Occlusal disharmonies modulate central catecholaminergic activity in the rat

Occlusal disharmonies have classically been thought to be involved in the e tiopathogenesis of bruxism, as have, more recently, alterations in central neurotransmission, particularly dopaminergic neurotransmission. However, th e connection between these two factors has still not been established. In t his study, we assessed the effects of diverse occlusal disharmonies, mainta ined for either 1 day or 14 days, on neurochemical indices of dopaminergic and noradrenergic activity in the striatum, frontal cortex, and hypothalamu s of the rat. The in vivo activity of tyrosine hydroxylase, determined as t he accumulation of 3,4-dihydroxyphenylalanine (DOPA), 30 min after the admi nistration of 3-hydroxybenzylhydrazine, a DOPA decarboxylase inhibitor, and dopamine and noradrenaline contents were quantified by high-performance li quid chromatography with electrochemical detection. The wearing of an acryl ic cap on both lower incisors for 1 day induced a significant increase in D OPA accumulation in the regions analyzed, with parallel increases in dopami ne levels in the hypothalamus and dopamine and noradrenaline in the frontal cortex. After the cap was maintained for 14 days, DOPA accumulation tended to return to control values, except in the left striatum, thereby causing an imbalance between hemispheres. Ln contrast, 1 or 14 days after the lower left and the upper right incisors were cut, less pronounced changes in cat echolaminergic neurotransmission were found in the brain areas studied. Mor eover, the cutting of one lower incisor did not modify either DOPA accumula tion or dopamine and noradrenaline contents in the striatum or hypothalamus . These results provide experimental evidence of a modulation of central ca techolaminergic neurotransmission by occlusal disharmonies, being dependent on the nature of the incisal alteration and on the time during which it wa s maintained.