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Romano A, Friuli M, Eramo B, Gallelli CA, Koczwara JB, Azari EK, Paquot A, Arnold M, Langhans W, Muccioli GG, Lutz TA, Gaetani S. "To brain or not to brain": evaluating the possible direct effects of the satiety factor oleoylethanolamide in the central nervous system. Front Endocrinol (Lausanne) 2023; 14:1158287. [PMID: 37234803 PMCID: PMC10206109 DOI: 10.3389/fendo.2023.1158287] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/03/2023] [Accepted: 04/12/2023] [Indexed: 05/28/2023] Open
Abstract
Introduction Oleoylethanolamide (OEA), an endogenous N-acylethanolamine acting as a gut-to-brain signal to control food intake and metabolism, has been attracting attention as a target for novel therapies against obesity and eating disorders. Numerous observations suggested that the OEA effects might be peripherally mediated, although they involve central pathways including noradrenergic, histaminergic and oxytocinergic systems of the brainstem and the hypothalamus. Whether these pathways are activated directly by OEA or whether they are downstream of afferent nerves is still highly debated. Some early studies suggested vagal afferent fibers as the main route, but our previous observations have contradicted this idea and led us to consider the blood circulation as an alternative way for OEA's central actions. Methods To test this hypothesis, we first investigated the impact of subdiaphragmatic vagal deafferentation (SDA) on the OEA-induced activation of selected brain nuclei. Then, we analyzed the pattern of OEA distribution in plasma and brain at different time points after intraperitoneal administration in addition to measuring food intake. Results Confirming and extending our previous findings that subdiaphragmatic vagal afferents are not necessary for the eating-inhibitory effect of exogenous OEA, our present results demonstrate that vagal sensory fibers are also not necessary for the neurochemical effects of OEA. Rather, within a few minutes after intraperitoneal administration, we found an increased concentration of intact OEA in different brain areas, associated with the inhibition of food intake. Conclusion Our results support that systemic OEA rapidly reaches the brain via the circulation and inhibits eating by acting directly on selected brain nuclei.
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Affiliation(s)
- Adele Romano
- Department of Physiology and Pharmacology “V. Erspamer”, Sapienza University of Rome, Rome, Italy
| | - Marzia Friuli
- Department of Physiology and Pharmacology “V. Erspamer”, Sapienza University of Rome, Rome, Italy
| | - Barbara Eramo
- Department of Physiology and Pharmacology “V. Erspamer”, Sapienza University of Rome, Rome, Italy
| | - Cristina Anna Gallelli
- Department of Physiology and Pharmacology “V. Erspamer”, Sapienza University of Rome, Rome, Italy
| | - Justyna Barbara Koczwara
- Department of Physiology and Pharmacology “V. Erspamer”, Sapienza University of Rome, Rome, Italy
| | | | - Adrien Paquot
- Bioanalysis and Pharmacology of Bioactive Lipids Research Group, Louvain Drug Research Institute, Université Catholique de Louvain, UCLouvain, Brussels, Belgium
| | - Myrtha Arnold
- Physiology and Behavior Laboratory, ETH Zurich, Zurich, Switzerland
| | | | - Giulio G. Muccioli
- Bioanalysis and Pharmacology of Bioactive Lipids Research Group, Louvain Drug Research Institute, Université Catholique de Louvain, UCLouvain, Brussels, Belgium
| | - Thomas Alexander Lutz
- Institute of Veterinary Physiology, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland
| | - Silvana Gaetani
- Department of Physiology and Pharmacology “V. Erspamer”, Sapienza University of Rome, Rome, Italy
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2
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Li H, Page AJ. Altered Vagal Signaling and Its Pathophysiological Roles in Functional Dyspepsia. Front Neurosci 2022; 16:858612. [PMID: 35527812 PMCID: PMC9072791 DOI: 10.3389/fnins.2022.858612] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Accepted: 03/28/2022] [Indexed: 11/20/2022] Open
Abstract
The vagus nerve is crucial in the bidirectional communication between the gut and the brain. It is involved in the modulation of a variety of gut and brain functions. Human studies indicate that the descending vagal signaling from the brain is impaired in functional dyspepsia. Growing evidence indicate that the vagal signaling from gut to brain may also be altered, due to the alteration of a variety of gut signals identified in this disorder. The pathophysiological roles of vagal signaling in functional dyspepsia is still largely unknown, although some studies suggested it may contribute to reduced food intake and gastric motility, increased psychological disorders and pain sensation, nausea and vomiting. Understanding the alteration in vagal signaling and its pathophysiological roles in functional dyspepsia may provide information for new potential therapeutic treatments of this disorder. In this review, we summarize and speculate possible alterations in vagal gut-to-brain and brain-to-gut signaling and the potential pathophysiological roles in functional dyspepsia.
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Affiliation(s)
- Hui Li
- Vagal Afferent Research Group, Adelaide Medical School, The University of Adelaide, Adelaide, SA, Australia
- Nutrition, Diabetes and Gut Health, Lifelong Health Theme, South Australian Health and Medical Research Institute, Adelaide, SA, Australia
- *Correspondence: Hui Li,
| | - Amanda J. Page
- Vagal Afferent Research Group, Adelaide Medical School, The University of Adelaide, Adelaide, SA, Australia
- Nutrition, Diabetes and Gut Health, Lifelong Health Theme, South Australian Health and Medical Research Institute, Adelaide, SA, Australia
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3
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Neural signalling of gut mechanosensation in ingestive and digestive processes. Nat Rev Neurosci 2022; 23:135-156. [PMID: 34983992 DOI: 10.1038/s41583-021-00544-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/16/2021] [Indexed: 12/29/2022]
Abstract
Eating and drinking generate sequential mechanosensory signals along the digestive tract. These signals are communicated to the brain for the timely initiation and regulation of diverse ingestive and digestive processes - ranging from appetite control and tactile perception to gut motility, digestive fluid secretion and defecation - that are vital for the proper intake, breakdown and absorption of nutrients and water. Gut mechanosensation has been investigated for over a century as a common pillar of energy, fluid and gastrointestinal homeostasis, and recent discoveries of specific mechanoreceptors, contributing ion channels and the well-defined circuits underlying gut mechanosensation signalling and function have further expanded our understanding of ingestive and digestive processes at the molecular and cellular levels. In this Review, we discuss our current understanding of the generation of mechanosensory signals from the digestive periphery, the neural afferent pathways that relay these signals to the brain and the neural circuit mechanisms that control ingestive and digestive processes, focusing on the four major digestive tract parts: the oral and pharyngeal cavities, oesophagus, stomach and intestines. We also discuss the clinical implications of gut mechanosensation in ingestive and digestive disorders.
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4
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O'Brien R, Buckley MM, O'Malley D. Divergent effects of exendin-4 and interleukin-6 on rat colonic secretory and contractile activity are associated with changes in regional vagal afferent signaling. Neurogastroenterol Motil 2021; 33:e14160. [PMID: 33945195 DOI: 10.1111/nmo.14160] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 03/10/2021] [Accepted: 03/24/2021] [Indexed: 12/13/2022]
Abstract
BACKGROUND The pro-inflammatory cytokine, interleukin (IL)-6 is elevated in individuals with the functional bowel disorder, irritable bowel syndrome (IBS). IL-6 can independently modify intestinal secreto-motor function, thereby contributing to IBS pathophysiology. Additionally, hormonal changes may underlie symptom flares. Post-prandial exacerbation of IBS symptoms has been linked to secretion of the incretin hormone, glucagon-like peptide-1 (GLP-1), which can also influence colonic secreto-motor activity. This study aimed to ascertain if the effects of GLP-1 on colonic secretory and contractile activity was impacted by elevated IL-6 levels and if sensory signals regarding such changes were reflected in altered vagal afferent activity. METHODS Colonic secretory currents and circular muscle contractile activity was investigated in Sprague Dawley rats using Ussing chamber and organ bath electrophysiology. Regional afferent signaling was assessed using extracellular electrophysiological recordings from colonic vagal afferents. KEY RESULTS Application of the GLP-1 receptor agonist, exendin-4 (Ex-4) in the presence of IL-6 potentiated colonic secretory currents and transepithelial resistance. Vagal afferent fibers originating in the submucosal layer exhibited larger responses to Ex-4 when IL-6 was also present. In contrast, co-application of Ex-4 and IL-6 to gut-bath chambers suppressed circular muscle contractile activity. The activity in extrinsic afferents originating in the colonic myenteric layer was similarly suppressed. CONCLUSIONS & INFERENCES Application of Ex-4 in the presence of IL-6 had divergent modulatory effects on colonic secretion and contractile activity. Similar patterns were observed in vagal afferent signaling originating in the submucosal and myenteric neuronal layers, indicating regional afferent activity reflected immune- and endocrine-mediated changes in colonic function.
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Affiliation(s)
- Rebecca O'Brien
- Department of Physiology, University College Cork, Cork, Ireland
| | - Maria M Buckley
- Department of Physiology, University College Cork, Cork, Ireland
| | - Dervla O'Malley
- Department of Physiology, University College Cork, Cork, Ireland.,APC Microbiome Ireland, University College Cork, Cork, Ireland
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5
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Abstract
PURPOSE OF REVIEW Despite the wide prevalence of gastro-esophageal reflux disease (GERD), the neurophysiological mechanisms underlying heartburn perception in the esophagus of patients with GERD remains incompletely understood. Recent studies have highlighted the potential influence sensory afferent nerves innervating the oesophageal epithelium may have on heartburn pathogenesis. The purpose of this review is to consider the current understanding of esophageal afferent neuronal innervation, including the nociceptive role of acid-sensing receptors expressed on these sensory nerves, in relation to pain perception in the esophagus of GERD patients. RECENT FINDINGS Central and peripheral pathways of sensitization following noxious stimulation of nociceptive receptors expressed on afferent nerves can regulate the strength of sensory nerve activation in the esophagus, which can result in the amplification or suppression of afferent signal transmission. The localization and characterization of mucosal sensory afferent nerves vary between GERD phenotypes and may explain the heterogeneity of symptom perception in patients with apparently similar levels of reflux. SUMMARY In this review, we discuss the relevance of afferent esophageal innervation in heartburn perception, with a particular focus on the pathways of reflux-induced activation of nociceptive nerves.
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6
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Buckley MM, O'Brien R, Brosnan E, Ross RP, Stanton C, Buckley JM, O'Malley D. Glucagon-Like Peptide-1 Secreting L-Cells Coupled to Sensory Nerves Translate Microbial Signals to the Host Rat Nervous System. Front Cell Neurosci 2020; 14:95. [PMID: 32425756 PMCID: PMC7203556 DOI: 10.3389/fncel.2020.00095] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Accepted: 03/30/2020] [Indexed: 02/06/2023] Open
Abstract
An intact gut epithelium preserves the immunological exclusion of “non-self” entities in the external environment of the gut lumen. Nonetheless, information flows continuously across this interface, with the host immune, endocrine, and neural systems all involved in monitoring the luminal environment of the gut. Both pathogenic and commensal gastrointestinal (GI) bacteria can modulate centrally-regulated behaviors and brain neurochemistry and, although the vagus nerve has been implicated in the microbiota-gut-brain signaling axis, the cellular and molecular machinery that facilitates this communication is unclear. Studies were carried out in healthy Sprague–Dawley rats to understand cross-barrier communication in the absence of disease. A novel colonic-nerve electrophysiological technique was used to examine gut-to-brain vagal signaling by bacterial products. Calcium imaging and immunofluorescent labeling were used to explore the activation of colonic submucosal neurons by bacterial products. The findings demonstrate that the neuromodulatory molecule, glucagon-like peptide-1 (GLP-1), secreted by colonic enteroendocrine L-cells in response to the bacterial metabolite, indole, stimulated colonic vagal afferent activity. At a local level indole modified the sensitivity of submucosal neurons to GLP-1. These findings elucidate a cellular mechanism by which sensory L-cells act as cross-barrier signal transducers between microbial products in the gut lumen and the host peripheral nervous system.
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Affiliation(s)
- Maria M Buckley
- Department of Physiology, University College Cork, Cork, Ireland.,APC Microbiome Ireland, University College Cork, Cork, Ireland
| | - Rebecca O'Brien
- Department of Physiology, University College Cork, Cork, Ireland
| | - Eilish Brosnan
- Department of Physiology, University College Cork, Cork, Ireland
| | - R Paul Ross
- APC Microbiome Ireland, University College Cork, Cork, Ireland.,College of Science, Engineering and Food Science, University College Cork, Cork, Ireland.,Teagasc Food Research Centre, Cork, Ireland
| | - Catherine Stanton
- APC Microbiome Ireland, University College Cork, Cork, Ireland.,Teagasc Food Research Centre, Cork, Ireland
| | - Julliette M Buckley
- Department of Surgery, University College Cork, Cork, Ireland.,Mater Private Hospital, Cork, Ireland
| | - Dervla O'Malley
- Department of Physiology, University College Cork, Cork, Ireland.,APC Microbiome Ireland, University College Cork, Cork, Ireland
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7
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Abstract
The transient receptor potential vanilloid 1 (TRPV1) is densely expressed in spinal sensory neurons as well as in cranial sensory neurons, including their central terminal endings. Recent work in the less familiar cranial sensory neurons, despite their many similarities with spinal sensory neurons, suggest that TRPV1 acts as a calcium channel to release a discrete population of synaptic vesicles. The modular and independent regulation of release offers new questions about nanodomain organization of release and selective actions of G protein–coupled receptors.
