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Kaji I, Akiba Y, Furuyama T, Adelson DW, Iwamoto K, Watanabe M, Kuwahara A, Kaunitz JD. Free fatty acid receptor 3 activation suppresses neurogenic motility in rat proximal colon. Neurogastroenterol Motil 2018; 30:10.1111/nmo.13157. [PMID: 28714277 PMCID: PMC5739952 DOI: 10.1111/nmo.13157] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Accepted: 06/14/2017] [Indexed: 02/06/2023]
Abstract
BACKGROUND Short-chain fatty acids (SCFA) are microbial fermentation products absorbed by the colon. We recently reported that activation of the SCFA receptor termed free fatty acid receptor 3 (FFA3), expressed on cholinergic nerves, suppresses nicotinic acetylcholine receptor (nAChR)-mediated transepithelial anion secretion. This study aimed to clarify how activation of neurally expressed FFA3 affects colonic motor function. METHODS FFA3-expressing myenteric neurons were identified by immunostaining; contractions of isolated circular muscle strips obtained from rat proximal colon were measured by isometric transducers. The effect of FFA3 agonists on defecation in vivo was examined in an exogenous serotonin-induced defecation model. KEY RESULTS FFA3 immunoreactivity was located in nitrergic and cholinergic neurons in the myenteric plexus. In isolated circular muscle strips without mucosa and submucosa, the addition of nicotine (10 μM) or serotonin transiently relaxed the muscle through nitrergic neurons, whereas high concentrations of nicotine (100 μM) induced large-amplitude contractions that were mediated by cholinergic neurons. Pretreatment with FFA3 agonists inhibited nicotine- or serotonin-induced motility changes but had no effect on bethanechol-induced direct muscle contractions. The Gi/o inhibitor pertussis toxin reversed the inhibitory effect of an FFA3 agonist AR420626 on nicotine-evoked contractions, suggesting that FFA3 activation suppresses nAChR-mediated neural activity in myenteric neurons, consistent with an FFA3-mediated antisecretory effect. In conscious rats, exogenous serotonin increased the volume of fecal output, compared with the vehicle- or AR420626-treated groups. Pretreatment with AR420626 significantly suppressed serotonin-induced fecal output. CONCLUSION AND INFERENCES FFA3 is a promising target for the treatment of neurogenic diarrheal disorders by suppressing nAChR-mediated neural pathways.
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Affiliation(s)
- Izumi Kaji
- Department of Medicine, University of California Los Angeles,Greater Los Angeles VA Healthcare System
| | - Yasutada Akiba
- Department of Medicine, University of California Los Angeles,Greater Los Angeles VA Healthcare System
| | - Takafumi Furuyama
- Neuroethology & Bioengineering, Graduate School of Life & Medical Sciences, Doshisha University,Japan Society for the Promotion of Science
| | | | - Kenichi Iwamoto
- Graduate School of Integrated Pharmaceutical and Nutritional Sciences, University of Shizuoka
| | - Masahiko Watanabe
- Department of Anatomy, Graduate School of Medicine, Hokkaido University
| | - Atsukazu Kuwahara
- Graduate School of Integrated Pharmaceutical and Nutritional Sciences, University of Shizuoka
| | - Jonathan D. Kaunitz
- Department of Medicine, University of California Los Angeles,Department of Surgery, University of California Los Angeles,Greater Los Angeles VA Healthcare System
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Matsumoto K, Nakajima T, Sakai H, Kato S, Sagara A, Arakawa K, Tashima K, Narita M, Horie S. Increased expression of 5-HT3 and NK 1 receptors in 5-fluorouracil-induced mucositis in mouse jejunum. Dig Dis Sci 2013; 58:3440-51. [PMID: 23695873 DOI: 10.1007/s10620-013-2709-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Accepted: 04/26/2013] [Indexed: 01/13/2023]
Abstract
BACKGROUND AND OBJECTIVE Although 5-fluorouracil (5-FU) is a widely used as chemotherapy agent, severe mucositis develops in approximately 80% of patients. 5-FU-induced small intestinal mucositis can cause nausea and vomiting. The current study was designed to investigate peripheral alterations due to the 5-FU-induced mucositis of neuronal and non-neuronal 5-HT3 and NK1 receptor expression by immunohistochemical analysis. METHODS 5-FU was administered by i.p. injection to C57BL/6 mice. After 4 days, segments of the jejunum were removed. The specimens were analyzed by immunohistochemistry, real-time PCR, and enzyme immunoassay. RESULTS The numbers of 5-HT3 receptor immunopositive cells and nerve fibers in mucosa were increased by 5-FU treatment. The 5-HT3 receptor immunopositive cell bodies were found only in jejunal submucosa and myenteric plexus in the 5-FU-treated mice. The numbers of NK1 receptor cells in mucosa and immunopositive expression of NK1 receptors in deep muscular plexus were dramatically increased in 5-FU-treated mice. Real-time PCR demonstrated that 5-FU treatment significantly increased mRNA levels of 5-HT3A, 5-HT3B, and NK1 receptors. The amounts of 5-HT and substance P increased after 5-FU treatment. The 5-HT3 or NK1 receptor immunopositive cells colocalized with both 5-HT and substance P. Furthermore, 5-HT3 and NK1 receptors colocalized with CD11b. CONCLUSIONS The 5-HT3 and NK1 immunopositive macrophages and mucosal mast cells in lamina propria release 5-HT and substance P, which in turn activate their corresponding receptors on mucosal cells in autocrine and paracrine manners. It is assumed to result in the release of 5-HT and substance P in mucosa.
