observed. These binding sites for BHSP are probably identical with the neuronal substance P receptors mediating mucosal ion transport.

Animals↗
PubMed1983

Pharmacological characterization of the opioid receptor in the submucous plexus of the guinea-pig oesophagus.

1 The cholinergically mediated electrically-induced contractions of the submucous plexus-longitudinal muscularis mucosae preparation of the guinea-pig oesophagus were used to study the actions of opioid peptides and morphine. 2 The twitch contractions of the tissue (0.1 Hz, 0.5 ms, supramaximal voltage) were inhibited by all the opioid peptides and morphine in a concentration-dependent manner. The order of potency was dynorphin-(1-13) greater than alpha-neo-endorphin greater than beta-endorphin greater than [D-Ala2]-methionine-enkephalin much greater than alpha-endorphin, methionine-enkephalin, leucine-enkephalin and morphine. 3 The inhibitory actions of dynorphin-(1-13) (20 nM), alpha-neo-endorphin (100 nM) and beta-endorphin (3 microM) were completely reversed either by naloxone (1 microM) or by morphine (100 microM). The Ke values of naloxone against dynorphin-(1-13) and alpha-neo-endorphin were 30 and 25 nM, respectively. 4 Increasing the concentration of calcium from 1.8 to 3.6 mM in Tyrode solution decreased the sensitivity of the tissue to dynorphin-(1-13) 7.4 times and to alpha-neo-endorphin 462 times. 5 The inhibitory actions of dynorphin-(1-13) (100 nM) and alpha-neo-endorphin (300 nM) were inversely related to stimulus frequency, being most active at low frequencies (0.1-1 Hz), and least active at high (30 Hz). 6 Exogenously applied acetylcholine produced concentration-dependent contractions of the isolated muscularis mucosae, with an EC50 of 72.6 +/- 4.5 nM. The contractile response of the oesophagus to acetylcholine was not affected by the pretreatment of the tissue with dynorphin-(1-13) (100 nM), alpha-neo-endorphin (300 nM) or beta-endorphin (3 microM). 7 It is concluded that the submucous plexus-longitudinal muscularis mucosae of the guinea-pig oesophagus is inhibited by opioid peptides acting at prejunctional opioid receptors, probably of the kappa-subtype.

Acetylcholine↗
PubMed1994

Neurokinin A mimics the slow excitatory postsynaptic current in submucous plexus neurons of the guinea-pig caecum.

Single microelectrode voltage-clamp recordings were made from submucous neurons of the guinea-pig caecum. The slow excitatory postsynaptic current was compared with the currents induced by neurokinin A and substance P. The current induced by neurokinin A (100-300 nM) was associated with a decreased membrane conductance and reversed in polarity between -90 and -100 mV. The neurokinin A current was reduced by Co2+ (1-2 mM), but was not affected by Cs+ (1-2 mM), Ba2+ (10-100 microM) or low Cl- (20-40 mM) solutions. In about 80% of the neurons, the current induced by substance P (100-300 nM) was associated with a decreased membrane conductance and did not reverse with hyperpolarization of the membrane potential up to -130 mV. The current was reduced by Co2+ (1-2 mM) and augmented by low Cl- (20-40 mM) solutions, but was not affected by Cs+ (1-2 mM) or Ba2+ (10-100 microM)-containing solutions. In about 20% of the neurons, the substance P current reversed in polarity between -100 and -120 mV. The slow excitatory postsynaptic current elicited by repetitive nerve stimulation (10-40 Hz, three to five pulses) was accompanied by a decreased membrane conductance, and reversed in polarity between -90 and -100 mV. The slow excitatory postsynaptic current was abolished by Co2+ (1-2 mM) or low Na+ (12 mM) solutions, but was not affected by Cs+ (1-2 mM), Ba2+ (10-100 microM) or low Cl- (20-40 mM) solutions. In such neurons, the neurokinin A current was reversed at approximately the same potential at which the slow excitatory postsynaptic current was reversed, while the substance P current was not reversed even by much stronger hyperpolarizations. It was concluded that the neurokinin A current was mainly due to depression of potassium conductances, while the substance P current resulted from both increased anion conductance and decreased potassium conductances. The conductance change underlying the slow excitatory postsynaptic current is similar to that caused by neurokinin A.

Animals↗
PubMed1995

An ultrastructural study of the submucous plexus of guinea pig intestine after unilateral vagotomy.

This study describes the degenerative changes of the axon terminals making synaptic contacts with the neurons in the submucous ganglia of guinea pig small and large intestines following left or right cervical vagotomy. There were no noticeable ultrastructural changes 1 d after the operation. Beginning at the 3rd postoperative day for the small intestines and the 5th day for the large intestines, some of the axon terminals presynaptic to the submucous neurons displayed different stages of degeneration. The most obvious feature of the degenerating terminals was the swelling and vacuolation of mitochondria with disrupted cristae; another change was the clumping of synaptic vesicles. In the animals killed 7 d after vagotomy, besides the above changes, the degenerating axon terminals also showed an accumulation of a variable amount of glycogen-like particles. The changes were most severe in the guinea pigs killed on the 10th postoperative day. The synaptic vesicles in some degenerating terminals were depleted. There were occasional degenerating nerve cell bodies in the submucous ganglia in the period studied. A variable number of lamellated bodies were found in some of the submucous neurons of 10 and 15 d postoperative animals. By 30 d after vagotomy, all the terminals presynaptic to the submucous neurons appeared normal. There was no significant difference in the total number of axon terminals between 10 d and 30 d after operation (P > 0.05). This suggests that either there had been successful reinnervation or new synaptic contacts had been established by sprouting from the unoperated vagus or other intrinsic neurons. The present quantitative studies also showed that the number of degenerating axon terminals in the submucous ganglia of duodenum after left vagotomy was higher than right vagotomy (P < 0.05). This feature was particularly evident in animals killed 10 d after the operation. The larger number of degenerating terminals in the submucous ganglia of duodenum after left vagotomy suggests that the presynaptic axon terminals in the submucous ganglia of different gut regions are not evenly distributed. Finally, the present study showed that the degenerative changes in the small intestine preceded the large intestine.

Animals↗