Regulation Of Gut Motility Research Articles

Brain or gut? Site of action of adrenomedullin to regulate gut motility

Brain or gut? Site of action of adrenomedullin to regulate gut motility

Glutamate stimulation of acetylcholine release from myenteric plexus is mediated by endogenous nitric oxide

Glutamate was found to be an excitatory neurotransmitter in the enteric nervous system. Although several lines of evidence indicate a role of glutamate in the regulation of gut motility and secretion the physiological significance of glutamatergic transmission is not clear yet. We studied the effect of glutamate on [ 3H]acetylcholine release and nicotinamide adenine dinucleotide phosphate-diaphorase staining in longitudinal muscle strips with attached myenteric plexus of guinea pig ileum. l-Glutamate (100 μM) significantly enhanced both the evoked [ 3H]acetylcholine release and the optical density of nicotinamide adenine dinucleotide phosphate-diaphorase positive neurones, i.e. the intensity of staining. The non-competitive N-methyl- d-aspartate receptor antagonist MK-801 (3 μM) abolished the stimulatory effect of l-glutamate on acetylcholine efflux. Similarly, the nitric oxide synthase inhibitor N ω-nitro- l-arginine (100 μM) significantly reduced the effect of l-glutamate on [ 3H]acetylcholine release and nicotinamide adenine dinucleotide phosphate-diaphorase staining. Our data suggest that endogenous nitric oxide seems to mediate the stimulatory effect of glutamate on acetylcholine release from guinea pig myenteric neurons.

Multilocal expression of B-type allatostatins in crickets ( Gryllus bimaculatus)

B-type allatostatins (AST) inhibit the biosynthesis of juvenile hormone (JH) in vitro in crickets, but are also present in other insects, where they may bare different functions. By means of one-step RT-PCR and in situ hybridization recently, we could show that the mRNA of the gene is expressed in various cells of the central nervous system, but also in endocrine cells of the gut. The latter results corroborated a function of these peptides in regulating gut motility. Here we report on the expression of the gene in the ovary, the fat body and the flight muscles of female adult crickets, which suggests further putative functions of the B-type allatostatins beyond their role as brain–gut peptides.

CAJAL-LIKE CELLS IN THE HUMAN UPPER URINARY TRACT

Interstitial cells of Cajal (ICCs) have an important role in the regulation of gut motility as they are responsible for the slow wave activity of smooth muscle. It is still unknown if ICCs also occur in the human upper urinary tract. Since these cells express and are marked by the c-kit receptor CD117, we investigated its occurrence and distribution along the human upper urinary tract. Tissues from 56 human ureters, spanning proximal, middle and distal ureter segments, were analyzed by indirect immunohistochemistry using the alkaline phosphatase-anti-alkaline phosphatase method and double labeling immunofluorescence on consecutive tissue sections. Several monoclonal and polyclonal antibodies to c-kit receptor were used in combination with various cell markers for histiocytic, mast cell, endothelial, epithelial, neuronal, smooth muscle and stem cell differentiation. The c-kit receptor was found in 3 cell types of the ureter and in round or spindle-shaped cells. Due to their antigenic profile the first one was revealed as mast cells occurring in all layers of the ureteral wall except the urothelium. In contrast, the population of spindle-shaped cells was only marked by c-kit receptor, thus, resembling ICCs. These ICC-like cells were found among the inner and outer smooth muscle layers, and in the lamina propria. They showed a slight decrease from proximal to distal ureteral segments. However, unlike intestinal ICCs their cytomorphology differed and some cells, representing the third group of c-kit receptor positive cells, were found within the urothelium. Our data demonstrate the presence of ICC-like cells and their ubiquitous distribution in the human ureter. The physiological importance and pathological significance of these findings must be evaluated by functional studies and investigations of certain pathological with urinary outflow disturbance conditions.

Inflammatory cells and the regulation of gut motility.

Inflammatory cells and the regulation of gut motility.

