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Wu Y, Han C, Luo R, Cai W, Xia Q, Jiang R, Ferdek PE, Liu T, Huang W. Molecular mechanisms of pain in acute pancreatitis: recent basic research advances and therapeutic implications. Front Mol Neurosci 2023; 16:1331438. [PMID: 38188196 PMCID: PMC10771850 DOI: 10.3389/fnmol.2023.1331438] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2023] [Accepted: 12/14/2023] [Indexed: 01/09/2024] Open
Abstract
Although severe abdominal pain is the main symptom of acute pancreatitis, its mechanisms are poorly understood. An emerging body of literature evidence indicates that neurogenic inflammation might play a major role in modulating the perception of pain from the pancreas. Neurogenic inflammation is the result of a crosstalk between injured pancreatic tissue and activated neurons, which leads to an auto-amplification loop between inflammation and pain during the progression of acute pancreatitis. In this review, we summarize recent findings on the role of neuropeptides, ion channels, and the endocannabinoid system in acute pancreatitis-related pain. We also highlight potential therapeutic strategies that could be applied for managing severe pain in this disease.
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Affiliation(s)
- Yongzi Wu
- West China Centre of Excellence for Pancreatitis, Institute of Integrated Traditional Chinese and Western Medicine, West China-Liverpool Biomedical Research Centre, West China Hospital, Sichuan University, Chengdu, China
| | - Chenxia Han
- West China Centre of Excellence for Pancreatitis, Institute of Integrated Traditional Chinese and Western Medicine, West China-Liverpool Biomedical Research Centre, West China Hospital, Sichuan University, Chengdu, China
| | - Rong Luo
- Laboratory of Anesthesia and Critical Care Medicine, National-Local Joint Engineering Research Center of Translational Medicine of Anesthesiology, West China Hospital, Sichuan University, Chengdu, China
| | - Wenhao Cai
- West China Centre of Excellence for Pancreatitis, Institute of Integrated Traditional Chinese and Western Medicine, West China-Liverpool Biomedical Research Centre, West China Hospital, Sichuan University, Chengdu, China
| | - Qing Xia
- West China Centre of Excellence for Pancreatitis, Institute of Integrated Traditional Chinese and Western Medicine, West China-Liverpool Biomedical Research Centre, West China Hospital, Sichuan University, Chengdu, China
| | - Ruotian Jiang
- Laboratory of Anesthesia and Critical Care Medicine, National-Local Joint Engineering Research Center of Translational Medicine of Anesthesiology, West China Hospital, Sichuan University, Chengdu, China
| | - Pawel E. Ferdek
- Department of Cell Biology, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Kraków, Poland
| | - Tingting Liu
- West China Centre of Excellence for Pancreatitis, Institute of Integrated Traditional Chinese and Western Medicine, West China-Liverpool Biomedical Research Centre, West China Hospital, Sichuan University, Chengdu, China
| | - Wei Huang
- West China Centre of Excellence for Pancreatitis, Institute of Integrated Traditional Chinese and Western Medicine, West China-Liverpool Biomedical Research Centre, West China Hospital, Sichuan University, Chengdu, China
- Institutes for Systems Genetics and Immunology and Inflammation, Frontiers Science Center for Disease-related Molecular Network, West China Hospital, Sichuan University, Chengdu, China
- West China Biobank, West China Hospital, Sichuan University, Chengdu, China
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Abboud C, Duveau A, Bouali-Benazzouz R, Massé K, Mattar J, Brochoire L, Fossat P, Boué-Grabot E, Hleihel W, Landry M. Animal models of pain: Diversity and benefits. J Neurosci Methods 2020; 348:108997. [PMID: 33188801 DOI: 10.1016/j.jneumeth.2020.108997] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Revised: 11/03/2020] [Accepted: 11/08/2020] [Indexed: 12/15/2022]
Abstract
Chronic pain is a maladaptive neurological disease that remains a major health problem. A deepening of our knowledge on mechanisms that cause pain is a prerequisite to developing novel treatments. A large variety of animal models of pain has been developed that recapitulate the diverse symptoms of different pain pathologies. These models reproduce different pain phenotypes and remain necessary to examine the multidimensional aspects of pain and understand the cellular and molecular basis underlying pain conditions. In this review, we propose an overview of animal models, from simple organisms to rodents and non-human primates and the specific traits of pain pathologies they model. We present the main behavioral tests for assessing pain and investing the underpinning mechanisms of chronic pathological pain. The validity of animal models is analysed based on their ability to mimic human clinical diseases and to predict treatment outcomes. Refine characterization of pathological phenotypes also requires to consider pain globally using specific procedures dedicated to study emotional comorbidities of pain. We discuss the limitations of pain models when research findings fail to be translated from animal models to human clinics. But we also point to some recent successes in analgesic drug development that highlight strategies for improving the predictive validity of animal models of pain. Finally, we emphasize the importance of using assortments of preclinical pain models to identify pain subtype mechanisms, and to foster the development of better analgesics.
