title: Chronic widespread pain: increased glutamate and lactate concentrations in the trapezius muscle and plasma.
abstract: BACKGROUND
  Chronic widespread pain (CWP), including fibromyalgia syndrome (FM), is associated with prominent negative consequences. CWP has been associated with alterations in the central processing of nociception. Whereas some researchers consider CWP/FM as a central hyperexcitability pain condition, others suggest that the central alterations are maintained by peripheral nociceptive input. Microdialysis can be used in vivo to study muscle alterations in chronic myalgia.
  
  
  OBJECTIVE
  : The aim of the study was to investigate the plasma and interstitial concentrations of metabolites and algesics in the trapezius muscle of women with CWP and in pain-free women (CON).
  
  
  METHODS
  Seventeen women with CWP and 24 CON went through a clinical examination and completed a questionnaire; the pressure pain thresholds in the upper and lower extremities were registered. Microdialysis was conducted in the trapezius muscle, and a blood sample was drawn. Muscle blood flow, interstitial muscle concentrations, and plasma concentrations of lactate, pyruvate, glutamate, glucose, and glycerol (not in the plasma) were determined.
  
  
  RESULTS
  CWP patients had significantly increased interstitial muscle (P=0.02 to 0.001) and plasma (P=0.026 to 0.017) concentrations of lactate and glutamate. No significant differences existed in blood flow between CWP and CON. The interstitial concentrations-but not the plasma levels-of glutamate and lactate correlated significantly with aspects of pain such as pressure pain thresholds of the trapezius (R=0.22) and tibialis anterior (R=0.18) and the mean pain intensity (R=0.10) in CWP but not in CON.
  
  
  CONCLUSIONS
  The present study supports the suggestion that aspects of pain and central alterations in CWP/FM are influenced by peripheral tissue alterations.
authors.affiliation: *Rehabilitation Medicine, Department of Medicine and Health Sciences (IMH) ‡Occupational and Environmental Medicine, Department of Clinical and Experimental Medicine (IKE), Faculty of Health Sciences, University of Linköping †Pain and Rehabilitation Centre §Centre of Occupational and Environmental Medicine, UHL, County Council, Linköping, Sweden.
authors.forename: Björn
authors.initials: B
authors.lastname: Gerdle
authors.forename: Britt
authors.initials: B
authors.lastname: Larsson
authors.forename: Frida
authors.initials: F
authors.lastname: Forsberg
authors.forename: Nazdar
authors.initials: N
authors.lastname: Ghafouri
authors.forename: Linn
authors.initials: L
authors.lastname: Karlsson
authors.forename: Niclas
authors.initials: N
authors.lastname: Stensson
authors.forename: Bijar
authors.initials: B
authors.lastname: Ghafouri
mesh_terms: D000328:Adult; D002247:Carbon Isotopes; D058443:Catastrophization; D059350:Chronic Pain / Q000097:blood* / Q000473:pathology* / Q000503:physiopathology / Q000523:psychology; D005260:Female; D018698:Glutamic Acid / Q000378:metabolism*; D006304:Health Status; D006801:Humans; D019344:Lactic Acid / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D018482:Muscle, Skeletal / Q000378:metabolism*; D017288:Pain Threshold / Q000502:physiology; D011788:Quality of Life; D012044:Regression Analysis; D011795:Surveys and Questionnaires
chemical_list: D002247:Carbon Isotopes; D019344:Lactic Acid; D018698:Glutamic Acid