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Kuramoto H, Koo A, Fothergill LJ, Hunne B, Yoshimura R, Kadowaki M, Furness JB. Morphologies and distributions of 5-HT containing enteroendocrine cells in the mouse large intestine. Cell Tissue Res 2021; 384:275-286. [PMID: 33547947 DOI: 10.1007/s00441-020-03322-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Accepted: 10/12/2020] [Indexed: 12/18/2022]
Abstract
Serotonin (5-HT)-containing gastrointestinal endocrine cells contribute to regulation of numerous bodily functions, but whether these functions are related to differences in cell shape is not known. The current study identified morphologies and localization of subtypes of 5-HT-containing enteroendocrine cells in the mouse large intestine. 5-HT cells were most frequent in the proximal colon compared with cecum and distal colon. The large intestine harbored both open (O) cells, with apical processes that reached the lumen, and closed (C) cells, not contacting the lumen, classified into O1, O2, and O3 and C1, C2, and C3 cells, by the lengths of their basal processes. O1 and C1 cells, with basal processes sometimes longer that 100 µm, were most common in the distal colon. Their long basal processes ran against the inner surfaces of the mucosal epithelial cells and were strongly immunoreactive for 5-HT; these processes are ideally placed to communicate with the epithelium and to react to mechanical forces. O2 and C2 cells that had similar but shorter basal processes were also most common in the distal colon. O3 and C3 cells had no or very short basal processes. The O3 open type 5-HT cells were abundant in the proximal colon, particularly at the luminal surface, where they could release 5-HT into the lumen to act on luminal 5-HT receptors. Numerous O3 type 5-HT cells occurred in the lower (submucosal) region of the crypts in all segments and might release 5-HT to influence cell renewal in the crypt proliferative zones.
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Affiliation(s)
- Hirofumi Kuramoto
- Department of Applied Biology, Kyoto Institute of Technology, Kyoto, 606-8585, Japan
| | - Ada Koo
- Department of Anatomy & Neuroscience, University of Melbourne, Parkville, VIC, 3010, Australia
| | - Linda J Fothergill
- Department of Anatomy & Neuroscience, University of Melbourne, Parkville, VIC, 3010, Australia.,Florey Institute of Neuroscience and Mental Health, Parkville, VIC, 3010, Australia
| | - Billie Hunne
- Department of Anatomy & Neuroscience, University of Melbourne, Parkville, VIC, 3010, Australia
| | - Ryoichi Yoshimura
- Department of Applied Biology, Kyoto Institute of Technology, Kyoto, 606-8585, Japan
| | - Makoto Kadowaki
- Division of Gastrointestinal Pathophysiology, Institute of Natural Medicine, University of Toyama, Toyama, 930-0194, Japan
| | - John B Furness
- Department of Anatomy & Neuroscience, University of Melbourne, Parkville, VIC, 3010, Australia. .,Florey Institute of Neuroscience and Mental Health, Parkville, VIC, 3010, Australia.