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Affiliation(s)
- Cynthia Abboud
- Univ. Bordeaux, CNRS, Interdisciplinary Institute for Neuroscience, IINS, UMR 5297, F-33000 Bordeaux, France; Univ. Bordeaux, CNRS, Institute for Neurodegenerative Diseases, IMN, UMR 5293, F-33000 Bordeaux, France; Faculty of Arts and Sciences, Holy Spirit University of Kaslik (USEK), Lebanon
| | - Alexia Duveau
- Univ. Bordeaux, CNRS, Institute for Neurodegenerative Diseases, IMN, UMR 5293, F-33000 Bordeaux, France
| | - Rabia Bouali-Benazzouz
- Univ. Bordeaux, CNRS, Institute for Neurodegenerative Diseases, IMN, UMR 5293, F-33000 Bordeaux, France
| | - Karine Massé
- Univ. Bordeaux, CNRS, Institute for Neurodegenerative Diseases, IMN, UMR 5293, F-33000 Bordeaux, France
| | - Joseph Mattar
- School of Medicine and Medical Sciences, Holy Spirit University of Kaslik (USEK), Lebanon
| | - Louison Brochoire
- Univ. Bordeaux, CNRS, Institute for Neurodegenerative Diseases, IMN, UMR 5293, F-33000 Bordeaux, France
| | - Pascal Fossat
- Univ. Bordeaux, CNRS, Institute for Neurodegenerative Diseases, IMN, UMR 5293, F-33000 Bordeaux, France
| | - Eric Boué-Grabot
- Univ. Bordeaux, CNRS, Institute for Neurodegenerative Diseases, IMN, UMR 5293, F-33000 Bordeaux, France
| | - Walid Hleihel
- School of Medicine and Medical Sciences, Holy Spirit University of Kaslik (USEK), Lebanon; Faculty of Arts and Sciences, Holy Spirit University of Kaslik (USEK), Lebanon
| | - Marc Landry
- Univ. Bordeaux, CNRS, Institute for Neurodegenerative Diseases, IMN, UMR 5293, F-33000 Bordeaux, France.
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Lin YT, Liu HL, Day YJ, Chang CC, Hsu PH, Chen JC. Activation of NPFFR2 leads to hyperalgesia through the spinal inflammatory mediator CGRP in mice. Exp Neurol 2017; 291:62-73. [DOI: 10.1016/j.expneurol.2017.02.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Revised: 01/25/2017] [Accepted: 02/01/2017] [Indexed: 01/22/2023]
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Marquez M, Boscan P, Weir H, Vogel P, Twedt DC. Comparison of NK-1 Receptor Antagonist (Maropitant) to Morphine as a Pre-Anaesthetic Agent for Canine Ovariohysterectomy. PLoS One 2015; 10:e0140734. [PMID: 26513745 PMCID: PMC4626099 DOI: 10.1371/journal.pone.0140734] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Accepted: 09/28/2015] [Indexed: 11/18/2022] Open
Abstract
OBJECTIVE To compare the NK-1 receptor antagonist maropitant to morphine during and after surgery in dogs undergoing ovariohysterectomy (OHE). METHODS 30 healthy female dogs were randomly divided to receive either a pre-anaesthetic dose of morphine (0.5 mg/kg SQ) or maropitant (1 mg/kg, SQ) prior to OHE. Anaesthesia was induced with propofol and maintained with isoflurane. Expired isoflurane concentration, heart rate (HR), systolic arterial pressure (SAP) and respiratory rate were measured. Post-operative pain scores and appetite were evaluated during the recovery period. Rescue analgesia (morphine 0.1 mg/kg IV) was administered as needed post-operatively based on blinded pain score assessments. RESULTS Although clinically comparable; during surgical stimulation, the maropitant group had lower HR (108±18 vs 115±24 bpm; p = 0.04), lower SAP (114±23 vs 125±23 mmHg; p = 0.003) and required slightly lower percent of isoflurane anaesthetic (1.35±0.2 vs 1.51±0.4%; p = 0.005), when compared to the morphine group. In the recovery period, the maropitant group had lower pain scores at extubation (1.7±0.7 vs 3.4±2.3; p = 0.0001) and were more likely to eat within 3 hours after extubation (64.7 vs 15.3%). However, post-operative rescue analgesia requirements were similar between groups. All other measured parameters were similar between groups. The overall difference observed between groups was small and all monitored and measured parameters were within the expected range for anesthetized dogs. CLINICAL SIGNIFICANCE No major differences in cardiorespiratory parameters or anaesthetic requirements were observed between maropitant and morphine when used as a pre-anesthetic agent for OHE. Further studies are necessary to fully elucidate the benefits of maropitant as a pre-anaesthetic agent for canine OHE.
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Affiliation(s)
- Megan Marquez
- Department of Clinical Sciences, Veterinary Teaching Hospital, Colorado State University, Fort Collins, Colorado, United States of America
| | - Pedro Boscan
- Department of Clinical Sciences, Veterinary Teaching Hospital, Colorado State University, Fort Collins, Colorado, United States of America
- * E-mail:
| | - Heather Weir
- Department of Clinical Sciences, Veterinary Teaching Hospital, Colorado State University, Fort Collins, Colorado, United States of America
| | - Pamela Vogel
- Department of Clinical Sciences, Veterinary Teaching Hospital, Colorado State University, Fort Collins, Colorado, United States of America
| | - David C. Twedt
- Department of Clinical Sciences, Veterinary Teaching Hospital, Colorado State University, Fort Collins, Colorado, United States of America
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Abstract
Modeling visceral pain requires an appreciation of the underlying neurobiology of visceral sensation, including characteristics of visceral pain that distinguish it from pain arising from other tissues, the unique sensory innervation of visceral organs, the functional basis of visceral pain, and the concept of viscero-somatic and viscero-visceral convergence. Further, stimuli that are noxious when applied to the viscera are different than stimuli noxious to skin, muscle, and joints, thus informing model development and assessment. Visceral pain remains an important and understudied area of pain research and basic science knowledge and mechanisms acquired using animal models can translate into approaches that can be applied to the study and development of future therapeutics.