Inflammatory Cells and the Regulation of Gut Motility

Inflammatory Cells and the Regulation of Gut Motility

Morphology and electrophysiology of neurons in dog paraventricular nucleus: in vitro study

The paraventricular nucleus (PVN) of the hypothalamus plays an important role in regulating gut motility. To date, there have been no intracellular electrophysiological studies of dog PVN neurons in vitro. The aims of this study were to: (1) adapt brain slice methods developed for studies of rodent CNS tissue to canine CNS tissue; and (2) study the electrophysiology and morphology of single neurons of the dog paraventricular nucleus (PVN). Coronal hypothalamic slice preparations (400 μm thick) of dog brain were used. Three groups of PVN neurons were classified based on their firing pattern. Continuous firing neurons ( n=32) exhibited continuous ongoing action potentials (APs). Burst firing neurons generated bursts of APs ( n=19). Intermittent firing neurons had only a few spontaneous APs. In contrast to continuous firing neurons, 14 of 19 burst firing neurons and 3 of 7 intermittent firing neurons responded to depolarizing current with a Ca 2+-dependent low-threshold potential. Twenty-one PVN neurons studied electrophysiologically were filled with biocytin. Continuous firing neurons ( n=12) had oval-shaped soma with two or three sparsely branched dendrites. Branched axons were found in two continuous firing neurons, in which one branch appeared to terminate locally. Burst firing neurons ( n=8) generally had triangular soma with 2 to 5 branched dendrites. In summary, the brain slice technique was used to study the morphology and electrophysiology of single neurons of the dog brain. Electrophysiological and morphological properties of the three neuron groups were identified and discussed.

Calcium imaging of gut activity.

The major cell types regulating gut motility include enteric neurones, interstitial cells of Cajal (ICC) and their effector smooth muscle cells. These cells are arranged conveniently in nested layers through the gut wall. Our knowledge of how many of these cells in each layer are integrated to produce the various patterns of motility is largely unknown. So far, much of our knowledge of gut motility has usually been obtained by examining point sources of activity (e.g. intracellular recordings from enteric neurones, ICC and smooth muscle cells), rather than the spread of activity through these spatially distributed nerve and ICC networks, or smooth muscle syncitia. Our understanding of how these cells are integrated to produce gut movements would be greatly enhanced if we could image the activity in many of these cells in each layer, or many cells in several layers, simultaneously. Calcium (Ca2+) is a major signalling and regulatory molecule in most cells. In fact, electrical excitability in enteric neurones, ICC and smooth muscle is associated with robust rises in intracellular Ca2+ that long outlast the electrical events (e.g. action potentials in neurones and smooth muscle) that gave rise to them. These prolonged Ca2+ responses, together with the development of several high quality Ca2+ indicators, has provided a unique opportunity to image many cells in intact tissues simultaneously using ICCD video-rate cameras along with conventional microscopy. However, confocal microscopy has also been used, and has several advantages over the above systems. These include reduced photo-toxicity and bleaching and the elimination of out of focus light from different layers within the tissue. So far, despite some limitations with the calcium imaging techniques, the spread of activity through the two layers of smooth muscle, ICC networks and myenteric neurones in intact preparations, or cultured myenteric neuronal networks, is beginning to yield exciting new data about how these different cells interact and process information.

Changes of gastrointestinal argyrophil endocrine cells in the osteoporotic SD rats induced by ovariectomy

The regional distributions and frequencies of argyrophil endocrine cells in gastrointestinal (GI) tract of osteoporotic Sprague-Dawley rat induced by ovariectomy were studied using Grimelius silver stain. The experimental animals were divided into two groups, one is non-ovariectomized group (Sham) and the other is ovariectomized group (OVX). Samples were collected from each part of GI tract (fundus, pylorus, duodenum, jejunum, ileum, cecum, colon and rectum) at 10th week after ovariectomy or sham operation. In this study, argyrophil cells were detected throughout the entire GI tract with various frequencies regardless of ovariectomy. Most of these argyrophil cells in the mucosa of GI tract were generally spherical or spindle in shape (open type cell) while cells showing round in shape (close type cell) were found occasionally in gastric and/or intestinal gland regions. The regional distributions of GI argyrophil endocrine cells in OVX were similar to those of Sham. However, significant decreases of argyrophil cells were detected in OVX compared to those of Sham except for the pylorus, jejunum and cecum. In pylorus and jejunum, argyrophil cells in OVX dramatically decreased compared to those of Sham but significances were not recorded. In addition, argyrophil cells in cecum of OVX showed similar frequency compared to that of Sham. The endocrine cells are the anatomical units responsible for the production of gut hormones that regulate gut motility and digestion including absorption, and a change in their density would reflect the change in the capacity of producing these hormones and regulating gut motility and digestion. Ovariectomy induced severe quantitative changes of GI argyrophil endocrine cell density, and the abnormality in density of GI endocrine cells may contribute to the development of gastrointestinal symptoms in osteoporosis such as impairments of calcium and some lipids, frequently encountered in patients with postmenopausal osteoporosis.