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Affiliation(s)
- Kenjiro Matsumoto
- Laboratory of Pharmacology, Faculty of Pharmaceutical Sciences, Josai International University, 1 Gumyo, Togane, Chiba, 283-8555, Japan,
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Anticancer drug irinotecan inhibits homomeric 5-HT3A and heteromeric 5-HT3AB receptor responses. Biochem Biophys Res Commun 2011; 415:416-20. [DOI: 10.1016/j.bbrc.2011.10.084] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2011] [Accepted: 10/17/2011] [Indexed: 11/21/2022]
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Kapeller J, Möller D, Lasitschka F, Autschbach F, Hovius R, Rappold G, Brüss M, Gershon MD, Niesler B. Serotonin receptor diversity in the human colon: Expression of serotonin type 3 receptor subunits 5-HT3C, 5-HT3D, and 5-HT3E. J Comp Neurol 2011; 519:420-32. [PMID: 21192076 DOI: 10.1002/cne.22525] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Since the first description of 5-HT₃ receptors more than 50 years ago, there has been speculation about the molecular basis of their receptor heterogeneity. We have cloned the genes encoding novel 5-HT3 subunits 5-HT3C, 5-HT3D, and 5-HT3E and have shown that these subunits are able to form functional heteromeric receptors when coexpressed with the 5-HT3A subunit. However, whether these subunits are actually expressed in human tissue remained to be confirmed. In the current study, we performed immunocytochemistry to locate the 5-HT3A as well as the 5-HT3C, 5-HT3D, and 5-HT3E subunits within the human colon. Western blot analysis was used to confirm subunit expression, and RT-PCR was employed to detect transcripts encoding 5-HT₃ receptor subunits in microdissected tissue samples. This investigation revealed, for the first time, that 5-HT3C, 5-HT3D, and 5-HT3E subunits are coexpressed with 5-HT3A in cell bodies of myenteric neurons. Furthermore, 5-HT3A and 5-HT3D were found to be expressed in submucosal plexus of the human large intestine. These data provide a strong basis for future studies of the roles that specific 5-HT₃ receptor subtypes play in the function of the enteric and central nervous systems and the contribution that specific 5-HT₃ receptors make to the pathophysiology of gastrointestinal disorders such as irritable bowel syndrome and dyspepsia.
