1
|
Sadighparvar S, Al-Hamed FS, Sharif-Naeini R, Meloto CB. Preclinical orofacial pain assays and measures and chronic primary orofacial pain research: where we are and where we need to go. FRONTIERS IN PAIN RESEARCH 2023; 4:1150749. [PMID: 37293433 PMCID: PMC10244561 DOI: 10.3389/fpain.2023.1150749] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Accepted: 04/11/2023] [Indexed: 06/10/2023] Open
Abstract
Chronic primary orofacial pain (OFP) conditions such as painful temporomandibular disorders (pTMDs; i.e., myofascial pain and arthralgia), idiopathic trigeminal neuralgia (TN), and burning mouth syndrome (BMS) are seemingly idiopathic, but evidence support complex and multifactorial etiology and pathophysiology. Important fragments of this complex array of factors have been identified over the years largely with the help of preclinical studies. However, findings have yet to translate into better pain care for chronic OFP patients. The need to develop preclinical assays that better simulate the etiology, pathophysiology, and clinical symptoms of OFP patients and to assess OFP measures consistent with their clinical symptoms is a challenge that needs to be overcome to support this translation process. In this review, we describe rodent assays and OFP pain measures that can be used in support of chronic primary OFP research, in specific pTMDs, TN, and BMS. We discuss their suitability and limitations considering the current knowledge of the etiology and pathophysiology of these conditions and suggest possible future directions. Our goal is to foster the development of innovative animal models with greater translatability and potential to lead to better care for patients living with chronic primary OFP.
Collapse
Affiliation(s)
- Shirin Sadighparvar
- Integrated Program in Neuroscience, McGill University, Montreal, QC, Canada
- The Alan Edwards Centre for Research on Pain, McGill University, Montreal, QC, Canada
| | | | - Reza Sharif-Naeini
- The Alan Edwards Centre for Research on Pain, McGill University, Montreal, QC, Canada
- Department of Physiology and Cell Information Systems, McGill University, Montreal, QC, Canada
| | - Carolina Beraldo Meloto
- The Alan Edwards Centre for Research on Pain, McGill University, Montreal, QC, Canada
- Faculty of Dental Medicine and Oral Health Sciences, McGill University, Montreal, QC, Canada
| |
Collapse
|
2
|
Zhang YY, Liu F, Fang ZH, Li YL, Liao HL, Song QX, Zhou C, Shen JF. Differential roles of NMDAR subunits 2A and 2B in mediating peripheral and central sensitization contributing to orofacial neuropathic pain. Brain Behav Immun 2022; 106:129-146. [PMID: 36038077 DOI: 10.1016/j.bbi.2022.08.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Revised: 07/27/2022] [Accepted: 08/23/2022] [Indexed: 11/29/2022] Open
Abstract
The spinal N-methyl-d-aspartate receptor (NMDAR), particularly their subtypes NR2A and NR2B, plays pivotal roles in neuropathic and inflammatory pain. However, the roles of NR2A and NR2B in orofacial pain and the exact molecular and cellular mechanisms mediating nervous system sensitization are still poorly understood. Here, we exhaustively assessed the regulatory effect of NMDAR in mediating peripheral and central sensitization in orofacial neuropathic pain. Von-Frey filament tests showed that the inferior alveolar nerve transection (IANX) induced ectopic allodynia behavior in the whisker pad of mice. Interestingly, mechanical allodynia was reversed in mice lacking NR2A and NR2B. IANX also promoted the production of peripheral sensitization-related molecules, such as interleukin (IL)-1β, tumor necrosis factor (TNF)-α, brain-derived neurotrophic factor (BDNF), and chemokine upregulation (CC motif) ligand 2 (CCL2), and decreased the inward potassium channel (Kir) 4.1 on glial cells in the trigeminal ganglion, but NR2A conditional knockout (CKO) mice prevented these alterations. In contrast, NR2B CKO only blocked the changes of Kir4.1, IL-1β, and TNF-α and further promoted the production of CCL2. Central sensitization-related c-fos, glial fibrillary acidic protein (GFAP), and ionized calcium-binding adaptor molecule 1 (Iba-1) were promoted and Kir4.1 was reduced in the spinal trigeminal caudate nucleus by IANX. Differential actions of NR2A and NR2B in mediating central sensitization were also observed. Silencing of NR2B was effective in reducing c-fos, GFAP, and Iba-1 but did not affect Kir4.1. In contrast, NR2A CKO only altered Iba-1 and Kir4.1 and further increased c-fos and GFAP. Gain-of-function and loss-of-function approaches provided insight into the differential roles of NR2A and NR2B in mediating peripheral and central nociceptive sensitization induced by IANX, which may be a fundamental basis for advancing knowledge of the neural mechanisms' reaction to nerve injury.