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Affiliation(s)
- Erica S Schwartz
- Center for Pain Research, Department of Anesthesiology, School of Medicine, University of Pittsburgh, W1444 BST-Starzl, 200 Lothrop St., Pittsburgh, PA, 15213, USA
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Fang X, Hu H, Xie J, Zhu H, Zhang D, Mo W, Zhang R, Yu M. An involvement of neurokinin-1 receptor in FcεRΙ-mediated RBL-2H3 mast cell activation. Inflamm Res 2012; 61:1257-63. [PMID: 22820943 PMCID: PMC3472057 DOI: 10.1007/s00011-012-0523-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2012] [Revised: 06/02/2012] [Accepted: 06/28/2012] [Indexed: 12/29/2022] Open
Abstract
OBJECTIVE AND DESIGN To determine whether the neurokinin-1 receptor (NK1R) plays a role in the activation of RBL-2H3 mast cells after FcεRΙ aggregation. MATERIALS AND METHODS NK1R expression in RBL-2H3 cells was inhibited by small hairpin RNA (shRNA) against NK1R, and determined by western blotting. For activation, both NK1R knockdown and control RBL-2H3 cells were sensitized by dinitrophenol (DNP)-specific IgE and stimulated with the antigen DNP-bovine serum albumin (BSA). Following the activation of RBL-2H3 cells, monocyte chemoattractant protein (MCP-1) production and intracellular calcium flux were monitored by ELISA and confocal microscopy assay, respectively. For investigation of the signaling mechanism, phosphorylation of mitogen-activated protein kinases (MAPKs) after RBL-2H3 cell activation was assessed by western blotting. RESULTS shRNA-NK1R mediated an effective inhibition of NK1R expression in RBL-2H3 cells. Protein production of MCP-1 was reduced by more than 55 % in NK1R knockdown RBL-2H3 cells compared with control RBL-2H3 cells. In addition, both calcium mobilization and phosphorylation levels of MAPKs (Erk1/2, JNK, and p38) after DNP-BSA stimulation (via FcεRΙ) were decreased due to the inhibition of NK1R expression. CONCLUSION NK1R is required for the activation of RBL-2H3 cells following FcεRΙ engagement and involved in the regulation of MAPK signaling pathways.
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Affiliation(s)
- Xiaoyun Fang
- The Key Laboratory of Molecular Medicine, Ministry of Education, Shanghai, 200032 People’s Republic of China
- Department of Biochemistry and Molecular Biology, Shanghai Medical College, Fudan University, Shanghai, 200032 People’s Republic of China
| | - Hua Hu
- Department of Otolaryngology, Huadong Hospital of Shanghai Medical College, Fudan University, Shanghai, 200032 People’s Republic of China
- Department of Otolaryngology, EENT Hospital of Shanghai Medical College, Fudan University, Shanghai, 200032 People’s Republic of China
| | - Jianhui Xie
- Department of Biochemistry and Molecular Biology, Shanghai Medical College, Fudan University, Shanghai, 200032 People’s Republic of China
| | - Haiyan Zhu
- Department of Biochemistry and Molecular Biology, Shanghai Medical College, Fudan University, Shanghai, 200032 People’s Republic of China
| | - Dongmei Zhang
- Department of Biochemistry and Molecular Biology, Shanghai Medical College, Fudan University, Shanghai, 200032 People’s Republic of China
| | - Wei Mo
- The Key Laboratory of Molecular Medicine, Ministry of Education, Shanghai, 200032 People’s Republic of China
- Department of Biochemistry and Molecular Biology, Shanghai Medical College, Fudan University, Shanghai, 200032 People’s Republic of China
| | - Ruxin Zhang
- Department of Otolaryngology, Huadong Hospital of Shanghai Medical College, Fudan University, Shanghai, 200032 People’s Republic of China
| | - Min Yu
- The Key Laboratory of Molecular Medicine, Ministry of Education, Shanghai, 200032 People’s Republic of China
- Department of Biochemistry and Molecular Biology, Shanghai Medical College, Fudan University, Shanghai, 200032 People’s Republic of China
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Pancreatic nociception--revisiting the physiology and pathophysiology. Pancreatology 2012; 12:104-12. [PMID: 22487519 DOI: 10.1016/j.pan.2012.02.010] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Revised: 01/23/2012] [Accepted: 02/19/2012] [Indexed: 12/11/2022]
Abstract
BACKGROUND Pain management of many pancreatic diseases remains a major clinical concern. This problem reflects our poor understanding of pain signaling from the pancreas. OBJECTIVES This review provides an overview of our current knowledge, with emphasis on current pain management strategies and recent experimental findings. METHODS A systematic search of the scientific literature was carried out using EMBASE, PubMed/MEDLINE, and the Cochrane Central Register of Controlled Trials for the years 1965-2011 to obtain access to all publications, especially randomized controlled trials, systematic reviews, and meta-analyses exploring pain and its management in disease states such as acute pancreatitis (AP), chronic pancreatitis (CP) and pancreatic cancer (PC). RESULTS Over the last decade, numerous molecular mediators such as nerve growth factor and the transient receptor potential (TRP) cation channel family have been implicated in afferent nerve signaling. More recent animal studies have indicated the location of the receptive fields for the afferent nerves in the pancreas and shown that these are activated by agents including cholecystokinin octapeptide, 5-hydroxytryptamine and bradykinin. Studies with PC specimens have shown that neuro-immune interactions occur and numerous agents including TRP cation channel V1, artemin and fractalkine have been implicated. Experimental studies in the clinical setting have demonstrated impairment of inhibitory pain modulation from supraspinal structures and implicated neuropathic pain mechanisms. CONCLUSIONS Our knowledge in this area remains incomplete. Characterization of the mediators and receptors/ion channels on the sensory nerve terminals are required in order to facilitate the development of new pharmaceutical treatments for AP and CP.
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Abstract
Chronic pancreatitis is typically a painful condition and it can be associated with a severe burden of disease. The pathogenesis of pain in this disorder is poorly understood and its treatment has been largely empirical, often consisting of surgical or other invasive methods, with an outcome that is variable and frequently unsatisfactory. Human and experimental studies have indicated a critical role for neuronal mechanisms that result in peripheral and central sensitization. The pancreatic nociceptor seems to be significantly affected in this condition, with increased excitability associated with downregulation of potassium currents. Some of the specific molecules implicated in this process include the vanilloid receptor, TRPV1, nerve growth factor, the protease activated receptor 2 and a variety of others that are discussed in this Review. Studies have also indicated novel therapeutic targets for this condition.
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Affiliation(s)
- Pankaj Jay Pasricha
- Stanford University School of Medicine, 300 Pasteur Drive, M211 Alway Building, Stanford, CA 94305, USA.