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Akiba Y, Maruta K, Narimatsu K, Said H, Kaji I, Kuri A, Iwamoto KI, Kuwahara A, Kaunitz JD. FFA2 activation combined with ulcerogenic COX inhibition induces duodenal mucosal injury via the 5-HT pathway in rats. Am J Physiol Gastrointest Liver Physiol 2017; 313:G117-G128. [PMID: 28526687 PMCID: PMC5582879 DOI: 10.1152/ajpgi.00041.2017] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Revised: 05/04/2017] [Accepted: 05/13/2017] [Indexed: 01/31/2023]
Abstract
Serotonin (5-HT), predominantly synthesized and released by enterochromaffin cells, is implicated in gastrointestinal symptoms such as emesis, abdominal pain, and diarrhea. Because luminal short-chain fatty acids (SCFAs) release 5-HT from enterochromaffin cells, which express the SCFA receptor free fatty acid receptor 2 (FFA2) in rat duodenum, we examined the effects of the selective FFA2 agonist phenylacetamide-1 (PA1) on duodenal 5-HT release with consequent bicarbonate secretion [duodenal bicarbonate secretion (DBS)] and on indomethacin (IND)-induced enteropathy. Intestinal injury was induced by IND (10 mg/kg sc) with or without PA1. We measured DBS in vivo in a duodenal loop perfused with PA1 while measuring 5-HT released in the portal vein. Duodenal blood flow was measured by laser-Doppler flowmetry. IND induced small intestinal ulcers with duodenal sparing. PA1 given with IND (IND + PA1) dose dependently induced duodenal erosions. IND + PA1-induced duodenal lesions were inhibited by the FFA2 antagonist GLPG-0974, ondansetron, or omeprazole but not by RS-23597 or atropine. Luminal perfusion of PA1 augmented DBS accompanied by increased portal blood 5-HT concentrations with approximately eight times more release at 0.1 mM than at 1 µM, with the effects inhibited by coperfusion of GLPG-0974. Luminal PA1 at 1 µM increased, but at 0.1 mM diminished, duodenal blood flow. Cosuperfusion of PA1 (0.1 mM) decreased acid-induced hyperemia, further reduced by IND pretreatment but restored by ondansetron. These results suggest that, although FFA2 activation enhances duodenal mucosal defenses, FFA2 overactivation during ulcerogenic cyclooxygenase inhibition may increase the vulnerability of the duodenal mucosa to gastric acid via excessive 5-HT release and 5-HT3 receptor activation, implicated in foregut-related symptoms such as emesis and epigastralgia.NEW & NOTEWORTHY Luminal free fatty acid receptor 2 agonists stimulate enterochromaffin cells and release serotonin, which enhances mucosal defenses in rat duodenum. However, overdriving serotonin release with high luminal concentrations of free fatty acid 2 ligands such as short-chain fatty acids injures the mucosa by decreasing mucosal blood flow. These results are likely implicated in serotonin-related dyspeptic symptom generation because of small intestinal bacterial overgrowth, which is hypothesized to generate excess SCFAs in the foregut, overdriving serotonin release from enterochromaffin cells.
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Affiliation(s)
- Yasutada Akiba
- 1Greater Los Angeles Veterans Affairs Healthcare System, Los Angeles, California; ,2Department of Medicine, School of Medicine, University of California Los Angeles, Los Angeles, California; ,4Brentwood Biomedical Research Institute, Los Angeles, California; and
| | - Koji Maruta
- 2Department of Medicine, School of Medicine, University of California Los Angeles, Los Angeles, California;
| | - Kazuyuki Narimatsu
- 2Department of Medicine, School of Medicine, University of California Los Angeles, Los Angeles, California;
| | - Hyder Said
- 2Department of Medicine, School of Medicine, University of California Los Angeles, Los Angeles, California;
| | - Izumi Kaji
- 1Greater Los Angeles Veterans Affairs Healthcare System, Los Angeles, California; ,2Department of Medicine, School of Medicine, University of California Los Angeles, Los Angeles, California; ,4Brentwood Biomedical Research Institute, Los Angeles, California; and
| | - Ayaka Kuri
- 5University of Shizuoka Graduate School of Integrated Pharmaceutical and Nutritional Sciences, Shizuoka, Japan
| | - Ken-ichi Iwamoto
- 5University of Shizuoka Graduate School of Integrated Pharmaceutical and Nutritional Sciences, Shizuoka, Japan
| | - Atsukazu Kuwahara
- 5University of Shizuoka Graduate School of Integrated Pharmaceutical and Nutritional Sciences, Shizuoka, Japan
| | - Jonathan D. Kaunitz