Collapse
Affiliation(s)
- Yan-Yan Zhang
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China; Department of Prosthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Fei Liu
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China; Department of Prosthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Zhong-Han Fang
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China; Department of Prosthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Yue-Ling Li
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China; Department of Prosthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Hong-Lin Liao
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China; Department of Prosthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Qin-Xuan Song
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China; Department of Prosthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Cheng Zhou
- Laboratory of Anesthesia and Critical Care Medicine, Translational Neuroscience Center, West China Hospital of Sichuan University, Chengdu, China
| | - Jie-Fei Shen
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China; Department of Prosthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
| |
Collapse
|
3
|
Benbow T, Teja F, Sheikhi A, Exposto FG, Svensson P, Cairns BE. Peripheral N-methyl-D-aspartate receptor activation contributes to monosodium glutamate-induced headache but not nausea behaviours in rats. Sci Rep 2022; 12:13894. [PMID: 35974090 PMCID: PMC9381496 DOI: 10.1038/s41598-022-18290-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Accepted: 08/09/2022] [Indexed: 12/29/2022] Open
Abstract
Monosodium glutamate induces behaviors thought to reflect headache and nausea in rats. We explored the effects of the N-methyl-d-aspartate receptor antagonist (2R)-amino-5-phosphonovaleric acid, the inotropic glutamate receptor antagonist kynurenic acid, and the CGRP receptor antagonist olcegepant, on monosodium glutamate-induced increases in nocifensive, headache-like and nausea behaviours. Effects of these antagonists on motor function were examined with a rotarod. The effect of the dopamine receptor antagonist metoclopramide and the serotonin 3 receptor antagonist ondansetron on nausea behaviour was also assessed. (2R)-amino-5-phosphonovaleric acid, and to a lesser extent, kynurenic acid and olcegepant, reduced nocifensive and headache-like behaviours evoked by monosodium glutamate. No alteration in motor function by (2R)-amino-5-phosphonovaleric acid, kynurenic acid or olcegepant was observed. No sex-related differences in the effectiveness of these agents were identified. Nausea behaviour was significantly more pronounced in male than in female rats. Olcegepant, ondansetron and metoclopramide ameliorated this nausea behaviour in male rats. Ondansetron and metoclopramide also reduced headache-like behaviour in male rats. These findings suggest that peripheral N-methyl-d-aspartate receptor activation underlies monosodium glutamate-induced headache-like behaviour but does not mediate the nausea behaviour in rats.
Collapse
Affiliation(s)
- Tarique Benbow
- Faculty of Pharmaceutical Sciences, University of British Columbia, 2405 Wesbrook Mall, Vancouver, V6T 1Z3, Canada
| | - Felisha Teja
- Faculty of Pharmaceutical Sciences, University of British Columbia, 2405 Wesbrook Mall, Vancouver, V6T 1Z3, Canada
| | - Afrooz Sheikhi
- Faculty of Pharmaceutical Sciences, University of British Columbia, 2405 Wesbrook Mall, Vancouver, V6T 1Z3, Canada
| | - Fernando G Exposto
- Section for Orofacial Pain and Jaw Function, Department of Dentistry and Oral Health, Aarhus University, Vennelyst Boulevard 9, 8000, Aarhus C, Denmark
| | - Peter Svensson
- Section for Orofacial Pain and Jaw Function, Department of Dentistry and Oral Health, Aarhus University, Vennelyst Boulevard 9, 8000, Aarhus C, Denmark
| | - Brian E Cairns
- Faculty of Pharmaceutical Sciences, University of British Columbia, 2405 Wesbrook Mall, Vancouver, V6T 1Z3, Canada.
