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Mo SY, Xue Y, Li Y, Zhang YJ, Xu XX, Fu KY, Sessle BJ, Xie QF, Cao Y. Descending serotonergic modulation from rostral ventromedial medulla to spinal trigeminal nucleus is involved in experimental occlusal interference-induced chronic orofacial hyperalgesia. J Headache Pain 2023; 24:50. [PMID: 37165344 PMCID: PMC10173589 DOI: 10.1186/s10194-023-01584-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Accepted: 04/21/2023] [Indexed: 05/12/2023] Open
Abstract
BACKGROUND Dental treatment associated with unadaptable occlusal alteration can cause chronic primary myofascial orofacial pain. The serotonin (5-HT) pathway from the rostral ventromedial medulla (RVM) exerts descending modulation on nociceptive transmission in the spinal trigeminal nucleus (Sp5) and facilitates chronic pain. The aim of this study was to investigate whether descending 5-HT modulation from the RVM to the Sp5 is involved in the maintenance of primary myofascial orofacial hyperalgesia after persistent experimental occlusal interference (PEOI) or after delayed removal of experimental occlusal interference (REOI). METHODS Expressions of 5-HT3A and 5-HT3B receptor subtypes in the Sp5 were assessed by immunofluorescence staining and Western blotting. The release and metabolism of 5-HT in the Sp5 were measured by high-performance liquid chromatography. Changes in the pain behavior of these rats were examined after specific pharmacologic antagonism of the 5-HT3 receptor, chemogenetic manipulation of the RVM 5-HT neurons, or selective down-regulation of 5-HT synthesis in the RVM. RESULTS Upregulation of the 5-HT3B receptor subtype in the Sp5 was found in REOI and PEOI rats. The concentration of 5-HT in Sp5 increased significantly only in REOI rats. Intrathecal administration of Y-25130 (a selective 5-HT3 receptor antagonist) dose-dependently reversed the hyperalgesia in REOI rats but only transiently reversed the hyperalgesia in PEOI rats. Chemogenetic inhibition of the RVM 5-HT neurons reversed the hyperalgesia in REOI rats; selective down-regulation of 5-HT in advance also prevented the development of hyperalgesia in REOI rats; the above two manipulations did not affect the hyperalgesia in PEOI rats. However, chemogenetic activation of the RVM 5-HT neurons exacerbated the hyperalgesia both in REOI and PEOI rats. CONCLUSIONS These results provide several lines of evidence that the descending pathway from 5-HT neurons in the RVM to 5-HT3 receptors in the Sp5, plays an important role in facilitating the maintained orofacial hyperalgesia after delayed EOI removal, but has a limited role in that after persistent EOI.
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Affiliation(s)
- Si-Yi Mo
- Department of Prosthodontics, Center for Oral and Jaw Functional Diagnosis, Treatment and Research, School and Hospital of Stomatology, Peking University, No.22, Zhongguancun South Avenue, Haidian District, Beijing, 100081, PR China
- National Center of Stomatology & National Clinical Research Center for Oral Diseases & National Engineering Laboratory for Digital and Material Technology of Stomatology & Beijing Key Laboratory of Digital Stomatology & Research Center of Engineering and Technology for Computerized Dentistry Ministry of Health & NMPA Key Laboratory for Dental Materials, Beijing, 100081, PR China
| | - Yang Xue
- Department of Prosthodontics, Center for Oral and Jaw Functional Diagnosis, Treatment and Research, School and Hospital of Stomatology, Peking University, No.22, Zhongguancun South Avenue, Haidian District, Beijing, 100081, PR China
- National Center of Stomatology & National Clinical Research Center for Oral Diseases & National Engineering Laboratory for Digital and Material Technology of Stomatology & Beijing Key Laboratory of Digital Stomatology & Research Center of Engineering and Technology for Computerized Dentistry Ministry of Health & NMPA Key Laboratory for Dental Materials, Beijing, 100081, PR China
| | - Yuan Li