Actions of orexin-A in the myenteric plexus of the guinea-pig small intestine.

Orexins and orexin-receptors are localized by displaying their immunoreactivity in the enteric nervous system. Intracellular recordings were made from isolated myenteric neurons to investigate actions of orexin-A in the myenteric plexus of the guinea-pig ileum. Superfusion of orexin-A caused membrane depolarizations in a subset of S and AH neurons. Orexin-A responses were preserved in Ca2+ free/high Mg2+ solution and associated with an increase in input membrane resistance; their reversal potential was about -90 mV. Orexin-A augmented nicotinic fast EPSPs, whereas it did not affect the postsynaptic sensitivity to acetylcholine; this indicates that orexin-A increased the presynaptic release of acetylcholine. In conclusion, orexin-A contributes in the regulation of gut motility via its pre- and postsynaptic actions in the myenteric plexus.

Glutamate in the enteric nervous system.

Several lines of evidence indicate a role for glutamate in the regulation of gut motility and secretion; however, the receptor subtypes that mediate the effects of this amino acid are still incompletely understood. There has, however, been recent progress in pharmacological characterization of enteric glutamate receptor subtypes. In the past two years, investigators have demonstrated that in addition to ionotropic glutamate receptors, the enteric nervous system contains functional group I metabotropic glutamate receptors that appear to participate in enteric reflexes. This opens up an entirely new arena in which to study the roles of glutamate in gut function and presents potential new target sites for drug development.

Chemical neuroanatomy of the vesicular amine transporters.

Acetylcholine, catecholamines, serotonin, and histamine are classical neurotransmitters. These small molecules also play important roles in the endocrine and immune/inflammatory systems. Serotonin secreted from enterochromaffin cells of the gut epithelium regulates gut motility; histamine secreted from basophils and mast cells is a major regulator of vascular permeability and skin inflammatory responses; epinephrine is a classical hormone released from the adrenal medulla. Each of these molecules is released from neural, endocrine, or immune/inflammatory cells only in response to specific physiological stimuli. Regulated secretion is possible because amines are stored in secretory vesicles and released via a stimulus-dependent exocytotic event. Amine storage-at concentrations orders of magnitude higher than in the cytoplasm-is accomplished in turn by specific secretory vesicle transporters that recognize the amines and move them from the cytosol into the vesicle. Immunohistochemical visualization of specific vesicular amine transporters (VATs) in neuronal, endocrine, and inflammatory cells provides important new information about how amine-handling cell phenotypes arise during development and how vesicular transport is regulated during homeostatic response events. Comparison of the chemical neuroanatomy of VATs and amine biosynthetic enzymes has also revealed cell groups that express vesicular transporters but not enzymes for monoamine synthesis, and vice versa: their function and regulation is a new topic of investigation in mammalian neurobiology. The chemical neuroanatomy of the vesicular amine transporters is reviewed here. These and similar data emerging from the study of the localization of the recently characterized vesicular inhibitory and excitatory amino acid transporters will contribute to understanding chemically coded synaptic circuitry in the brain, and amine-handling neuroendocrine and immune/inflammatory cell regulation.

The role of 5-hydroxytryptamine 3 and 5-hydroxytryptamine 4 receptors in the regulation of gut motility in the ferret

The role of 5-hydroxytryptamine (5-HT) 3 and 5-HT 4 receptors in the regulation of gut motility in the ferret was investigated. The selective 5-HT 3 receptor antagonist ramosetron (1 – 10 μg kg s.c.) prolonged the interval of gastric antral migrating motor complex, but had only slight effect on small intestinal and colonic motility in unfed animals. The selective 5-HT 4 receptor antagonist SB 204070 did not affect motility throughout gut in unfed animals. Neither ramosetron nor SB 204070 affected the motility throughout gut in fed animals. In conclusion, neither 5-HT 3 nor 5-HT 4 receptors tonically regulate ferret gut motility except that S-HT 3 receptors have a key role in the occurrence of migrating motor complex specifically in the stomach. The role of 5-HT 3 and 5-HT 4 receptor system in the regulation of gut motility in ferrets is similar to that in other mammalian species studied, including humans. This similarity suggests that the ferret is a suitable model animal to study gut motor functions in humans.

