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Okada M, Taniguchi S, Takeshima C, Taniguchi H, Kitakoji H, Itoh K, Takahashi T, Imai K. Using a radiopaque marker with radiography for evaluating colonic transit by geometric center in conscious rats: A novel method. Auton Neurosci 2020; 230:102760. [PMID: 33340814 DOI: 10.1016/j.autneu.2020.102760] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2020] [Revised: 11/18/2020] [Accepted: 11/29/2020] [Indexed: 02/07/2023]
Abstract
This study developed a new method using radiopaque markers under X-ray to measure rat colonic transit by geometric center repeatedly and/or over a time series in the same individually. Additionally, the utility of this method was shown by elucidating the innervation of the autonomic nerve on colonic transit in detail with a pharmacological technique in conscious rats. An in-dwelling silastic cannula was inserted into the cecum and the proximal part was moved through the abdominal wall, where it was fixed to the posterior neck skin. Twenty markers were administered from the cannula to the proximal colon with saline on the fifth day after surgery. The markers were observed with soft X-ray before required repeated short anesthesia. Experimentation 1: Rats were measured colonic transit twice over 2 days with no administration. Experimentation 2: Rats were administered saline on the first day and pharmacology on the second day intraperitoneally before measurement. Experimentation 1: The markers administrated from the cannula and transited from proximal colon to distal colon over a time series. It showed no significant difference in complication rates between 2 days. Experimentation 2: The colonic transit was increasingly accelerated by neostigmine and phentolamine but not propranolol. Significant changes in 1.0 mg/kg atropine were noted although no differences were found between control and 0.05 mg/kg atropine and between each other's. We have presented the method using radiopaque markers under X-ray with short anesthesia for evaluating the colonic transit. The methods could show rat colonic transit changes in detail with a pharmacological technique.
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Affiliation(s)
- Misaki Okada
- Department of Acupuncture and Moxibustion, Meiji University of Integrative Medicine, Honoda, Hiyoshi-cho, Nantan-shi, Kyoto 629-0392, Japan
| | - Sazu Taniguchi
- Department of Acupuncture and Moxibustion, Meiji University of Integrative Medicine, Honoda, Hiyoshi-cho, Nantan-shi, Kyoto 629-0392, Japan; The Japan School of Acupuncture, Moxibustion and Physiotherapy, 20-1 Sakuragaoka-cho, Shibuya-ku, Tokyo 150-0031, Japan
| | - Chiaki Takeshima
- Graduate School of Acupuncture and Moxibustion, Meiji University of Integrative Medicine, Honoda, Hiyoshi-cho, Nantan-shi, Kyoto 629-0392, Japan
| | - Hiroshi Taniguchi
- Department of Acupuncture and Moxibustion, Meiji University of Integrative Medicine, Honoda, Hiyoshi-cho, Nantan-shi, Kyoto 629-0392, Japan; Department of Acupuncture and Moxibustion, Tokyo Ariake University of Medical and Health Sciences, 2-9-1 Ariake, Koto-ku, Tokyo 135-0063, Japan
| | - Hiroshi Kitakoji
- Department of Acupuncture and Moxibustion, Meiji University of Integrative Medicine, Honoda, Hiyoshi-cho, Nantan-shi, Kyoto 629-0392, Japan; Department of Acupuncture and Moxibustion, Takarazuka University of Medical and Health Care, 1 Hanayashikimidorigaoka, Takarazuka-shi, Hyogo 666-0162, Japan
| | - Kazunori Itoh
- Department of Acupuncture and Moxibustion, Meiji University of Integrative Medicine, Honoda, Hiyoshi-cho, Nantan-shi, Kyoto 629-0392, Japan
| | - Toku Takahashi
- Department of Surgery, Medical College of Wisconsin, 8701 W Watertown Plank Rd, Milwaukee, WI 53226, USA
| | - Kenji Imai
- Department of Acupuncture and Moxibustion, Meiji University of Integrative Medicine, Honoda, Hiyoshi-cho, Nantan-shi, Kyoto 629-0392, Japan; Department of Acupuncture and Moxibustion, Faculty of Health Science, Teikyo Heisei University, 2-51-4 Higashi-ikebukuro, Toshima-ku, Tokyo 170-8445, Japan.