| |
Collapse
|
4
|
Lindquist KA, Belugin S, Hovhannisyan AH, Corey TM, Salmon A, Akopian AN. Identification of Trigeminal Sensory Neuronal Types Innervating Masseter Muscle. eNeuro 2021; 8:ENEURO.0176-21.2021. [PMID: 34580157 PMCID: PMC8513531 DOI: 10.1523/eneuro.0176-21.2021] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Revised: 08/18/2021] [Accepted: 09/01/2021] [Indexed: 11/21/2022] Open
Abstract
Understanding masseter muscle (MM) innervation is critical for the study of cell-specific mechanisms of pain induced by temporomandibular disorder (TMDs) or after facial surgery. Here, we identified trigeminal (TG) sensory neuronal subtypes (MM TG neurons) innervating MM fibers, masseteric fascia, tendons, and adjusted tissues. A combination of patch clamp electrophysiology and immunohistochemistry (IHC) on TG neurons back-traced from reporter mouse MM found nine distinct subtypes of MM TG neurons. Of these neurons, 24% belonged to non-peptidergic IB-4+/TRPA1- or IB-4+/TRPA1+ groups, while two TRPV1+ small-sized neuronal groups were classified as peptidergic/CGRP+ One small-sized CGRP+ neuronal group had a unique electrophysiological profile and were recorded from Nav1.8- or trkC+ neurons. The remaining CGRP+ neurons were medium-sized, could be divided into Nav1.8-/trkC- and Nav1.8low/trkC+ clusters, and showed large 5HT-induced current. The final two MM TG neuronal groups were trkC+ and had no Nav1.8 and CGRP. Among MM TG neurons, TRPV1+/CGRP- (somatostatin+), tyrosine hydroxylase (TH)+ (C-LTMR), TRPM8+, MrgprA3+, or trkB+ (Aδ-LTMR) subtypes have not been detected. Masseteric muscle fibers, tendons and masseteric fascia in mice and the common marmoset, a new world monkey, were exclusively innervated by either CGRP+/NFH+ or CGRP-/NFH+ medium-to-large neurons, which we found using a Nav1.8-YFP reporter, and labeling with CGRP, TRPV1, neurofilament heavy chain (NFH) and pgp9.5 antibodies. These nerves were mainly distributed in tendon and at junctions of deep-middle-superficial parts of MM. Overall, the data presented here demonstrates that MM is innervated by a distinct subset of TG neurons, which have unique characteristics and innervation patterns.
Collapse
Affiliation(s)
- Karen A Lindquist
- Integrated Biomedical Sciences (IBMS) Program, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229
| | - Sergei Belugin
- Endodontics, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229
| | - Anahit H Hovhannisyan
- Endodontics, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229
| | - Tatiana M Corey
- Laboratory Animal Resources Departments, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229
| | - Adam Salmon
- Molecular Medicine, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229
- Sam and Ann Barshop Institute for Longevity and Aging Studies, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229
- South Texas Veterans Health Care System, Geriatric Research Education and Clinical Center San Antonio, TX 78229
| | - Armen N Akopian
- Integrated Biomedical Sciences (IBMS) Program, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229
- Endodontics, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229
- Pharmacology, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229
| |
Collapse
|
5
|
Benbow T, Cairns BE. Dysregulation of the peripheral glutamatergic system: A key player in migraine pathogenesis? Cephalalgia 2021; 41:1249-1261. [PMID: 34148407 PMCID: PMC8504403 DOI: 10.1177/03331024211017882] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Background Although the role of glutamate in migraine pathogenesis remains uncertain, there has been significant interest in the development of drug candidates that target glutamate receptors. Activation of trigeminovascular afferent fibers is now recognized as a crucial step to the onset of a migraine episode. New evidence suggests a dysfunction in peripheral glutamate regulation may play a role in this process. Objective To provide a narrative review of the role of peripheral glutamate dysfunction in migraine. Method A review of recent literature from neurobiological, pharmacological and genomic studies was conducted to support peripheral glutamate dysfunction as a potential element in migraine pathogenesis. Results Studies in rats suggest that elevated blood glutamate mechanically sensitizes trigeminal afferent fibers and stimulates the release of calcitonin-gene related peptide and other neuropeptides to promote and maintain neurogenic inflammation. These effects may be driven by upregulation of glutamate receptors, and modifications to reuptake and metabolic pathways of glutamate. Furthermore, genome wide association studies have found polymorphisms in glutamate receptor and transporter genes that are associated with migraine. Conclusion The role of peripheral glutamate signalling in the onset and maintenance of migraine is not completely elucidated and future studies are still needed to confirm its role in migraine pathogenesis.