- 1Greater Los Angeles Veterans Affairs Healthcare System, Los Angeles, California; ,2Department of Medicine, School of Medicine, University of California Los Angeles, Los Angeles, California; ,3Department of Surgery, School of Medicine, University of California Los Angeles, Los Angeles, California; ,4Brentwood Biomedical Research Institute, Los Angeles, California; and
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Kaji I, Akiba Y, Said H, Narimatsu K, Kaunitz JD. Luminal 5-HT stimulates colonic bicarbonate secretion in rats. Br J Pharmacol 2015; 172:4655-70. [PMID: 26061462 DOI: 10.1111/bph.13216] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2014] [Revised: 04/16/2015] [Accepted: 05/09/2015] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND AND PURPOSE The bioactive monoamine 5-HT, implicated in the pathogenesis of functional gastrointestinal disorders, is abundantly synthesized and stored in rat proximal colonic mucosa and released to the gut lumen and subepithelial space. Despite much data regarding its expression and function, the effects of luminal 5-HT on colonic anion secretion have not been fully investigated. EXPERIMENTAL APPROACH We measured short-circuit current (Isc ) as an indicator of ion transport in mucosa-submucosa or mucosa-only preparations of rat proximal colon. Total CO2 output was measured in vitro and in vivo. Immunohistochemistry was performed to investigate the localization of 5-HT4 , NOS1 and NOS2. KEY RESULTS Luminal 5-HT gradually increased the amplitude and sustained the elevation of Isc . Luminal 5-HT-evoked ΔIsc was acetazolamide sensitive and HCO3 (-) dependent, consistent with cytosolic carbonic anhydrase-dependent electrogenic HCO3 (-) secretion, while not affected by tetrodotoxin (TTX), atropine or indomethacin. Pretreatment with the selective 5-HT4 antagonist GR113808, but not antagonists for 5-HT3 , 5-HT6 or 5-HT7 , inhibited luminal 5-HT-evoked ΔIsc . Furthermore, luminal cisapride and tegaserod increased Isc to the same extent as did 5-HT in the presence of indomethacin and TTX. Removal of the submucosa or pretreatment with NOS inhibitors enhanced luminal 5-HT-evoked ΔIsc , suggesting that NO synthesized in the submucosa suppresses mucosal anion secretion. NOS1 and NOS2 were immunostained in the submucosal neurons and glial cells respectively. Luminal 5-HT-evoked HCO3 (-) secretion was confirmed in vivo, inhibited by co-perfusion of GR113808, but not by ondansetron. CONCLUSIONS AND IMPLICATIONS A novel apical 5-HT4 -mediated HCO3 (-) secretory pathway and an NO-dependent inhibitory mechanism are present in the proximal colon. Luminal 5-HT-evoked HCO3 (-) secretion may be important for the maintenance of mucosal integrity by regulating luminal pH.
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Affiliation(s)
- I Kaji
- Department of Medicine, University of California, Los Angeles, CA, USA.,Brentwood Biomedical Research Institute, Los Angeles, CA, USA
| | - Y Akiba
- Department of Medicine, University of California, Los Angeles, CA, USA.,Brentwood Biomedical Research Institute, Los Angeles, CA, USA.,Greater Los Angeles Veterans Affairs Healthcare System, CA, USA
| | - H Said
- College of Letters and Sciences, University of California, Los Angeles, CA, USA
| | - K Narimatsu
- Department of Medicine, University of California, Los Angeles, CA, USA
| | - J D Kaunitz
- Department of Medicine, University of California, Los Angeles, CA, USA.,Department of Surgery, School of Medicine, University of California, Los Angeles, CA, USA.,Brentwood Biomedical Research Institute, Los Angeles, CA, USA.,Greater Los Angeles Veterans Affairs Healthcare System, CA, USA
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Takahashi T. Interdigestive migrating motor complex -its mechanism and clinical importance. J Smooth Muscle Res 2014; 49:99-111. [PMID: 24662475 PMCID: PMC5137267 DOI: 10.1540/jsmr.49.99] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Migrating motor complex (MMC) is well characterized by the appearance of gastrointestinal
(GI) contractions in the interdigestive state. The physiological importance of gastric MMC
is a mechanical and chemical cleansing of the empty stomach in preparation for the next
meal. MMC cycle is mediated via the interaction between motilin and 5-hydroxytryptamine
(5-HT) by the positive feedback mechanism in conscious dogs. Luminal administration of
5-HT initiates duodenal phase II and phase III with a concomitant increase of plasma
motilin release. Duodenal 5-HT concentration is increased during gastric phase II and
phase III. Intravenous infusion of motilin increases luminal 5-HT content and induces
phase III. 5-HT4 antagonists significantly inhibit both of gastric and
intestinal phase III, while 5-HT3 antagonists inhibit only gastric phase III.