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Camargol EA, Zanonil CI, Toyamal MH, Muscaral MN, Dochertyl RJ, Costal SK. Abdominal hyperalgesia in secretory phospholipase A2-induced rat pancreatitis: Distinct roles of NK1receptors. Eur J Pain 2012; 15:900-6. [DOI: 10.1016/j.ejpain.2011.04.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2010] [Revised: 02/19/2011] [Accepted: 04/05/2011] [Indexed: 11/28/2022]
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Abstract
Pancreatic pain is often severe and difficult to treat clinically. Many animal models that mimic pancreatic pain are typically short term and invasive in nature. The present chapter describes the development and characterization of two non-invasive rat models of pancreatitis, one acute and one chronic. The two models described here are simple to replicate, giving them advantage over other animal models of pancreatic inflammation. A goal of this chapter is also to detail their usefulness as visceral pain models.
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Liao XZ, Zhou MT, Mao YF, Xu H, Chen H, Sun JH, Xiong YC. Analgesic effects of gabapentin on mechanical hypersensitivity in a rat model of chronic pancreatitis. Brain Res 2010; 1337:104-12. [PMID: 20417627 DOI: 10.1016/j.brainres.2010.04.035] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2009] [Revised: 04/15/2010] [Accepted: 04/16/2010] [Indexed: 02/08/2023]
Abstract
Gabapentin, an anticonvulsant, is widely accepted as an alternative therapeutic agent for neuropathic pain and has proved to produce analgesic effects in a mouse model of visceral pain. However, it is unknown whether gabapentin is also analgesically effective in chronic pancreatitis. The aim of the present study was to investigate the role and underlying mechanisms of gabapentin in a rat model of chronic pancreatitis. Chronic pancreatitis induced by dibutyltin dichloride (DBTC) produced a marked increase in mechanical sensitivity of the abdomen after the establishment of the model. During the first day to the sixth day in the fourth week, Gabapentin was administered intraperitoneally daily at a dose of 100mg/kg. The behavioral test began 1h after drug administration. The analgesic effect of gabapentin was not evident with a single injection, but gabapentin significantly reduced the responsive frequencies to mechanical stimulation in rats with chronic pancreatitis from the third day to the end of the experiment. To explore the underlying mechanisms, the expression of alpha(2)delta-1 calcium channel subunit was examined in the thoracic spinal cord (T8-11). There was no significant change in alpha(2)delta-1 level of T8-11 following the first injection. But after the sixth injection, the alpha(2)delta-1 level of T8-11 in rats with chronic pancreatitis was declined. Taken together, the present study suggested that repeated administration of gabapentin daily could reduce mechanical hypersensitivity in the upper abdomen and produce an analgesic effect in a rat model of chronic pancreatitis. The down-regulation of alpha(2)delta-1 calcium channel subunit might be one of the mechanisms underlying the analgesic effect of gabapentin.
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Affiliation(s)
- Xing-zhi Liao
- Department of Anesthesiology, Changhai Hospital, Second Military Medical University, Shanghai 200433, China
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Lee KE, Winkelstein BA. Joint distraction magnitude is associated with different behavioral outcomes and substance P levels for cervical facet joint loading in the rat. THE JOURNAL OF PAIN 2009; 10:436-45. [PMID: 19327645 DOI: 10.1016/j.jpain.2008.11.009] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2008] [Revised: 10/26/2008] [Accepted: 11/20/2008] [Indexed: 01/30/2023]
Abstract
UNLABELLED The facet joint is a common source of pain in both the neck and low back, and can be injured by abnormal loading of the spinal joints. Whereas a host of nociceptive changes including neuronal activation, neuropeptide expression, and inflammatory mediator responses has been reported for rat models of joint pain, no such responses have been explicitly investigated or quantified for painful mechanical injury to the facet joint. Two magnitudes of joint loading were separately imposed in a rat model of cervical facet joint distraction: Painful and nonpainful distractions. Behavioral outcomes were defined by assessing mechanical hyperalgesia in the shoulders and forepaws. Substance P (SP) mRNA and protein levels were quantified in the dorsal root ganglion (DRG) and spinal cord at days 1 and 7 following distraction. Painful distraction produced mechanical hyperalgesia that was significantly greater (P < .010) than that for a nonpainful distraction. Painful distraction significantly increased spinal SP mRNA (P = .048) and SP protein expression in the DRG (P = .013) at day 7 compared to nonpainful distraction. However, spinal SP protein for painful distraction was significantly less (P = .024) than that for nonpainful distraction at day 1. Joint distractions producing different behavioral outcomes modulate SP mRNA and protein in the DRG and spinal cord, suggesting that SP responses may be involved with different temporal responses in painful joint loading. PERSPECTIVE SP mRNA and protein in the DRG and spinal cord are quantified at 2 time points after cervical facet joint distractions that separately do or do not produce mechanical hyperalgesia. Studies describe a role for SP to contribute to pain produced by mechanical joint loading.