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Edwinson AL, Grover M. Measurement of novel intestinal secretory and barrier pathways and effects of proteases. Neurogastroenterol Motil 2019; 31:e13547. [PMID: 30843358 PMCID: PMC6407641 DOI: 10.1111/nmo.13547] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/28/2018] [Revised: 12/02/2018] [Accepted: 12/17/2018] [Indexed: 02/08/2023]
Abstract
The epithelial lining of the gastrointestinal (GI) tract in conjunction with the enteric nervous system (ENS) plays an important role in mediating solute absorption and secretion. A dysregulated ionic movement across the epithelium can result in GI diseases that manifest as either watery diarrhea or constipation. Hirschsprung disease is an example of an ENS disorder characterized by absence of enteric ganglia in distal gut resulting in obstructive phenotype. Receptor rearranged during transfection (RET) gene variants are the most commonly recognized genetic associations with Hirschsprung disease. In this issue of Neurogastroenterology and Motility, Russell et al demonstrate that RET mediates colonic ion transport through modulation of cholinergic nerves. They go on to show inhibition of RET can attenuate accelerated transit in a rat model. Normalizing secretory and absorptive defects has been an attractive therapeutic strategy. In addition to the intrinsic regulation of secretory processes, luminal mediators like bile acids, short-chain fatty acids, and proteases can affect both secretion and barrier function of the intestinal epithelium. Elevated levels of proteases have been identified in a wide range of GI diseases including irritable bowel syndrome. Proteases are known to cause visceral hypersensitivity and barrier disruption in vitro and in animal models. The goals of this review are to describe fundamental concepts related to intestinal epithelial secretion, the utility of Ussing chambers to measure ionic mechanisms and to discuss examples of novel signaling pathways; namely the RET signaling cascade in secretomotor neurons and effects of luminal proteases on barrier and ionic secretion.
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Affiliation(s)
- Adam L. Edwinson
- Division of Gastroenterology & Hepatology, Mayo Clinic, Rochester, MN, USA
| | - Madhusudan Grover
- Division of Gastroenterology & Hepatology, Mayo Clinic, Rochester, MN, USA,Correspondence: Madhusudan Grover, MD, Assistant Professor of Medicine and Physiology, Enteric NeuroScience Program, Division of Gastroenterology and Hepatology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA, Tel: 507-284-2478, Fax: 507-266-0350,
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Russell JP, Mohammadi E, Ligon C, Latorre R, Johnson AC, Hoang B, Krull D, Ho MWY, Eidam HS, DeMartino MP, Cheung M, Oliff AI, Kumar S, Greenwood-Van Meerveld B. Enteric RET inhibition attenuates gastrointestinal secretion and motility via cholinergic signaling in rat colonic mucosal preparations. Neurogastroenterol Motil 2019; 31:e13479. [PMID: 30311722 DOI: 10.1111/nmo.13479] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/18/2018] [Revised: 08/14/2018] [Accepted: 09/01/2018] [Indexed: 12/23/2022]
Abstract
BACKGROUND The expression of RET in the developing enteric nervous system (ENS) suggests that RET may contribute to adult intestinal function. ENS cholinergic nerves play a critical role in the control of colonic function through the release of acetylcholine (ACh). In the current study, we hypothesized that a RET-mediated mechanism may regulate colonic ion transport and motility through modulation of cholinergic nerves. METHODS The effect of RET inhibition on active ion transport was assessed electrophysiologically in rat colonic tissue mounted in Ussing chambers via measurements of short circuit current (Isc) upon electrical field stimulation (EFS) or pharmacologically with cholinergic agonists utilizing a gastrointestinal (GI)-restricted RET inhibitor. We assessed the effect of the RET inhibitor on propulsive motility via quantification of fecal pellet output (FPO) induced by the acetylcholinesterase inhibitor neostigmine. KEY RESULTS We found that enteric ganglia co-expressed RET and choline acetyltransferase (ChAT) transcripts. In vitro, the RET kinase inhibitor GSK3179106 attenuated the mean increase in Isc induced by either EFS or carbachol but not bethanechol. In vivo, GSK3179106 significantly reduced the prokinetic effect of neostigmine. CONCLUSION AND INFERENCES Our findings provide evidence that RET-mediated mechanisms regulate colonic function by maintaining cholinergic neuronal function and enabling ACh-evoked chloride secretion and motility. We suggest that modulating the cholinergic control of the colon via a RET inhibitor may represent a novel target for the treatment of intestinal disorders associated with increased secretion and accelerated GI transit such as irritable bowel syndrome with diarrhea (IBS-D).
