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Leech T, Peiris M. Mucosal neuroimmune mechanisms in gastro-oesophageal reflux disease (GORD) pathogenesis. J Gastroenterol 2024; 59:165-178. [PMID: 38221552 PMCID: PMC10904498 DOI: 10.1007/s00535-023-02065-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2023] [Accepted: 11/30/2023] [Indexed: 01/16/2024]
Abstract
Gastro-oesophageal reflux disease (GORD) is a chronic condition characterised by visceral pain in the distal oesophagus. The current first-line treatment for GORD is proton pump inhibitors (PPIs), however, PPIs are ineffective in a large cohort of patients and long-term use may have adverse effects. Emerging evidence suggests that nerve fibre number and location are likely to play interrelated roles in nociception in the oesophagus of GORD patients. Simultaneously, alterations in cells of the oesophageal mucosa, namely epithelial cells, mast cells, dendritic cells, and T lymphocytes, have been a focus of GORD research for several years. The oesophagus of GORD patients exhibits both macro- and micro-inflammation as a response to chronic acidic reflux at the epithelium. In other conditions of the GI tract, such as IBS and IBD, well-characterised bidirectional processes between immune cells and mucosal nerve fibres contribute to pathogenesis and symptom generation. Sensory alterations in these conditions such as nerve fibre outgrowth and hypersensitivity can be driven by inflammatory processes, which promote visceral pain signalling. This review will examine what is currently known of the molecular pathways linking inflammation and sensory perception leading to the development of GORD symptoms and explore potentially relevant mechanisms in other GI regions which may indicate new areas in GORD research.
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Affiliation(s)
- Tom Leech
- Centre for Neuroscience, Surgery and Trauma, Blizard Institute, Faculty of Medicine and Dentistry, Queen Mary University of London, 4 Newark Street, London, E1 2AT, UK
| | - Madusha Peiris
- Centre for Neuroscience, Surgery and Trauma, Blizard Institute, Faculty of Medicine and Dentistry, Queen Mary University of London, 4 Newark Street, London, E1 2AT, UK.
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2
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Wang Q, Caraballo SG, Rychkov G, McGovern AE, Mazzone SB, Brierley SM, Harrington AM. Comparative localization of colorectal sensory afferent central projections in the mouse spinal cord dorsal horn and caudal medulla dorsal vagal complex. J Comp Neurol 2024; 532:e25546. [PMID: 37837642 DOI: 10.1002/cne.25546] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Revised: 09/04/2023] [Accepted: 10/03/2023] [Indexed: 10/16/2023]
Abstract
The distal colon and rectum (colorectum) are innervated by spinal and vagal afferent pathways. The central circuits into which vagal and spinal afferents relay colorectal nociceptive information remain to be comparatively assessed. To address this, regional colorectal retrograde tracing and colorectal distension (CRD)-evoked neuronal activation were used to compare the circuits within the dorsal vagal complex (DVC) and dorsal horn (thoracolumbar [TL] and lumbosacral [LS] spinal levels) into which vagal and spinal colorectal afferents project. Vagal afferent projections were observed in the nucleus tractus solitarius (NTS), area postrema (AP), and dorsal motor nucleus of the vagus (DMV), labeled from the rostral colorectum. In the NTS, projections were opposed to catecholamine and pontine parabrachial nuclei (PbN)-projecting neurons. Spinal afferent projections were labeled from rostral through to caudal aspects of the colorectum. In the dorsal horn, the number of neurons activated by CRD was linked to pressure intensity, unlike in the DVC. In the NTS, 13% ± 0.6% of CRD-activated neurons projected to the PbN. In the dorsal horn, at the TL spinal level, afferent input was associated with PbN-projecting neurons in lamina I (LI), with 63% ± 3.15% of CRD-activated neurons in LI projecting to the PbN. On the other hand, at the LS spinal level, only 18% ± 0.6% of CRD-activated neurons in LI projected to the PbN. The collective data identify differences in the central neuroanatomy that support the disparate roles of vagal and spinal afferent signaling in the facilitation and modulation of colorectal nociceptive responses.