Collapse
Affiliation(s)
- Tarique Benbow
- Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, Canada
| | - Brian E Cairns
- Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, Canada
| |
Collapse
|
6
|
Shimada A, Alhilou AM, Svensson P, Ernberg M, Christidis N. Functional Change in Experimental Allodynia After Glutamate-Induced Pain in the Human Masseter Muscle. FRONTIERS IN ORAL HEALTH 2020; 1:609082. [PMID: 35047987 PMCID: PMC8757840 DOI: 10.3389/froh.2020.609082] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2020] [Accepted: 10/23/2020] [Indexed: 11/13/2022] Open
Abstract
Background: Glutamate, as well as nerve growth factor (NGF), is involved in nociception from peripheral tissues, such as muscles. However, the potential interaction between glutamate and NGF still remains unclear. This study investigated the interaction between glutamate-induced masseter muscle pain and NGF-induced allodynia on pain perception and jaw function in healthy individuals, and any possible sex differences in the response. Materials and Methods: Thirty pain-free adult participants (15 men and 15 women, mean age ± SD: 24 ± 4 years) participated in this study consisting of three sessions (Day 0, Day 3, and Day 4). NGF (5 μg/mL, 1.0 mL) was injected into the masseter muscle on Day 0 to induce muscle allodynia. On Day 3, glutamate (1M, 0.2 mL) was injected into the same masseter muscle. Before and after injections on Day 0 and 3, and post-injection (Day 4), spontaneous pain, temporal summation pain, as well as functional pain and fatigue in response to chewing were assessed with validated scales, and the pressure pain threshold (PPT) was recorded. Results: Spontaneous pain intensity was significantly higher after glutamate than NGF (P < 0.001). PPTs, temporal summation pain and functional measures were all reduced 3 days after NGF injection (P's < 0.001). Injection of glutamate on Day 3 did not further affect PPTs or temporal summation pain and there were no sex differences in the effects (P > 0.189). Chewing pain (P = 0.022) and fatigue increased after glutamate injection to a higher degree in the women than men (P = 0.037). Conclusion: Taken together, while glutamate injected into the NGF-sensitized muscle was painful, it did not alter muscle tenderness in women vs. men. However, pain and fatigue evoked by jaw function were higher in women after glutamate injection. This suggest that sex differences reported for masseter myalgia, mimicked by glutamate and NGF mediated pain in this study, may be greater for measures of perceived jaw function, which should be considered in a clinical evaluation.