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Affiliation(s)
- Johannes Kapeller
- Department of Human Molecular Genetics, University of Heidelberg, Germany
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Li Z, Caron MG, Blakely RD, Margolis KG, Gershon MD. Dependence of serotonergic and other nonadrenergic enteric neurons on norepinephrine transporter expression. J Neurosci 2010; 30:16730-40. [PMID: 21148012 PMCID: PMC3066093 DOI: 10.1523/jneurosci.2276-10.2010] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The norepinephrine transporter (NET), which is expressed on the plasma membranes of noradrenergic neurons, is important in terminating neurotransmission. The noradrenergic sympathetic neurons that innervate the bowel express NET, but they are extrinsic and their cell bodies are not components of the enteric nervous system (ENS). Subsets of neurons were nevertheless found in the murine ENS that express transcripts encoding NET, NET protein, and dopamine β-hydroxylase; these neurons lack tyrosine hydroxylase (TH) and thus are not catecholaminergic. Enteric NET expression, moreover, preceded the ingrowth of sympathetic axons during development and did not disappear when the gut was extrinsically denervated. Transiently catecholaminergic (TC), neural crest-derived precursors of enteric neurons expressed NET at embryonic day 10 (E10) and NET expression in the fetal gut peaked coincidentally with early neurogenesis at E12. Serotonergic neurons, which are born early from TC progenitors, were found to express NET in the adult ENS, as did also other early-born neurons containing calretinin or neuronal nitric oxide synthase (nNOS) immunoreactivities. NET was not expressed in TH-immunoreactive dopaminergic neurons, which are born perinatally. Genetic deletion of NET almost eliminated tryptophan hydroxylase 2 expression and significantly reduced the numbers of total, 5-HT- and calretinin-immunoreactive enteric neurons, without affecting the immunoreactivities of nNOS or TH. These observations indicate that TC precursors of subsets of noncatecholaminergic enteric neurons express NET that persists in the successors of these cells despite their loss of TH. NET expression is essential for development and/or survival of some (5-HT- and calretinin-expressing), but not all (nNOS-expressing), of these neurons.
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Affiliation(s)
- Zhishan Li
- Department of Pathology and Cell Biology, Columbia University, New York, New York 10032, USA.
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Prause AS, Stoffel MH, Portier CJ, Mevissen M. Expression and function of 5-HT7 receptors in smooth muscle preparations from equine duodenum, ileum, and pelvic flexure. Res Vet Sci 2009; 87:292-9. [PMID: 19364615 DOI: 10.1016/j.rvsc.2009.03.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2008] [Revised: 01/27/2009] [Accepted: 03/13/2009] [Indexed: 11/26/2022]
Abstract
In horses, gastrointestinal (GI) disorders occur frequently and cause a considerable demand for efficient medication. 5-Hydroxytryptamine receptors (5-HT) have been reported to be involved in GI tract motility and thus, are potential targets for treating functional bowel disorders. Our studies extend current knowledge on the 5-HT(7) receptor in equine duodenum, ileum and pelvic flexure by studying its expression throughout the intestine and its role in modulating contractility in vitro by immunofluorescence and organ bath experiments, respectively. 5-HT(7) immunoreactivity was demonstrated in both smooth muscle layers, particularly in the circular one, and within the myenteric plexus. Interstitial cells of Cajal (ICC), identified by c-Kit labeling, show a staining pattern similar to that of 5-HT(7) immunoreactivity. The selective 5-HT(7) receptor antagonist SB-269970 increased the amplitude of contractions in spontaneous contracting specimens of the ileum and in electrical field-stimulated specimens of the pelvic flexure concentration-dependently. Our in vitro experiments suggest an involvement of the 5-HT(7) receptor subtype in contractility of equine intestine. While the 5-HT(7) receptor has been established to be constitutively active and inhibits smooth muscle contractility, our experiments demonstrate an increase in contractility by the 5-HT(7) receptor ligand SB-269970, suggesting it exerting inverse agonist properties.
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Affiliation(s)
- Andrea S Prause
- Division Veterinary Pharmacology and Toxicology, University of Berne, 3012 Berne, Switzerland
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Batista Lobo S, Denyer M, Britland S, Javid FA. Development of an intestinal cell culture model to obtain smooth muscle cells and myenteric neurones. J Anat 2007; 211:819-29. [PMID: 17979953 PMCID: PMC2375843 DOI: 10.1111/j.1469-7580.2007.00820.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
This paper reports on the development of an entirely new intestinal smooth muscle cell (ISMC) culture model using rat neonates for use in pharmacological research applications. Segments of the duodenum, jejunum and ileum were obtained from Sprague-Dawley rat neonates. The cell extraction technique consisted of ligating both ends of the intestine and incubating (37 degrees C) in 0.25% trypsin for periods of 30-90 min. Isolated cells were suspended in DMEM-HEPES, plated and allowed to proliferate for 7 days. Cell culture quality was assessed via a series of viability tests using the dye exclusion assay. In separate experiments, tissues were exposed to trypsin for varying durations and subsequently histological procedures were applied. Cell purification techniques included differential adhesion technique for minimizing fibroblasts. Selective treatments with neurotoxin scorpion venom (30 microg mL(-1)) and anti-mitotic cytosine arabinoside (6 microm) were also applied to purify respectively ISMC and myenteric neurones selectively. The different cell populations were identified in regard to morphology and growth characteristics via immunocytochemistry using antibodies to smooth muscle alpha-actin, alpha-actinin and serotonin-5HT3 receptors. Based on both viability and cell confluence experiments, results demonstrated that intestinal cells were best obtained from segments of the ileum dissociated in trypsin for 30 min. This provided the optimum parameters to yield highly viable cells and confluent cultures. The finding was further supported by histological studies demonstrating that an optimum incubation time of 30 min is required to isolate viable cells from the muscularis externae layer. When cell cultures were treated with cytosine arabinoside, the non-neuronal cells were abolished, resulting in the proliferation of cell bodies and extended neurites. Conversely, cultures treated with scorpion venom resulted in complete abolition of neurones and proliferation of increasing numbers of ISMC, which were spindle-shaped and uniform throughout the culture. When characterized by immunocytochemistry, neurones were stained with antibody to 5HT3 receptors but not with antibodies to alpha-smooth muscle actin and alpha-actinin. Conversely, ISMC were stained with antibodies to alpha-smooth muscle actin and alpha-actinin but not with antibody to 5HT3 receptors. The present study provides evidence that our method of dissociation and selectively purifying different cell populations will allow for pharmacological investigation of each cell type on different or defined mixtures of different cell types.