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Affiliation(s)
- QingQing Wang
- Visceral Pain Research Group, College of Medicine and Public Health, Flinders Health and Medical Research Institute, Flinders University, Adelaide, South Australia, Australia
- Hopwood Centre for Neurobiology, Lifelong Health, South Australian Health and Medical Research Institute (SAHMRI), Adelaide, South Australia, Australia
| | - Sonia Garcia Caraballo
- Visceral Pain Research Group, College of Medicine and Public Health, Flinders Health and Medical Research Institute, Flinders University, Adelaide, South Australia, Australia
- Hopwood Centre for Neurobiology, Lifelong Health, South Australian Health and Medical Research Institute (SAHMRI), Adelaide, South Australia, Australia
| | - Grigori Rychkov
- Hopwood Centre for Neurobiology, Lifelong Health, South Australian Health and Medical Research Institute (SAHMRI), Adelaide, South Australia, Australia
- School of Biomedicine, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, South Australia, Australia
| | - Alice E McGovern
- Department of Anatomy and Physiology, The University of Melbourne, Melbourne, Victoria, Australia
| | - Stuart B Mazzone
- Department of Anatomy and Physiology, The University of Melbourne, Melbourne, Victoria, Australia
| | - Stuart M Brierley
- Visceral Pain Research Group, College of Medicine and Public Health, Flinders Health and Medical Research Institute, Flinders University, Adelaide, South Australia, Australia
- Hopwood Centre for Neurobiology, Lifelong Health, South Australian Health and Medical Research Institute (SAHMRI), Adelaide, South Australia, Australia
- School of Biomedicine, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, South Australia, Australia
| | - Andrea M Harrington
- Visceral Pain Research Group, College of Medicine and Public Health, Flinders Health and Medical Research Institute, Flinders University, Adelaide, South Australia, Australia
- Hopwood Centre for Neurobiology, Lifelong Health, South Australian Health and Medical Research Institute (SAHMRI), Adelaide, South Australia, Australia
- School of Biomedicine, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, South Australia, Australia
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Harrington AM, Caraballo SG, Maddern JE, Grundy L, Castro J, Brierley SM. Colonic afferent input and dorsal horn neuron activation differs between the thoracolumbar and lumbosacral spinal cord. Am J Physiol Gastrointest Liver Physiol 2019; 317:G285-G303. [PMID: 31188624 DOI: 10.1152/ajpgi.00013.2019] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The distal colon is innervated by the splanchnic and pelvic nerves, which relay into the thoracolumbar and lumbosacral spinal cord, respectively. Although the peripheral properties of the colonic afferent nerves within these pathways are well studied, their input into the spinal cord remain ill defined. The use of dual retrograde tracing from the colon wall and lumen, in conjunction with in vivo colorectal distension and spinal neuronal activation labeling with phosphorylated MAPK ERK 1/2 (pERK), allowed us to identify thoracolumbar and lumbosacral spinal cord circuits processing colonic afferent input. In the thoracolumbar dorsal horn, central projections of colonic afferents were primarily labeled from the wall of the colon and localized in laminae I and V. In contrast, lumbosacral projections were identified from both lumen and wall tracing, present within various dorsal horn laminae, collateral tracts, and the dorsal gray commissure. Nonnoxious in vivo colorectal distension evoked significant neuronal activation (pERK-immunoreactivity) within the lumbosacral dorsal horn but not in thoracolumbar regions. However, noxious in vivo colorectal distension evoked significant neuronal activation in both the thoracolumbar and lumbosacral dorsal horn, with the distribution of activated neurons correlating to the pattern of traced projections. Dorsal horn neurons activated by colorectal distension were identified as possible populations of projection neurons or excitatory and inhibitory interneurons based on their neurochemistry. Our findings demonstrate how colonic afferents in splanchnic and pelvic pathways differentially relay mechanosensory information into the spinal cord and contribute to the recruitment of spinal cord pathways processing non-noxious and noxious stimuli.NEW & NOTEWORTHY In mice, retrograde tracing from the colon wall and lumen was used to identify unique populations of afferent neurons and central projections within the spinal cord dorsal horn. We show that there are pronounced differences between the spinal cord regions in the distribution pattern of colonic afferent central projections and the pattern of dorsal horn neuron activation evoked by colorectal distension. These findings demonstrate how colonic afferent input influences spinal processing of colonic mechanosensation.