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Affiliation(s)
- Kathryn E Lee
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104-6392, USA
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Carmichael NME, Charlton MP, Dostrovsky JO. Sex differences in inflammation evoked by noxious chemical, heat and electrical stimulation. Brain Res 2009; 1276:103-11. [PMID: 19374887 DOI: 10.1016/j.brainres.2009.04.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2009] [Revised: 04/02/2009] [Accepted: 04/06/2009] [Indexed: 12/18/2022]
Abstract
Neurogenic inflammation (NI) is a feature of several inflammatory pain conditions in which females are overrepresented. Therefore, we asked if there are sex differences in the inflammatory response evoked by well known neurogenic stimuli. We compared the amount of plasma extravasation (PE), a measure of inflammation, in the hindpaw skin of male and female rats caused by subcutaneous injection of capsaicin, application of noxious heat (51 degrees C water bath) or electrical stimulation of the saphenous nerve. We also compared the amount of PE in males and females evoked by substance P (SP), the principal neurogenic mediator of PE. PE was quantified using a video camera and digital image analysis to measure changes in reflectance (pixel intensity, PI) of skin due to accumulation of extravasated Evans blue (EB) dye. The increase in PI induced by capsaicin was significantly greater in females compared to males (p<0.001) and in estrus, diestrus, and metestrus females compared to proestrus females. The time to reach maximal capsaicin-induced PE was two times longer in estrus, diestrus, and metestrus females compared to males (p<0.05). PE induced by heat was also significantly greater in females compared to males (p<0.001), however, there was no sex-related difference in PE induced by electrical stimulation or by injection of SP. These findings show that females have a greater inflammatory response when inflammation is induced by capsaicin and noxious heat suggesting possible sex-related changes in TRPV-1 receptor mediated mechanisms. These results add to the growing list of sex difference responses to noxious somatic stimulation.
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Affiliation(s)
- Nicole M E Carmichael
- Physiology Department, University of Toronto, Medical Science Building, 1 King's College Circle, Toronto, Ontario, Canada.
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Vera-Portocarrero LP, Ossipov MH, King T, Porreca F. Reversal of inflammatory and noninflammatory visceral pain by central or peripheral actions of sumatriptan. Gastroenterology 2008; 135:1369-78. [PMID: 18694754 PMCID: PMC4028637 DOI: 10.1053/j.gastro.2008.06.085] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2008] [Revised: 06/23/2008] [Accepted: 06/26/2008] [Indexed: 12/31/2022]
Abstract
BACKGROUND & AIMS Sumatriptan is used specifically to relieve headache pain. The possible efficacy of sumatriptan was investigated in 2 models of visceral pain. METHODS Pancreatic inflammation was induced by intravenous injection of dibutyltin dichloride. Noninflammatory irritable bowel syndrome was induced by intracolonic instillation of sodium butyrate. The effects of systemic sumatriptan on referred hypersensitivity were tested in both models. Effects of sumatriptan within the rostral ventromedial medulla (RVM), a site of descending modulation of visceral pain, was determined by (1) testing the effects of RVM administration of 5HT1(B/D) antagonists on systemic sumatriptan action and (2) determining whether RVM application of sumatriptan reproduced the actions of systemic drug administration. RESULTS Systemic sumatriptan elicited a dose- and time-related blockade of referred hypersensitivity in both models that was blocked by systemic administration of either 5HT1(B) or 5HT1(D) antagonists. Sumatriptan administered into the RVM similarly produced dose- and time-related blockade of referred hypersensitivity in both visceral pain models. This was blocked by local microinjection of the 5HT1(B) antagonist but not the 5HT1(D) antagonist. Microinjection of 5HT1(B) or 5HT1(D) antagonists into the RVM did not block the effects of systemic sumatriptan. CONCLUSIONS Our findings suggest that sumatriptan suppresses either inflammatory or noninflammatory visceral pain, most likely through peripheral 5HT1(B)/(D) receptors. Actions at 5HT1(B) receptors within the RVM offer an additional potential site of action for the modulation of visceral pain by triptans. These studies offer new insights into the development of strategies that may improve therapy of visceral pain conditions using already available medications.
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Amella C, Cappello F, Kahl P, Fritsch H, Lozanoff S, Sergi C. Spatial and temporal dynamics of innervation during the development of fetal human pancreas. Neuroscience 2008; 154:1477-87. [DOI: 10.1016/j.neuroscience.2008.04.050] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2008] [Revised: 04/21/2008] [Accepted: 04/22/2008] [Indexed: 01/13/2023]
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Yang H, McNearney TA, Chu R, Lu Y, Ren Y, Yeomans DC, Wilson SP, Westlund KN. Enkephalin-encoding herpes simplex virus-1 decreases inflammation and hotplate sensitivity in a chronic pancreatitis model. Mol Pain 2008; 4:8. [PMID: 18307791 PMCID: PMC2292157 DOI: 10.1186/1744-8069-4-8] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2008] [Accepted: 02/28/2008] [Indexed: 12/15/2022] Open
Abstract
Background A chronic pancreatitis model was developed in young male Lewis rats fed a high-fat and alcohol liquid diet beginning at three weeks. The model was used to assess time course and efficacy of a replication defective herpes simplex virus type 1 vector construct delivering human cDNA encoding preproenkephalin (HSV-ENK). Results Most surprising was the relative lack of inflammation and tissue disruption after HSV-ENK treatment compared to the histopathology consistent with pancreatitis (inflammatory cell infiltration, edema, acinar cell hypertrophy, fibrosis) present as a result of the high-fat and alcohol diet in controls. The HSV-ENK vector delivered to the pancreatic surface at week 3 reversed pancreatitis-associated hotplate hypersensitive responses for 4–6 weeks, while control virus encoding β-galactosidase cDNA (HSV-β-gal) had no effect. Increased Fos expression seen bilaterally in pain processing regions in control animals with pancreatitis was absent in HSV-ENK-treated animals. Increased met-enkephalin staining was evident in pancreas and lower thoracic spinal cord laminae I–II in the HSV-ENK-treated rats. Conclusion Thus, clear evidence is provided that site specific HSV-mediated transgene delivery of human cDNA encoding preproenkephalin ameliorates pancreatic inflammation and significantly reduces hypersensitive hotplate responses for an extended time consistent with HSV mediated overexpression, without tolerance or evidence of other opiate related side effects.
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Affiliation(s)
- Hong Yang
- Dept of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, TX, USA.
