title: Dopamine in plasma - a biomarker for myofascial TMD pain?
abstract: BACKGROUND
  Dopaminergic pathways could be involved in the pathophysiology of myofascial temporomandibular disorders (M-TMD). This study investigated plasma levels of dopamine and serotonin (5-HT) in patients with M-TMD and in healthy subjects.
  
  
  METHODS
  Fifteen patients with M-TMD and 15 age- and sex-matched healthy subjects participated. The patients had received an M-TMD diagnosis according to the Research Diagnostic Criteria for TMD. Perceived mental stress, pain intensity (0-100-mm visual analogue scale), and pressure pain thresholds (PPT, kPa) over the masseter muscles were assessed; a venous blood sample was taken.
  
  
  RESULTS
  Dopamine in plasma differed significantly between patients with M-TMD (4.98 ± 2.55 nM) and healthy controls (2.73 ± 1.24 nM; P < 0.01). No significant difference in plasma 5-HT was observed between the groups (P = 0.75). Patients reported significantly higher pain intensities (P < 0.001) and had lower PPTs (P < 0.01) compared with the healthy controls. Importantly, dopamine in plasma correlated significantly with present pain intensity (r = 0.53, n = 14, P < 0.05) and perceived mental stress (r = 0.34, n = 28, P < 0.05).
  
  
  CONCLUSIONS
  The results suggest that peripheral dopamine might be involved in modulating peripheral pain. This finding, in addition to reports in other studies, suggests that dopaminergic pathways could be implicated in the pathophysiology of M-TMD but also in other chronic pain conditions. More research is warranted to elucidate the role of peripheral dopamine in the pathophysiology of chronic pain.
authors.affiliation: Center for Oral Rehabilitation, Östergötland County Council, Linköping, Sweden. andreas.dawson@regionostergotland.se.|Department of Orofacial Pain and Jaw Function, Faculty of Odontology, Malmö University, Malmö, Sweden. andreas.dawson@regionostergotland.se.|Department of Dental Medicine, Karolinska Institutet, Huddinge, Sweden; Faculty of Odontology Malmö University, Malmö Sweden; Department of Dentistry, Aarhus University, Aarhus, Denmark. andreas.dawson@regionostergotland.se.
authors.forename: Andreas
authors.initials: A
authors.lastname: Dawson
authors.affiliation: Rehabilitation Medicine, Department of Medicine and Health Sciences, Faculty of Health Sciences, Linköping University and Pain and Rehabilitation Centre, Östergötland County Council, Linköping, Sweden.
authors.forename: Niclas
authors.initials: N
authors.lastname: Stensson
authors.affiliation: Rehabilitation Medicine, Department of Medicine and Health Sciences, Faculty of Health Sciences, Linköping University and Pain and Rehabilitation Centre, Östergötland County Council, Linköping, Sweden.|Occupational and Environmental Medicine, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University and Centre of Occupational and Environmental Medicine, Östergötland County Council, Linköping, Sweden.
authors.forename: Bijar
authors.initials: B
authors.lastname: Ghafouri
authors.affiliation: Rehabilitation Medicine, Department of Medicine and Health Sciences, Faculty of Health Sciences, Linköping University and Pain and Rehabilitation Centre, Östergötland County Council, Linköping, Sweden.
authors.forename: Björn
authors.initials: B
authors.lastname: Gerdle
authors.affiliation: Department of Orofacial Pain and Jaw Function, Faculty of Odontology, Malmö University, Malmö, Sweden.|Department of Rehabilitation Medicine, Skåne University Hospital, Lund, Sweden.|Department of Dental Medicine, Karolinska Institutet, Huddinge, Sweden; Faculty of Odontology Malmö University, Malmö Sweden; Department of Dentistry, Aarhus University, Aarhus, Denmark.
authors.forename: Thomas
authors.initials: T
authors.lastname: List
authors.affiliation: Section of Clinical Oral Physiology, Department of Dentistry, Aarhus University, Aarhus, Denmark.|Center for Functionally Integrative Neuroscience (CFIN), MindLab, Aarhus University Hospital, Aarhus, Denmark.|Section of Orofacial Pain and Jaw Function, Department of Dental Medicine, Karolinska Institutet, Huddinge, Sweden.|Department of Dental Medicine, Karolinska Institutet, Huddinge, Sweden; Faculty of Odontology Malmö University, Malmö Sweden; Department of Dentistry, Aarhus University, Aarhus, Denmark.
authors.forename: Peter
authors.initials: P
authors.lastname: Svensson
authors.affiliation: Section of Orofacial Pain and Jaw Function, Department of Dental Medicine, Karolinska Institutet, Huddinge, Sweden.|Department of Dental Medicine, Karolinska Institutet, Huddinge, Sweden; Faculty of Odontology Malmö University, Malmö Sweden; Department of Dentistry, Aarhus University, Aarhus, Denmark.
authors.forename: Malin
authors.initials: M
authors.lastname: Ernberg
mesh_terms: D000293:Adolescent; D000328:Adult; D015415:Biomarkers / Q000097:blood; D004298:Dopamine / Q000097:blood*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010146:Pain / Q000097:blood* / Q000175:diagnosis*; D010147:Pain Measurement / Q000379:methods; D017288:Pain Threshold / Q000502:physiology; D013706:Temporomandibular Joint Dysfunction Syndrome / Q000097:blood* / Q000175:diagnosis*; D055815:Young Adult
chemical_list: D015415:Biomarkers; D004298:Dopamine
keywords: 5-HT; Bruxism; Dopamine; Masseter muscle; Temporomandibular joint disorders