Collapse
Affiliation(s)
- Akiko Shimada
- Department of Geriatric Dentistry, Osaka Dental University, Osaka, Japan
| | - Abdelrahman M Alhilou
- Division of Oral Diagnostics and Rehabilitation, Department of Dental Medicine, Karolinska Institutet, Huddinge, Sweden.,Scandinavian Center for Orofacial Neurosciences (SCON), Huddinge, Sweden.,Department of Restorative Dentistry, College of Dentistry, Umm Al-Qura University, Mecca, Saudi Arabia
| | - Peter Svensson
- Section of Orofacial Pain and Jaw Function, Department of Dentistry and Oral Health, Aarhus University, Aarhus, Denmark.,Faculty of Odontology, Malmö University, Malmö, Sweden
| | - Malin Ernberg
- Division of Oral Diagnostics and Rehabilitation, Department of Dental Medicine, Karolinska Institutet, Huddinge, Sweden.,Scandinavian Center for Orofacial Neurosciences (SCON), Huddinge, Sweden
| | - Nikolaos Christidis
- Division of Oral Diagnostics and Rehabilitation, Department of Dental Medicine, Karolinska Institutet, Huddinge, Sweden.,Scandinavian Center for Orofacial Neurosciences (SCON), Huddinge, Sweden
| |
Collapse
|
7
|
Mai L, Huang F, Zhu X, He H, Fan W. Role of Nerve Growth Factor in Orofacial Pain. J Pain Res 2020; 13:1875-1882. [PMID: 32801845 PMCID: PMC7399448 DOI: 10.2147/jpr.s250030] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2020] [Accepted: 07/06/2020] [Indexed: 12/18/2022] Open
Abstract
Some chronic pain conditions in the orofacial region are common and the mechanisms underlying orofacial pain are unresolved. Nerve growth factor (NGF) is a member of a family of neurotrophins and regulates the growth, maintenance and development of neurons. Increasing evidence suggests that NGF plays a crucial role in the generation of pain and hyperalgesia in different pain states. This review investigates the role of NGF in orofacial pain and their underlying cellular mechanisms, which may provide essential guidance to drug-discovery programmes. A systemic literature search was conducted in Pubmed focusing on NGF and orofacial pain. Articles were reviewed, and those discussing in vitro studies, animal evidence, clinical course, and possible mechanisms were summarized. We found a hyperalgesic effect of NGF in peripheral sensitization in orofacial pain models. We also summarize the current knowledge regarding NGF-dependent pain mechanism, which is initiated by retrograde transport of the ligand-receptor complex, ensuing transcriptional regulation of many important nociceptor genes involved in nociceptive processing. Phase III trials suggest that anti-NGF drug is endorsed with anti-inflammatory and pain-relieving effects with good tolerance in a variety of pain conditions, including pain associated with osteoarthritis and chronic lower back pain. Based on the data reviewed herein, NGF is believed to be an important hyperalgesic mediator in orofacial pain. The identification of underlying mechanisms and pathways of orofacial pain opens new frontiers for pain management.
Collapse
Affiliation(s)
- Lijia Mai
- Department of Anesthesiology, Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-sen University, Guangzhou 510080, People's Republic of China.,Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, 510080, People's Republic of China
| | - Fang Huang
- Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, 510080, People's Republic of China
| | - Xiao Zhu
- The Marine Biomedical Research Institute, Guangdong Medical University, Zhanjiang 524023, People's Republic of China
| | - Hongwen He
- Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, 510080, People's Republic of China
| | - Wenguo Fan
- Department of Anesthesiology, Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-sen University, Guangzhou 510080, People's Republic of China.,Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, 510080, People's Republic of China
| |
Collapse
|
8
|
Wong H, Cairns BE. Cannabidiol, cannabinol and their combinations act as peripheral analgesics in a rat model of myofascial pain. Arch Oral Biol 2019; 104:33-39. [PMID: 31158702 DOI: 10.1016/j.archoralbio.2019.05.028] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Revised: 05/15/2019] [Accepted: 05/27/2019] [Indexed: 11/16/2022]
Abstract
OBJECTIVE This study investigated whether local intramuscular injection of non-psychoactive cannabinoids, cannabidiol (CBD), cannabinol (CBN), cannabichromene (CBC) and their combinations can decrease nerve growth factor (NGF)-induced masticatory muscle sensitization in female rats. DESIGN In awake rats, changes in mechanical sensitivity induced by intramuscular injection of NGF and cannabinoids were measured by applying an electronic von Frey hair over the masseter muscle to measure the withdrawal response. The effect of CBD (5 mg/ml) and CBN (1 mg/ml) or their combinations CBD/CBN (1:1 mg/ml or 5:1 mg/ml) were assessed. To confirm a peripheral action, electrophysiological experiments were undertaken in anesthetized rats to examine whether intramuscular injections of CBD (5 mg/ml) and CBN (1 mg/ml) altered the mechanical threshold of masticatory muscle mechanoreceptors. RESULTS In behavioral experiments, CBD (5 mg/ml) or CBN (1 mg/ml) decreased NGF-induced mechanical sensitization. Combinations of CBD/CBN induced a longer-lasting reduction of mechanical sensitization than either compound alone. No significant change in mechanical withdrawal threshold was observed in the contralateral masseter muscles and no impairment of motor function was found with the inverted screen test after any of the treatments. Consistent with behavioral results, CBD (5 mg/ml), CBN (1 mg/ml) and the combination of CBD/CBN (1:1 mg/ml) increased the mechanical threshold of masseter muscle mechanoreceptors. However, combining CBD/CBN (5:1 mg/ml) at a higher ratio reduced the duration of this effect. This may indicate an inhibitory effect of higher concentrations of CBD on CBN. CONCLUSIONS These results suggest that peripheral application of these non-psychoactive cannabinoids may provide analgesic relief for chronic muscle pain disorders such as temporomandibular disorders and fibromyalgia without central side effects.
