title: Elevated levels of beta-endorphin in temporomandibular joint synovial lavage fluid of patients with closed lock.
abstract: OBJECTIVE
  To investigate the presence of endogenous beta-endorphin, an opioid, in the synovial lavage fluid of the temporomandibular joint (TMJ), and to compare the concentration of 3-endorphin in patients with closed lock with that in symptom-free subjects.
  
  
  METHODS
  Thirty-eight patients (38 joints) with closed lock diagnosed on the basis of the results of clinical examination and magnetic resonance imaging (MRI) and 11 healthy volunteers (19 joints) were examined. Samples of lavage fluid were obtained prior to arthrocentesis by washing the joint with saline. Samples were assayed for beta-endorphin by an enzyme immunoassay, and concentrations of protein were measured by a bicinchoninic acid assay. Subjective pain was assessed by patients using a visual analog scale. Bone changes in the condyle were assessed by MRI, and synovitis was assessed on the basis of arthroscopic findings.
  
  
  RESULTS
  beta-endorphin was present in the synovial fluid of the TMJ, and the concentration was significantly higher in patients with closed lock of the TMJ compared to symptom-free volunteers. The beta-endorphin levels were not, however, significantly correlated with clinical parameters in the patients.
  
  
  CONCLUSIONS
  The study results support recent findings that some opioids and their receptors exist not only within the central nervous system but also in the TMJ region, and that opioid concentrations are higher in patients with pain and dysfunction of the TMJ.
authors.affiliation: Section of Orthodontics, Department of Oral Functional Science, Division of Oral Medical Science, Graduate School of Dental Medicine, Hokkaido University, Kita 13, Nishi 7, Kita-ku Sapporo 060-8586, Japan. kajii@den.hokudai.ac.jp
authors.forename: Takashi S
authors.initials: TS
authors.lastname: Kajii
authors.forename: Toru
authors.initials: T
authors.lastname: Okamoto
authors.forename: Sinya
authors.initials: S
authors.lastname: Yura
authors.forename: Akiko
authors.initials: A
authors.lastname: Mabuchi
authors.forename: Junichiro
authors.initials: J
authors.lastname: Iida
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D005157:Facial Pain / Q000378:metabolism; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D007202:Indicators and Reagents; D004204:Joint Dislocations / Q000378:metabolism; D008297:Male; D008335:Mandibular Condyle / Q000473:pathology; D008875:Middle Aged; D010147:Pain Measurement; D011804:Quinolines; D012737:Sex Factors; D018709:Statistics, Nonparametric; D013582:Synovial Fluid / Q000737:chemistry / Q000378:metabolism*; D013585:Synovitis / Q000378:metabolism; D013705:Temporomandibular Joint Disorders / Q000378:metabolism*; D001615:beta-Endorphin / Q000032:analysis / Q000378:metabolism*
chemical_list: D007202:Indicators and Reagents; D011804:Quinolines; D001615:beta-Endorphin; C047117:bicinchoninic acid