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Affiliation(s)
- S Batista Lobo
- School of Pharmacy, University of Bradford and Institute of Pharmaceutical Innovation, Bradford, UK.
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Nylander O, Pihl L. Luminal hypotonicity increases duodenal mucosal permeability by a mechanism involving 5-hydroxytryptamine. Acta Physiol (Oxf) 2006; 186:45-58. [PMID: 16497179 DOI: 10.1111/j.1748-1716.2005.01507.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
AIM To investigate whether 5-hydroxytryptamine (5-HT) participates in the mediation of the hypotonicity-induced increase in duodenal mucosal permeability. METHODS Proximal duodenum in anaesthetized rats was perfused in situ with a hypotonic NaCl solution and effects on duodenal motility, net fluid flux, mucosal permeability [blood-to-lumen clearance of (51)Cr-ethylenediaminetetraacetic acid (EDTA)] and the release of 5-HT into the luminal solution studied in the presence of the cyclooxygenase inhibitor indomethacin. RESULTS Perfusion of the duodenum with 50 mm NaCl increased mucosal permeability eightfold, increased the luminal output of 5-HT twofold and induced net fluid absorption. This rise in permeability was enhanced 25% by 5-HT (3 x 10(-3) m), reduced by the 5-HT(3)-receptor antagonists granisetron (10(-4)-3 x 10(-4) m) or ondansetron (10(-5)-10(-4) m) or by the 5-HT(4) receptor antagonist SB 203186 (10(-4) m). The 5-HT(3/4) receptor antagonist tropisetron, at 10(-4) m, did not affect while 3 x 10(-4) and 3 x 10(-3) m augmented the hypotonicity-induced increase in mucosal permeability. Lidocaine (1.1 x 10(-3) m) similarly potentiated while tetrodotoxin (TTX) (5 x 10(-5) m) inhibited the hypotonicity-induced increase in mucosal permeability. Compared with animals treated with indomethacin alone ondansetron and granisetron augmented (by 30-40%) while tropisetron and lidocaine reduced (by 60-70%) the hypotonicity-induced net fluid absorption. Tetrodotoxin and all 5-HT receptor antagonists, except tropisetron, depressed duodenal motility. CONCLUSIONS Luminal hypotonicity increases duodenal mucosal permeability by a neural mechanism involving 5-HT acting on 5-HT(3) and 5-HT(4) receptors. 5-HT also appears to participate in the regulation of the hypotonicity-induced fluid flux.
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Affiliation(s)
- O Nylander
- Department of Neuroscience, Division of Physiology, Biomedical Center, Uppsala University, Uppsala, Sweden.
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Michel K, Zeller F, Langer R, Nekarda H, Kruger D, Dover TJ, Brady CA, Barnes NM, Schemann M. Serotonin excites neurons in the human submucous plexus via 5-HT3 receptors. Gastroenterology 2005; 128:1317-26. [PMID: 15887114 DOI: 10.1053/j.gastro.2005.02.005] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
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.