- Department of Prosthodontics, Center for Oral and Jaw Functional Diagnosis, Treatment and Research, School and Hospital of Stomatology, Peking University, No.22, Zhongguancun South Avenue, Haidian District, Beijing, 100081, PR China
- National Center of Stomatology & National Clinical Research Center for Oral Diseases & National Engineering Laboratory for Digital and Material Technology of Stomatology & Beijing Key Laboratory of Digital Stomatology & Research Center of Engineering and Technology for Computerized Dentistry Ministry of Health & NMPA Key Laboratory for Dental Materials, Beijing, 100081, PR China
| | - Yao-Jun Zhang
- Department of Prosthodontics, Center for Oral and Jaw Functional Diagnosis, Treatment and Research, School and Hospital of Stomatology, Peking University, No.22, Zhongguancun South Avenue, Haidian District, Beijing, 100081, PR China
- National Center of Stomatology & National Clinical Research Center for Oral Diseases & National Engineering Laboratory for Digital and Material Technology of Stomatology & Beijing Key Laboratory of Digital Stomatology & Research Center of Engineering and Technology for Computerized Dentistry Ministry of Health & NMPA Key Laboratory for Dental Materials, Beijing, 100081, PR China
| | - Xiao-Xiang Xu
- Department of Prosthodontics, Center for Oral and Jaw Functional Diagnosis, Treatment and Research, School and Hospital of Stomatology, Peking University, No.22, Zhongguancun South Avenue, Haidian District, Beijing, 100081, PR China.
- National Center of Stomatology & National Clinical Research Center for Oral Diseases & National Engineering Laboratory for Digital and Material Technology of Stomatology & Beijing Key Laboratory of Digital Stomatology & Research Center of Engineering and Technology for Computerized Dentistry Ministry of Health & NMPA Key Laboratory for Dental Materials, Beijing, 100081, PR China.
| | - Kai-Yuan Fu
- National Center of Stomatology & National Clinical Research Center for Oral Diseases & National Engineering Laboratory for Digital and Material Technology of Stomatology & Beijing Key Laboratory of Digital Stomatology & Research Center of Engineering and Technology for Computerized Dentistry Ministry of Health & NMPA Key Laboratory for Dental Materials, Beijing, 100081, PR China
- Center for Temporomandibular Disorders and Orofacial Pain, School and Hospital of Stomatology, Peking University, Beijing, 100081, PR China
| | - Barry J Sessle
- Faculty of Dentistry & Department of Physiology, Temerty Faculty of Medicine & Centre for the Study of Pain, University of Toronto, Toronto, ON, M5G 1G6, Canada
| | - Qiu-Fei Xie
- Department of Prosthodontics, Center for Oral and Jaw Functional Diagnosis, Treatment and Research, School and Hospital of Stomatology, Peking University, No.22, Zhongguancun South Avenue, Haidian District, Beijing, 100081, PR China
- National Center of Stomatology & National Clinical Research Center for Oral Diseases & National Engineering Laboratory for Digital and Material Technology of Stomatology & Beijing Key Laboratory of Digital Stomatology & Research Center of Engineering and Technology for Computerized Dentistry Ministry of Health & NMPA Key Laboratory for Dental Materials, Beijing, 100081, PR China
| | - Ye Cao
- Department of Prosthodontics, Center for Oral and Jaw Functional Diagnosis, Treatment and Research, School and Hospital of Stomatology, Peking University, No.22, Zhongguancun South Avenue, Haidian District, Beijing, 100081, PR China.
- National Center of Stomatology & National Clinical Research Center for Oral Diseases & National Engineering Laboratory for Digital and Material Technology of Stomatology & Beijing Key Laboratory of Digital Stomatology & Research Center of Engineering and Technology for Computerized Dentistry Ministry of Health & NMPA Key Laboratory for Dental Materials, Beijing, 100081, PR China.
- Key Laboratory for Neuroscience, Ministry of Education/National Health Commission of the People's Republic of China, Peking University, Beijing, 100083, PR China.