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Affiliation(s)
- John P Russell
- Virtual Proof of Concept Discovery Performance Unit, GlaxoSmithKline, King of Prussia, Pennsylvania
| | - Ehsan Mohammadi
- Oklahoma Center for Neuroscience, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma
| | - Casey Ligon
- Oklahoma Center for Neuroscience, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma
| | - Rocco Latorre
- Oklahoma Center for Neuroscience, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma
| | - Anthony C Johnson
- Oklahoma Center for Neuroscience, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma
| | - Bao Hoang
- Exploratory Biomarker Assay Group, GlaxoSmithKline, Collegeville, Pennsylvania
| | - David Krull
- Exploratory Biomarker Assay Group, GlaxoSmithKline, Collegeville, Pennsylvania
| | - Melisa W-Y Ho
- Virtual Proof of Concept Discovery Performance Unit, GlaxoSmithKline, King of Prussia, Pennsylvania
| | - Hilary S Eidam
- Virtual Proof of Concept Discovery Performance Unit, GlaxoSmithKline, King of Prussia, Pennsylvania
| | - Michael P DeMartino
- Virtual Proof of Concept Discovery Performance Unit, GlaxoSmithKline, King of Prussia, Pennsylvania
| | - Mui Cheung
- Virtual Proof of Concept Discovery Performance Unit, GlaxoSmithKline, King of Prussia, Pennsylvania
| | - Allen I Oliff
- Virtual Proof of Concept Discovery Performance Unit, GlaxoSmithKline, King of Prussia, Pennsylvania
| | - Sanjay Kumar
- Virtual Proof of Concept Discovery Performance Unit, GlaxoSmithKline, King of Prussia, Pennsylvania
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Pauwelyn V, Ceelen W, Lefebvre RA. Synergy between 5-HT 4 receptor stimulation and phosphodiesterase 4 inhibition in facilitating acetylcholine release in human large intestinal circular muscle. Neurogastroenterol Motil 2018; 30. [PMID: 28799255 DOI: 10.1111/nmo.13162] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/10/2017] [Accepted: 06/20/2017] [Indexed: 02/08/2023]
Abstract
BACKGROUND Gastroprokinetic properties of 5-HT4 receptor agonists, such as prucalopride, are attributed to activation of 5-HT4 receptors on cholinergic nerves innervating smooth muscle in the gastrointestinal smooth muscle layer, increasing acetylcholine release and muscle contraction. In porcine stomach and colon, phosphodiesterase (PDE) 4 has been shown to control the signaling pathway of these 5-HT4 receptors. The aim of this study was to investigate the PDE-mediated control of these 5-HT4 receptors in human large intestine. METHODS Circular smooth muscle strips were prepared from human large intestine; after incubation with [³H]-choline, electrically induced tritium outflow was determined as a measure for acetylcholine release. The influence of PDE inhibition on the facilitating effect of prucalopride on electrically induced acetylcholine release was studied. KEY RESULTS The non-selective PDE inhibitor IBMX enhanced the facilitating effect of prucalopride on electrically induced acetylcholine release. The selective inhibitors vinpocetine (PDE1), EHNA (PDE2) and cilostamide (PDE3) did not influence, while rolipram and roflumilast (PDE4) enhanced the prucalopride-induced facilitation to the same extent as IBMX. CONCLUSIONS & INFERENCES In human large intestinal circular muscle, the intracellular pathway of 5-HT4 receptors facilitating cholinergic neurotransmission to large intestinal circular smooth muscle is controlled by PDE4. If the synergy between 5-HT4 receptor agonism and PDE4 inhibition is confirmed in a functional assay with electrically induced cholinergic contractions of human large intestinal circular smooth muscle strips, combination of a selective 5-HT4 receptor agonist with a selective PDE4 inhibitor might enhance the in vivo prokinetic effect of the 5-HT4 receptor agonist in the large intestine.