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Affiliation(s)
- Andrea M Harrington
- Visceral Pain Research Group, Centre for Neuroscience, College of Medicine and Public Health, Flinders University, Bedford Park, SA, Australia.,Centre for Nutrition and Gastrointestinal Diseases, Faculty of Health and Medical Sciences, University of Adelaide, South Australian Health and Medical Research Institute, North Terrace, Adelaide, SA, Australia.,Hopwood Centre for Neurobiology, Lifelong Health Theme, South Australian Health and Medical Research Institute, North Terrace, Adelaide, SA, Australia
| | - Sonia Garcia Caraballo
- Visceral Pain Research Group, Centre for Neuroscience, College of Medicine and Public Health, Flinders University, Bedford Park, SA, Australia.,Centre for Nutrition and Gastrointestinal Diseases, Faculty of Health and Medical Sciences, University of Adelaide, South Australian Health and Medical Research Institute, North Terrace, Adelaide, SA, Australia.,Hopwood Centre for Neurobiology, Lifelong Health Theme, South Australian Health and Medical Research Institute, North Terrace, Adelaide, SA, Australia
| | - Jessica E Maddern
- Visceral Pain Research Group, Centre for Neuroscience, College of Medicine and Public Health, Flinders University, Bedford Park, SA, Australia.,Centre for Nutrition and Gastrointestinal Diseases, Faculty of Health and Medical Sciences, University of Adelaide, South Australian Health and Medical Research Institute, North Terrace, Adelaide, SA, Australia.,Hopwood Centre for Neurobiology, Lifelong Health Theme, South Australian Health and Medical Research Institute, North Terrace, Adelaide, SA, Australia
| | - Luke Grundy
- Visceral Pain Research Group, Centre for Neuroscience, College of Medicine and Public Health, Flinders University, Bedford Park, SA, Australia.,Centre for Nutrition and Gastrointestinal Diseases, Faculty of Health and Medical Sciences, University of Adelaide, South Australian Health and Medical Research Institute, North Terrace, Adelaide, SA, Australia.,Hopwood Centre for Neurobiology, Lifelong Health Theme, South Australian Health and Medical Research Institute, North Terrace, Adelaide, SA, Australia
| | - Joel Castro
- Visceral Pain Research Group, Centre for Neuroscience, College of Medicine and Public Health, Flinders University, Bedford Park, SA, Australia.,Centre for Nutrition and Gastrointestinal Diseases, Faculty of Health and Medical Sciences, University of Adelaide, South Australian Health and Medical Research Institute, North Terrace, Adelaide, SA, Australia.,Hopwood Centre for Neurobiology, Lifelong Health Theme, South Australian Health and Medical Research Institute, North Terrace, Adelaide, SA, Australia
| | - Stuart M Brierley
- Visceral Pain Research Group, Centre for Neuroscience, College of Medicine and Public Health, Flinders University, Bedford Park, SA, Australia.,Centre for Nutrition and Gastrointestinal Diseases, Faculty of Health and Medical Sciences, University of Adelaide, South Australian Health and Medical Research Institute, North Terrace, Adelaide, SA, Australia.,Hopwood Centre for Neurobiology, Lifelong Health Theme, South Australian Health and Medical Research Institute, North Terrace, Adelaide, SA, Australia
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Hu Y, Yu X, Yu S. QX-314 inhibits acid-induced activation of esophageal nociceptive C fiber neurons. Neurogastroenterol Motil 2019; 31:e13543. [PMID: 30663188 PMCID: PMC6452878 DOI: 10.1111/nmo.13543] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Revised: 12/10/2018] [Accepted: 12/14/2018] [Indexed: 01/16/2023]