These suggest that gastric MMC is regulated via vagus, 5-HT3/4 receptors and
motilin, while intestinal MMC is regulated via intrinsic primary afferent neurons (IPAN)
and 5-HT4 receptors. We propose the possibility that maximally released motilin
by a positive feedback depletes 5-HT granules in the duodenal EC cells, resulting in no
more contractions. Stress is highly associated with the pathogenesis of functional
dyspepsia (FD). Acoustic stress attenuates gastric phase III without affecting intestinal
phase III in conscious dogs, via reduced vagal activity. Subset of FD patients shows
reduced vagal activity and impaired gastric phase III. The impaired gastric MMC may
aggravate dyspeptic symptoms following a food ingestion. Maintaining MMC cycle in the
interdigestive state is an important factor to prevent the postprandial dyspeptic
symptoms.
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Affiliation(s)
- Toku Takahashi
- Department of Surgery and Department of Neurology, Medical College of Wisconsin and Zablocki VA Medical Center, Milwaukee, Wisconsin, USA
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Takahashi T. Mechanism of interdigestive migrating motor complex. J Neurogastroenterol Motil 2012; 18:246-57. [PMID: 22837872 PMCID: PMC3400812 DOI: 10.5056/jnm.2012.18.3.246] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2012] [Revised: 05/13/2012] [Accepted: 05/23/2012] [Indexed: 12/15/2022] Open
Abstract
Migrating motor complex (MMC) is well characterized by the appearance of gastrointestinal contractions in the interdigestive state. This review article discussed the mechanism of gastrointestinal MMC. Luminal administration of 5-hydroxytryptamine (5-HT) initiates duodenal phase II followed by gastrointestinal phase III with a concomitant increase of plasma motilin release in conscious dogs. Duodenal 5-HT concentration is increased during gastric phase II and phase III. Intravenous infusion of motilin increases luminal 5-HT content and induces gastrointestinal phase III. 5-HT(4) antagonists significantly inhibits both of gastric and intestinal phase III, while 5-HT(3) antagonists inhibited only gastric phase III. These suggest that gastrointestinal MMC cycle is mediated via the interaction between motilin and 5-HT by the positive feedback mechanism. Gastric MMC is regulated via vagus, 5-HT(3/4) receptors and motilin, while intestinal MMC is regulated via intrinsic primary afferent neurons and 5-HT(4) receptors. Stress is highly associated with the pathogenesis of functional dyspepsia. Acoustic stress attenuates gastric phase III without affecting intestinal phase III in conscious dogs, via reduced vagal activity and increased sympathetic activity. It has been shown that subset of functional dyspepsia patients show reduced vagal activity and impaired gastric phase III. The physiological importance of gastric MMC is a mechanical and chemical cleansing of the empty stomach in preparation for the next meal. The impaired gastric MMC may aggravate dyspeptic symptoms following a food ingestion. Thus, maintaining gastric MMC in the interdigestive state is an important factor to prevent the postprandial dyspeptic symptoms.