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Affiliation(s)
- V Pauwelyn
- Department of Pharmacology - Heymans Institute, Ghent University, Ghent, Belgium
| | - W Ceelen
- Department of Gastrointestinal Surgery, Ghent University Hospital, Ghent, Belgium
| | - R A Lefebvre
- Department of Pharmacology - Heymans Institute, Ghent University, Ghent, Belgium
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Lefebvre RA, Van Colen I, Pauwelyn V, De Maeyer JH. Synergistic effect between 5-HT4 receptor agonist and phosphodiesterase 4-inhibitor in releasing acetylcholine in pig gastric circular muscle in vitro. Eur J Pharmacol 2016; 781:76-82. [PMID: 27060014 DOI: 10.1016/j.ejphar.2016.04.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Revised: 03/31/2016] [Accepted: 04/04/2016] [Indexed: 01/14/2023]
Abstract
5-HT4 receptor agonists have a gastroprokinetic effect by facilitating acetylcholine release from cholinergic nerves innervating gastrointestinal smooth muscle. The role of phosphodiesterase (PDE) 4 in the signal transduction pathway of the 5-HT4 receptors located on the cholinergic neurons towards the circular muscle layer in pig stomach was investigated by analysis of acetylcholine release. Circular muscle strips were prepared from pig proximal stomach and tritium outflow, induced by electrical field stimulation, was studied as a marker for acetylcholine release after incubation with [(3)H]-choline. The PDE4-inhibitor roflumilast concentration-dependently (0.1-1µM) enhanced the facilitating effect of a submaximally effective concentration of the 5-HT4 receptor agonist prucalopride (0.01µM) on electrically induced acetylcholine release. Roflumilast (0.3µM) enhanced acetylcholine release per se but in the combined presence of roflumilast and prucalopride, acetylcholine release was enhanced more than the sum of the effect of the 2 compounds alone. The 5-HT4 receptor agonist velusetrag concentration-dependently (0.01-0.1µM) enhanced acetylcholine release; the effect of the minimally effective concentration (0.01µM) was significantly enhanced by 1µM of the PDE4-inhibitor rolipram, again to a level higher than the sum of the effect of the 2 compounds alone. The synergistic effect between 5-HT4 receptor agonists and PDE4-inhibitors demonstrates that the intracellular pathway of the 5-HT4 receptors located on cholinergic neurons towards pig gastric circular muscle is controlled by PDE4. Combining a 5-HT4 receptor agonist with a PDE4-inhibitor might thus enhance its gastroprokinetic effect.
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Affiliation(s)
- Romain A Lefebvre
- Heymans Institute of Pharmacology, Ghent University, De Pintelaan 185, B-9000 Gent, Belgium.