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Affiliation(s)
- Michael C. Andresen
- Department of Physiology and Pharmacology, Oregon Health & Science University, Portland, OR, 97239, USA
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8
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Deane AM, Chapman MJ, Reintam Blaser A, McClave SA, Emmanuel A. Pathophysiology and Treatment of Gastrointestinal Motility Disorders in the Acutely Ill. Nutr Clin Pract 2018; 34:23-36. [PMID: 30294835 DOI: 10.1002/ncp.10199] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Gastrointestinal dysmotility causes delayed gastric emptying, enteral feed intolerance, and functional obstruction of the small and large intestine, the latter functional obstructions being frequently termed ileus and Ogilvie syndrome, respectively. In addition to meticulous supportive care, drug therapy may be appropriate in certain situations. There is, however, considerable variation among individuals regarding what gastric residual volume identifies gastric dysmotility and would encourage use of a promotility drug. While the administration of either metoclopramide or erythromycin is supported by evidence it appears that, dual-drug therapy (erythromycin and metoclopramide) reduces the rate of treatment failure. There is a lack of evidence to guide drug therapy of ileus, but neither erythromycin nor metoclopramide appear to have a role. Several drugs, including ghrelin agonists, highly selective 5-hydroxytryptamine receptor agonists, and opiate antagonists are being studied in clinical trials. Neostigmine, when infused at a relatively slow rate in patients receiving continuous hemodynamic monitoring, may alleviate the need for endoscopic decompression in some patients.
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Affiliation(s)
- Adam M Deane
- Intensive Care Unit, Royal Melbourne Hospital, University of Melbourne, Parkville, Australia
| | - Marianne J Chapman
- Discipline of Acute Care Medicine, University of Adelaide, Adelaide, Australia.,Department of Critical Care Services, Royal Adelaide Hospital, Adelaide, Australia
| | - Annika Reintam Blaser
- Department of Anaesthesiology and Intensive Care, University of Tartu, Tartu, Estonia.,Center of Intensive Care Medicine, Lucerne Cantonal Hospital, Lucerne, Switzerland
| | - Stephen A McClave
- Department of Medicine, University of Louisville, Louisville, Kentucky, USA
| | - Anton Emmanuel
- Department of Neuro-Gastroenterology, University College London, London, UK
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9
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Bishnoi M, Khare P, Brown L, Panchal SK. Transient receptor potential (TRP) channels: a metabolic TR(i)P to obesity prevention and therapy. Obes Rev 2018; 19:1269-1292. [PMID: 29797770 DOI: 10.1111/obr.12703] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2018] [Revised: 03/26/2018] [Accepted: 04/11/2018] [Indexed: 12/13/2022]
Abstract
Cellular transport of ions, especially by ion channels, regulates physiological function. The transient receptor potential (TRP) channels, with 30 identified so far, are cation channels with high calcium permeability. These ion channels are present in metabolically active tissues including adipose tissue, liver, gastrointestinal tract, brain (hypothalamus), pancreas and skeletal muscle, which suggests a potential role in metabolic disorders including obesity. TRP channels have potentially important roles in adipogenesis, obesity development and its prevention and therapy because of their physiological properties including calcium permeability, thermosensation and taste perception, involvement in cell metabolic signalling and hormone release. This wide range of actions means that organ-specific actions are unlikely, thus increasing the possibility of adverse effects. Delineation of responses to TRP channels has been limited by the poor selectivity of available agonists and antagonists. Food constituents that can modulate TRP channels are of interest in controlling metabolic status. TRP vanilloid 1 channels modulated by capsaicin have been the most studied, suggesting that this may be the first target for effective pharmacological modulation in obesity. This review shows that most of the TRP channels are potential targets to reduce metabolic disorders through a range of mechanisms.
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Affiliation(s)
- M Bishnoi
- Department of Food and Nutritional Biotechnology, National Agri-Food Biotechnology Institute, S.A.S. Nagar (Mohali), Punjab, India.,Functional Foods Research Group, Institute for Agriculture and the Environment, University of Southern Queensland, Toowoomba, QLD, Australia
| | - P Khare
- Department of Food and Nutritional Biotechnology, National Agri-Food Biotechnology Institute, S.A.S. Nagar (Mohali), Punjab, India
| | - L Brown
- Functional Foods Research Group, Institute for Agriculture and the Environment, University of Southern Queensland, Toowoomba, QLD, Australia.,School of Health and Wellbeing, University of Southern Queensland, Toowoomba, QLD, Australia
| | - S K Panchal
- Functional Foods Research Group, Institute for Agriculture and the Environment, University of Southern Queensland, Toowoomba, QLD, Australia
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10
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Schueler RO, White G, Schueler RL, Steiner JM, Wassef A. Canine pancreatic lipase immunoreactivity concentrations associated with intervertebral disc disease in 84 dogs. J Small Anim Pract 2018; 59:305-310. [PMID: 29355958 DOI: 10.1111/jsap.12818] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2017] [Revised: 11/28/2017] [Accepted: 12/20/2017] [Indexed: 12/21/2022]
Abstract
OBJECTIVE To determine the differences in serum canine pancreatic lipase immunoreactivity between dogs with intervertebral disc herniation and healthy control dogs. MATERIALS AND METHODS Eighty-four client-owned dogs with intervertebral disc herniation, diagnosed by neurologic examination and imaging, and 18 healthy control dogs. Samples of whole blood were collected within 90 minutes of admission. Serum canine pancreatic lipase immunoreactivity concentrations were measured by a commercial immunoassay and evaluated for association with intervertebral disc herniation, signalment, neurolocalisation and the preadmission administration of glucocorticosteriods or non-steroidal anti-inflammatory drugs. RESULTS Serum canine pancreatic lipase immunoreactivity concentrations were statistically increased in dogs with intervertebral disc herniation (P<0·01, n=38). A subgroup of dogs (19/38) with elevated canine pancreatic lipase immunoreactivity concentrations was re-evaluated between 2 and 4 weeks later, and 15 had resolution of clinical signs and values less than 200 μg/L. Serum canine pancreatic lipase immunoreactivity concentrations were not significantly correlated with clinical gastrointestinal disease, neurolocalisation or the preadmission administration of corticosteroids or non-steroidal anti-inflammatory drugs. CLINICAL SIGNIFICANCE These results suggest that serum canine pancreatic lipase immunoreactivity concentrations are significantly elevated in dogs with intervertebral disc herniation.
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Affiliation(s)
- R O Schueler
- Veterinary Neurology and Rehabilitation Center, Westminster, Maryland, 21158, USA
| | - G White
- Fresno Veterinary Specialty and Emergency Center, Fresno, California, 93710, USA
| | - R L Schueler
- Veterinary Neurology and Rehabilitation Center, Westminster, Maryland, 21158, USA
| | - J M Steiner
- Department of Small Animal Clinical Sciences, Texas A&M University, College Station, Texas, 77843, USA
| | - A Wassef
- Fresno Veterinary Specialty and Emergency Center, Fresno, California, 93710, USA
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11
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Richards JR, Lapoint JM, Burillo-Putze G. Cannabinoid hyperemesis syndrome: potential mechanisms for the benefit of capsaicin and hot water hydrotherapy in treatment. Clin Toxicol (Phila) 2017; 56:15-24. [DOI: 10.1080/15563650.2017.1349910] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- John R. Richards
- Department of Emergency Medicine, University of California Davis Medical Center, Sacramento, CA, USA
| | - Jeff M. Lapoint
- Department of Emergency Medicine, Southern California Permanente Medical Group, San Diego, CA, USA
| | - Guillermo Burillo-Putze
- Área de Toxicología Clínica, Servicio de Urgencias, Universidad Europea de Canarias, Tenerife, Spain
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12
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Han T, Tang Y, Li J, Xue B, Gong L, Li J, Yu X, Liu C. Nitric oxide donor protects against acetic acid-induced gastric ulcer in rats via S-nitrosylation of TRPV1 on vagus nerve. Sci Rep 2017; 7:2063. [PMID: 28522805 PMCID: PMC5437002 DOI: 10.1038/s41598-017-02275-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Accepted: 04/10/2017] [Indexed: 12/19/2022] Open
Abstract
This study was conducted to investigate the effects of nitric oxide (NO) in acetic acid-induced gastric ulcer of rats and the underlying mechanisms. We found that peritoneal injection of sodium nitroprusside (SNP), a NO donor, decreased the ulcer area, inflammatory cell infiltration and MPO degree in acetic acid-induced gastric ulcer in rats. This effect was abolished by a transient receptor potential vanilloid 1 (TRPV1) antagonist or prior subdiaphragmatic vagotomy. SNP increased the jejunal mesenteric afferent discharge in a dose-depended manner, which was largely diminished by pretreatment of S-nitrosylation blocker N-ethylmaleimide, TRPV1 antagonist capsazepine, genetic deletion of TRPV1, or vagotomy. Whole-cell patch clamp recording showed that SNP depolarized the resting membrane potential of NG neurons, and enhanced capsaicin-induced inward current, which were both blocked by N-ethylmaleimide. Our results suggest that NO donor SNP alleviates acetic acid-induced gastric ulcer in rats via vagus nerve, while S-nitrosylation of TRPV1 may participate in this route. Our findings reveal a new mechanism for vagal afferent activation, and a new potential anti-inflammatory target.
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Affiliation(s)
- Ting Han
- Department of Physiology, School of Basic Medical Sciences, Shandong University Cheeloo Medical College, Shandong, China
| | - Yan Tang
- Department of Physiology, School of Basic Medical Sciences, Shandong University Cheeloo Medical College, Shandong, China
| | - Jing Li
- Department of Physiology, School of Basic Medical Sciences, Shandong University Cheeloo Medical College, Shandong, China
| | - Bing Xue
- Department of Physiology, School of Basic Medical Sciences, Shandong University Cheeloo Medical College, Shandong, China
| | - Liping Gong
- Department of Physiology, School of Basic Medical Sciences, Shandong University Cheeloo Medical College, Shandong, China
| | - Jingxin Li
- Department of Physiology, School of Basic Medical Sciences, Shandong University Cheeloo Medical College, Shandong, China
| | - Xiao Yu
- Department of Physiology, School of Basic Medical Sciences, Shandong University Cheeloo Medical College, Shandong, China
| | - Chuanyong Liu
- Department of Physiology, School of Basic Medical Sciences, Shandong University Cheeloo Medical College, Shandong, China. .,Provincial Key Lab of Mental Disorder, School of Basic Medical Sciences, Shandong University Cheeloo Medical College, Shandong, China.
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13
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Zafra MA, Molina F, Puerto A. Chemical afferent vagal axotomy blocks re-intake after partial withdrawal of gastric food contents. Nutr Neurosci 2016; 20:587-597. [DOI: 10.1080/1028415x.2016.1208970] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
- María A. Zafra
- Department of Psychobiology, University of Granada, Campus de Cartuja, Granada 18071, Spain
| | - Filomena Molina
- Department of Psychobiology, University of Granada, Campus de Cartuja, Granada 18071, Spain
| | - Amadeo Puerto
- Department of Psychobiology, University of Granada, Campus de Cartuja, Granada 18071, Spain
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14
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Abstract
A large body of research has been dedicated to the effects of gastrointestinal peptides on vagal afferent fibres, yet multiple lines of evidence indicate that gastrointestinal peptides also modulate brainstem vagal neurocircuitry, and that this modulation has a fundamental role in the physiology and pathophysiology of the upper gastrointestinal tract. In fact, brainstem vagovagal neurocircuits comprise highly plastic neurons and synapses connecting afferent vagal fibres, second order neurons of the nucleus tractus solitarius (NTS), and efferent fibres originating in the dorsal motor nucleus of the vagus (DMV). Neuronal communication between the NTS and DMV is regulated by the presence of a variety of inputs, both from within the brainstem itself as well as from higher centres, which utilize an array of neurotransmitters and neuromodulators. Because of the circumventricular nature of these brainstem areas, circulating hormones can also modulate the vagal output to the upper gastrointestinal tract. This Review summarizes the organization and function of vagovagal reflex control of the upper gastrointestinal tract, presents data on the plasticity within these neurocircuits after stress, and discusses the gastrointestinal dysfunctions observed in Parkinson disease as examples of physiological adjustment and maladaptation of these reflexes.