Collapse
Affiliation(s)
- Hayes Wong
- Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Brian E Cairns
- Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, BC, Canada.
| |
Collapse
|
9
|
Viatchenko-Karpinski V, Erol F, Ling J, Reed W, Gu JG. Orofacial operant behaviors and electrophysiological properties of trigeminal ganglion neurons following masseter muscle inflammation in rats. Neurosci Lett 2018; 694:208-214. [PMID: 30503926 DOI: 10.1016/j.neulet.2018.11.057] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Revised: 11/27/2018] [Accepted: 11/28/2018] [Indexed: 10/27/2022]
Abstract
Orofacial muscle pain is a significant clinical problem because it affects eating, speaking, and other orofacial functions in patients. However, mechanisms underlying orofacial muscle pain are not fully understood. In the present study we induced orofacial muscle pain by injecting Complete Freund's Adjuvant (CFA) into masseter muscle of rats and assessed pain by the orofacial operant test. In comparison with the control group, CFA-injected animals (CFA group) showed decreases in operant behaviors, suggesting the presence of orofacial pain. Trigeminal ganglion (TG) neurons innervating masseter muscles were retrograde-labeled with DiI and their electrophysiological properties studied using patch-clamp recordings. About 20% of DiI-labeled TG neurons showed spontaneous action potentials (APs) in the CFA group but none in the control group. AP rheobase levels were significantly lower in DiI-labeled TG neurons of the CFA group than in the control group. Membrane input resistance of DiI-labeled TG neurons was significantly higher in the CFA group than in the control group. Several other membrane parameters were also different between DiI-labeled TG neurons of the CFA and control groups. Voltage-dependent currents were examined and the most significant changes following CFA were background K+ currents, which showed significantly smaller in DiI-labeled TG neurons of CFA group compared to the control group. Collectively, orofacial muscle pain in CFA model is accompanied with changes of electrophysiological properties and background K+ currents in TG neurons that innervate masseter muscles.
Collapse
Affiliation(s)
- Viacheslav Viatchenko-Karpinski
- Departments of Anesthesiology and Perioperative Medicine, University of Alabama at Birmingham, Birmingham, AL, 35294, United States
| | - Ferhat Erol
- Departments of Anesthesiology and Perioperative Medicine, University of Alabama at Birmingham, Birmingham, AL, 35294, United States
| | - Jennifer Ling
- Departments of Anesthesiology and Perioperative Medicine, University of Alabama at Birmingham, Birmingham, AL, 35294, United States
| | - William Reed
- Departments of Physical Therapy, University of Alabama at Birmingham, Birmingham, AL, 35294, United States
| | - Jianguo G Gu
- Departments of Anesthesiology and Perioperative Medicine, University of Alabama at Birmingham, Birmingham, AL, 35294, United States.