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Affiliation(s)
- Toku Takahashi
- Department of Surgery, Medical College of Wisconsin and Zablocki VA Medical Center, Milwaukee, Wisconsin, USA
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Mechanism of interdigestive migrating motor complex in conscious dogs. J Gastroenterol 2010; 45:506-14. [PMID: 20033824 DOI: 10.1007/s00535-009-0190-z] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/12/2009] [Accepted: 12/09/2009] [Indexed: 02/04/2023]
Abstract
BACKGROUND The migrating motor complex (MMC) is well characterized by the appearance of gastrointestinal contractions in the interdigestive state. This study was designed to clarify the mechanisms of gastric MMC (G-MMC) and intestinal MMC (I-MMC) in conscious dogs. METHODS Five strain gauge transducers were implanted on the stomach and intestine. To investigate the correlation between luminal 5-HT and phase III contractions, gastric and duodenal juices were collected during the MMC cycle. The 5-HT concentrations in gastric and duodenal juice were measured by HPLC. To investigate whether luminal 5-HT initiates MMC, 5-HT (10(-8)-10(-6) M, 10 ml) was administered into the duodenum 20 min after gastric phase III. To investigate the involvement of 5-HT(3) or 5-HT(4) receptors in mediating G-MMC and I-MMC, 5-HT(3) antagonists (ondansetron) or 5-HT(4) antagonists (GR 125,487) were infused for 120 min. RESULTS Luminal administration of 5-HT (10(-6) M) initiated duodenal phase II followed by G-MMC and I-MMC with a concomitant increased release of plasma motilin. The duodenal 5-HT concentration was significantly increased during phase II (59 +/- 9 ng/ml) and phase III (251 +/- 21 ng/ml) compared to that of phase I (29 +/- 5 ng/ml). On the other hand, the 5-HT content in the stomach was not significantly changed throughout the MMC cycle. Intravenous infusion of motilin (0.3 microg/kg/h) increased the luminal 5-HT content and induced G-MMC and I-MMC. 5-HT(4) antagonists significantly inhibited both G-MMC and I-MMC, while 5-HT(3) antagonists inhibited only G-MMC. CONCLUSION It is suggested that the MMC cycle is mediated by a positive feedback mechanism via the interaction between motilin and 5-HT.
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Mueller MH, Xue B, Glatzle J, Hahn J, Grundy D, Kreis ME. Extrinsic afferent nerve sensitivity and enteric neurotransmission in murine jejunum in vitro. Am J Physiol Gastrointest Liver Physiol 2009; 297:G655-62. [PMID: 19679823 DOI: 10.1152/ajpgi.00128.2009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Enteric and extrinsic sensory neurons respond to similar stimuli. Thus they may be activated in series or in parallel. Because signal transmission via synapses or mediator release would depend on calcium, we investigated its role for extrinsic afferent sensitivity to chemical and mechanical stimulation. Extracellular multiunit afferent recordings were made in vitro from paravascular nerve bundles supplying the mouse jejunum. Intraluminal pressure and afferent nerve responses were recorded under control conditions and under four conditions designed to interfere with enteric neurotransmission. We found that phasic intestinal contractions ceased after switching perfusion to Ca(2+)-free buffer with or without a purinergic P2 receptor antagonist, pyridoxal phosphate-6-azo(benzene-2,4-disulfonic acid) (PPADS) or cadmium (blocking all Ca(2+)-channels) but not following omega-conotoxin GVIA (N-type Ca(2+)-channel blocker). Luminal HCl (pH 2) and 5-HT (500 microM) evoked peak firing of 17 +/- 4 impulses per second (imp/s) (n = 10) and 21 +/- 4 imp/s (n = 13) under control conditions. These responses were reduced to 4 +/- 2 imp/s and 5 +/- 2 imp/s by cadmium (n = 7, P < 0.05), to 7 +/- 2 imp/s and 6 +/- 1 imp/s by Ca(2+)-free perfusion (n = 6, P < 0.05), and to 3 +/- 1 imp/s and 4 +/- 1 imp/s by Ca(2+)-free perfusion with PPADS (n = 6, P < 0.05). Responses were unchanged by omega-conotoxin GVIA. Mechanical ramp distension of the intestinal segment to 60 cmH(2)O was not altered by any of the experimental conditions. We concluded that HCl and 5-HT activate extrinsic afferents via a calcium-dependent mechanism, which is unlikely to involve enteric neurons carrying N-type calcium channels. Extrinsic mechanosensitivity is independent of enteric neurotransmission. It appears that cross talk from the enteric to the extrinsic nervous system does not mediate extrinsic afferent sensitivity.