Abstract
INTRODUCTION Acid reflux in the esophagus can induce painful sensations such as heartburn and non-cardiac chest pain. These nociceptive symptoms are initiated by activation of TRPV1-positive afferent C fibers in the esophagus. The present study aimed to explore a novel C fiber inhibition approach. We hypothesized that activation of TRPV1 by acid enabled QX-314, a membrane impermeable sodium channel blocker, to inhibit acid-induced activation of esophageal nociceptive C fiber neurons. METHOD We determined the inhibitory effect of QX-314 in the presence of acid in guinea pig esophageal nociceptive vagal jugular C fiber neurons by both patch clamp recording in neuron soma and by extra-cellular recording at nerve terminals. KEY RESULTS Our data demonstrated QX-314 alone did not inhibit sodium currents. However, when applied along with capsaicin to activate TRPV1, QX-314 was able to block sodium currents in esophageal-specific jugular C fiber neurons. We then showed that in the presence of acid, QX-314 significantly blocked acid-evoked activation of jugular C fiber neurons. This effect was attenuated by TRPV1 antagonist AMG9810, suggesting acid-mediated inhibitory effect of QX-314 was TRPV1-dependent. Finally, we provided evidence at nerve endings that acid-evoked action potential discharges in esophageal jugular C fibers were inhibited by QX-314 when applied in the presence of acid. CONCLUSION AND INFERENCES Our data demonstrated that activation of TRPV1 by acid enabled membrane impermeable sodium channel blocker QX-314 to inhibit acid-induced activation in esophageal nociceptive C fibers. This supports a localized application of QX-314 in the esophagus to block esophageal nociception in acid reflux disorders.
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Affiliation(s)
| | | | - Shaoyong Yu
- Corresponding: Shaoyong Yu, MD, MPH., Johns Hopkins University School of Medicine, Ross Research Building, Room 945, 720 Rutland Ave, Baltimore 21205, Phone: (410) 502-2455,
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Yu X, Yu M, Liu Y, Yu S. TRP channel functions in the gastrointestinal tract. Semin Immunopathol 2015; 38:385-96. [PMID: 26459157 DOI: 10.1007/s00281-015-0528-y] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 09/07/2015] [Indexed: 12/14/2022]
Abstract
Transient receptor potential (TRP) channels are predominantly distributed in both somatic and visceral sensory nervous systems and play a crucial role in sensory transduction. As the largest visceral organ system, the gastrointestinal (GI) tract frequently accommodates external inputs, which stimulate sensory nerves to initiate and coordinate sensory and motor functions in order to digest and absorb nutrients. Meanwhile, the sensory nerves in the GI tract are also able to detect potential tissue damage by responding to noxious irritants. This nocifensive function is mediated through specific ion channels and receptors expressed in a subpopulation of spinal and vagal afferent nerve called nociceptor. In the last 18 years, our understanding of TRP channel expression and function in GI sensory nervous system has been continuously improved. In this review, we focus on the expressions and functions of TRPV1, TRPA1, and TRPM8 in primary extrinsic afferent nerves innervated in the esophagus, stomach, intestine, and colon and briefly discuss their potential roles in relevant GI disorders.