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Makar D, Nazemi A, Gong SG, Bhardwaj N, De Guzman R, Sessle BJ, Cioffi I. Development of a model to investigate the effects of prolonged ischaemia on the muscles of mastication of male Sprague Dawley rats. Arch Oral Biol 2023; 146:105602. [PMID: 36543038 DOI: 10.1016/j.archoralbio.2022.105602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Revised: 12/02/2022] [Accepted: 12/04/2022] [Indexed: 12/12/2022]
Abstract
OBJECTIVE The aims of this study were to develop a novel rodent model of masticatory muscle ischaemia via unilateral ligation of the external carotid artery (ECA), and to undertake a preliminary investigation to characterize its downstream effects on mechanosensitivity and cellular features of the masseter and temporalis muscles. DESIGN The right ECA of 18 male Sprague-Dawley rats was ligated under general anaesthesia. Mechanical detection thresholds (MDTs) at the masseter and temporalis bilaterally were measured immediately before ECA ligation and after euthanasia at 10-, 20-, and 35-days (n = 6 rats/timepoint). Tissue samples from both muscles and sides were harvested for histological analyses and for assessing changes in the expression of markers of hypoxia and muscle degeneration (Hif-1α, VegfA, and Fbxo32) via real time PCR. Data were analyzed using mixed effect models and non-parametric tests. Statistical significance was set at p < 0.05. RESULTS MDTs were higher in the right than left hemiface (p = 0.009) after 20 days. Histological changes indicative of muscle degeneration and fibrosis were observed in the right muscles. Hif-1α, VegfA, and Fbxo32 were more highly expressed in the masseter than temporalis muscles (all p < 0.05). Hif-1α and, VegfA did not change significantly with time in all muscles (all p > 0.05). Fbxo32 expression gradually increased in the right masseter (p = 0.024) and left temporalis (p = 0.05). CONCLUSIONS ECA ligation in rats induced hyposensitivity in the homolateral hemiface after 20 days accompanied by tissue degenerative changes. Our findings support the use of this model to study pathophysiologic mechanisms of masticatory muscle ischaemia in larger investigations.
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Affiliation(s)
- D Makar
- University of Toronto, Faculty of Dentistry, Centre for Multimodal Sensorimotor and Pain Research, Toronto, ON, Canada; University of Toronto, Faculty of Dentistry, Graduate Orthodontics, Toronto, ON, Canada
| | - A Nazemi
- University of Toronto, Faculty of Dentistry, Centre for Multimodal Sensorimotor and Pain Research, Toronto, ON, Canada
| | - S G Gong
- University of Toronto, Faculty of Dentistry, Graduate Orthodontics, Toronto, ON, Canada
| | - N Bhardwaj
- University of Toronto, Faculty of Medicine, Department of Comparative Medicine, Toronto, ON, Canada; Peter Gilgan Centre for Research and Learning, Sickkids Hospital, Toronto, ON, Canada
| | - R De Guzman
- University of Toronto, Faculty of Medicine, Department of Comparative Medicine, Toronto, ON, Canada
| | - B J Sessle
- University of Toronto, Faculty of Dentistry, Toronto, ON, Canada; University of Toronto, Faculty of Medicine, Department of Physiology, Toronto, ON, Canada
| | - I Cioffi
- University of Toronto, Faculty of Dentistry, Centre for Multimodal Sensorimotor and Pain Research, Toronto, ON, Canada; Mount Sinai Hospital, Department of Dentistry, Toronto, ON, Canada; University of Toronto, Faculty of Dentistry, Graduate Orthodontics, Toronto, ON, Canada.