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Affiliation(s)
- Klaus Michel
- Department of Human Biology, Technische Universität Munich, Freising, Germany
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Bhattacharya A, Dang H, Zhu QM, Schnegelsberg B, Rozengurt N, Cain G, Prantil R, Vorp DA, Guy N, Julius D, Ford APDW, Lester HA, Cockayne DA. Uropathic observations in mice expressing a constitutively active point mutation in the 5-HT3A receptor subunit. J Neurosci 2004; 24:5537-48. [PMID: 15201326 PMCID: PMC6729324 DOI: 10.1523/jneurosci.5658-03.2004] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Mutant mice with a hypersensitive serotonin (5-HT)3A receptor were generated through targeted exon replacement. A valine to serine mutation (V13'S) in the channel-lining M2 domain of the 5-HT3A receptor subunit rendered the 5-HT3 receptor 70-fold more sensitive to serotonin and produced constitutive activity when combined with the 5-HT3B subunit. Mice homozygous for the mutant allele (5-HT3Avs/vs) had decreased levels of 5-HT3A mRNA. Measurements on sympathetic ganglion cells in these mice showed that whole-cell serotonin responses were reduced, and that the remaining 5-HT3 receptors were hypersensitive. Male 5-HT3Avs/vs mice died at 2-3 months of age, and heterozygous (5-HT3Avs/+) males and homozygous mutant females died at 4-6 months of age from an obstructive uropathy. Both male and female 5-HT3A mutant mice had urinary bladder mucosal and smooth muscle hyperplasia and hypertrophy, whereas male mutant mice had additional prostatic smooth muscle and urethral hyperplasia. 5-HT3A mutant mice had marked voiding dysfunction characterized by a loss of micturition contractions with overflow incontinence. Detrusor strips from 5-HT3Avs/vs mice failed to contract to neurogenic stimulation, despite overall normal responses to a cholinergic agonist, suggestive of altered neuronal signaling in mutant mouse bladders. Consistent with this hypothesis, decreased nerve fiber immunoreactivity was observed in the urinary bladders of 5-HT3Avs/vs compared with 5-HT3A wild-type (5-HT3A+/+) mice. These data suggest that persistent activation of the hypersensitive and constitutively active 5-HT3A receptor in vivo may lead to excitotoxic neuronal cell death and functional changes in the urinary bladder, resulting in bladder hyperdistension, urinary retention, and overflow incontinence.
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Mazzia C, Hicks GA, Clerc N. Neuronal location of 5-hydroxytryptamine3 receptor-like immunoreactivity in the rat colon. Neuroscience 2003; 116:1033-41. [PMID: 12617944 DOI: 10.1016/s0306-4522(02)00775-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The presence of 5-hydroxytryptamine(3) receptors on enteric neurons is known from pharmacological data that date back more than 40 years. However, an adequate account of which neurons bear these receptors has not been made because suitable antisera have not been available. We have found that the majority of antisera that have been raised against sequences from the 5-hydroxytryptamine(3) receptor also recognize pre-prosomatostatin. We report that this source of false labeling can be eliminated by pre-incubating the antisera with a peptide designed for this purpose. We have used the pre-absorbed antiserum to localize 5-hydroxytryptamine(3) receptors in the rat colon. Immunoreactive nerve cell bodies occurred in the myenteric and submucosal ganglia. The majority had smooth cell bodies and long, smooth processes, that is, Dogiel type II morphology. The initial segments of the long processes of the Dogiel type II neurons were strongly immunoreactive. About 12% of immunoreactive myenteric nerve cells were of the same or smaller size, and had multiple short filamentous processes. Some of the immunoreactive Dogiel type II neurons were also immunoreactive for calretinin in both plexuses, and the majority were immunoreactive for calbindin in submucosal ganglia. Specific immunoreactivity occurred in non-varicose, but not in varicose, fibers in the myenteric and submucosal ganglia, and in fiber bundles that traversed the longitudinal and circular muscle layers. Immunoreactive varicose fibers were observed only in the mucosa. It is concluded that 5-hydroxytryptamine(3) receptors occur on intrinsic sensory neurons in the rat colon, and on extrinsic sensory nerve fibers that innervate the colon.
