title: Increased plasma glutamate, glycine, and arginine levels in complex regional pain syndrome type 1.
abstract: BACKGROUND
  Various inflammatory mediators have been identified as potential contributors to complex regional pain syndrome type 1 (CRPS1), but these mediators do not entirely explain certain manifestations of the syndrome, such as pain. The objective of this study was to investigate the role of amino acids in the pathogenesis of CRPS1.
  
  
  METHODS
  We used HPLC to determine plasma concentrations of 16 amino acids, especially those related to the NMDA receptor (e.g., glutamate and glycine) and nitric oxide (NO) synthesis (e.g., arginine and citrulline) in patients with CRPS1 (n=64) and age- and sex-matched healthy controls (n=51). Patients rated pain intensity (visual analog scale) and the subjective experience of pain intensity (McGill Pain Questionnaire). Psychological dysfunction was assessed using the SCL-90.
  
  
  RESULTS
  Relative to controls, in CRPS1 patients, plasma levels of glutamate, arginine, taurine, and glycine were increased, and plasma levels of glutamine and the ratio of citrulline to arginine were decreased. Remarkably, in CRPS1 patients there was a highly significant inverse correlation between glutamine and glutamate, although the sum of molar concentrations of glutamate and glutamine remains unchanged. Subjective measures of pain and indicators of psychoneuroticism and emotional instability did not correlate with amino acid levels.
  
  
  CONCLUSIONS
  This study shows for the first time a pronounced increase in amino acid levels in this chronic pain syndrome. The marked differences in glutamate, glutamine, glycine, taurine and arginine levels between patients and controls suggest the involvement of both the NDMA receptor and the endothelium-dependent arginine-NO system in CRPS1.
authors.affiliation: Department of Anesthesiology, Erasmus MC, Rotterdam, The Netherlands.
authors.forename: F
authors.initials: F
authors.lastname: Wesseldijk
authors.forename: D
authors.initials: D
authors.lastname: Fekkes
authors.forename: F J P M
authors.initials: FJ
authors.lastname: Huygen
authors.forename: M
authors.initials: M
authors.lastname: van de Heide-Mulder
authors.forename: F J
authors.initials: FJ
authors.lastname: Zijlstra
mesh_terms: D000596:Amino Acids / Q000097:blood*; D002853:Chromatography, Liquid / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D010147:Pain Measurement / Q000379:methods; D011788:Quality of Life; D012019:Reflex Sympathetic Dystrophy / Q000097:blood* / Q000523:psychology; D018709:Statistics, Nonparametric; D013654:Taurine / Q000097:blood
chemical_list: D000596:Amino Acids; D013654:Taurine