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Affiliation(s)
- Mario H Mueller
- Department of Surgery and 2Walter-Brendel Institute of Surgical Research, Ludwig-Maximilian's University, Munich, Germany
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Taniguchi H, Ariga H, Zheng J, Ludwig K, Mantyh C, Pappas TN, Takahashi T. Endogenous ghrelin and 5-HT regulate interdigestive gastrointestinal contractions in conscious rats. Am J Physiol Gastrointest Liver Physiol 2008; 295:G403-11. [PMID: 18566321 DOI: 10.1152/ajpgi.90260.2008] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Endogenous ghrelin causes interdigestive contractions of the stomach in rats. In contrast, previous studies showed that 5-HT(3) and 5-HT(4) receptors were involved in regulating intestinal interdigestive contractions. We studied the possible role of endogenous ghrelin and 5-HT regulating interdigestive gastrointestinal (GI) contractions in rats. Four strain gauge transducers were implanted on the antrum, duodenum, and proximal and distal jejunum. After an overnight fast, GI contractions were recorded in freely moving conscious rats and ghrelin receptor antagonists [(d-lys3)GHRP6; 1 micromol/kg], 5-HT(3) antagonists (Ondansetron; 0.5 mg/kg) and 5-HT(4) antagonists (GR 125,487; 1 mg/kg) were administered (bolus iv). To evaluate the relationship between the luminal concentrations of 5-HT and phase III-like contractions of the duodenum, duodenal juice was collected via the intraduodenal catheter. 5-HT content of the duodenal juice was measured by HPLC. (d-lys3)GHRP6 significantly attenuated the occurrence and amplitude of phase III-like contractions of the antrum, but not the duodenum and jejunum. 5-HT(4) antagonists significantly reduced spontaneous phase III-like contractions of the jejunum, without affecting those of the antrum and duodenum. In contrast, 5-HT(3) antagonists did not affect phase III-like contractions in GI tract. Luminal concentration of 5-HT at the phase III-like contraction (36.0 +/- 13.3 ng/ml, n = 9) was significantly higher than that at the phase I-like contractions of the duodenum (4.9 +/- 1.6 ng/ml, n = 9, P < 0.05). It is suggested that released ghrelin from the gastric mucosa mediates gastric phase III-like contractions, whereas 5-HT released from enterochromaffin cells of the duodenal mucosa mediates intestinal phase III-like contractions via 5-HT(4) receptors.
