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

Abstract

ObjectiveThe 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. DesignMRS 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. ResultsRepeated-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). ConclusionsThese 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.