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15
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Capsaicin, Nociception and Pain. Molecules 2016; 21:molecules21060797. [PMID: 27322240 PMCID: PMC6273518 DOI: 10.3390/molecules21060797] [Citation(s) in RCA: 124] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Revised: 06/06/2016] [Accepted: 06/14/2016] [Indexed: 12/13/2022] Open
Abstract
Capsaicin, the pungent ingredient of the hot chili pepper, is known to act on the transient receptor potential cation channel vanilloid subfamily member 1 (TRPV1). TRPV1 is involved in somatic and visceral peripheral inflammation, in the modulation of nociceptive inputs to spinal cord and brain stem centers, as well as the integration of diverse painful stimuli. In this review, we first describe the chemical and pharmacological properties of capsaicin and its derivatives in relation to their analgesic properties. We then consider the biochemical and functional characteristics of TRPV1, focusing on its distribution and biological effects within the somatosensory and viscerosensory nociceptive systems. Finally, we discuss the use of capsaicin as an agonist of TRPV1 to model acute inflammation in slices and other ex vivo preparations.
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16
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Wang EM, Li WT, Yan XJ, Chen X, Liu Q, Feng CC, Cao ZJ, Fang JY, Chen SL. Vagal afferent-dependent cholecystokinin modulation of visceral pain requires central amygdala NMDA-NR2B receptors in rats. Neurogastroenterol Motil 2015. [PMID: 26197883 DOI: 10.1111/nmo.12633] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
BACKGROUND Cholecystokinin (CCK), a gut hormone that is released during feeding, exerts gastrointestinal effects in part through vagal pathway. It is reported to be a potential trigger for increased postprandial visceral sensitivity in healthy subjects and, especially in patients with irritable bowel syndrome. NR2B-containing N-methyl-d-aspartate (NMDA) receptors in the central amygdala (CeA) participate in pain modulation. Systemically administered CCK activates the CeA-innervating neurons. Here, we investigated whether CCK modulation of visceral sensitivity is mediated through CeA NMDA-NR2B receptors and whether this modulation involves vagal pathway. METHODS We first examined the visceromotor response (VMR) to colorectal distention (CRD) following i.p. injection of CCK octapeptide (CCK-8) in a rat model. Next, the NR2B antagonist ifenprodil and the NR2A antagonist NVP-AAM077 were microinjected into the CeA before systemic CCK injection. NR2B phosphorylation was detected by Western blot. To down-regulate NR2B gene expression, NR2B-specific small interfering RNA (siRNA) was delivered into CeA neurons by electroporation. In addition, the effects of functional deafferentation by perivagal application of capsaicin and pretreatment with the CCK1 receptor antagonist devazepide were investigated. KEY RESULTS CCK-8 increased VMR to CRD in a dose-dependent manner. This effect was blunted by intra-CeA administration of ifenprodil (but not NVP-AAM077) and was accompanied by phosphorylation of NR2B subunits in the CeA. CCK failed to increase VMR to CRD in NR2B siRNA-treated rats. Perivagal capsaicin application and pretreatment with devazepide prevented CCK-induced pronociception and CeA NR2B phosphorylation. CONCLUSIONS & INFERENCES The pronociception induced by systemic CCK, which is vagal afferent-dependent, requires activation of CeA NMDA-NR2B receptors.
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Affiliation(s)
- E M Wang
- Division of Gastroenterology and Hepatology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai Institute of Digestive Disease, Shanghai, China
| | - W T Li
- Division of Gastroenterology and Hepatology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai Institute of Digestive Disease, Shanghai, China
| | - X J Yan
- Division of Gastroenterology and Hepatology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai Institute of Digestive Disease, Shanghai, China
| | - X Chen
- Division of Gastroenterology and Hepatology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai Institute of Digestive Disease, Shanghai, China
| | - Q Liu
- Division of Gastroenterology and Hepatology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai Institute of Digestive Disease, Shanghai, China
| | - C C Feng
- Division of Gastroenterology and Hepatology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai Institute of Digestive Disease, Shanghai, China
| | - Z J Cao
- Division of Gastroenterology and Hepatology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai Institute of Digestive Disease, Shanghai, China
| | - J Y Fang
- Division of Gastroenterology and Hepatology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai Institute of Digestive Disease, Shanghai, China
| | - S L Chen
- Division of Gastroenterology and Hepatology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai Institute of Digestive Disease, Shanghai, China
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17
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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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18
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Karimian Azari E, Ramachandran D, Weibel S, Arnold M, Romano A, Gaetani S, Langhans W, Mansouri A. Vagal afferents are not necessary for the satiety effect of the gut lipid messenger oleoylethanolamide. Am J Physiol Regul Integr Comp Physiol 2014; 307:R167-78. [DOI: 10.1152/ajpregu.00067.2014] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The endogenous lipid messenger oleoylethanolamide (OEA) inhibits eating and modulates fat metabolism supposedly through the activation of peroxisome proliferator-activated receptor-α (PPARα) and vagal sensory fibers. We tested in adult male rats whether OEA stimulates fatty acid oxidation (FAO) and ketogenesis and whether it increases plasma levels of the satiating gut peptides glucagon-like peptide-1 (GLP-1) and peptide YY (PYY). We also explored whether OEA still inhibits eating after subdiaphragmatic vagal deafferentation (SDA). We found that intraperitoneally injected OEA (10 mg/kg body wt) reduced ( P < 0.05) food intake mainly by increasing meal latency and that this effect was stronger in rats fed a 60% high-fat diet (HFD) than in chow-fed rats. OEA increased ( P < 0.05) postprandial plasma nonesterified fatty acids and β-hydroxybutyrate (BHB) in the hepatic portal vein (HPV) and vena cava (VC) 30 min after injection, which was more pronounced in HFD- than in chow-fed rats. OEA also increased the protein expression of the key ketogenetic enzyme, mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase, in the jejunum of HFD-fed rats, but not in the liver or duodenum of either diet group. Furthermore, OEA decreased GLP-1 and PYY concentrations ( P < 0.05) in the HPV and VC 30 min after administration. Finally, OEA reduced food intake in SDA and sham-operated rats similarly. Our findings indicate that neither intact abdominal vagal afferents nor prandial increases in GLP-1 or PYY are necessary for the satiety effect of OEA. The enhanced FAO and ketogenesis raise the possibility of an involvement of intestine-derived BHB in OEA's satiety effect under certain conditions.
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Affiliation(s)
| | - Deepti Ramachandran
- Physiology and Behavior Laboratory, ETH Zurich, Schwerzenbach, Switzerland; and
| | - Sandra Weibel
- Physiology and Behavior Laboratory, ETH Zurich, Schwerzenbach, Switzerland; and
| | - Myrtha Arnold
- Physiology and Behavior Laboratory, ETH Zurich, Schwerzenbach, Switzerland; and
| | - Adele Romano
- Department of Physiology and Pharmacology “V. Erspamer”, Sapienza University of Rome, Rome, Italy
| | - Silvana Gaetani
- Department of Physiology and Pharmacology “V. Erspamer”, Sapienza University of Rome, Rome, Italy
| | - Wolfgang Langhans
- Physiology and Behavior Laboratory, ETH Zurich, Schwerzenbach, Switzerland; and
| | - Abdelhak Mansouri
- Physiology and Behavior Laboratory, ETH Zurich, Schwerzenbach, Switzerland; and
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19
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Feng CC, Yan XJ, Chen X, Wang EM, Liu Q, Zhang LY, Chen J, Fang JY, Chen SL. Vagal anandamide signaling via cannabinoid receptor 1 contributes to luminal 5-HT modulation of visceral nociception in rats. Pain 2014; 155:1591-1604. [PMID: 24813296 DOI: 10.1016/j.pain.2014.05.005] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Revised: 04/24/2014] [Accepted: 05/02/2014] [Indexed: 12/19/2022]
Abstract
Serotonin (5-HT) plays pivotal roles in the pathogenesis of postinfectious irritable bowel syndrome (PI-IBS), and luminal 5-HT time-dependently modulates visceral nociception. We found that duodenal biopsies from PI-IBS patients exhibited increased 5-HT and decreased anandamide levels and that decreased anandamide was associated with abdominal pain severity, indicating a link between 5-HT and endocannabinoid signaling pathways in PI-IBS. To understand this, we investigated the role of endocannabinoids in 5-HT modulation of visceral nociception in a rat model. Acute intraduodenally applied 5-HT attenuated the visceromotor response (VMR) to colorectal distention, and this was reversed by the cannabinoid receptor 1 (CB1) antagonist AM251. Duodenal anandamide (but not 2-arachidonoylglycerol) content was greatly increased after luminal 5-HT treatment. This effect was abrogated by the 5-HT 3 receptor (5-HT3R) antagonist granisetron, which was luminally delivered to preferentially target vagal terminals. Chemical denervation of vagal afferents blocked 5-HT-evoked antinociception and anandamide release. Chronic luminal 5-HT exposure for 5 days increased baseline VMR and VMR post-5-HT (days 4 and 5). Duodenal levels of anandamide and N-acyl-phosphatidylethanolamine-specific phospholipase D (NAPE-PLD, the anandamide-synthesizing enzyme) protein gradually declined from day 1 to 5. The time-dependent effects of 5-HT were abolished by daily granisetron pretreatment. Daily pretreatment with CB1 agonists or anandamide from day 3 attenuated 5-HT-induced hyperalgesia. These data suggest that vagal 5-HT3R-mediated duodenal anandamide release contributes to acute luminal 5-HT-induced antinociception via CB1 signaling, whereas decreased anandamide is associated with hyperalgesia upon chronic 5-HT treatment. Further understanding of peripheral vagal anandamide signaling may provide insights into the mechanisms underlying 5-HT-related IBS.
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Affiliation(s)
- Chen-Chen Feng
- Department of Gastroenterology, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai Institute of Digestive Disease, 145 Middle Shandong Road, Shanghai, China Department of pharmaceutics, Key Laboratory of Smart Drug Delivery, Ministry of Education & PLA, School of Pharmacy, Fudan University, 826 Zhangheng Road, Shanghai, China
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20
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Brozmanová M, Mazúrová L, Tatár M, Kollárik M. Evaluation of the effect of GABA(B) agonists on the vagal nodose C-fibers in the esophagus. Physiol Res 2013; 62:285-95. [PMID: 23489191 DOI: 10.33549/physiolres.932429] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Clinical studies showed that GABA(B) receptor agonists improve symptoms in patients with gastroesophageal reflux disease. One proposed mechanism of this effect is direct inhibition of the gastroesophageal vagal tension mechanosensors by GABA(B) agonists leading to reduction of reflux. In addition to tension mechanosensors, the vagal nodose ganglion supplies the esophagus with nociceptive C-fibers that likely contribute to impairment of esophageal reflex regulation in diseases. We hypothesized that GABA(B) agonists inhibit mechanically-induced activation of vagal esophageal nodose C-fibers in baseline and/or in sensitized state induced by inflammatory mediators. Ex vivo extracellular recordings were made from the esophageal nodose C-fibers in the isolated vagally-innervated guinea pig esophagus. We found that the selective GABA(B) agonist baclofen (100-300 microM) did not inhibit activation of esophageal nodose C-fibers evoked by esophageal distention (10-60 mmHg). The mechanical response of esophageal nodose C-fibers can be sensitized by different pathways including the stimulation of the histamine H(1) receptor and the stimulation the adenosine A(2A) receptor. Baclofen failed to inhibit mechanical sensitization of esophageal nodose C-fibers induced by histamine (100 microM) or the selective adenosine A(2A) receptor agonist CGS21680 (3 nM). Our data suggest that the direct mechanical inhibition of nodose C-fibers in the esophagus is unlikely to contribute to beneficial effects of GABA(B) agonists in patients with esophageal diseases.
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Affiliation(s)
- M Brozmanová
- Department of Pathophysiology, Jessenius Faculty of Medicine, Comenius University, Martin, Slovakia.