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Affiliation(s)
- Hiroshi Taniguchi
- Department of Surgery, Duke University Medical Center, Durham, North Carolina, USA
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Tsukamoto K, Ariga H, Mantyh C, Pappas TN, Yanagi H, Yamamura T, Takahashi T. Luminally released serotonin stimulates colonic motility and accelerates colonic transit in rats. Am J Physiol Regul Integr Comp Physiol 2007; 293:R64-9. [PMID: 17442783 DOI: 10.1152/ajpregu.00856.2006] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Enterochromaffin (EC) cells of the epithelial cells release 5-HT into the lumen, as well as basolateral border. However, the physiological role of released 5-HT into the lumen is poorly understood. Concentrations of 5-HT in the colonic mucosa, colonic lumen, and feces were measured by HPLC in rats. To investigate whether intraluminal 5-HT accelerates colonic transit, 5-HT and (51)Cr were administered into the lumen of the proximal colon, and colonic transit was measured. To investigate whether 5-HT is released into the lumen, we used an ex vivo model of isolated vascularly and luminally perfused rat proximal colon. To investigate whether luminal 5-HT is involved in regulating stress-induced colonic motility, the distal colonic motility was recorded under the stress loading, and a 5-HT(3) receptor antagonist (ondansetron, 10(-6) M, 0.5 ml) was administered intraluminally of the distal colon. Tissue content of 5-HT in the proximal colon (15.2 +/- 4.3 ng/mg wet tissue) was significantly higher than that in the distal colon (3.3 +/- 0.7 ng/mg wet tissue), while fecal content and luminal concentration of 5-HT was almost the same between the proximal and distal colon. Luminal administration of 5-HT (10(-6)-10(-5) M) significantly accelerated colonic transit. Elevation of intraluminal pressure by 10 cmH(2)O significantly increased the luminal concentration of 5-HT but not the vascular concentration of 5-HT. Stress-induced stimulation of the distal colonic motility was significantly attenuated by the luminal administration of ondansetron. These results suggest that luminally released 5-HT from EC cells plays an important role in regulating colonic motility in rats.
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Affiliation(s)
- Kiyoshi Tsukamoto
- Department of Surgery, Duke University Medical Center, Durham, NC 27710, USA
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Dong H, Smith A, Hovaida M, Chow JY. Role of Ca2+-activated K+ channels in duodenal mucosal ion transport and bicarbonate secretion. Am J Physiol Gastrointest Liver Physiol 2006; 291:G1120-8. [PMID: 16763288 DOI: 10.1152/ajpgi.00566.2005] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Stimulation of muscarinic receptors in the duodenal mucosa raises cytosolic free Ca(2+) concentration ([Ca(2+)](cyt)), thereby regulating duodenal epithelial ion transport. However, little is known about the downstream molecular targets that account for this Ca(2+)-mediated biological action. Ca(2+)-activated K(+) (K(Ca)) channels are candidates, but the expression and function of duodenal K(Ca) channels are poorly understood. Therefore, we determined whether K(Ca) channels are expressed in the duodenal mucosa and investigated their involvement in Ca(2+)-mediated duodenal epithelial ion transport. Two selective blockers of intermediate-conductance Ca(2+)-activated K(+) (IK(Ca)) channels, clotrimazole (30 muM) and 1-[(2-chlorophenyl)diphenylmethyl]-1H-pyrazole (TRAM-34; 10 muM), significantly inhibited carbachol (CCh)-induced duodenal short-circuit current (I(sc)) and duodenal mucosal bicarbonate secretion (DMBS) in mice but did not affect responses to forskolin and heat-stable enterotoxin of Escherichia coli. Tetraethylammonium, 4-aminopyridine, and BaCl(2) failed to inhibit CCh-induced I(sc) and DMBS. A-23187 (10 muM), a Ca(2+) ionophore, and 1-ethyl-2-benzimidazolinone (1-EBIO; 1 mM), a selective opener of K(Ca) channels, increased both I(sc) and DMBS. The effect of 1-EBIO was more pronounced with serosal than mucosal addition. Again, both clotrimazole and TRAM-34 significantly reduced A23187- or 1-EBIO-induced I(sc) and DMBS. Moreover, clotrimazole (20 mg/kg ip) significantly attenuated acid-stimulated DMBS of mice in vivo. Finally, the molecular identity of IK(Ca) channels was verified as KCNN4 (SK4) in freshly isolated murine duodenal mucosae by RT-PCR and Western blotting. Together, our results suggest that the IK(Ca) channel is one of the downstream molecular targets for [Ca(2+)](cyt) to mediate duodenal epithelial ion transport.
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Affiliation(s)
- Hui Dong
- Division of Gastroenterology, Department of Medicine, School of Medicine, University of California, San Diego, California, USA.
