pain.
Arthritis Rheum. 2009 Sep 29;60(10):3146-3152.
Harris RE, Sundgren PC, Craig AD, Kirshenbaum E, Sen A, Napadow V, Clauw DJ.
University of Michigan, Ann Arbor.
OBJECTIVE: Central pain augmentation resulting from enhanced excitatory
and/or decreased inhibitory neurotransmission is a proposed mechanism
underlying the pathophysiology of functional pain syndromes such as
fibromyalgia (FM). Multiple functional magnetic resonance imaging studies
implicate the insula as a region of heightened neuronal activity in this
condition. Since glutamate (Glu) is a major cortical excitatory
neurotransmitter that functions in pain neurotransmission, we undertook this
study to test our hypothesis that increased levels of insular Glu would be
present in FM patients and that the concentration of this molecule would be
correlated with pain report.
METHODS: Nineteen FM patients and 14 age- and sex-matched pain-free controls
underwent pressure pain testing and a proton magnetic resonance spectroscopy
session in which the right anterior insula and right posterior insula were
examined at rest.
RESULTS: Compared with healthy controls, FM patients had significantly
higher levels of Glu (mean +/- SD 8.09 +/- 0.72 arbitrary institutional
units versus 6.86 +/- 1.29 arbitrary institutional units; P = 0.009) and
combined glutamine and Glu (i.e., Glx) (mean +/- SD 12.38 +/- 0.94 arbitrary
institutional units versus 10.59 +/- 1.48 arbitrary institutional units; P =
0.001) within the right posterior insula. No significant differences between
groups were detected in any of the other major metabolites within this
region (P > 0.05 for all comparisons), and no group differences were
detected for any metabolite within the right anterior insula (P > 0.11 for
all comparisons). Within the right posterior insula, higher levels of Glu
and Glx were associated with lower pressure pain thresholds across both
groups for medium pain (for Glu, r = -0.43, P = 0.012; for Glx, r = -0.50, P
= 0.003).
CONCLUSION: Enhanced glutamatergic neurotransmission resulting from higher
concentrations of Glu within the posterior insula may play a role in the
pathophysiology of FM and other central pain augmentation syndromes.
PMID: 19790053 [PubMed - as supplied by publisher]