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Affiliation(s)
- C Mazzia
- Laboratoire Intégration des Informations Sensorielles, CNRS, Bâtiment LNB (N'), 31 Chemin Joseph Aiguier, 13402, Marseille, Cedex, France
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Liu MT, Rayport S, Jiang Y, Murphy DL, Gershon MD. Expression and function of 5-HT3 receptors in the enteric neurons of mice lacking the serotonin transporter. Am J Physiol Gastrointest Liver Physiol 2002; 283:G1398-411. [PMID: 12388212 DOI: 10.1152/ajpgi.00203.2002] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The actions of enteric 5-HT are terminated by 5-HT transporter (SERT)-mediated uptake, and gastrointestinal motility is abnormal in SERT -/- mice. We tested the hypothesis that adaptive changes in enteric 5-HT(3) receptors help SERT -/- mice survive despite inefficient 5-HT inactivation. Expression of mRNA encoding enteric 5-HT(3A) subunits was similar in SERT +/+ and -/- mice, but that of 5-HT(3B) subunits was fourfold less in SERT -/- mice. 5-HT(3B) mRNA was found, by in situ hybridization, in epithelial cells and enteric neurons. 5-HT evoked a fast inward current in myenteric neurons that was pharmacologically identified as 5-HT(3) mediated. The EC(50) of the 5-HT response was lower in SERT +/+ (18 microM) than in SERT -/- (36 microM) mice and desensitized rapidly in a greater proportion of SERT -/- neurons; however, peak amplitudes, steady-state current, and decay time constants were not different. Adaptive changes thus occur in the subunit composition of enteric 5-HT(3) receptors of SERT -/- mice that are reflected in 5-HT(3) receptor affinity and desensitization.
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Affiliation(s)
- Min-Tsai Liu
- Department of Anatomy and Cell Biology, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA.
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Glatzle J, Sternini C, Robin C, Zittel TT, Wong H, Reeve JR, Raybould HE. Expression of 5-HT3 receptors in the rat gastrointestinal tract. Gastroenterology 2002; 123:217-26. [PMID: 12105850 DOI: 10.1053/gast.2002.34245] [Citation(s) in RCA: 130] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
BACKGROUND & AIMS Functional effects mediated via the 5-hydroxytryptamine3 receptor (5-HT3R) can be elicited from both extrinsic and intrinsic neurons innervating the gastrointestinal (GI) tract. Clinically, 5-HT3 antagonists are important in the treatment of emesis and have been used for the treatment of symptoms in functional bowel disease. The aim of the present study was to elucidate the cellular sites of 5-HT3R expression in the rat GI tract using immunohistochemistry. METHODS Immunohistochemistry was performed in fixed cryostat sections and whole mounts of stomach and intestine of fasted rats, using an affinity-purified antibody directed to a 19-amino acid sequence of the cytoplasmic loop of the 5-HT3R. RESULTS 5-HT3R immunoreactivity was localized to numerous neurons of the myenteric and submucosal plexus, concentrated primarily near the neuronal plasma membrane, and to fibers in the circular and longitudinal muscles, submucosa, and mucosa. 5-HT3R immunoreactivity was also expressed by interstitial cells of Cajal and a few endocrine cells. Numerous 5-HT3R-positive myenteric neurons were cholinergic, and few neurons coexpressed VIP or SP immunoreactivity. Fibers immunoreactive for 5-HT3R in the duodenal but not ileal mucosa were markedly reduced by subdiaphragmatic vagotomy or chemical denervation of vagal afferents. CONCLUSIONS These findings indicate that 5-HT3Rs are expressed by distinct cells in the GI tract, including functionally distinct classes of neurons, interstitial cells of Cajal, and endocrine cells. The effects of serotonin mediated by 5-HT3Rs involve the activation of neuronal and nonneuronal pathways.
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Affiliation(s)
- Jörg Glatzle
- Department of Anatomy, Physiology, and Cell Biology, University of California Davis School of Veterinary Medicine, Davis, California 95616, USA
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Fiorica-Howells E, Hen R, Gingrich J, Li Z, Gershon MD. 5-HT(2A) receptors: location and functional analysis in intestines of wild-type and 5-HT(2A) knockout mice. Am J Physiol Gastrointest Liver Physiol 2002; 282:G877-93. [PMID: 11960784 DOI: 10.1152/ajpgi.00435.2001] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The distribution and function of the 5-hydroxytryptamine (5-HT(2A)) receptor were investigated in the intestines of wild-type (5-HT(2A) +/+) and knockout (5-HT(2A) -/-) mice. In 5-HT(2A) +/+ mice, rats, and guinea pigs, 5-HT(2A) receptor immunoreactivity was found on circular and longitudinal smooth muscle cells, neurons, enterocytes, and Paneth cells. Muscular 5-HT(2A) receptors were concentrated in caveolae; neuronal 5-HT(2A) receptors were found intracellularly and on the plasma membranes of nerve cell bodies and axons. Neuronal 5-HT(2A) immunoreactivity was detected as early as E14 in ganglia, intravillus nerves, and the deep muscle plexus. The 5-HT(2A) -/- colon did not express 5-HT(2A) receptors and did not contract in response to exogenous 5-HT. 5-HT(2A) -/- enterocytes were smaller, Paneth cells fewer, and muscle layers thinner (and showed degeneration) compared with those of 5-HT(2A) +/+ littermates. The 5-HT(2A) receptor may thus be required for the maintenance and/or development of enteric neuroeffectors and other enteric functions, although gastrointestinal and colonic transit times in 5-HT(2A) -/- and +/+ mice did not differ significantly.