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Affiliation(s)
- Xiaoyun Yu
- Division of Gastroenterology & Hepatology, Department of Medicine, Johns Hopkins University School of Medicine, Ross Research Building, Room 945, 720 Rutland Ave, Baltimore, MD, 21205, USA
| | - Mingran Yu
- Division of Gastroenterology & Hepatology, Department of Medicine, Johns Hopkins University School of Medicine, Ross Research Building, Room 945, 720 Rutland Ave, Baltimore, MD, 21205, USA
| | - Yingzhe Liu
- Division of Gastroenterology & Hepatology, Department of Medicine, Johns Hopkins University School of Medicine, Ross Research Building, Room 945, 720 Rutland Ave, Baltimore, MD, 21205, USA
| | - Shaoyong Yu
- Division of Gastroenterology & Hepatology, Department of Medicine, Johns Hopkins University School of Medicine, Ross Research Building, Room 945, 720 Rutland Ave, Baltimore, MD, 21205, USA.
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Blackshaw LA. Transient receptor potential cation channels in visceral sensory pathways. Br J Pharmacol 2014; 171:2528-36. [PMID: 24641218 DOI: 10.1111/bph.12641] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Revised: 01/09/2014] [Accepted: 01/20/2014] [Indexed: 01/03/2023] Open
Abstract
The extensive literature on this subject is in direct contrast to the limited range of clinical uses for ligands of the transient receptor potential cation channels (TRPs) in diseases of the viscera. TRPV1 is the most spectacular example of this imbalance, as it is in other systems, but it is nonetheless the only TRP target that is currently targeted clinically in bladder sensory dysfunction. It is not clear why this discrepancy exists, but a likely answer is in the promiscuity of TRPs as sensors and transducers for environmental mechanical and chemical stimuli. This review first describes the different sensory pathways from the viscera, and on which nociceptive and non-nociceptive neurones within these pathways TRPs are expressed. They not only fulfil roles as both mechano- and chemo-sensors on visceral afferents, but also form an effector mechanism for cell activation after activation of GPCR and cytokine receptors. Their role may be markedly changed in diseased states, including chronic pain and inflammation. Pain presents the most obvious potential for further development of therapeutic interventions targeted at TRPs, but forms of inflammation are emerging as likely to benefit also. However, despite much basic research, we are still at the beginning of exploring such potential in visceral sensory pathways.
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Affiliation(s)
- L Ashley Blackshaw
- Wingate Institute for Neurogastroenterology, Centre for Digestive Diseases, Blizard Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK
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Yu X, Hu Y, Yu S. Effects of acid on vagal nociceptive afferent subtypes in guinea pig esophagus. Am J Physiol Gastrointest Liver Physiol 2014; 307:G471-8. [PMID: 24994852 PMCID: PMC4137112 DOI: 10.1152/ajpgi.00156.2014] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Acid reflux-induced heartburn and noncardiac chest pain are processed peripherally by sensory nerve endings in the wall of the esophagus, but the underlying mechanism is still unclear. This study aims to determine the effects of acid on esophageal vagal nociceptive afferent subtypes. Extracellular single-unit recordings were performed in guinea pig vagal nodose or jugular C fiber neurons by using ex vivo esophageal-vagal preparations with intact nerve endings in the esophagus. We recorded action potentials (AP) of esophageal nodose or jugular C fibers evoked by acid perfusion and compared esophageal distension-evoked AP before and after acid perfusion. Acid perfusion for 30 min (pH range 7.4 to 5.8) did not evoke AP in nodose C fibers but significantly decreased their responses to esophageal distension, which could be recovered after washing out acid for 90 min. In jugular C fibers, acid perfusion not only evoked AP but also inhibited their responses to esophageal distension, which were not recovered after washing out acid for 120 min. Lower concentration of capsaicin perfusion mimicked acid-induced effects in nodose and jugular C fibers. Pretreatment with TRPV1 antagonist AMG9810, but not acid-sensing ion channel (ASIC) inhibitor amiloride, significantly inhibited acid-induced effects in nodose and jugular C fiber. These results demonstrate that esophageal vagal nociceptive afferent nerve subtypes display distinctive responses to acid. Acid activates jugular, but not nodose, C fibers and inhibits both of their responses to esophageal distension. These effects are mediated mainly through TRPV1. This inhibitory effect is a novel finding and may contribute to esophageal sensory/motor dysfunction in acid reflux diseases.