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21
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Krarup AL, Ny L, Gunnarsson J, Hvid-Jensen F, Zetterstrand S, Simrén M, Funch-Jensen P, Hansen MB, Drewes AM. Randomized clinical trial: inhibition of the TRPV1 system in patients with nonerosive gastroesophageal reflux disease and a partial response to PPI treatment is not associated with analgesia to esophageal experimental pain. Scand J Gastroenterol 2013; 48:274-84. [PMID: 23320520 DOI: 10.3109/00365521.2012.758769] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
OBJECTIVE Many patients with nonerosive reflux disease (NERD) have insufficient relief on proton pump inhibitors (PPIs). Some patients have a hypersensitive esophagus and may respond to transient receptor potential vanilloid 1 (TRPV1) antagonists. Aim. To investigate the effect of the TRPV1 antagonist AZD1386 on experimental esophageal pain in NERD patients. MATERIAL AND METHODS Enrolled patients had NERD and a partial PPI response (moderate-to-severe heartburn or regurgitation ≥3 days/week before enrolment despite ≥6 weeks' PPI therapy). Fourteen patients (21-69 years, 9 women) were block-randomized into this placebo-controlled, double-blinded, crossover study examining efficacy of a single dose (95 mg) of AZD1386. On treatment days, each participant's esophagus was stimulated with heat, distension, and electrical current at teaching hospitals in Denmark and Sweden. Heat and pressure pain served as somatic control stimuli. Per protocol results were analyzed. RESULTS Of 14 randomized patients, 12 were treated with AZD1386. In the esophagus AZD1386 did not significantly change the moderate pain threshold for heat [-3%, 95% confidence interval (CI), -22;20%], distension (-11%, 95% CI, -28;10%), or electrical current (6%, 95% CI, -10;25%). Mean cutaneous heat tolerance increased by 4.9°C (95% CI, 3.7;6.2°C). AZD1386 increased the maximum body temperature by a mean of 0.59°C (95% CI, 0.40-0.79°C), normalizing within 4 h. CONCLUSIONS AZD1386 had no analgesic effect on experimental esophageal pain in patients with NERD and a partial PPI response, whereas it increased cutaneous heat tolerance. TRPV1 does not play a major role in heat-, mechanically and electrically evoked esophageal pain in these patients. ClinicalTrials.gov identifier: D9127C00002.
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Affiliation(s)
- Anne Lund Krarup
- Mech-Sense, Department of Gastroenterology and Hepatology, Aarhus University Hospital, Aalborg, Denmark.
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22
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Browning KN, Babic T, Holmes GM, Swartz E, Travagli RA. A critical re-evaluation of the specificity of action of perivagal capsaicin. J Physiol 2013; 591:1563-80. [PMID: 23297311 DOI: 10.1113/jphysiol.2012.246827] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Perivagal application of capsaicin (1% solution) is considered to cause a selective degeneration of vagal afferent C fibres and has been used extensively to examine the site of action of many gastrointestinal (GI) neuropeptides. The actions of both capsaicin and GI neuropeptides may not be restricted to vagal afferent fibres, however, as other non-sensory neurones have displayed sensitivity to capsaicin and brainstem microinjections of these neuropeptides induce GI effects similar to those obtained upon systemic application. The aim of the present study was to test the hypothesis that perivagal capsaicin induces degeneration of vagal efferents controlling GI functions. Experiments were conducted 7-14 days after 30 min unilateral perivagal application of 0.1-1% capsaicin. Immunohistochemical analyses demonstrated that, as following vagotomy, capsaicin induced dendritic degeneration, decreased choline acetyltransferase but increased nitric oxide synthase immunoreactivity in rat dorsal motor nucleus of the vagus (DMV) neurones. Electrophysiological recordings showed a decreased DMV input resistance and excitability due, in part, to the expression of a large conductance calcium-dependent potassium current and the opening of a transient outward potassium window current at resting potential. Furthermore, the number of DMV neurones excited by thyrotrophin-releasing hormone and the gastric motility response to DMV microinjections of TRH were decreased significantly. Our data indicate that perivagal application of capsaicin induced DMV neuronal degeneration and decreased vagal motor responses. Treatment with perivagal capsaicin cannot therefore be considered selective for vagal afferent C fibres and, consequently, care is needed when using perivagal capsaicin to assess the mechanism of action of GI neuropeptides.
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Affiliation(s)
- K N Browning
- Department of Neural and Behavioral Sciences, Penn State College of Medicine, 500 University Drive, MC H109, Hershey, PA 17033, USA
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23
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Nawrot-Porąbka K, Jaworek J, Leja-Szpak A, Szklarczyk J, Konturek SJ, Reiter RJ. Luminal melatonin stimulates pancreatic enzyme secretion via activation of serotonin-dependent nerves. Pharmacol Rep 2013; 65:494-504. [PMID: 23744434 DOI: 10.1016/s1734-1140(13)71025-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Revised: 11/26/2012] [Indexed: 01/07/2023]
Abstract
BACKGROUND Serotonin (5-HT) is released from enterochromaffin cells in the gastrointestinal tract. 5-HT, via the activation of 5-HT2 and 5-HT3 receptors on vagal fibers, mediates pancreatic secretion through the mechanism independent from cholecystokinin. Melatonin (5-HT derivative) or L-tryptophan (melatonin or 5-HT precursor) given systemically or intraduodenally to the rats stimulate amylase secretion, but the mechanism is not clear. The aim of this study was to investigate the involvement of 5-HT in the pancreatostimulatory effect of melatonin or L-tryptophan, administered intraduodenally. METHODS Wistar rats were surgically equipped with silicone catheters; inserted into pancreato-biliary duct and into the duodenum. Melatonin, L-tryptophan or 5-HT were given to the rats as a bolus. Combination of 5-HT2 or 5-HT3 receptor antagonists: ketanserin (100 μg/kg) and MDL72222 (250 μg/kg) was given intraperitoneally to the animals, 15 min. prior to the administration of the examined substances. The role of the vagal nerve, sensory fibers and CCK in the control of pancreatic exocrine function were determined. Blood samples were taken for the determination of 5-HT. RESULTS Melatonin, 5-HT or L-tryptophan increased pancreatic amylase secretion. The stimulatory effect of the above substances was decreased by pretreatment of the rats with ketanserin and MDL72222. Bilateral vagotomy completely abolished the increase of amylase output caused by 5-HT, while capsaicin deactivation of sensory nerves or blockade of CCK1 receptor only partially reversed the stimulatory effect of 5-HT on the pancreas. Intraduodenal L-tryptophan, but not melatonin, increased plasma 5-HT concentrations in a dose- and time-dependent manner. CONCLUSION Stimulation of pancreatic exocrine function caused by intraluminal administration of melatonin, or L-tryptophan is modified, at least in part, by serotoninergic mechanisms and vagal nerves.
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Affiliation(s)
- Katarzyna Nawrot-Porąbka
- Department of Medical Physiology, Faculty of Health Sciences, Jagiellonian University School of Medicine, Michałowskiego 12, PL 31-126 Kraków, Poland
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Browning KN, Wan S, Baptista V, Travagli RA. Vanilloid, purinergic, and CCK receptors activate glutamate release on single neurons of the nucleus tractus solitarius centralis. Am J Physiol Regul Integr Comp Physiol 2011; 301:R394-401. [PMID: 21543639 DOI: 10.1152/ajpregu.00054.2011] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Baroreceptor inputs to nucleus of the tractus solitarius medialis (mNTS) neurons can be differentiated, among other features, by their response to vanilloid or purinergic agonists, active only on C- or A-fibers, respectively. A major aim of this study was to examine whether neurons of NTS centralis (cNTS), a subnucleus dominated by esophageal inputs, exhibit a similar dichotomy. Since it has been suggested that cholecystokinin (CCK), exerts its gastrointestinal (GI)-related effects via paracrine activation of vagal afferent C-fibers, we tested whether CCK-sensitive fibers impinging upon cNTS neurons are responsive to vanilloid but not purinergic agonists. Using whole cell patch-clamp recordings from cNTS, we recorded miniature excitatory postsynaptic currents (mEPSCs) to test the effects of the vanilloid agonist capsaicin, the purinergic agonist α,β-methylene-ATP (α,β-Met-ATP), and/or CCK-octapeptide (CCK-8s). α,β-Met-ATP, capsaicin; and CCK-8s increased EPSC frequency in 37, 71, and 46% of cNTS neurons, respectively. Approximately 30% of cNTS neurons were responsive to both CCK-8s and α,β-Met-ATP, to CCK-8s and capsaicin, or to α,β-Met-ATP and capsaicin, while 32% of neurons were responsive to all three agonists. All neurons responding to either α,β-Met-ATP or CCK-8s were also responsive to capsaicin. Perivagal capsaicin, which is supposed to induce a selective degeneration of C-fibers, decreased the number of cNTS neurons responding to capsaicin or CCK-8s but not those responding to α,β-Met-ATP. In summary, GI inputs to cNTS neurons cannot be distinguished on the basis of their selective responses to α,β-Met-ATP or capsaicin. Our data also indicate that CCK-8s increases glutamate release from purinergic and vanilloid responsive fibers impinging on cNTS neurons.
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Affiliation(s)
- Kirsteen N Browning
- Neural and Behavioral Sciences, Penn State College of Medicine, Hershey, Pennsylvania 17033-0850, USA
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25
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Schwartz ES, Christianson JA, Chen X, La JH, Davis BM, Albers KM, Gebhart G. Synergistic role of TRPV1 and TRPA1 in pancreatic pain and inflammation. Gastroenterology 2011; 140:1283-1291.e1-2. [PMID: 21185837 PMCID: PMC3066263 DOI: 10.1053/j.gastro.2010.12.033] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/06/2010] [Revised: 12/10/2010] [Accepted: 12/20/2010] [Indexed: 12/11/2022]
Abstract
BACKGROUND & AIMS The transient receptor potential (TRP) channels TRPV1 and TRPA1 have each been associated with regulation of efferent properties of primary afferent neurons that initiate neurogenic inflammation and are required for the development of inflammatory hyperalgesia. To evaluate the role of these channels in producing pain during pancreatic inflammation, we studied pancreatic nodose ganglion (NG) and dorsal root ganglion (DRG) sensory neurons (identified by content of retrograde tracer) and behavioral outcomes in a mouse model of acute pancreatitis. METHODS Pancreatic inflammation was induced by 8 hourly injections of cerulein (50 μg/kg). The extent of inflammation, pancreatic neuron TRP channel expression and function and excitability, and pain-related behaviors were evaluated over the course of the following week. RESULTS Histology and myeloperoxidase activity confirmed pancreatic inflammation that was associated with increased excitability and messenger RNA expression of the TRP channels in NG and DRG pancreatic neurons. Calcium imaging of pancreatic NG and DRG neurons from mice given cerulein revealed increased responses to TRP agonists. TRPV1 and TRPA1 antagonists attenuated cerulein-induced pain behaviors and pancreatic inflammation; they had a synergistic effect. CONCLUSIONS Pancreatic inflammation significantly increased the expression and functional properties of TRPV1 and TRPA1, as well as the excitability of pancreatic sensory neurons in vagal and spinal pathways. TRP channel antagonists acted synergistically to reverse pancreatic inflammation and associated pain behaviors; reagents that target interactions between these channels might be developed to reduce pain in patients with acute pancreatitis.