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Carmichael NME, Charlton MP, Dostrovsky JO. Activation of the 5-HT1B/D receptor reduces hindlimb neurogenic inflammation caused by sensory nerve stimulation and capsaicin. Pain 2007; 134:97-105. [PMID: 17499925 DOI: 10.1016/j.pain.2007.03.037] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2006] [Revised: 03/26/2007] [Accepted: 03/27/2007] [Indexed: 10/23/2022]
Abstract
Activation of the 5-HT(1B/D) receptor inhibits cerebrovascular neurogenic inflammation (NI). The aim of this study was to determine if the 5-HT(1B/D) receptor agonist sumatriptan can also inhibit NI in other regions of the body. NI was assessed by measuring plasma extravasation (PE) and changes in blood flow in the rat hindpaw. Sumatriptan was administered locally (20 microl, 50 or 100 nM, s.c.) into the dorso-medial region of one hindpaw. The other paw was pre-treated with vehicle (20 microl of 0.9% saline) and served as a control. NI was induced after treatment with sumatriptan/vehicle by injecting capsaicin (15 microl, 1%, s.c.) into each paw or by electrically stimulating the saphenous nerve (4 Hz, 30s). Sumatriptan administered locally or systemically (300 microg/kg, i.v.) significantly reduced saphenous nerve and capsaicin-induced PE and vasodilation. The systemic and local inhibitory actions of sumatriptan are mediated by the 5-HT(1B/D) receptor as pre-treatment with the 5-HT(1B/D) antagonist GR127935 (GR; 15 microl, 1 microM, s.c. or 0.2 micromol/kg, i.v.) completely blocked the inhibitory effect of sumatriptan on capsaicin-induced vasodilation and reduced the inhibitory effect of sumatriptan on capsaicin and electrically induced-PE. Neither PE induced by local injection of substance P (SP) (20 pmol, 20 microl, s.c.) nor vasodilation induced by local CGRP injection was affected by pre-treatment with sumatriptan. These findings indicate that both local and systemic activation of the 5-HT(1B/D) receptor by sumatriptan reduce NI induced by nerve stimulation or capsaicin presumably by inhibiting neuropeptide release. 5-HT(1B/D) receptor agonists may be useful for the treatment of non-trigeminal pain conditions involving NI.
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Affiliation(s)
- Nicole M E Carmichael
- University of Toronto, Department of Physiology, Medical Science Building, Rm. 3305, 1 King's College Circle, Toronto, Ont., Canada M5S1A8.
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Broccardo M, Linari G, Agostini S, Amadoro G, Carpino F, Ciotti MT, Petrella C, Petrozza V, Severini C, Improta G. Expression of NK-1 and NK-3 tachykinin receptors in pancreatic acinar cells after acute experimental pancreatitis in rats. Am J Physiol Gastrointest Liver Physiol 2006; 291:G518-24. [PMID: 16782701 DOI: 10.1152/ajpgi.00505.2005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Activation of neurokinin (NK)-1 receptors but not of NK-3 stimulates amylase release from isolated pancreatic acini of the rat. Immunofluorescence studies show that NK-1 receptors are more strongly expressed than NK-3 receptors on pancreatic acinar cells under basal conditions. No studies have examined the expression of the two NK receptor populations in pancreatic acini during pancreatitis in rats. We therefore investigated the relationships between expression of these two tachykinin receptors and experimental acute pancreatitis induced by stimulating pancreatic amylase with caerulein (CK) in rats. Hyperstimulation of the pancreas by CK caused an increase in plasma amylase and pancreatic water content and resulted in morphological evidence of cytoplasmic vacuolization. Immunofluorescence analysis revealed a similar percentage of NK-1 receptor antibody immunoreactive acinar cells in rats with pancreatitis and in normal rat tissue but a larger percentage of NK-3 receptor immunoreactive cells in acute pancreatitis than in normal pancreas. Western blot analysis of NK-1 and NK-3 receptor protein levels after CK-induced pancreatitis showed no change in NK-1 receptors but a stronger increase in NK-3 receptor expression in pancreatic acini compared with normal rats thus confirming the immunofluorescence data. These new findings support previous evidence that substance P-mediated functions within the pancreas go beyond sensory signal transduction contributing to neurogenic inflammation, and they suggest that substance P plays a role in regulating pancreatic exocrine secretion via acinar NK-1 receptors. The significant increase in NK-3 receptors during pancreatic stimulation suggests that NK-3 receptors also intervene in the pathogenesis of mild acute pancreatitis in rats.
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Affiliation(s)
- Maria Broccardo
- Dipartimento di Fisiologia Umana e Farmacologia "V. Erspamer" Università di Roma "La Sapienza"- P.le A. Moro 5-00185 Roma, Italia
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Xu GY, Winston JH, Shenoy M, Yin H, Pasricha PJ. Enhanced excitability and suppression of A-type K+ current of pancreas-specific afferent neurons in a rat model of chronic pancreatitis. Am J Physiol Gastrointest Liver Physiol 2006; 291:G424-31. [PMID: 16645160 DOI: 10.1152/ajpgi.00560.2005] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Chronic pancreatitis (CP) is a relatively common disorder, characterized by glandular insufficiency and chronic, often intractable, pain. The mechanism of pain in CP is poorly understood. We have previously developed a model of trinitrobenzene sulphonic acid (TNBS)-induced CP that results in nociceptive sensitization in rats. This study was designed to examine changes in the excitability and alteration of voltage-gated K(+) currents of dorsal root ganglia (DRG) neurons innervating the pancreas. CP was induced in adult rats by an intraductal injection of TNBS. DRG neurons innervating the pancreas were identified by 1,1'-dioleyl-3,3,3',3-tetramethylindocarbocyanine methanesulfonate fluorescence labeling. Perforated patch-clamp recordings were made from acutely dissociated DRG neurons from control and TNBS-treated rats. Pancreas-specific DRG neurons displayed more depolarized resting potentials in TNBS-treated rats than those in controls (P < 0.02). Some neurons from the TNBS-treated group exhibited spontaneous firings. TNBS-induced CP also resulted in a dramatic reduction in rheobase (P < 0.05) and a significant increase in the number of action potentials evoked at twice rheobase (P < 0.05). Under voltage-clamp conditions, neurons from both groups exhibited transient A-type (I(A)) and sustained outward rectifier K(+) currents (I(K)). Compared with controls, the average I(A) but not the average I(K) density was significantly reduced in the TNBS-treated group (P < 0.05). The steady-state inactivation curve for I(A) was displaced by approximately 20 mV to more hyperpolarized levels after the TNBS treatment. These data suggest that TNBS treatment increases the excitability of pancreas-specific DRG neurons by suppressing I(A) density, thus identifying for the first time a specific molecular mechanism underlying chronic visceral pain and sensitization in CP.
