Objective: Recent scientific findings have re-invigorated interest in examining the role of gamma-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 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 3 Tesla proton magnetic resonance spectroscopy session in which the right anterior insula, right posterior insula, anterior cingulate and occipital cortex were examined at rest.
Compared with healthy controls, FM patients had significantly lower levels of GABA in the right anterior insula (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 versus 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 for the FM patients (rho=0.63; p=0.02).
Conclusion: 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.
Source: Arthritis & Rheumatism, Sep 13, 2011. PMID: 21913179, by Foerster BR, Petrou M, Edden RA, Phd PC, Schmidt-Wilcke T, Lowe SE, Phd SE, Clauw DJ, Harris RE. Department of Radiology, Division of Neuroradiology, University of Michigan, Ann Arbor; Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland; Ann Arbor VA Healthcare System, Ann Arbor, Michigan. [Email: firstname.lastname@example.org]