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Affiliation(s)
- Erica S. Schwartz
- Center for Pain Research, University of Pittsburgh School of Medicine, Pittsburgh, PA, 200 Lothrop St, Pittsburgh, PA 15213, Department of Medicine, Division of Gastroenterology, Hepatology and Nutrition, University of Pittsburgh School of Medicine, Pittsburgh, PA, 200 Lothrop St, Pittsburgh, PA 15213, Department of Anesthesiology, University of Pittsburgh School of Medicine, Pittsburgh, PA, 200 Lothrop St, Pittsburgh, PA 15213
| | - Julie A. Christianson
- Center for Pain Research, University of Pittsburgh School of Medicine, Pittsburgh, PA, 200 Lothrop St, Pittsburgh, PA 15213, Department of Medicine, Division of Gastroenterology, Hepatology and Nutrition, University of Pittsburgh School of Medicine, Pittsburgh, PA, 200 Lothrop St, Pittsburgh, PA 15213
| | - Xiaowei Chen
- Center for Pain Research, University of Pittsburgh School of Medicine, Pittsburgh, PA, 200 Lothrop St, Pittsburgh, PA 15213, Department of Anesthesiology, University of Pittsburgh School of Medicine, Pittsburgh, PA, 200 Lothrop St, Pittsburgh, PA 15213
| | - Jun-Ho La
- Center for Pain Research, University of Pittsburgh School of Medicine, Pittsburgh, PA, 200 Lothrop St, Pittsburgh, PA 15213, Department of Anesthesiology, University of Pittsburgh School of Medicine, Pittsburgh, PA, 200 Lothrop St, Pittsburgh, PA 15213
| | - Brian M. Davis
- Center for Pain Research, University of Pittsburgh School of Medicine, Pittsburgh, PA, 200 Lothrop St, Pittsburgh, PA 15213, Department of Medicine, Division of Gastroenterology, Hepatology and Nutrition, University of Pittsburgh School of Medicine, Pittsburgh, PA, 200 Lothrop St, Pittsburgh, PA 15213
| | - Kathryn M. Albers
- Center for Pain Research, University of Pittsburgh School of Medicine, Pittsburgh, PA, 200 Lothrop St, Pittsburgh, PA 15213, Department of Medicine, Division of Gastroenterology, Hepatology and Nutrition, University of Pittsburgh School of Medicine, Pittsburgh, PA, 200 Lothrop St, Pittsburgh, PA 15213
| | - G.F. Gebhart
- Center for Pain Research, University of Pittsburgh School of Medicine, Pittsburgh, PA, 200 Lothrop St, Pittsburgh, PA 15213, Department of Medicine, Division of Gastroenterology, Hepatology and Nutrition, University of Pittsburgh School of Medicine, Pittsburgh, PA, 200 Lothrop St, Pittsburgh, PA 15213, Department of Anesthesiology, University of Pittsburgh School of Medicine, Pittsburgh, PA, 200 Lothrop St, Pittsburgh, PA 15213
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Holzer P. Transient receptor potential (TRP) channels as drug targets for diseases of the digestive system. Pharmacol Ther 2011; 131:142-70. [PMID: 21420431 PMCID: PMC3107431 DOI: 10.1016/j.pharmthera.2011.03.006] [Citation(s) in RCA: 172] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2011] [Accepted: 03/01/2011] [Indexed: 12/12/2022]
Abstract
Approximately 20 of the 30 mammalian transient receptor potential (TRP) channel subunits are expressed by specific neurons and cells within the alimentary canal. They subserve important roles in taste, chemesthesis, mechanosensation, pain and hyperalgesia and contribute to the regulation of gastrointestinal motility, absorptive and secretory processes, blood flow, and mucosal homeostasis. In a cellular perspective, TRP channels operate either as primary detectors of chemical and physical stimuli, as secondary transducers of ionotropic or metabotropic receptors, or as ion transport channels. The polymodal sensory function of TRPA1, TRPM5, TRPM8, TRPP2, TRPV1, TRPV3 and TRPV4 enables the digestive system to survey its physical and chemical environment, which is relevant to all processes of digestion. TRPV5 and TRPV6 as well as TRPM6 and TRPM7 contribute to the absorption of Ca²⁺ and Mg²⁺, respectively. TRPM7 participates in intestinal pacemaker activity, and TRPC4 transduces muscarinic acetylcholine receptor activation to smooth muscle contraction. Changes in TRP channel expression or function are associated with a variety of diseases/disorders of the digestive system, notably gastro-esophageal reflux disease, inflammatory bowel disease, pain and hyperalgesia in heartburn, functional dyspepsia and irritable bowel syndrome, cholera, hypomagnesemia with secondary hypocalcemia, infantile hypertrophic pyloric stenosis, esophageal, gastrointestinal and pancreatic cancer, and polycystic liver disease. These implications identify TRP channels as promising drug targets for the management of a number of gastrointestinal pathologies. As a result, major efforts are put into the development of selective TRP channel agonists and antagonists and the assessment of their therapeutic potential.
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Affiliation(s)
- Peter Holzer
- Research Unit of Translational Neurogastroenterology, Institute of Experimental and Clinical Pharmacology, Medical University of Graz, Universitätsplatz 4, A-8010 Graz, Austria.
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Yamamoto K, Noguchi J, Yamada C, Watabe AM, Kato F. Distinct target cell-dependent forms of short-term plasticity of the central visceral afferent synapses of the rat. BMC Neurosci 2010; 11:134. [PMID: 20961403 PMCID: PMC2978217 DOI: 10.1186/1471-2202-11-134] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2010] [Accepted: 10/20/2010] [Indexed: 11/25/2022] Open
Abstract
Background The visceral afferents from various cervico-abdominal sensory receptors project to the dorsal vagal complex (DVC), which is composed of the nucleus of the solitary tract (NTS), the area postrema and the dorsal motor nucleus of the vagus nerve (DMX), via the vagus and glossopharyngeal nerves and then the solitary tract (TS) in the brainstem. While the excitatory transmission at the TS-NTS synapses shows strong frequency-dependent suppression in response to repeated stimulation of the afferents, the frequency dependence and short-term plasticity at the TS-DMX synapses, which also transmit monosynaptic information from the visceral afferents to the DVC neurons, remain largely unknown. Results Recording of the EPSCs activated by paired or repeated TS stimulation in the brainstem slices of rats revealed that, unlike NTS neurons whose paired-pulse ratio (PPR) is consistently below 0.6, the distribution of the PPR of DMX neurons shows bimodal peaks that are composed of type I (PPR, 0.6-1.5; 53% of 120 neurons recorded) and type II (PPR, < 0.6; 47%) neurons. Some of the type I DMX neurons showed paired-pulse potentiation. The distinction of these two types depended on the presynaptic release probability and the projection target of the postsynaptic cells; the distinction was not dependent on the location or soma size of the cell, intensity or site of the stimulation, the latency, standard deviation of latency or the quantal size. Repeated stimulation at 20 Hz resulted in gradual and potent decreases in EPSC amplitude in the NTS and type II DMX neurons, whereas type I DMX neurons displayed only slight decreases, which indicates that the DMX neurons of this type could be continuously activated by repeated firing of primary afferent fibers at a high (~10 Hz) frequency. Conclusions These two general types of short-term plasticity might contribute to the differential activation of distinct vago-vagal reflex circuits, depending on the firing frequency and type of visceral afferents.
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Affiliation(s)
- Kiyofumi Yamamoto
- Laboratory of Neurophysiology, Department of Neuroscience, Jikei University School of Medicine, Minato-ku, Tokyo 105-8461, Japan
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Identifying the Ion Channels Responsible for Signaling Gastro-Intestinal Based Pain. Pharmaceuticals (Basel) 2010; 3:2768-2798. [PMID: 27713376 PMCID: PMC4034097 DOI: 10.3390/ph3092768] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2010] [Revised: 08/05/2010] [Accepted: 08/20/2010] [Indexed: 12/20/2022] Open
Abstract
We are normally unaware of the complex signalling events which continuously occur within our internal organs. Most of us only become cognisant when sensations of hunger, fullness, urgency or gas arise. However, for patients with organic and functional bowel disorders pain is an unpleasant and often debilitating reminder. Furthermore, chronic pain still represents a large unmet need for clinical treatment. Consequently, chronic pain has a considerable economic impact on health care systems and the afflicted individuals. In order to address this need we must understand how symptoms are generated within the gut, the molecular pathways responsible for generating these signals and how this process changes in disease states.
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van Boxel OS, ter Linde JJM, Siersema PD, Smout AJPM. Role of chemical stimulation of the duodenum in dyspeptic symptom generation. Am J Gastroenterol 2010; 105:803-11; quiz 802, 812. [PMID: 20234343 DOI: 10.1038/ajg.2010.100] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The response to chemical stimuli such as acid, nutrients, and capsaicin at the level of the duodenum is increasingly recognized as important in the etiology of dyspeptic symptoms. Increased duodenal acid exposure has been reported for patients with dyspeptic symptoms. Duodenal hypersensitivity to acid and the enhancing effect of duodenal acid on gastroduodenal mechanosensitivity may also contribute to dyspeptic symptom generation. Serotonergic signaling pathways may be involved in acid-induced dyspeptic symptoms. As for nutrients, lipid has been unequivocally shown to have a function in the pathogenesis of dyspeptic symptoms. Cholecystokinin (CCK) is an important mediator of the effects of duodenal lipid on gastroduodenal sensorimotor activities. It is unclear whether CCK hypersecretion or hypersensitivity to CCK is responsible for symptoms in dyspeptic patients. The presence of capsaicin in the duodenum evokes symptoms and affects gastric sensorimotor function. In patients with dyspepsia, capsaicin-induced symptoms appeared to occur earlier and to be more severe, however the effects of duodenal infusion and putative consequent gastric sensorimotor abnormalities have not been examined. Capsaicin activates transient receptor potential ion channel of the vanilloid type I, which can also be activated and sensitized by acid. The interaction between the different chemical stimuli is complex and has not yet been studied in patients with dyspeptic symptoms. In conclusion, the mechanisms underlying an enhanced response to duodenal chemical stimulation in patients with dyspeptic symptoms are partially understood. At the level of the duodenum, abnormalities may exist in stimulus intensity, mucosal mRNA expression, biosynthesis, release, or inactivation of mucosal mediators, or receptor expression on afferent nerve endings. Elucidation of the abnormalities involved will provide a basis for rational treatment of dyspeptic symptoms.
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Affiliation(s)
- O S van Boxel
- Department of Gastroenterology and Hepatology, University Medical Center Utrecht, Utrecht, The Netherlands.
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Abstract
OBJECTIVES Capsaicin/vanilloid (transient receptor potential vanilloid 1, (TRPV1) receptor has been shown to be expressed in gastrointestinal tract and play a role as a member of sensory ion channel superfamily. The G315C polymorphism affects the TRPV1 gene and alters its protein level. We aimed to investigate the effect of TRPV1 G315C polymorphism on functional dyspepsia (FD) in a Japanese population. METHODS TRPV1 G315C polymorphism was genotyped in 98 subjects with no upper abdominal symptoms and 109 patients with FD. Severity of 7 upper gastrointestinal symptoms was assessed during cold water, and cold carbonated water drinking for randomly selected 20 healthy subjects. RESULTS We found a significant inverse association between TRPV1 315CC genotype and FD [CC vs. others; odds ratio (OR)=0.40, 95% confidence interval (CI)=0.38-0.82]. We also found that the same genotype held a lower risk of both epigastric pain syndrome (OR=0.25, 95% CI=0.09-0.73), postprandial syndrome (OR=0.27, 95% CI=0.07-0.96) according to Rome III, and Helicobacter pylori positive FD (OR=0.28, 95% CI=0.10-0.79). The evolution of symptom severity scale of 7 total symptoms (P=0.004), and heavy feeling in stomach (P=0.02) during cold carbonated water drinking were significantly lower among 315CC genotypes compared with others. CONCLUSIONS Homozygous TRPV1 315C influences the susceptibility to FD through altering the upper gastrointestinal sensation.
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Roles of gastro-oesophageal afferents in the mechanisms and symptoms of reflux disease. Handb Exp Pharmacol 2009:227-57. [PMID: 19655109 DOI: 10.1007/978-3-540-79090-7_7] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Oesophageal pain is one of the most common reasons for physician consultation and/or seeking medication. It is most often caused by acid reflux from the stomach, but can also result from contractions of the oesophageal muscle. Different forms of pain are evoked by oesophageal acid, including heartburn and non-cardiac chest pain, but the basic mechanisms and pathways by which these are generated remain to be elucidated. Both vagal and spinal afferent pathways are implicated by basic research. The sensitivity of afferent fibres within these pathways may become altered after acid-induced inflammation and damage, but the severity of symptoms in humans does not necessarily correlate with the degree of inflammation. Gastro-oesophageal reflux disease (GORD) is caused by transient relaxations of the lower oesophageal sphincter, which are triggered by activation of gastric vagal mechanoreceptors. Vagal afferents are therefore an emerging therapeutic target for GORD. Pain in the absence of excess acid reflux remains a major challenge for treatment.
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Tan LL, Bornstein JC, Anderson CR. Neurochemical and morphological phenotypes of vagal afferent neurons innervating the adult mouse jejunum. Neurogastroenterol Motil 2009; 21:994-1001. [PMID: 19413682 DOI: 10.1111/j.1365-2982.2009.01322.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Whilst much is known about the function and influence of vagal afferents on the mammalian upper gastrointestinal tract, the phenotypes of the different types of vagal afferent neurons innervating the jejunum is unknown. We have previously shown that spinal afferents supplying the jejunum are predominantly medium-sized sensory neurons that express specific combinations of transient receptor potential vanilloid type 1 (TRPV1), neuronal nitric oxide synthase (NOS) and calcitonin-gene related peptide (CGRP) and that they lack binding for isolectin B4 (IB4). This study aimed to identify the chemical phenotypes and somal sizes of jejunal afferent neurons in the mouse vagal ganglion. Jejunal vagal afferents were identified by retrograde labelling with sub-serosal injections of cholera toxin B (CTB) into the jejunal wall and assessed for IB4-binding, TRPV1-, NOS- and CGRP-immunoreactivities using fluorescent microscopy. Almost all (99%) of CTB-labelled vagal afferent neurons were small- and medium-sized sensory cells. Most (81%) jejunal vagal afferents bound IB4 but fewer (32%) expressed TRPV1. A quarter (25%) of those that bound IB4 co-expressed TRPV1-immunoreactivity whilst 77% of TRPV1-expressing jejunal vagal afferent neurons bound IB4. NOS (0%) and CGRP (0%) expression was absent from all CTB-labelled cells examined. In conclusion, vagal afferents innervating the jejunum differ in their expression of IB4, TRPV1, CGRP and NOS from their spinal counterparts, suggesting that the peripheral endings for extrinsic sensory neurons terminating within the enteric nervous system can be identified selectively.
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Affiliation(s)
- L L Tan
- Department of Physiology, University of Melbourne, Parkville, VIC, Australia.