Sst1 mRNA is the prominent somatostatin receptor mRNA in the rat gastrointestinal tract: reverse transcription polymerase chain reaction and in situ-hybridization study

The inhibitory peptide hormone somatostatin and its receptors (sst1–sst5) regulate many physiological functions in the gastrointestinal tract. In an attempt to correlate the various effects of somatostatin in gastrointestinal physiology to individual sst subtypes sst1–sst5, mRNAs have been localized by semiquantitative reverse transcription polymerase chain reaction amplification and in situ hybridization of sst1 and sst3 in the rat alimentary tract. sst1–sst4 mRNAs were found throughout the gastrointestinal tract, sst1 mRNA being more abundant than sst2 and much more abundant than sst3 and sst4 mRNAs. sst5 transcripts were at the detection threshold. sst1 and sst3 mRNAs are present in enterocytes and enteric neurons suggesting a role of these subtypes in the somatostatin-mediated inhibition of acetylcholine release from myenteric neurons and of secretomotor neuron activity in the submucous plexus. The presence of sst3 mRNA in smooth muscle cells points to an additional role of this receptor in regulating gut motility.

Ontogeny of galanin‐immunoreactive elements in the intrinsic nervous system of the chicken gut

Galanin is a brain-gut peptide that is present in the central and peripheral nervous systems. In the gut, it is contained exclusively in intrinsic and extrinsic nerve supplies, and it is involved overall in the regulation of gut motility. To obtain information about the ontogeny of galanin, we undertook an immunohistochemical study of chicken embryos. The time of first appearance and the distribution patterns of galanin were investigated with fluorescence and streptavidin-biotin-peroxidase (ABC) immunohistochemical protocols by using a galanin polyclonal antiserum. The various regions of the gut and the pancreas were obtained from chicken embryos aged from 3 days of incubation to hatching. All specimens were fixed in buffered picric acid-paraformaldehyde, frozen, and cut with a cryostat. Galanin-immunoreactive neuroblasts were first detected at 4 days in the mesenchyme of the proventriculus/gizzard primordium and within the Remak ganglion. They then extended cranially and caudally, reaching all of the other gut regions at 6.5 days. Galanin-immunoreactive nerve elements mainly occupied the sites of myenteric and submucous plexuses. From day 15, galanin-immunoreactive nerve fibers tended to invade the circular muscular layer and part of the lamina propria of the mucosa. In the pancreas, weak galanin-immunoreactive nerve elements were detected at 5.5 days. They tended to be distributed among the glandular lobules according to the organ differentiation. The widespread distribution during the earlier embryonic stages represents evidence indicating that the neuropeptide galanin may have a role as a differentiating or growth factor. From late embryonic life, its predominant presence in sympathetic nerves and in muscular layers fits with the functions demonstrated previously in adults of other vertebrates for galanin as a modulator of intestinal motility. Anat Rec 254:28–38, 1999. © 1999 Wiley-Liss, Inc.

Ontogeny of galanin-immunoreactive elements in the intrinsic nervous system of the chicken gut.

