GABA and glutamate levels in occlusal splint-wearing males with possible bruxism

Abstract

Objective: The inhibitory neurotransmitter γ-aminobutyric acid (GABA) plays an important role in the pathophysiology of anxiety behavioural disorders such as panic disorder and post-traumatic stress disorder and is also implicated in the manifestation of tooth-grinding and clenching behaviours generally known as bruxism. In order to test whether the stress-related behaviours of tooth-grinding and clenching share similar underlying mechanisms involving GABA and other metabolites as do anxiety-related behavioural disorders, we performed a Magnetic Resonance Spectroscopy (MRS) study for accurate, in vivo metabolite quantification in anxiety-related brain regions.

Design: MRS was performed in the right hippocampus and right thalamus involved in the hypothalamic-pituitary-adrenal axis system, together with a motor planning region (dorsal anterior cingulate cortex/pre-supplementary motor area) and right dorsolateral prefrontal cortex (DLPFC). Eight occlusal splint-wearing men (OCS) with possible tooth-grinding and clenching behaviours and nine male controls (CON) with no such behaviour were studied.

Results: Repeated-measures ANOVA showed significant Group×Region interaction for GABA+ (p = 0.001) and glutamate (Glu) (p = 0.031). Between-group post hoc ANOVA showed significantly lower levels of GABA+ (p = 0.003) and higher levels of Glu (p = 0.002) in DLPFC of OCS subjects. These GABA+ and Glu group differences remained significant (GABA+, p = 0.049; Glu, p = 0.039) after the inclusion of anxiety as a covariate. Additionally, GABA and Glu levels in the DLPFC of all subjects were negatively related (Pearson's r = -0.75, p = 0.003).

Conclusions: These findings indicate that the oral behaviours of tooth-grinding and clenching, generally known as bruxism, may be associated with disturbances in brain GABAergic and glutamatergic systems.

Keywords: Anxiety; Bruxism; GABA; MRS; Metabolites; Pathophysiology.

Copyright © 2015 Elsevier Ltd. All rights reserved.

Figures

Figure 1

Sagittal and axial views showing representative VOI placement in the thalamus, hippocampus, DLPFC and dACC/preSMA (left column) and the respective short TE single voxel 1H PRESS spectra (middle column) and MEGA-PRESS GABA spectra (right column). The GABA+ peak at 3 ppm is very prominent for all four regions of interest. VOI = Volume Of Interest.

Figure 2

In the DLPFC, a significant negative correlation (Pearson coefficient=−0.754, p=0.003) is present between GABA+ and Glu concentrations.

Figure 3

In the hippocampus, a significant positive correlation (Pearson coefficient=0.783, p=0.004) is present between GABA+ and Glu concentrations.