| | - Inge Van Colen
- Heymans Institute of Pharmacology, Ghent University, De Pintelaan 185, B-9000 Gent, Belgium
| | - Vicky Pauwelyn
- Heymans Institute of Pharmacology, Ghent University, De Pintelaan 185, B-9000 Gent, Belgium
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Comparative functional selectivity of imidafenacin and propiverine, antimuscarinic agents, for the urinary bladder over colon in conscious rats. Naunyn Schmiedebergs Arch Pharmacol 2015. [DOI: 10.1007/s00210-015-1155-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Fujikawa Y, Tominaga K, Tanaka F, Tanigawa T, Watanabe T, Fujiwara Y, Arakawa T. Enteric glial cells are associated with stress-induced colonic hyper-contraction in maternally separated rats. Neurogastroenterol Motil 2015; 27:1010-23. [PMID: 25960044 DOI: 10.1111/nmo.12577] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/25/2014] [Accepted: 04/05/2015] [Indexed: 12/20/2022]
Abstract
BACKGROUND Enteric glial cells (EGCs) play important roles in enteric integrity and regulation of gastrointestinal function. However, whether EGCs undergo pathophysiological changes in stress-associated gastrointestinal disorders is unknown. We investigated structural and functional alterations in colonic EGCs and their roles in colonic contraction in an irritable bowel syndrome (IBS) model. METHODS As a chronic stress, male Wistar rats underwent 3-h maternal separation during postnatal days 2-14. As an acute stress, we used water-immersion stress (4 h) in adulthood (at 8 weeks). We quantitatively and morphologically evaluated enteric neurons and EGCs using whole-mount longitudinal muscle-myenteric plexus preparations. Colonic contraction was analyzed with electrical field stimulation (EFS). KEY RESULTS Glial fibrillary acidic protein (GFAP) expression and the number of total, cholinergic, and nitrergic neurons were unchanged in maternally separated rats with acute stress (combined stress: an IBS model) compared with controls. However, the density of GFAP-positive EGC processes that apparently overlapped with the neurons and the extent of bulbous swelling of terminals increased according to the stress intensity: control, acute stress, maternal separation, and combined stress. EFS-induced colonic contractions were significantly greater in the combined stress rats than in controls. Higher dose of fluorocitrate, a selective inhibitor of EGC metabolism, was required to inhibit both EFS-induced contraction and EGCs activation in the combined stress rats than in controls. CONCLUSIONS & INFERENCES Colonic EGCs exhibited structural alterations according to the stress intensity. EGCs were associated with stress-induced colonic hyper-contraction in the combined stress rats, which may underlie the pathogenesis of IBS.
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Affiliation(s)
- Y Fujikawa
- Department of Gastroenterology, Osaka City University Graduate School of Medicine, Osaka, Japan
| | - K Tominaga
- Department of Gastroenterology, Osaka City University Graduate School of Medicine, Osaka, Japan
| | - F Tanaka
- Department of Gastroenterology, Osaka City University Graduate School of Medicine, Osaka, Japan
| | - T Tanigawa
- Department of Gastroenterology, Osaka City University Graduate School of Medicine, Osaka, Japan
| | - T Watanabe
- Department of Gastroenterology, Osaka City University Graduate School of Medicine, Osaka, Japan
| | - Y Fujiwara
- Department of Gastroenterology, Osaka City University Graduate School of Medicine, Osaka, Japan
| | - T Arakawa
- Department of Gastroenterology, Osaka City University Graduate School of Medicine, Osaka, Japan
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Broad J, Kung VWS, Boundouki G, Aziz Q, De Maeyer JH, Knowles CH, Sanger GJ. Cholinergic interactions between donepezil and prucalopride in human colon: potential to treat severe intestinal dysmotility. Br J Pharmacol 2014; 170:1253-61. [PMID: 24032987 DOI: 10.1111/bph.12397] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2013] [Revised: 08/27/2013] [Accepted: 08/30/2013] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND AND PURPOSE Cholinesterase inhibitors such as neostigmine are used for acute colonic pseudo-obstruction, but cardio-bronchial side-effects limit use. To minimize side-effects, lower doses could be combined with a 5-HT4 receptor agonist, which also facilitates intestinal cholinergic activity. However, safety concerns, especially in the elderly, require drugs with good selectivity of action. These include the AChE inhibitor donepezil (used for Alzheimer's disease, with reduced cardio-bronchial liability) and prucalopride, the first selective, clinically available 5-HT4 receptor agonist. This study examined their individual and potential synergistic activities in human colon. EXPERIMENTAL APPROACH Neuronally mediated muscle contractions and relaxations of human colon were evoked by electrical field stimulation (EFS) and defined phenotypically as cholinergic, nitrergic or tachykinergic using pharmacological tools; the effects of drugs were determined as changes in 'area under the curve'. KEY RESULTS Prucalopride increased cholinergically mediated contractions (EC50 855 nM; 33% maximum increase), consistent with its ability to stimulate intestinal motility; donepezil (477%) and neostigmine (2326%) had greater efficacy. Concentrations of donepezil (30-100 nM) found in venous plasma after therapeutic doses had minimal ability to enhance cholinergic activity. However, donepezil (30 nM) together with prucalopride (3, 10 μM) markedly increased EFS-evoked contractions compared with prucalopride alone (P = 0.04). For example, the increases observed with donepezil and prucalopride 10 μM together or alone were, respectively, 105 ± 35%, 4 ± 6% and 35 ± 21% (n = 3-7, each concentration). CONCLUSIONS AND IMPLICATIONS Potential synergy between prucalopride and donepezil activity calls for exploration of this combination as a safer, more effective treatment of colonic pseudo-obstruction.