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Affiliation(s)
| | | | - Shaoyong Yu
- Division of Gastroenterology and Hepatology, Johns Hopkins University School of Medicine, Baltimore, Maryland
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Matsumoto K, Hosoya T, Ishikawa E, Tashima K, Amagase K, Kato S, Murayama T, Horie S. Distribution of transient receptor potential cation channel subfamily V member 1-expressing nerve fibers in mouse esophagus. Histochem Cell Biol 2014; 142:635-44. [PMID: 25002127 DOI: 10.1007/s00418-014-1246-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/27/2014] [Indexed: 12/11/2022]
Abstract
Transient receptor potential cation channel subfamily V member 1 (TRPV1) plays a role in esophageal function. However, the distribution of TRPV1 nerve fibers in the esophagus is currently not well understood. In the present study, we investigated the distribution of TRPV1 and neurotransmitters released from TRPV1 nerve fibers in the mouse lower esophagus. Furthermore, we investigated changes in the presence of TRPV1 in the mouse model of esophagitis. Numerous TRPV1-immunoreactive nerve fibers were seen in both the submucosal layer and myenteric plexus of the lower esophagus and colocalized with calcitonin gene-related peptide (CGRP). TRPV1 colocalized with substance P in axons in the submucosal layer and myenteric plexus. TRPV1 colocalized with neuronal nitric oxide synthase in the myenteric plexus. We observed some colocalization of CGRP with the vesicular acetylcholine (ACh) transporter, packaging of ACh into synaptic vesicles after its synthesis in terminal cytoplasm, in the submucosal layer and myenteric plexus. In the esophagitis model, the number of the TRPV1 nerve fibers did not change, but their immunoreactive intensity increased compared with sham-operated mice. Inhibitory effect of exogenous capsaicin on electrically stimulated twitch contraction significantly increased in esophagitis model compared with the effect in sham-operated mice. Overall, these results suggest that TRPV1 nerve fibers projecting to both the submucosal and muscle layer of the esophagus are extrinsic spinal and vagal afferent neurons. Furthermore, TRPV1 nerve fibers contain CGRP, substance P, nitric oxide, and ACh. Therefore, acid influx-mediated TRPV1 activation may play a role in regulating esophageal relaxation.
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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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Localization of receptors for calcitonin-gene-related peptide to intraganglionic laminar endings of the mouse esophagus: peripheral interaction between vagal and spinal afferents? Histochem Cell Biol 2013; 141:321-35. [PMID: 24203088 DOI: 10.1007/s00418-013-1162-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/23/2013] [Indexed: 12/11/2022]
Abstract
The calcitonin-gene-related peptide (CGRP) receptor is a heterodimer of calcitonin-receptor-like receptor (CLR) and receptor-activity-modifying protein 1 (RAMP1). Despite the importance of CGRP in regulating gastrointestinal functions, nothing is known about the distribution and function of CLR/RAMP1 in the esophagus, where up to 90 % of spinal afferent neurons contain CGRP. We detected CLR/RAMP1 in the mouse esophagus using immunofluorescence and confocal laser scanning microscopy and examined their relationship with neuronal elements of the myenteric plexus. Immunoreactivity for CLR and RAMP1 colocalized with VGLUT2-positive intraganglionic laminar endings (IGLEs), which were contacted by CGRP-positive varicose axons presumably of spinal afferent origin, typically at sites of CRL/RAMP1 immunoreactivity. This provides an anatomical basis for interaction between spinal afferent fibers and IGLEs. Immunoreactive CLR and RAMP1 also colocalized in myenteric neurons. Thus, CGRP-containing spinal afferents may interact with both vagal IGLEs and myenteric neurons in the mouse esophagus, possibly modulating motility reflexes and inflammatory hypersensitivity.
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