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Yu PL, Fujimura M, Hayashi N, Nakamura T, Fujimiya M. Mechanisms in regulating the release of serotonin from the perfused rat stomach. Am J Physiol Gastrointest Liver Physiol 2001; 280:G1099-105. [PMID: 11352802 DOI: 10.1152/ajpgi.2001.280.6.g1099] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The mechanisms regulating the release of serotonin into the portal circulation as well as into the gastric lumen were studied in the isolated vascularly and luminally perfused rat stomach. Immunohistochemical study of the rat stomach showed that serotonin-containing enterochromaffin (EC) cells were densely packed in the antral mucosa, sparsely scattered in the corpus, and not found in the fundus. Such morphological findings suggest that serotonin detected in this study may have originated from antral EC cells. Luminal acidification stimulated the vascular release of serotonin but did not affect the luminal release of serotonin. The basal release of serotonin into the vasculature was 10 times higher than that into the gastric lumen at intragastric pH 2. The vascular release of serotonin is regulated by stimulation from cholinergic nicotinic mechanisms, whereas inhibitory neurotransmitters such as vasoactive intestinal peptide and NO are probably not involved. Somatostatin and peptide YY originating from endocrine cells may exert direct inhibitory effects, possibly via somatostatin and peptide YY receptors on the EC cells, and a cholinergic muscarinic mechanism may exert indirect effects on the vascular release of serotonin via the muscarinic receptor on the endocrine cells.
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Affiliation(s)
- P L Yu
- Department of 2nd Surgery, Shiga University of Medical Science, Seta, Otsu, Shiga 520-2192, Japan
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12
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Gregory PC, Rayner DV, Wenham G. Initiation of migrating myoelectric complex in sheep by duodenal acidification and hyperosmolarity: role of vagus nerves. J Physiol 1984; 355:509-21. [PMID: 6492001 PMCID: PMC1193507 DOI: 10.1113/jphysiol.1984.sp015435] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Gastrointestinal motility was studied in conscious sheep by X-radiography and by electromyography from chronically implanted electrodes before and after total thoracic vagotomy. Duodenal infusion of 0.5-3 mmol HCl (0.035-0.1 M-HCl) induced premature duodenal regular spiking activity (r.s.a.) within 1-7 min in fifteen of seventeen sheep studied when infused at 20 min after a natural r.s.a. There was no correlation between abomasal pH and any phase of the migrating myoelectric complex (m.m.c.). Duodenal alkalinization by infusion of 0.3 M-Tris buffer (pH 10.2) or 0.1 M-NaHCO3 had no influence on the occurrence of the m.m.c. Duodenal infusion of 20-50 ml 0.5 M-NaCl induced a premature duodenal r.s.a. within 1-5 min in seven of eight sheep. Vagotomy did not prevent the initiation or migration of the m.m.c., but reduced the rate of propagation of the r.s.a. from 40.5 +/- 7.2 (mean +/- S.E. of mean) to 16.7 +/- 0.1 cm/min in the duodenum, from 27.3 +/- 4.1 to 16.6 +/- 0.8 cm/min in the jejunum, and from 21.4 +/- 1.1 to 13.7 +/- 0.7 cm/min in the proximal ileum. Initially the frequency of r.s.a. increased, especially in the duodenum where they recurred at an interval of 98.4 +/- 6.8 min before vagotomy; and at 23.4 +/- 1.8 min in the first 24 h after vagotomy; the interval had lengthened to 86.7 +/- 5.2 min 2-3 weeks after vagotomy. Premature duodenal r.s.a. was not induced by duodenal infusion of HCl in five, or by duodenal infusion of hyperosmolar NaCl in three chronically vagotomized sheep. It is concluded that the vagus nerves contribute to the regulation of the frequency and propagation of the m.m.c. in sheep; duodenal acidification is not essential nor is it the normal stimulus for initiation of r.s.a., but duodenal infusion of HCl or hyperosmolar NaCl can initiate a premature duodenal r.s.a. via the vagus nerves.
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