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Affiliation(s)
- Guang-Yin Xu
- Div. of Gastroenterology and Hepatology, Dept. of Internal Medicine, Univ. of Texas Medical Branch, Galveston, Texas 77555, USA.
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Vera-Portocarrero LP, Xie JY, Yie JX, Kowal J, Ossipov MH, King T, Porreca F. Descending facilitation from the rostral ventromedial medulla maintains visceral pain in rats with experimental pancreatitis. Gastroenterology 2006; 130:2155-64. [PMID: 16762636 DOI: 10.1053/j.gastro.2006.03.025] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2005] [Accepted: 02/22/2006] [Indexed: 02/08/2023]
Abstract
BACKGROUND & AIMS Pain is a main complaint of patients with pancreatitis. We hypothesized that such pain is mediated through ascending pathways via the nucleus gracilis (NG) and is dependent on descending facilitatory influences from the rostral ventromedial medulla (RVM). METHODS A rat model of persistent experimental pancreatitis was used. After establishment of pancreatitis, rats received microinjection of lidocaine in the NG or in the RVM to determine the importance of neural activity at these supraspinal sites in the expression of abdominal hypersensitivity evoked by von Frey filaments (ie, pancreatic pain). Rats also were pretreated for 28 days before induction of pancreatitis with a single RVM microinjection of dermorphin-saporin to eliminate cells that drive descending facilitation. Dynorphin content was measured in the spinal cord of pancreatitic rats and the effects of spinal antidynorphin antiserum in pancreatic pain were assessed. RESULTS Microinjection of lidocaine into either the NG or the RVM produced a time-related reversal of pancreatitis-induced pain. Pancreatitis significantly increased thoracic spinal dynorphin content and spinal antidynorphin antiserum elicited a time-related reversal of abdominal hypersensitivity. RVM dermorphin-saporin injection prevented the maintenance, but not the expression, of pancreatitis abdominal hypersensitivity and also prevented the increase of spinal dynorphin content in animals with pancreatitis. CONCLUSIONS Our findings suggest that descending facilitation from the RVM plays a critical role in the maintenance, but not the expression, of pancreatic pain. These results provide a novel insight into the role of descending pathways and spinal plasticity in the maintenance of visceral pain from pancreatitis.
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Wick EC, Hoge SG, Grahn SW, Kim E, Divino LA, Grady EF, Bunnett NW, Kirkwood KS. Transient receptor potential vanilloid 1, calcitonin gene-related peptide, and substance P mediate nociception in acute pancreatitis. Am J Physiol Gastrointest Liver Physiol 2006; 290:G959-69. [PMID: 16399878 DOI: 10.1152/ajpgi.00154.2005] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The mechanism of pancreatitis-induced pain is unknown. In other tissues, inflammation activates transient receptor potential vanilloid 1 (TRPV1) on sensory nerves to liberate CGRP and substance P (SP) in peripheral tissues and the dorsal horn to cause neurogenic inflammation and pain, respectively. We evaluated the contribution of TRPV1, CGRP, and SP to pancreatic pain in rats. TRPV1, CGRP, and SP were coexpressed in nerve fibers of the pancreas. Injection of the TRPV1 agonist capsaicin into the pancreatic duct induced endocytosis of the neurokinin 1 receptor in spinal neurons in the dorsal horn (T10), indicative of SP release upon stimulation of pancreatic sensory nerves. Induction of necrotizing pancreatitis by treatment with L-arginine caused a 12-fold increase in the number of spinal neurons expressing the proto-oncogene c-fos in laminae I and II of L1, suggesting activation of nociceptive pathways. L-arginine also caused a threefold increase in spontaneous abdominal contractions detected by electromyography, suggestive of referred pain. Systemic administration of the TRPV1 antagonist capsazepine inhibited c-fos expression by 2.5-fold and abdominal contractions by 4-fold. Intrathecal, but not systemic, administration of antagonists of CGRP (CGRP(8-37)) and SP (SR140333) receptors attenuated c-fos expression in spinal neurons by twofold. Thus necrotizing pancreatitis activates TRPV1 on pancreatic sensory nerves to release SP and CGRP in the dorsal horn, resulting in nociception. Antagonism of TRPV1, SP, and CGRP receptors may suppress pancreatitis pain.
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Affiliation(s)
- Elizabeth C Wick
- Departments of Surgery and Physiology, Univ. of California-San Francisco, 521 Parnassus Avenue, Rm C341, San Francisco, CA 94143-0790, USA
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Wick EC, Pikios S, Grady EF, Kirkwood KS. Calcitonin gene-related peptide partially mediates nociception in acute experimental pancreatitis. Surgery 2006; 139:197-201. [PMID: 16455328 DOI: 10.1016/j.surg.2005.08.024] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2005] [Revised: 08/04/2005] [Accepted: 08/05/2005] [Indexed: 10/25/2022]
Abstract
BACKGROUND The mechanism by which pancreatitis causes pain is unknown. The neuropeptide calcitonin gene-related peptide (CGRP) is released after sensory nerve activation and promotes nociceptive signaling in models of visceral pain. We hypothesized that acute pancreatitis leads to the activation of pancreatic sensory neurons that release CGRP in the dorsal horn of the spinal cord. This signal is ultimately transmitted to the brain, and pain is sensed. METHODS To induce pancreatitis, rats were injected with l-arginine (500 mg/kg) intraperitoneally or saline (control). Pancreatitis was confirmed by measuring serum amylase and evaluating pancreatic histology. Activation of nociceptive pathways was evaluated by counting Fos-like immunoreactive nuclei (FLI) in the dorsal horn of the spinal cord at T3-L1. Some animals received the CGRP antagonist CGRP(8-37) (50 microg intrathecally) 2 hours before perfusion. Animals were compared using a 2-tailed t test. RESULTS l-Arginine treatment induced acute necrotizing pancreatitis in the rat at 24 hours. l-Arginine (24 hours) increased FLI in the dorsal horn of the spinal cord, with a peak effect at L1. Intrathecal administration of CGRP(8-37) significantly decreased the number of FLI nuclei in the dorsal horn of the spinal cord in T11-L1. CONCLUSIONS Nociception in the l-arginine model of acute pancreatitis is partially mediated by the release of CGRP in the dorsal horn of the spinal cord. Antagonism of CGRP or its receptors may be useful in treating pain from acute pancreatitis.