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MESH Headings
- Animals
- Enterocytes/chemistry
- Enterocytes/pathology
- Enterocytes/ultrastructure
- Female
- Fetus/cytology
- Gastric Emptying/physiology
- Gastrointestinal Motility/physiology
- Immunohistochemistry
- Intestines/chemistry
- Intestines/innervation
- Intestines/pathology
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Microscopy, Immunoelectron
- Muscle, Smooth/chemistry
- Muscle, Smooth/innervation
- Muscle, Smooth/pathology
- Myenteric Plexus/chemistry
- Myenteric Plexus/ultrastructure
- Paneth Cells/chemistry
- Paneth Cells/pathology
- Rats
- Rats, Sprague-Dawley
- Receptor, Serotonin, 5-HT2A
- Receptors, Serotonin/analysis
- Receptors, Serotonin/genetics
- Receptors, Serotonin/metabolism
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Affiliation(s)
- Elena Fiorica-Howells
- Department of Anatomy and Cell Biology, Columbia University, College of Physicians and Surgeons, New York, New York 10032, USA.
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Li JP, Chang TM, Chey WY. Roles of 5-HT receptors in the release and action of secretin on pancreatic secretion in rats. Am J Physiol Gastrointest Liver Physiol 2001; 280:G595-602. [PMID: 11254485 DOI: 10.1152/ajpgi.2001.280.4.g595] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
5-Hydroxytryptamine (serotonin, 5-HT) is a hormone and neurotransmitter regulating gastrointestinal functions. 5-HT receptors are widely distributed in gastrointestinal mucosa and the enteric nervous system. Duodenal acidification stimulates not only the release of both 5-HT and secretin but also pancreatic exocrine secretion. We investigated the effect of 5-HT receptor antagonists on the release of secretin and pancreatic secretion of water and bicarbonate induced by duodenal acidification in anesthetized rats. Both the 5-HT(2) receptor antagonist ketanserin and the 5-HT(3) receptor antagonist ondansetron at 1-100 microg/kg dose-dependently inhibited acid-induced increases in plasma secretin concentration and pancreatic exocrine secretion. Neither the 5-HT(1) receptor antagonists pindolol and 5-HTP-DP nor the 5-HT(4) receptor antagonist SDZ-205,557 affected acid-evoked release of secretin or pancreatic secretion. None of the 5-HT receptor antagonists affected basal pancreatic secretion or plasma secretin concentration. Ketanserin or ondansetron at 10 microg/kg or a combination of both suppressed the pancreatic secretion in response to intravenous secretin at 2.5 and 5 pmol x kg(-1) x h(-1) by 55-75%, but not at 10 pmol x kg(-1) x h(-1). Atropine (50 microg/kg) significantly attenuated the inhibitory effect of ketanserin on pancreatic secretion but not on the release of secretin. These observations suggest that 5-HT(2) and 5-HT(3) receptors mediate duodenal acidification-induced release of secretin and pancreatic secretion of fluid and bicarbonate. Also, regulation of pancreatic exocrine secretion through 5-HT(2) receptors may involve a cholinergic pathway in the rat.