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Peles S, Medda BK, Zhang Z, Banerjee B, Lehmann A, Shaker R, Sengupta JN. Differential effects of transient receptor vanilloid one (TRPV1) antagonists in acid-induced excitation of esophageal vagal afferent fibers of rats. Neuroscience 2009; 161:515-25. [PMID: 19324074 DOI: 10.1016/j.neuroscience.2009.03.040] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2009] [Revised: 02/17/2009] [Accepted: 03/17/2009] [Indexed: 12/17/2022]
Abstract
Gastro-esophageal acid reflux can stimulate esophageal vagal sensory afferents by activating proton-sensitive ion channel transient receptor vanilloid one (TRPV1). The objective of this study was to investigate the response characteristics of vagal afferent fibers of rats to acid (0.1 N HCl) and capsaicin (CAP) following esophagitis and differential effects of two classes of TRPV1 antagonists on responses of vagal afferent fibers. The chronic reflux was induced by ligating the fundus of the stomach and partial constriction of pylorus. Extracellular single fiber recordings were made from the cervical vagal afferent fibers from naive control and fundus-ligated (FL) esophagitis rats. Innervations of fibers were identified to esophageal distension (ED) and subsequently tested to CAP and acid before and after injection of TRPV1 antagonist JYL1421 or AMG9810 (10 micromol/kg i.v.). Seventy-five vagal afferent fibers from 70 rats were identified to ED. Intra-esophageal CAP (0.1 ml of 1 mg/ml) excited 39.5% (17/43, 5/22 from naive and 12/21 from FL rats) fibers. In contrast, i.v. injection of CAP (0.03-0.3 micromol/kg) dose-dependently excited 72% (42/58) fibers. Responses to CAP were significantly greater for fibers from FL rats (n=32) than naive rats (n=25). TRPV1 antagonists JYL1421 and AMG9810 (10 micromol/kg) significantly blocked response to CAP. Intra-esophageal acid infusion stimulated 5/17 (29.4%) fibers from naive rats and 12/28 (42%) from FL rats. Effect of acid was significantly blocked by AMG9810, but not by JYL1421. Results indicate that following esophagitis the number of fibers responsive to CAP and acid is greater than noninflamed esophagus, which may contribute to esophageal hypersensitivity. Acid-induced excitation of vagal sensory afferents can be differentially attenuated by different classes of TRPV1 antagonists. Therefore, TRPV1 antagonists play a key role in attenuation of hypersensitivity following reflux-induced esophagitis. The use of TRPV1 antagonists could be an alternative to the traditional symptoms-based treatment of chronic acid reflux and esophageal hypersensitivity.
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Affiliation(s)
- S Peles
- Division of Gastroenterology and Hepatology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
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Fasanella KE, Christianson JA, Chanthaphavong RS, Davis BM. Distribution and neurochemical identification of pancreatic afferents in the mouse. J Comp Neurol 2008; 509:42-52. [PMID: 18418900 DOI: 10.1002/cne.21736] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Dysfunction of primary afferents innervating the pancreas has been shown to contribute to the development of painful symptoms during acute and chronic pancreatitis. To investigate the distribution and neurochemical phenotype of pancreatic afferents, Alexa Fluor-conjugated cholera toxin B (CTB) was injected into the pancreatic head (CTB-488) and tail (CTB-555) of adult male mice to label neurons retrogradely in both the dorsal root ganglia (DRG) and nodose ganglia (NG). The NG and DRG (T5-T13) were processed for fluorescent immunohistochemistry and visualized by using confocal microscopy. Spinal pancreatic afferents were observed from T5 to T13, with the greatest contribution coming from T9-T12. The pancreatic afferents were equally distributed between right and left spinal ganglia; however, the innervation from the left NG was significantly greater than from the right. For both spinal and vagal afferents there was significantly greater innervation of the pancreatic head relative to the tail. The total number of retrogradely labeled afferents in the nodose was very similar to the total number of DRG afferents. The neurochemical phenotype of DRG neurons was dominated by transient receptor potential vanilloid 1 (TRPV1)-positive neurons (75%), GDNF family receptor alpha-3 (GFRalpha3)-positive neurons (67%), and calcitonin gene-related peptide (CGRP)-positive neurons(65%) neurons. In the NG, TRPV1-, GFRalpha3-, and CGRP-positive neurons constituted only 35%, 1%, and 15% of labeled afferents, respectively. The disparity in peptide and receptor expression between pancreatic afferents in the NG and DRG suggests that even though they contribute a similar number of primary afferents to the pancreas, these two populations may differ in regard to their nociceptive properties and growth factor dependency.
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Affiliation(s)
- Kenneth E Fasanella
- Department of Medicine, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania 15261, USA
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Brierley SM, Page AJ, Hughes PA, Adam B, Liebregts T, Cooper NJ, Holtmann G, Liedtke W, Blackshaw LA. Selective role for TRPV4 ion channels in visceral sensory pathways. Gastroenterology 2008; 134:2059-69. [PMID: 18343379 PMCID: PMC2504007 DOI: 10.1053/j.gastro.2008.01.074] [Citation(s) in RCA: 191] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/26/2007] [Accepted: 01/18/2008] [Indexed: 12/17/2022]
Abstract
BACKGROUND & AIMS Although there are many candidates as molecular mechanotransducers, so far there has been no evidence for molecular specialization of visceral afferents. Here, we show that colonic afferents express a specific molecular transducer that underlies their specialized mechanosensory function: the transient receptor potential channel, vanilloid 4 (TRPV4). METHODS We found TRPV4 mRNA is highly enriched in colonic sensory neurons compared with other visceral and somatic sensory neurons. TRPV4 protein was found in colonic nerve fibers from patients with inflammatory bowel disease, and it colocalized in a subset of fibers with the sensory neuropeptide CGRP in mice. We characterized the responses of 8 subtypes of vagal, splanchnic, and pelvic mechanoreceptors. RESULTS Mechanosensory responses of colonic serosal and mesenteric afferents were enhanced by a TRPV4 agonist and dramatically reduced by targeted deletion of TRPV4 or by a TRP antagonist. Other subtypes of vagal and pelvic afferents, by contrast, were unaffected by these interventions. The behavioral responses to noxious colonic distention were also substantially reduced in mice lacking TRPV4. CONCLUSIONS These data indicate that TRPV4 contributes to mechanically evoked visceral pain, with relevance to human disease. In view of its distribution in favor of specific populations of visceral afferents, we propose that TRPV4 may present a selective novel target for the reduction of visceral pain, which is an important opportunity in the absence of current treatments.
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Affiliation(s)
- Stuart M Brierley
- Discipline of Physiology, School of Molecular and Biomedical Sciences, The University of Adelaide, Nerve-Gut Research Laboratory, Department of Gastroenterology & Hepatology, Hanson Institute, Royal Adelaide Hospital, Adelaide, AUSTRALIA
| | - Amanda J Page
- Discipline of Physiology, School of Molecular and Biomedical Sciences, The University of Adelaide, Discipline of Medicine, The University of Adelaide, Nerve-Gut Research Laboratory, Department of Gastroenterology & Hepatology, Hanson Institute, Royal Adelaide Hospital, Adelaide, AUSTRALIA
| | - Patrick A Hughes
- Discipline of Physiology, School of Molecular and Biomedical Sciences, The University of Adelaide, Nerve-Gut Research Laboratory, Department of Gastroenterology & Hepatology, Hanson Institute, Royal Adelaide Hospital, Adelaide, AUSTRALIA
| | - Birgit Adam
- Nerve-Gut Research Laboratory, Department of Gastroenterology & Hepatology, Hanson Institute, Royal Adelaide Hospital, Adelaide, AUSTRALIA
| | - Tobias Liebregts
- Nerve-Gut Research Laboratory, Department of Gastroenterology & Hepatology, Hanson Institute, Royal Adelaide Hospital, Adelaide, AUSTRALIA
| | - Nicole J Cooper
- Nerve-Gut Research Laboratory, Department of Gastroenterology & Hepatology, Hanson Institute, Royal Adelaide Hospital, Adelaide, AUSTRALIA
| | - Gerald Holtmann
- Discipline of Medicine, The University of Adelaide, Nerve-Gut Research Laboratory, Department of Gastroenterology & Hepatology, Hanson Institute, Royal Adelaide Hospital, Adelaide, AUSTRALIA
| | - Wolfgang Liedtke
- Center for Translational Neuroscience, Duke University, Durham, North Carolina 27710, USA
| | - L Ashley Blackshaw
- Discipline of Physiology, School of Molecular and Biomedical Sciences, The University of Adelaide, Discipline of Medicine, The University of Adelaide, Nerve-Gut Research Laboratory, Department of Gastroenterology & Hepatology, Hanson Institute, Royal Adelaide Hospital, Adelaide, AUSTRALIA
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Qin C, Farber JP, Foreman RD. Intraesophageal chemicals enhance responsiveness of upper thoracic spinal neurons to mechanical stimulation of esophagus in rats. Am J Physiol Gastrointest Liver Physiol 2008; 294:G708-16. [PMID: 18187515 DOI: 10.1152/ajpgi.00477.2007] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Esophageal hypersensitivity is one of the most common causes of noncardiac chest pain in patients. In this study, we investigated whether exposure of the esophagus to acid and other chemical irritants affected activity of thoracic spinal neurons responding to esophageal distension (ED) in rats. Extracellular potentials of single thoracic (T3) spinal neurons were recorded in pentobarbital sodium-anesthetized, -paralyzed, and -ventilated male rats. ED (0.2 or 0.4 ml, 20 s) was produced by water inflation of a latex balloon placed orally into the middle thoracic region of the esophagus. The chemicals were administered via a tube that was passed through the stomach and placed in the thoracic esophagus. To irritate the esophagus, 0.2 ml of HCl (0.01 N), bradykinin (10 microg/ml), or capsaicin (10 microg/ml) were injected for 1-2 min. Only neurons excited by ED were included in this study. Results showed that intraesophageal instillation of HCl, bradykinin, and capsaicin increased activity in 3/20 (15%), 7/25 (28%), and 9/20 (45%) neurons but enhanced excitatory responses to ED in 9/17 (53%), 8/15 (53%), and 7/11 (64%) of the remaining spinal neurons, respectively. Furthermore, intraesophageal chemicals were more likely to enhance the responsiveness of low-threshold neurons than high-threshold neurons to the esophageal mechanical stimulus. Normal saline (pH 7.4, 0.2 ml) or vehicle instilled in the esophagus did not significantly affect activity or ED responses of neurons. We conclude that enhanced responses of thoracic spinal neurons to ED by the chemically challenged esophagus may provide a possible pathophysiological basis for visceral hypersensitivity in patients with gastroesophageal reflux and/or esophagitis.
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Affiliation(s)
- Chao Qin
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73190, USA.
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Zhong F, Christianson JA, Davis BM, Bielefeldt K. Dichotomizing axons in spinal and vagal afferents of the mouse stomach. Dig Dis Sci 2008; 53:194-203. [PMID: 17510799 DOI: 10.1007/s10620-007-9843-z] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/24/2007] [Accepted: 04/05/2007] [Indexed: 12/23/2022]
Abstract
UNLABELLED Visceral sensory input is typically poorly localized. We hypothesized that gastric sensory neurons frequently dichotomize, innervating more than one anatomically distinct region and contributing to the poor spatial discrimination. METHODS The neurochemical phenotype and projections of gastro-duodenal sensory neurons were determined in adult mice. Choleratoxin B (CTB) coupled to different fluorophors was injected into fundus, corpus, antrum, and/or distal duodenum. Immunoreactivity for TRPV1, neurofilament (N52), calcitonin gene-related peptide (CGRP), presence of isolectin B4 (IB4) and labeling for retrograde labels was determined. RESULTS Depending on the distance between injection sites, staining for two retrograde tracers was seen in 6-48% of neurons. Most dorsal root ganglion (DRG) neurons showed immunoreactivity for TRPV1 and CGRP. In contrast, about half of the gastric nodose ganglion (NG) neurons had TRPV1 immunoreactivity or showed IB4 labeling with only 10% CGRP-positive neurons. N52 immunoreactivity was present in one-fourth of gastroduodenal DRG and NG neurons. CONCLUSION Visceral sensory neurons have neurochemical properties and may project to more than one anatomically distinct area. Neurons with such dichotomizing axons may contribute to the poor ability to localize or discriminate visceral stimuli.