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Affiliation(s)
- J Broad
- Neurogastroenterology Group, Blizard Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK
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Priem EK, De Maeyer JH, Lefebvre RA. Influence of phosphodiesterases on basal and 5-HT4 receptor facilitated cholinergic contractility in pig descending colon. Eur J Pharmacol 2013; 705:156-63. [DOI: 10.1016/j.ejphar.2013.02.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2012] [Revised: 01/10/2013] [Accepted: 02/05/2013] [Indexed: 12/17/2022]
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Priem E, Van Colen I, De Maeyer JH, Lefebvre RA. The facilitating effect of prucalopride on cholinergic neurotransmission in pig gastric circular muscle is regulated by phosphodiesterase 4. Neuropharmacology 2011; 62:2126-35. [PMID: 22266217 DOI: 10.1016/j.neuropharm.2011.12.020] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2011] [Revised: 12/05/2011] [Accepted: 12/20/2011] [Indexed: 01/01/2023]
Abstract
The influence of the selective 5-HT(4) receptor agonist prucalopride on acetylcholine release from cholinergic nerve endings innervating pig gastric circular muscle and the possible regulation of this effect by phosphodiesterases (PDEs) was investigated, as PDEs have been shown to control the response to 5-HT(4) receptor activation in pig left atrium. Circular muscle strips were prepared from pig proximal stomach and either submaximal cholinergic contractions or tritium outflow after incubation with [(3)H]-choline, induced by electrical field stimulation, were studied. Prucalopride concentration-dependently increased the amplitude of submaximal cholinergic contractions and of acetylcholine release induced by electrical field stimulation. The effect of the highest concentration tested (0.3 μM) on cholinergic contractions was antagonized by the selective 5-HT(4) receptor antagonist GR113808 but not by granisetron or methysergide; the antagonism of prucalopride by GR113808 was confirmed in the release assay. The non-selective PDE-inhibitor 3-isobutyl-methyl-xanthine (IBMX) concentration-dependently reduced the amplitude of the cholinergic contractions; 3 μM IBMX reduced the cholinergic contractions maximally by 16% but it enhanced the facilitating effect of prucalopride from 51 to 83%. IBMX (10 μM) induced and enhanced the facilitating effect of prucalopride on electrically induced acetylcholine release. The selective inhibitors vinpocetine (PDE1), EHNA (PDE2) and cilostamide (PDE3) did not influence the effect of prucalopride on acetylcholine release but the PDE4-inhibitor rolipram (1 μM) enhanced the facilitating effect of prucalopride to the same extent as IBMX. These results demonstrate that 5-HT(4) receptors are present on the cholinergic nerves towards the pig gastric circular muscle, facilitating acetylcholine release; the intracellular transduction pathway of this facilitation is regulated by PDE4. Combination of a 5-HT(4) receptor agonist with selective inhibition of the PDE involved in this regulation of transmitter release might enhance the prokinetic effect of the 5-HT(4) receptor agonist.
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Affiliation(s)
- Evelien Priem
- Heymans Institute of Pharmacology, Ghent University, De Pintelaan 185, B-9000 Gent, Belgium
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