Galanin is a brain-gut peptide that is present in the central and peripheral nervous systems. In the gut, it is contained exclusively in intrinsic and extrinsic nerve supplies, and it is involved overall in the regulation of gut motility. To obtain information about the ontogeny of galanin, we undertook an immunohistochemical study of chicken embryos. The time of first appearance and the distribution patterns of galanin were investigated with fluorescence and streptavidin-biotin-peroxidase (ABC) immunohistochemical protocols by using a galanin polyclonal antiserum. The various regions of the gut and the pancreas were obtained from chicken embryos aged from 3 days of incubation to hatching. All specimens were fixed in buffered picric acid-paraformaldehyde, frozen, and cut with a cryostat. Galanin-immunoreactive neuroblasts were first detected at 4 days in the mesenchyme of the proventriculus/gizzard primordium and within the Remak ganglion. They then extended cranially and caudally, reaching all of the other gut regions at 6.5 days. Galanin-immunoreactive nerve elements mainly occupied the sites of myenteric and submucous plexuses. From day 15, galanin-immunoreactive nerve fibers tended to invade the circular muscular layer and part of the lamina propria of the mucosa. In the pancreas, weak galanin-immunoreactive nerve elements were detected at 5.5 days. They tended to be distributed among the glandular lobules according to the organ differentiation. The widespread distribution during the earlier embryonic stages represents evidence indicating that the neuropeptide galanin may have a role as a differentiating or growth factor. From late embryonic life, its predominant presence in sympathetic nerves and in muscular layers fits with the functions demonstrated previously in adults of other vertebrates for galanin as a modulator of intestinal motility.

Electrical characteristics and responses to jejunal distension of neurons in Remak's juxta-jejunal ganglia of the domestic fowl.

1. Remak's nerve is a ganglionated nerve trunk found only in birds that runs parallel to the gut from the duodenal-jejunal junction to the cloaca. We report the first electrophysiological characterization of these neurons and their responses to gut distension. 2. A segment of chicken jejunum with attached Remak's nerve was pinned in an electrophysiological chamber. Neurons in Remak's ganglia were impaled with microelectrodes. The adjacent segment of gut was distended with fluid. 3. One hundred and thirty neurons were characterized into three electrophysiological classes: (i) tonic neurons (74%) fired action potentials spontaneously (frequency 3.5 Hz) and continuously (up to 40 Hz) throughout a depolarizing current pulse; (ii) AD neurons (22%) fired a brief burst of action potentials (1-10), which were followed by a prolonged after-depolarization (AD) of duration 2.8 +/- 0.3 s; and (iii) phasic neurons (4%) fired an initial burst of action potentials followed by an after-hyperpolarization (duration, 520.0 +/- 32.0 ms). Tetrodotoxin (1 microM) abolished action potentials in tonic and AD neurons as well as the after-depolarization. 4. Spontaneous fast excitatory postsynaptic potentials (FEPSPs) occurred in all classes of neurons; they were not observed, however, in ganglia isolated from the jejunum. 5. Intracellular injection of biocytin revealed that neurons could be characterized into four morphological classes. Tonic neurons, which had long and extensive dendritic trees, were Remak's Type I, II and IV neurons. AD neurons also comprised Remak's type II neurons. Phasic neurons were Remak's Type III neurons. Most neurons had axons that projected orally along Remak's nerve. 6. Distension of the jejunum evoked FEPSPs and action potentials in tonic neurons, and repetitive bursts of action potentials (1-4) followed by an after-depolarization in AD neurons. All responses to distension were blocked by hexamethonium (300 microM) and tetrodotoxin (1 microM). 7. In conclusion, neurons in Remak's juxta-jejunal nerve appear to regulate gut motility. Three distinct electrophysiological classes of neurons were observed, all of which appear to be activated by distension sensitive cholinergic intestinofugal neurons in the jejunum.

Immunochemical demonstration of Eisenia tetradecapeptide, a bioactive peptide isolated from the gut of the earthworm Eisenia foetida, in tissues of the earthworm.

The quantity and localization of Eisenia tetradecapeptide which was isolated from the gut of the earthworm Eisenia foetida were examined in tissues of the same species by enzyme-linked immunosorbent assay and immunohistochemistry. Analysis by enzyme-linked immunosorbent assay showed that Eisenia-tetradecapeptide-like immunoreactivity was present in both the central nervous system (cerebral ganglion, subesophageal ganglion, ventral ganglia, and ventral nerve cord) and the gut (esophagus, crop, gizzard, and intestine). The central nervous system contained a higher amount of Eisenia-tetradecapeptide-like immunoreactivity (1.3 pmol/mg wet weight) than the gut (0.2-0.6 pmol/mg wet weight). Eisenia-tetradecapeptide-like immunoreactivity was scarcely detected in the body-wall muscle, nephridia, and sexual organs (testis, ovary, seminal vesicle, and ovisac). Immunohistochemical analysis demonstrated that intense Eisenia-tetradecapeptide-like immunopositive cells and nerve fibers were present in the central nervous system. Immunoreactivity was found in the epithelial cells lining the esophagus and in the submucous plexus in various parts of the gut. Thus, the present study suggests that Eisenia tetradecapeptide is a neuropeptide and/or peptide hormone present in both the central nervous system and the gut of the earthworm and that its role involves the regulation of gut motility.