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Affiliation(s)
- Elizabeth C Wick
- Department of Surgery, University of California, San Francisco, USA
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Vera-Portocarrero L, Westlund KN. Role of neurogenic inflammation in pancreatitis and pancreatic pain. Neurosignals 2006; 14:158-65. [PMID: 16215298 PMCID: PMC2766588 DOI: 10.1159/000087654] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2005] [Indexed: 12/18/2022] Open
Abstract
Pain arising from pancreatic diseases can become chronic and difficult to treat. There is a paucity of knowledge regarding the mechanisms that sensitize neural pathways that transmit noxious information from visceral organs. In this review, neurogenic inflammation is presented as a possible amplifier of the noxious signal from peripheral organs including the pancreas. The nerve pathways that transmit pancreatic pain are also reviewed as a conduit of the amplified signals. It is likely that components of these visceral pain pathways can also be sensitized after neurogenic inflammation.
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Winston JH, He ZJ, Shenoy M, Xiao SY, Pasricha PJ. Molecular and behavioral changes in nociception in a novel rat model of chronic pancreatitis for the study of pain. Pain 2006; 117:214-22. [PMID: 16098667 DOI: 10.1016/j.pain.2005.06.013] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2005] [Revised: 06/03/2005] [Accepted: 06/13/2005] [Indexed: 01/08/2023]
Abstract
The approach to the management of painful chronic pancreatitis has been empirical, primarily due to the lack of information about biological mechanisms producing pain. To facilitate research into pain mechanisms, our aim was to assess a rat model of chronic pancreatitis induced by pancreatic infusion of trinitrobenzene sulfonic acid as a model of painful pancreatitis. Nociception was assessed by measuring mechanical sensitivity of the abdomen and by recording the number of nocifensive behaviors in response to electrical stimulation of the pancreas. Expression of neuropeptides calcitonin gene-related peptide (CGRP) and substance P (SP) in the thoracic dorsal root ganglia receiving input from the pancreas and nerve growth factor (NGF) in the pancreas were measured. Rats with pancreatitis exhibited marked increase in sensitivity to mechanical probing of the abdomen and increased sensitivity to noxious electrical stimulation of the pancreas. There were significant increases in NGF protein in the pancreas and in expression of neuropeptides CGRP and SP in the sensory neurons from dorsal root ganglia receiving input from the pancreas. We have established quantitative measures of referred nociception and pancreatic hyperalgesia in a rat model of chronic pancreatitis that bears histological similarities to the human disease. This model has considerable construct, face and predictive validity for the human condition. It is of importance for the study of the pathogenesis of pain in this condition and can facilitate the development of new therapeutic options.
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Affiliation(s)
- John H Winston
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, The University of Texas Medical Branch, 4.106 McCullough Building, 301 University Boulevard, Galveston TX 77555-0764, USA
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Rothman SM, Kreider RA, Winkelstein BA. Spinal neuropeptide responses in persistent and transient pain following cervical nerve root injury. Spine (Phila Pa 1976) 2005; 30:2491-6. [PMID: 16284585 DOI: 10.1097/01.brs.0000186316.38111.4b] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN Behavioral and immunohistochemical analysis in rat models of persistent and transient allodynia. OBJECTIVES To examine separate cervical nerve root injuries (compression, transection) for producing behavioral hypersensitivity and investigate spinal neuropeptides to understand relationships to pain symptoms. SUMMARY OF BACKGROUND DATA Mechanical cervical nerve root injury can be a source of neck pain. Painful lumbar radiculopathy models show that different nerve root ligation intensities produce differential allodynia responses. Spinal neuropeptides can mediate pain responses. Yet, little is known about their contributions to pain in the cervical spine. METHODS Rats underwent separate procedures on the right C7 nerve roots: transection (n = 12), 10-gf compression for 15 minutes (n = 11), or sham (n = 5). Ipsilateral forepaw mechanical allodynia was measured after surgery for 7 days. C7 spinal cord tissue was analyzed by immunohistochemistry for substance P and calcitonin gene-related peptide (CGRP) expression on days 1 and 7 for each injury; densitometry quantified immunoreactivity in lamina I of the ipsilateral dorsal horn. RESULTS Both injuries immediately produced significant increases in allodynia. Sensitivity was sustained following root compression, and at day 7, was not different from day 1. By day 7 after transection, allodynia had returned to baseline and sham levels, significantly decreasing from day 1 (P = 0.0012). Spinal substance P and CGRP were increased over normal at day 1 for both injuries and decreased with time for CGRP after transection, which paralleled behaviors. For individual rats, substance P was significantly (P < 0.001) correlated with CGRP expression for both injuries. CONCLUSIONS Compression and transection of the cervical nerve root produce different forepaw allodynia responses, with persistent and transient sensitivity, respectively. Spinal neuropeptide expression in these models parallels this sensitivity, suggesting their potential role in pain symptoms.
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Affiliation(s)
- Sarah M Rothman
- Department of Bioengineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6392, USA
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