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Affiliation(s)
- Fang Zhong
- Division of Gastroenterology, University of Pittsburgh, Pittsburgh, PA 15213, USA
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Gonlachanvit S, Fongkam P, Wittayalertpanya S, Kullavanijaya P. Red chili induces rectal hypersensitivity in healthy humans: possible role of 5HT-3 receptors on capsaicin-sensitive visceral nociceptive pathways. Aliment Pharmacol Ther 2007; 26:617-25. [PMID: 17661765 DOI: 10.1111/j.1365-2036.2007.03396.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
BACKGROUND Red chili has been reported to modulate visceral hypersensitivity, probably by the action of its active ingredient, capsaicin. The role of 5HT-3 receptors on capsaicin-sensitive visceral nociceptive pathways is unknown. AIM To test the hypothesis that capsaicin-containing red chili induces rectal hypersensitivity in healthy humans and 5HT-3 receptors participate in this effect. METHODS Eighteen healthy volunteers, each underwent three rectal barostat studies under three conditions: (i) oral placebo; (ii) oral chili (5 g daily x 3 days); and (iii) oral chili with 1-mg intravenous (i.v.) granisetron, in randomized, double-blinded, cross-over fashions. Rectal sensation was evaluated by using a 5-point Likert scale. RESULTS Chili ingestion significantly decreased rectal threshold for first, moderate and severe urgency (18 +/- 0.9, 24 +/- 1.2, and 38 +/- 1.5 mmHg, respectively) compared with placebo (22 +/- 0.9, 31 +/- 1.3, and 45 +/- 1.4 mmHg, respectively, P < 0.01). The threshold for first, moderate and severe urgency after chili with i.v. granisetron was 20 +/- 0.9, 28 +/- 1.2 and 44 +/- 1.3 mmHg, respectively. This is a significant increase compared with chili ingestion without granisetron (P < 0.05). After placebo ingestion, i.v. granisetron produced no effect on rectal sensation compared with i.v. placebo in 10 healthy volunteers (P > 0.05). CONCLUSIONS Low-dose granisetron, a 5HT-3 receptor antagonist, partially reversed chili-induced rectal hypersensitivity but had no effect on rectal perception induced only by mechanical balloon distention. This study suggests that 5HT-3 receptors may be involved in chili-induced rectal hypersensitivity and potentially participate in the capsaicin-sensitive nociceptive pathways of the human gut.
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Affiliation(s)
- S Gonlachanvit
- GI Motility Research Unit, Division of Gastroenterology, Department of Internal Medicine, Chulalongkorn University, Rama 4 Road, Bangkok 10330, Thailand.
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Viard E, Zheng Z, Wan S, Travagli RA. Vagally mediated, nonparacrine effects of cholecystokinin-8s on rat pancreatic exocrine secretion. Am J Physiol Gastrointest Liver Physiol 2007; 293:G493-500. [PMID: 17569741 DOI: 10.1152/ajpgi.00118.2007] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Cholecystokinin (CCK) has been proposed to act in a vagally dependent manner to increase pancreatic exocrine secretion via actions exclusively at peripheral vagal afferent fibers. Recent evidence, however, suggests the CCK-8s may also affect brain stem structures directly. We used an in vivo preparation with the aims of 1) investigating whether the actions of intraduodenal casein perfusion to increase pancreatic protein secretion also involved direct actions of CCK at the level of the brain stem and, if so, 2) determining whether, in the absence of vagal afferent inputs, CCK-8s applied to the dorsal vagal complex (DVC) can also modulate pancreatic exocrine secretion (PES). Sprague-Dawley rats (250-400 g) were anesthetized and the common bile-pancreatic duct was cannulated to collect PES. Both vagal deafferentation and pretreatment with the CCK-A antagonist lorglumide on the floor of the fourth ventricle decreased the casein-induced increase in PES output. CCK-8s microinjection (450 pmol) in the DVC significantly increased PES; the increase was larger when CCK-8s was injected in the left side of the DVC. Protein secretion returned to baseline levels within 30 min. Microinjection of CCK-8s increased PES (although to a lower extent) also in rats that underwent complete vagal deafferentation. These data indicate that, as well as activating peripheral vagal afferents, CCK-8s increases pancreatic exocrine secretion via an action in the DVC. Our data suggest that the CCK-8s-induced increases in PES are due mainly to a paracrine effect of CCK; however, a relevant portion of the effects of CCK is due also to an effect of the peptide on brain stem vagal circuits.
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Affiliation(s)
- Eddy Viard
- Department of Neuroscience, Pennington Biomedical Research Center-Louisiana State University System, 6400 Perkins Rd., Baton Rouge, LA 70808, USA
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Lang PM, Grafe P. Chemosensitivity of unmyelinated axons in isolated human gastric vagus nerve. Auton Neurosci 2007; 136:100-4. [PMID: 17543588 DOI: 10.1016/j.autneu.2007.05.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2007] [Revised: 04/30/2007] [Indexed: 10/23/2022]
Abstract
Vagal afferent neurons from the stomach may be activated not only by chemical stimuli in the mucosa but also by circulating factors. In the present study, we have used electrophysiological techniques to characterize functional activity of several receptors for chemical mediators on unmyelinated axons in isolated fascicles of human gastric vagus nerve. Application of agonists at the nicotinic acetylcholine receptor (nAChR), 5-HT(3) subtype of serotonin receptor, and the transient receptor potential vanilloid receptor-1 (TRPV1) resulted in a change in the height and/or threshold of the C-fiber compound action potential. These effects were blocked by specific antagonists of nAChR (mecamylamine), 5-HT(3) (Y-25130), and TRPV1 (capsazepine). We conclude that the chemosensitivity of unmyelinated vagal axons can be studied using isolated segments of human gastric vagus nerve. The presence of receptors indicates that circulating factors may modify vagal afferent neurons also by effects on the axonal membrane.
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MESH Headings
- Action Potentials/drug effects
- Action Potentials/physiology
- Aged
- Axons/drug effects
- Axons/physiology
- Capsaicin/pharmacology
- Cell Membrane/drug effects
- Cell Membrane/physiology
- Chemoreceptor Cells/drug effects
- Chemoreceptor Cells/physiology
- Female
- Gastric Mucosa/innervation
- Gastric Mucosa/physiology
- Humans
- Male
- Membrane Potentials/drug effects
- Membrane Potentials/physiology
- Middle Aged
- Nerve Fibers, Unmyelinated/drug effects
- Nerve Fibers, Unmyelinated/physiology
- Neurons, Afferent/drug effects
- Neurons, Afferent/physiology
- Nicotinic Agonists/pharmacology
- Nodose Ganglion/drug effects
- Nodose Ganglion/physiology
- Organ Culture Techniques
- Receptors, Nicotinic/drug effects
- Receptors, Nicotinic/physiology
- Receptors, Serotonin, 5-HT3/drug effects
- Receptors, Serotonin, 5-HT3/physiology
- Serotonin Receptor Agonists/pharmacology
- TRPV Cation Channels/drug effects
- TRPV Cation Channels/physiology
- Vagus Nerve/drug effects
- Vagus Nerve/physiology
- Visceral Afferents/drug effects
- Visceral Afferents/physiology
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Affiliation(s)
- Philip M Lang
- Department of Anesthesiology, University of Munich, Germany.
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41
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Lennerz JKM, Dentsch C, Bernardini N, Hummel T, Neuhuber WL, Reeh PW. Electrophysiological characterization of vagal afferents relevant to mucosal nociception in the rat upper oesophagus. J Physiol 2007; 582:229-42. [PMID: 17478536 PMCID: PMC2075303 DOI: 10.1113/jphysiol.2007.130823] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Emerging evidence indicates a nociceptive role of vagal afferents. A distinct oesophageal innervation in the rat, with muscular and mucosal afferents travelling predominantly in the recurrent (RLN) and superior laryngeal nerve (SLN), respectively, enabled characterization of mucosal afferents with nociceptive properties, using novel isolated oesophagus-nerve preparations. SLN and RLN single-fibre recordings identified 55 and 14 units, respectively, with none conducting faster than 8.7 m s(-1). Mucosal response characteristics in the SLN distinguished mechanosensors (n = 13), mechanosensors with heat sensitivity (18) from those with cold sensitivity (19) and a mechanoinsensitive group (5). The mechanosensitive fibres, all slowly adapting, showed a unimodal distribution of mechanical thresholds (1.4-128 mN, peak approximately 5.7 mN). No difference in response characteristics of C and Adelta fibres was encountered. Mucosal proton stimulation (pH 5.4 for 3 min), mimicking gastro-oesophageal reflux disease (GORD), revealed in 31% of units a desensitizing response that peaked around 20 s and faded within 60 s. Cold stimulation (15 degrees C) was proportionally encoded but the response showed slow adaptation. In contrast, the noxious heat (48 degrees C) response showed no obvious adaptation with discharge rates reflecting the temperature's time course. Polymodal (69%) mucosal units, > 30% proton sensitive, were found in each fibre category and were considered nociceptors; they are tentatively attributed to vagal nerve endings type I, IV and V, previously morphologically described. All receptive fields were mapped and the distribution indicates that the posterior upper oesophagus may serve as a 'cutbank', detecting noxious matters, ingested or regurgitated, and triggering nocifensive reflexes such as bronchoconstriction in GORD.
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Affiliation(s)
- J K M Lennerz
- Department of Physiology and Pathophysiology, Friedrich-Alexander-University Erlangen-Nürnberg, Universitätsstrasse 17, 91054 Erlangen, Germany
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42
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Kollarik M, Ru F, Undem BJ. Acid-sensitive vagal sensory pathways and cough. Pulm Pharmacol Ther 2006; 20:402-11. [PMID: 17289409 PMCID: PMC2577168 DOI: 10.1016/j.pupt.2006.11.010] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/02/2006] [Accepted: 11/28/2006] [Indexed: 02/03/2023]
Abstract
Acid is an important mediator in the pathogenesis of cough. Inhalation of exogenous acid triggers cough and endogenous acid may contribute to cough in respiratory diseases. Acid directly stimulates vagal bronchopulmonary sensory nerves that regulate the cough reflex. Consistent with their putative role in defence against aspiration and inhaled irritants, Adelta-fibre nociceptors in the large airways are most efficiently stimulated by rapid acidification. In contrast, acid-sensitive properties of the C-fibre nociceptors allow for continuous monitoring of pH which is likely important in inflammation. Acid is also the single most important mediator in the pathogenesis of cough due to gastro-oesophageal reflux (GOR). The cough pathways can be sensitized by the sensory inputs from the oesophagus. This sensitization is likely mediated by a subset of the vagal oesophageal sensory nerves distinguished by discriminative responsiveness to noxious stimuli (nociceptors). The receptors underlying acid sensitivity of vagal sensory nerves are incompletely understood. The role of TRPV1 has been established but the roles of acid-sensing ion channels (ASIC) and other receptors await more definitive investigation. Here, we provide a brief overview of the cough-related acid-sensitive sensory pathways and discuss the mechanisms of acid sensitivity.
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Affiliation(s)
- Marian Kollarik
- The Johns Hopkins School of Medicine, Johns Hopkins Asthma and Allergy Center, Baltimore, MD 21224, USA.
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43
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Baptista V, Browning KN, Travagli RA. Effects of cholecystokinin-8s in the nucleus tractus solitarius of vagally deafferented rats. Am J Physiol Regul Integr Comp Physiol 2006; 292:R1092-100. [PMID: 17122331 PMCID: PMC3062489 DOI: 10.1152/ajpregu.00517.2006] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have shown recently that cholecystokinin octapeptide (CCK-8s) increases glutamate release from nerve terminals onto neurons of the nucleus tractus solitarius pars centralis (cNTS). The effects of CCK on gastrointestinal-related functions have, however, been attributed almost exclusively to its paracrine action on vagal afferent fibers. Because it has been reported that systemic or perivagal capsaicin pretreatment abolishes the effects of CCK, the aim of the present work was to investigate the response of cNTS neurons to CCK-8s in vagally deafferented rats. In surgically deafferented rats, intraperitoneal administration of 1 or 3 mug/kg CCK-8s increased c-Fos expression in cNTS neurons (139 and 251% of control, respectively), suggesting that CCK-8s' effects are partially independent of vagal afferent fibers. Using whole cell patch-clamp techniques in thin brain stem slices, we observed that CCK-8s increased the frequency of spontaneous and miniature excitatory postsynaptic currents in 43% of the cNTS neurons via a presynaptic mechanism. In slices from deafferented rats, the percentage of cNTS neurons receiving glutamatergic inputs responding to CCK-8s decreased by approximately 50%, further suggesting that central terminals of vagal afferent fibers are not the sole site for the action of CCK-8s in the brain stem. Taken together, our data suggest that the sites of action of CCK-8s include the brain stem, and in cNTS, the actions of CCK-8s are not restricted to vagal central terminals but that nonvagal synapses are also involved.
