title: Reduced insular γ-aminobutyric acid in fibromyalgia.
abstract: OBJECTIVE
  Recent scientific findings have reinvigorated interest in examining the role of γ-aminobutyric acid (GABA), the major inhibitory central nervous system neurotransmitter, in chronic pain conditions. Decreased inhibitory neurotransmission is a proposed mechanism in the pathophysiology of chronic pain syndromes such as fibromyalgia (FM). The purpose of this study was to test the hypothesis that decreased levels of insular and anterior cingulate GABA would be present in FM patients, and that the concentration of this neurotransmitter would be correlated with pressure-pain thresholds.
  
  
  METHODS
  Sixteen FM patients and 17 age- and sex-matched healthy controls underwent pressure-pain testing and a 3T proton magnetic resonance spectroscopy session in which the right anterior insula, right posterior insula, anterior cingulate, and occipital cortex were examined in subjects at rest.
  
  
  RESULTS
  GABA levels in the right anterior insula were significantly lower in FM patients compared with healthy controls (mean ± SD 1.17 ± 0.24 arbitrary institutional units versus 1.42 ± 0.32 arbitrary institutional units; P = 0.016). There was a trend toward increased GABA levels in the anterior cingulate of FM patients compared with healthy controls (P = 0.06). No significant differences between groups were detected in the posterior insula or occipital cortex (P > 0.05 for all comparisons). Within the right posterior insula, higher levels of GABA were positively correlated with pressure-pain thresholds in the FM patients (Spearman's rho = 0.63; P = 0.02).
  
  
  CONCLUSIONS
  Diminished inhibitory neurotransmission resulting from lower concentrations of GABA within the right anterior insula may play a role in the pathophysiology of FM and other central pain syndromes.
authors.affiliation: University of Michigan and Ann Arbor VA Healthcare System, Ann Arbor, Michigan, USA. compfun@umich.edu
authors.forename: Bradley R
authors.initials: BR
authors.lastname: Foerster
authors.forename: Myria
authors.initials: M
authors.lastname: Petrou
authors.forename: Richard A E
authors.initials: RA
authors.lastname: Edden
authors.forename: Pia C
authors.initials: PC
authors.lastname: Sundgren
authors.forename: Tobias
authors.initials: T
authors.lastname: Schmidt-Wilcke
authors.forename: Suzan E
authors.initials: SE
authors.lastname: Lowe
authors.forename: Steven E
authors.initials: SE
authors.lastname: Harte
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Clauw
authors.forename: Richard E
authors.initials: RE
authors.lastname: Harris
mesh_terms: D000328:Adult; D002540:Cerebral Cortex / Q000378:metabolism*; D005260:Female; D005356:Fibromyalgia / Q000378:metabolism*; D006179:Gyrus Cinguli / Q000378:metabolism; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008875:Middle Aged; D009778:Occipital Lobe / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D005680:gamma-Aminobutyric Acid