| |
Collapse
|
10
|
Exposto FG, Masuda M, Castrillon EE, Svensson P. Effects of nerve growth factor experimentally-induced craniofacial muscle sensitization on referred pain frequency and number of headache days: A double-blind, randomized placebo-controlled study. Cephalalgia 2018. [PMID: 29528692 DOI: 10.1177/0333102418758481] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
OBJECTIVE To assess if repeated intramuscular injections of nerve growth factor into the temporalis and masseter muscles increase mechanical sensitivity and entropy scores. Furthermore, to investigate if increased mechanical sensitivity would lead to increased prevalence of referred pain in the studied individuals. Finally, if increased muscle sensitization would lead to an increase in number of headache days during the experimental period. METHODS The present double-blind, randomized placebo-controlled study recruited 16 healthy participants who were injected with nerve growth-factor, on 2 days, into the masseter and temporalis muscles and isotonic saline on the contralateral side. Mechanical sensitivity was assessed at seven different time-points (total of 21 days) by application of three different forces to 15 different sites of both muscles. Participants were asked after each force application if they experienced referred pain and were asked to keep a headache diary during the experimental period. RESULTS In summary, a) repeated intramuscular injections of nerve-growth-factor caused an increase in mechanical sensitivity for the masseter but not the temporalis muscle, and an increase in entropy scores when compared to the isotonic saline side. b) Both referred pain frequency and number of headache days were not increased following nerve-growth-factor injections. CONCLUSIONS These findings support the idea that mechanical sensitization in the masseter and temporalis muscles differs following injections of nerve growth factor. Furthermore, referred pain and headache frequency do not seem to be related to nerve growth factor sensitization in this model. These findings support the idea that in healthy individuals referred pain may be an epiphenomenon of the muscle in response to noxious input.
Collapse
Affiliation(s)
- F G Exposto
- 1 Section of Orofacial Pain and Jaw Function, Department of Dentistry and Oral Health, Health, Aarhus University, Aarhus, Denmark.,2 Scandinavian Center for Orofacial Neurosciences (SCON), Aarhus, Denmark
| | - M Masuda
- 3 Department of Oral Function and Rehabilitation, Nihon University School of Dentistry at Matsudo, Japan
| | - E E Castrillon
- 1 Section of Orofacial Pain and Jaw Function, Department of Dentistry and Oral Health, Health, Aarhus University, Aarhus, Denmark.,2 Scandinavian Center for Orofacial Neurosciences (SCON), Aarhus, Denmark
| | - P Svensson
- 1 Section of Orofacial Pain and Jaw Function, Department of Dentistry and Oral Health, Health, Aarhus University, Aarhus, Denmark.,2 Scandinavian Center for Orofacial Neurosciences (SCON), Aarhus, Denmark.,4 Department of Dental Medicine, Karolinska Institutet, Huddinge, Sweden
| |
Collapse
|
11
|
Wong H, Hossain S, Cairns BE. Delta-9-tetrahydrocannabinol decreases masticatory muscle sensitization in female rats through peripheral cannabinoid receptor activation. Eur J Pain 2017; 21:1732-1742. [DOI: 10.1002/ejp.1085] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/21/2017] [Indexed: 01/09/2023]
Affiliation(s)
- H Wong
- Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, BC, Canada
| | - S Hossain
- InMed Pharmaceuticals Inc., Vancouver, BC, Canada
| | - B E Cairns
- Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, BC, Canada
| |
Collapse
|
12
|
Abstract
This paper examines current knowledge about putative "pro-algesic" dietary components, and discusses whether limiting the intake of these substances can help improve chronic pain. Although there is a common impression that numerous food components, natural and synthetic, can cause or worsen pain symptoms, very few of these substances have been investigated. This article focuses on four substances, monosodium glutamate, aspartame, arachidonic acid, and caffeine, where research shows that overconsumption may induce or worsen pain. For each substance, the mechanism whereby it may act to induce pain is examined, and any clinical trials examining the effectiveness of reducing the intake of the substance discussed. While all four substances are associated with pain, decreased consumption of them does not consistently reduce pain.
Collapse
Affiliation(s)
- Brian Edwin Cairns
- a Faculty of Pharmaceutical Sciences , The University of British Columbia , Vancouver , Canada.,b Center for Neuroplasticity and Pain, SMI, Department of Health Science and Technology, Faculty of Medicine , Aalborg University , Aalborg East , Denmark
| |
Collapse
|