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Affiliation(s)
- V Baptista
- Department of Neuroscience, Pennington Biomedical Research Center, Louisiana State University System, 6400 Perkins Road, Baton Rouge, LA 70808, USA
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44
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Bielefeldt K, Zhong F, Koerber HR, Davis BM. Phenotypic characterization of gastric sensory neurons in mice. Am J Physiol Gastrointest Liver Physiol 2006; 291:G987-97. [PMID: 16728726 DOI: 10.1152/ajpgi.00080.2006] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Recent studies suggest that the capsaicin receptor [transient receptor potential vanilloid (TRPV)1] may play a role in visceral mechanosensation. To address the potential role of TRPV1 in vagal sensory neurons, we developed a new in vitro technique allowing us to determine TRPV1 expression directly in physiologically characterized gastric sensory neurons. Stomach, esophagus, and intact vagus nerve up to the central terminations were carefully dissected and placed in a perfusion chamber. Intracellular recordings were made from the soma of nodose neurons during mechanical stimulation of the stomach. Physiologically characterized neurons were labeled iontophoretically with neurobiotin and processed for immunohistochemical experiments. As shown by action potential responses triggered by stimulation of the upper thoracic vagus with a suction electrode, essentially all abdominal vagal afferents in mice conduct in the C-fiber range. Mechanosensitive gastric afferents encode stimulus intensities over a wide range without apparent saturation when punctate stimuli are used. Nine of 37 mechanosensitive vagal afferents expressed TRPV1 immunoreactivity, with 8 of the TRPV1-positive cells responding to stretch. A small number of mechanosensitive gastric vagal afferents express neurofilament heavy chains and did not respond to stretch. By maintaining the structural and functional integrity of vagal afferents up to the nodose ganglion, physiological and immunohistochemical properties of mechanosensory gastric sensory neurons can be studied in vitro. Using this novel technique, we identified TRPV1 immunoreactivity in only one-fourth of gastric mechanosensitive neurons, arguing against a major role of this ion channel in sensation of mechanical stimuli under physiological conditions.
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Affiliation(s)
- Klaus Bielefeldt
- Department of Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA.
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45
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Wynn G, Burnstock G. Adenosine 5'-triphosphate and its relationship with other mediators that activate pelvic nerve afferent neurons in the rat colorectum. Purinergic Signal 2006; 2:517-26. [PMID: 18404489 PMCID: PMC2104004 DOI: 10.1007/s11302-005-5305-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2005] [Revised: 11/17/2005] [Accepted: 11/18/2005] [Indexed: 11/26/2022] Open
Abstract
Evidence of a role for purinergic signalling in visceral afferents involving P2X2, P2X3 and P2Y1 receptors exists, which appears to be important during inflammation. This study aimed to evaluate the degree of interaction between adenosine 5′-triphosphate (ATP) and other mediators that activate sensory nerves in the colorectum. Recordings from pelvic nerve afferents were made during application of agents to the in-vitro colorectal preparation. Analysis allowed calculation of single unit activity. When applied individually, bradykinin (78%) and 5-hydoxytryptamine (77%) activated the greatest number of neurons, followed by substance P, protons, ATP and capsaicin. Prostaglandin E2 stimulated the least number (54%) and had a longer latency. Seventy-seven percent of all units studied either responded to both ATP and capsaicin or to neither, giving the greatest degree of activity correlation. Five percent of units were activated by all seven agents and no units were activated by a single agent alone. 5-hydroxytryptamine, capsaicin and protons, when co-applied with ATP, increased pelvic nerve activity to a greater degree than the sum of the individual responses. It is concluded that ATP activates pelvic nerve afferents and acts synergistically with protons, capsaicin and 5-hydroxytryptamine. The pattern of neuronal activation suggests that visceral afferents are polymodal but the receptor expression on their terminals is variable.
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Affiliation(s)
- Gregory Wynn
- Autonomic Neuroscience Centre, Royal Free and University College School of Medicine, Rowland Hill Street, London, NW3 2PF UK
| | - Geoffrey Burnstock
- Autonomic Neuroscience Centre, Royal Free and University College School of Medicine, Rowland Hill Street, London, NW3 2PF UK
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46
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Hanacek J, Tatar M, Widdicombe J. Regulation of cough by secondary sensory inputs. Respir Physiol Neurobiol 2006; 152:282-97. [PMID: 16584927 DOI: 10.1016/j.resp.2006.02.014] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2005] [Revised: 02/13/2006] [Accepted: 02/16/2006] [Indexed: 11/24/2022]
Abstract
We have reviewed the role of afferent inputs and blood chemical changes to the central nervous system, and the way in which they modify the cough and expiration reflexes (CR and ER). Slowly adapting pulmonary stretch receptors (SARs) augment the CR, insofar as when their activity is abolished the CRs from the tracheobronchial (TB) tree and larynx are abolished or weakened. However, stimulation of SARs by lung inflation has an inconsistent effect on the CR. Activation of SARs strongly potentiates the ER from the vocal folds, by a reflex mechanism, and inhibition of SARs weakens the ER. Bronchopulmonary C-fibre receptors inhibit the CR, as do capsaicin-sensitive afferents from the heart and splanchnic bed, cutaneous cold receptors and those that respond to chest wall vibration. Nasal receptors responsive to the irritant agent capsaicin potentiate the reflex. Acute hypoxia also augments the CR, and the reflex is down-regulated by carotid body resection. On the other hand, the CR is inhibited by prolonged hypoxia and hyperoxia, and by hypercapnia. Thus different inputs to the cough-controlling mechanism in the brainstem have very varied effects on the CR. We conclude that the sensitivities of the CR and ER can be modified in a large variety of physiological and clinical conditions, and that there is no clear relationship between the reflexes and changes in breathing caused by the interventions.
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Affiliation(s)
- Jan Hanacek
- Comenius University, Department of Pathophysiology, School of Medicine, 037 53 Martin, Slovakia
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47
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Holzer P. Gastrointestinal pain in functional bowel disorders: sensory neurons as novel drug targets. Expert Opin Ther Targets 2006; 8:107-23. [PMID: 15102553 DOI: 10.1517/14728222.8.2.107] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Functional bowel disorders (FBDs) are defined by symptoms of gastrointestinal (GI) dysfunction, discomfort and pain in the absence of a demonstrable organic cause. Since the prevalence of FBDs, particularly functional dyspepsia and irritable bowel syndrome, can be as high as 20%, FBDs represent a significant burden in terms of direct healthcare and productivity costs. There is emerging evidence that the discomfort and pain experienced by many FBD patients is due to persistent hypersensitivity of primary afferent neurons, which may develop in response to infection, inflammation or other insults. This concept identifies vagal and spinal sensory neurons as important targets for novel therapies of GI hyperalgesia. Sensory neuron-specific targets can be grouped into three categories: receptors and sensors at the peripheral nerve terminals, ion channels relevant to nerve excitability and conduction and transmitter receptors. Particular therapeutic potential is attributed to targets that are selectively expressed by afferent neurons, such as the transient receptor potential channel TRPV1, acid-sensing ion channels and tetrodotoxin-resistant Na + channels.
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Affiliation(s)
- Peter Holzer
- Medical University of Graz, Department of Experimental and Clinical Pharmacology, Austria.
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48
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Mithieux G, Misery P, Magnan C, Pillot B, Gautier-Stein A, Bernard C, Rajas F, Zitoun C. Portal sensing of intestinal gluconeogenesis is a mechanistic link in the diminution of food intake induced by diet protein. Cell Metab 2005; 2:321-9. [PMID: 16271532 DOI: 10.1016/j.cmet.2005.09.010] [Citation(s) in RCA: 139] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2005] [Revised: 08/01/2005] [Accepted: 09/30/2005] [Indexed: 12/24/2022]
Abstract
Protein feeding is known to decrease hunger and subsequent food intake in animals and humans. It has also been suggested that glucose appearance into portal vein, as occurring during meal assimilation, may induce comparable effects. Here, we connect these previous observations by reporting that intestinal gluconeogenesis (i.e., de novo synthesis of glucose) is induced during the postabsorptive time (following food digestion) in rats specifically fed on protein-enriched diet. This results in glucose release into portal blood, counterbalancing the lowering of glycemia resulting from intestinal glucose utilization. Comparable infusions into the portal vein of control postabsorptive rats (fed on starch-enriched diet) decrease food consumption and activate the hypothalamic nuclei regulating food intake. Similar hypothalamic activation occurs on protein feeding. All these effects are absent after denervation of the portal vein. Thus, portal sensing of intestinal gluconeogenesis may be a novel mechanism connecting the macronutrient composition of diet to food intake.
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Affiliation(s)
- Gilles Mithieux
- Institut National de la Sante et de la Recherche Medicale, U449, Lyon, F-69372, France.
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Holzer P, Painsipp E, Schuligoi R. Differential effects of intragastric acid and capsaicin on gastric emptying and afferent input to the rat spinal cord and brainstem. BMC Neurosci 2005; 6:60. [PMID: 16162281 PMCID: PMC1239919 DOI: 10.1186/1471-2202-6-60] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2005] [Accepted: 09/14/2005] [Indexed: 11/25/2022] Open
Abstract
Background Hydrochloric acid (HCl) is a potential threat to the integrity of the gastric mucosa and is known to contribute to upper abdominal pain. We have previously found that gastric mucosal challenge with excess HCl is signalled to the rat brainstem, but not spinal cord, as visualized by expression of c-fos messenger ribonucleic acid (mRNA), a surrogate marker of neuronal excitation. This study examined whether gastric mucosal exposure to capsaicin, a stimulant of nociceptive afferents that does not damage the gastric mucosa, is signalled to both brainstem and spinal cord and whether differences in the afferent signalling of gastric HCl and capsaicin challenge are related to different effects on gastric emptying. Results Rats were treated intragastrically with vehicle, HCl or capsaicin, activation of neurons in the brainstem and spinal cord was visualized by in situ hybridization autoradiography for c-fos mRNA, and gastric emptying deduced from the retention of intragastrically administered fluid. Relative to vehicle, HCl (0.5 M) and capsaicin (3.2 mM) increased c-fos transcription in the nucleus tractus solitarii by factors of 7.0 and 2.1, respectively. Capsaicin also caused a 5.2-fold rise of c-fos mRNA expression in lamina I of the caudal thoracic spinal cord, although the number of c-fos mRNA-positive cells in this lamina was very small. Thus, on average only 0.13 and 0.68 c-fos mRNA-positive cells were counted in 0.01 mm sections of the unilateral lamina I following intragastric administration of vehicle and capsaicin, respectively. In contrast, intragastric HCl failed to induce c-fos mRNA in the spinal cord. Measurement of gastric fluid retention revealed that HCl suppressed gastric emptying while capsaicin did not. Conclusion The findings of this study show that gastric mucosal exposure to HCl and capsaicin is differentially transmitted to the brainstem and spinal cord. Since only HCl blocks gastric emptying, it is hypothesized that the two stimuli are transduced by different afferent pathways. We infer that HCl is exclusively signalled by gastric vagal afferents whereas capsaicin is processed both by gastric vagal and intestinal spinal afferents.
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Affiliation(s)
- Peter Holzer
- Department of Experimental and Clinical Pharmacology, Medical University of Graz, Universitätsplatz 4, A-8010 Graz, Austria
| | - Evelin Painsipp
- Department of Experimental and Clinical Pharmacology, Medical University of Graz, Universitätsplatz 4, A-8010 Graz, Austria
| | - Rufina Schuligoi
- Department of Experimental and Clinical Pharmacology, Medical University of Graz, Universitätsplatz 4, A-8010 Graz, Austria
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Jammes Y, Trousse D, Delpierre S. Identification and properties of parietal pleural afferents in rabbits. J Physiol 2005; 567:641-50. [PMID: 15975985 PMCID: PMC1474184 DOI: 10.1113/jphysiol.2005.089029] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Although pain and dyspnoea are common symptoms in pleural diseases, there are few studies on the sensory innervation of the pleura. Using rabbits, after removal of all muscles in the intercostal space to be studied, we investigated the afferents of the internal intercostal nerve by applying to the internal thoracic wall pieces of gauze soaked in warmed (37 degrees C), buffered saline (mechanical stimulation) or solutions containing lactic acid, inflammatory mediators or capsaicin (chemical stimulation). The afferent conduction velocity ranged from 0.5 to 14 m s(-1). Most units (97%) were activated by mechanical stimulation of the pleura (local positive pressure range = 4.5-8.5 cmH2O) and we found a linear relationship between the discharge rate of afferents and the force applied to the thoracic wall. The majority of mechanosensitive units (70%) also responded to one or several chemical agents. Thus, the afferents were activated by lactic acid (49%) and/or a mixture of inflammatory mediators (50%). Local application of capsaicin elicited an initial increased or decreased background afferent activity in 57% of the afferents, a delayed decrease in firing rate being noted in some units initially activated by capsaicin. Capsaicin blocked the afferent response to a further application of inflammatory mediators but did not affect the mechanosensitive units. Thus, sensory endings connected with thin myelinated and unmyelinated fibres in the internal intercostal nerve detect the mechanical and chemical events of pleural diseases.
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Affiliation(s)
- Yves Jammes
- Laboratoire de Physiopathologie Respiratoire (UPRES EA 2201), Faculté de Médecine, Boulevard Pierre Dramard, 13916 cedex 20, Marseille, France.
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