Contribution of sacral spinal cord neurons to the autonomic and somatic consequences of withdrawal from morphine in the rat

In this study, we monitored Fos-like immunoreactivity in the sacral spinal cord to identify neurons that are likely to contribute to the autonomic manifestations of opioid antagonist-precipitated withdrawal in morphine-tolerant rats. Injection of systemic antagonist increased the Fos-like immunoreactivity throughout the first sacral segment, particularly in laminae I/II, X, and in the sacral parasympathetic nucleus (SPN). Selective peripheral withdrawal, with a hydrophilic antagonist that does not cross the blood-brain barrier (BBB), induced diarrhea, but no other withdrawal signs were evident. Compared to rats that withdrew systemically, peripheral withdrawal evoked significantly less Fos-like immunoreactivity in laminae V/VI, X and the SPN. By contrast, selective spinal withdrawal, by intrathecal injection of an opioid antagonist that does not cross the BBB, provoked hyperactivity of the hindlimbs and tail, but no diarrhea. These animals demonstrated significantly increased Fos-like immunoreactivity in laminae I/II, V/VI, the SPN, and the ventral horn compared to rats that withdrew systemically. Animals treated neonatally with capsaicin, to eliminate C-fiber input, demonstrated withdrawal behavior similar to intact withdrawing rats, except that the capsaicin-pretreated rats had significantly greater weight loss. However, this group had less Fos-like immunoreactivity in laminae V/VI, X and the SPN compared to the intact withdrawing rats. These data suggest that withdrawal from morphine evokes hyperactivity of sacral neurons, particularly those involved in regions that process nociceptive and autonomic information. Peripheral withdrawal is sufficient to induce diarrhea, but it does not fully explain the associated weight loss. Unmyelinated primary afferents may contribute a tonic peripheral inhibition of circuits that regulate gut motility and intestinal fluid transport. Taken together, these data suggest that chronic exposure to opioids induces a latent sensitization in sacral cord neurons that can be manifested as neuronal hyperactivity during withdrawal; this mechanism may underlie withdrawal-induced hyperalgesia and gut hypermotility.

Identification of the dipteran Leu-callatostatin peptide family: the pattern of precursor processing revealed by isolation studies in Calliphora vomitoria

Information from the Leu-callatostatin gene sequences of the blowflies Calliphora vomitoria and Lucilia cuprina was used to develop antisera specific for the variable post-tyrosyl amino-acid residues Ser, Ala and Asn of the common Leu-callatostatin C-terminal pentapeptide sequence −YXFGL-NH2. Radioimmunoassays based on these antisera were used to purify peptides from an extract of 40 000 blowfly heads. Five neuropeptides of the Leu-callatostatin family were identified. Three have a seryl residue in the post-tyrosyl position. Two of these are octapeptides that differ only at the N-terminal residue; NRPYSFGL-NH2 and ARPYSFGL-NH2, whilst the third is the heptapeptide derived by N-terminal trimming; RPYSFGL-NH2. Two octapeptides in which X is Ala and Asn were also identified; VERYAFGL-NH2 and LPVYNFGL-NH2. The latter peptide is derived by processing at the internal dibasic site of a putative heneicosapeptide encoded by the DNA. These findings stress the necessity to have putative structures verified at the peptide level. Potent, reversible inhibitory effects on the spontaneous contractile activity of the blowfly rectum were recorded for ARPYSFGL-NH2 (monophasic dose-response curve with an IC50 = 10 fM) and for LPVYNFGL-NH2 (biphasic dose-response curve with IC50 values of approximately 1 fM and 1 nM). It is suggested that regulation of gut motility in insects, rather than an allatostatic function, may represent an ancestral and universal function of the allatostatins. One of the reasons for the large number of members of the Leu-callatostatin family appears to be in the provision of an integrated form of gut motility control, with different peptides controlling specific regions of the gut.