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Affiliation(s)
- J P Li
- Konar Center for Digestive and Liver Diseases, School of Medicine and Dentistry, University of Rochester, Rochester, New York 14642, USA
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Doucet E, Hamon M, Emerit MB. Immunolabelling of the rat intestinal tract with antibodies specific to the long form of the 5-hydroxytryptamine3 receptor. Neuroscience 1998; 87:691-707. [PMID: 9758234 DOI: 10.1016/s0306-4522(98)00184-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The mouse 5-hydroxytryptamine3 (5-HT3) type of serotonin receptors is expressed as two forms, 5-HT3R-A(L) and 5-HT3R-A(S), generated by alternative splicing of its primary transcript, that differ by a stretch of six amino acids in the second intracellular loop domain. Because this six-amino acid region contains a putative phosphorylation site that may be important for the function and/or regulation of 5HT3R-A(L) receptor, specifically, we developed polyclonal antibodies as appropriate tools for studies relevant to this question. Antibodies against a 20-amino acid peptide corresponding to the sequence of 5-HT3R-A(L) at the level of this six-amino acid region were obtained as soon as one month after injection of this synthetic peptide to rabbits. Immunocytochemistry with these antibodies led to a strong positive labelling of plasma membrane, reticulum and Golgi apparatus of COS-7 cells expressing cloned murine 5-HT3R-A(L), whereas COS-7 cells expressing similar levels of 5-HT3R-A(S) exhibited only a very weak labelling. Immunoblots of fusion proteins combining glutathion-S-transferase and the second cytoplasmic loop of 5-HT3R-A(L) or 5-HT3R-A(S) revealed a c. 20-fold selectivity of the antibodies for the first, long form, as evaluated by densitometric analysis of enhanced chemiluminescence detection. Similarly, immunoblots of COS-7 cells transfected with cloned 5-HT3 receptors showed that the anti-peptide antibodies detected a band at 53,000 mol. wt only in cells transfected with 5-HT3R-A(L). Under optimal conditions, antibodies immunoprecipitated 52% of 5-HT3R-A(L), but only 11% of 5-HT3R-A(S), solubilized from COS-7 cells transfected with the respective encoding plasmids. In the rat, no immunoautoradiographic labelling by the anti-peptide antibodies could be detected in brain structures which had previously been described to express preferentially a short form of the 5-HT3 receptor. In contrast, a strong immunolabelling was found in the intestinal mucosa, especially in the rat fetus (at the 17th embryonic day), suggesting the possible participation of the 5-HT3R-A(L) isoform in the development of this tissue. These results show that specific antibodies are useful tools for the visualization of the least abundant 5-HT3 receptor isoform in rat tissue.
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Affiliation(s)
- E Doucet
- INSERM U288, Neuropsychopharmacologie Moléculaire, Cellulaire et Fonctionnelle, Faculté de Médecine Pitié Salpêtrière, Paris, France
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Abstract
The 5HT3 receptor (5HT3R) is a serotonin-gated ion channel whose expression is restricted to a subset of cells within the central and peripheral nervous systems. In vitro analysis shows that a small proximal region of the TATA-less 5HT3R promoter is sufficient to direct neuronal-specific reporter gene expression. Three potential regulatory elements conserved between the mouse and human genes were identified within this proximal promoter, two of which are known sites for the ubiquitously expressed factors Sp1 and nuclear factor 1 (NF1). Surprisingly, mutation of the NF1 binding site abolished all reporter activity in cell transfection studies, suggesting that this element is essential for neuronal-specific transcriptional activity of the 5HT3R. Furthermore, a complex of neuronal proteins that includes a member(s) of the NF1 family binds to this site, as shown by gel mobility super shift and DNaseI footprinting analyses. Although NF1 has been proposed to mediate basal transcription of many ubiquitously expressed genes, our data suggest that a member of the NF1 transcription factor family participates in neuronal-specific gene expression by promoting interactions with other regulatory factors found in sensory ganglia.
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Akuzawa S, Miyake A, Miyata K, Fukutomi H. Comparison of [3H]YM060 binding to native and cloned rat 5-HT3 receptors. Eur J Pharmacol 1996; 296:227-30. [PMID: 8838461 DOI: 10.1016/0014-2999(95)00798-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
We characterized [3H]YM060 ([methyl-3H]-(-)-(R)-5-[(methyl-1H- indol-3-yl)carbonyl]-4,5,6,7-tetrahydro-1H-benzimidazole monohydrochloride) binding in membrane homogenates prepared from three different rat tissues (cerebral cortex, ileum and colon), and compared the binding characteristics between the native and cloned rat 5-HT3 receptors. The dissociation constant (Kd) of [3H]YM060 was similar in all membranes. In competition studies, the affinity of 5-HT3 receptor agonists and antagonists was similar between the native and the cloned rat 5-HT3 receptors. In conclusion, intra-species difference of 5-HT3 receptor was not observed in rats and pharmacological properties of the cloned rat 5-HT3 receptor were nearly identical to that of the native rat 5-HT3 receptor.
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Affiliation(s)
- S Akuzawa
- Department of Internal Medicine, University of Tsukuba, Ibaraki, Japan
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