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Boorman DC, Keay KA. Sex differences in morphine sensitivity are associated with differential glial expression in the brainstem of rats with neuropathic pain. J Neurosci Res 2022; 100:1890-1907. [PMID: 35853016 PMCID: PMC9543783 DOI: 10.1002/jnr.25103] [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: 03/15/2022] [Revised: 06/20/2022] [Accepted: 06/22/2022] [Indexed: 11/11/2022]
Abstract
Chronic pain is more prevalent and reported to be more severe in women. Opioid analgesics are less effective in women and result in stronger nauseant effects. The neurobiological mechanisms underlying these sex differences have yet to be clearly defined, though recent research has suggested neuronal–glial interactions are likely involved. We have previously shown that similar to people, morphine is less effective at reducing pain behaviors in female rats. In this study, we used the immunohistochemical detection of glial fibrillary acidic protein (GFAP) expression to investigate sex differences in astrocyte density and morphology in six medullary regions known to be modulated by pain and/or opioids. Morphine administration had small sex‐dependent effects on overall GFAP expression, but not on astrocyte morphology, in the rostral ventromedial medulla, the subnucleus reticularis dorsalis, and the area postrema. Significant sex differences in the density and morphology of GFAP immunopositive astrocytes were detected in all six regions. In general, GFAP‐positive cells in females showed smaller volumes and reduced complexity than those observed in males. Furthermore, females showed lower overall GFAP expression in all regions except for the area postrema, the critical medullary region responsible for opioid‐induced nausea and emesis. These data support the possibility that differences in astrocyte activity might underlie the sex differences seen in the processing of opioids in the context of chronic neuropathic pain.
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Affiliation(s)
- Damien C. Boorman
- School of Medical Sciences and the Brain and Mind Centre The University of Sydney Camperdown New South Wales Australia
| | - Kevin A. Keay
- School of Medical Sciences and the Brain and Mind Centre The University of Sydney Camperdown New South Wales Australia
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Cao Y. Occlusal disharmony and chronic oro-facial pain: from clinical observation to animal study. J Oral Rehabil 2021; 49:116-124. [PMID: 34333797 DOI: 10.1111/joor.13236] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Revised: 06/24/2021] [Accepted: 07/17/2021] [Indexed: 12/21/2022]
Abstract
BACKGROUND Occlusion can be viewed as the most sensitive susceptor of the central nervous system in the oro-facial region. Its inalienable relationships to the temporomandibular joint, the muscles, the stomatognathic system and even the central nervous system are self-evident. Almost all the dental treatments inevitably change the occlusion, potentially or actually, locally or extensively, and immediately or gradually. OBJECTIVE The objective of this study was to present a narrative literature on occlusal disharmony and chronic oro-facial pain. METHODS Literature reviews focusing on clinical studies about the relationship between occlusal disharmony and myofascial oro-facial pain, and related preclinical studies about the animal models of, as well as the peripheral and central mechanisms underlying this condition related to, occlusal disharmony were used as starting point and guidelines to describe the topics mentioned. A search of the PubMed database was performed mainly with the following search terms: "occlusion," "occlusal interference," "occlusal disharmony," "occlusal change," "oro-facial pain" and "myofascial pain." RESULTS Relevant literature from the past 70 years until the present day was meticulously studied. The literature review together with three related characteristic clinical cases revealed an intimate association between occlusal disharmony and chronic oro-facial pain, involving pathological changes, extending from the peripheral tissues to the central nervous system. The patients suffered from psychological distress, sleep disturbance and poor life quality. CONCLUSION Occlusal disharmony-related oro-facial pain is a clinical problem that deserves attention, although there are no universally accepted clinical protocols. The existing literature provides some constructive suggestions, but further research is needed.
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Affiliation(s)
- Ye Cao
- Department of Prosthodontics, Center for Oral and Jaw Functional Diagnosis, Treatment and Research, Peking University School and Hospital of Stomatology, Beijing, China.,Center for TMD & Orofacial Pain, Peking University School and Hospital of Stomatology, Beijing, China.,National Clinical Research Center for Oral Diseases, National Engineering Laboratory for Digital and Material Technology of Stomatology, Beijing Key Laboratory of Digital Stomatology, Beijing, China
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