Abstract
BackgroundDopaminergic pathways could be involved in the pathophysiology of myofascial temporomandibular disorders (M-TMD). This study investigated plasma levels of dopamine and serotonin (5-HT) in patients with M-TMD and in healthy subjects.MethodsFifteen patients with M-TMD and 15 age- and sex-matched healthy subjects participated. The patients had received an M-TMD diagnosis according to the Research Diagnostic Criteria for TMD. Perceived mental stress, pain intensity (0–100-mm visual analogue scale), and pressure pain thresholds (PPT, kPa) over the masseter muscles were assessed; a venous blood sample was taken.ResultsDopamine in plasma differed significantly between patients with M-TMD (4.98 ± 2.55 nM) and healthy controls (2.73 ± 1.24 nM; P < 0.01). No significant difference in plasma 5-HT was observed between the groups (P = 0.75). Patients reported significantly higher pain intensities (P < 0.001) and had lower PPTs (P < 0.01) compared with the healthy controls. Importantly, dopamine in plasma correlated significantly with present pain intensity (r = 0.53, n = 14, P < 0.05) and perceived mental stress (r = 0.34, n = 28, P < 0.05).ConclusionsThe results suggest that peripheral dopamine might be involved in modulating peripheral pain. This finding, in addition to reports in other studies, suggests that dopaminergic pathways could be implicated in the pathophysiology of M-TMD but also in other chronic pain conditions. More research is warranted to elucidate the role of peripheral dopamine in the pathophysiology of chronic pain.
Highlights
Dopaminergic pathways could be involved in the pathophysiology of myofascial temporomandibular disorders (M-TMD)
Pressure pain threshold, and perceived mental stress Patients with M-TMD had significantly higher present pain intensity (P < 0.001; Fig. 2) and perceived mental stress (P < 0.05; Fig. 3) and significantly lower pressure pain threshold (PPT) compared with healthy subjects (P < 0.01; Fig. 2)
PPT, perceived mental stress, and the levels of dopamine in plasma were normally distributed, while 5-HT levels in plasma were normally distributed after Ln-transformation
Summary
Dopaminergic pathways could be involved in the pathophysiology of myofascial temporomandibular disorders (M-TMD). This study investigated plasma levels of dopamine and serotonin (5-HT) in patients with M-TMD and in healthy subjects. Dopamine and 5-hydroxytryptamine (5-HT) are neurotransmitters found in the central (CNS) and peripheral nervous systems, and in plasma. In the CNS, dopamine is involved in motor control, cognition, and the reward system [1], but possibly in pain perception [2]. “a repetitive jaw-muscle activity characterized by clenching or grinding of the teeth and/or by bracing or thrusting the mandible” [4], has been linked to disturbances in the central dopaminergic system [5], as has another motor function disorder, Parkinson’s disease [6]. Aside from motor function-related disturbances, the most self-reported symptom in patients with Parkinson’s disease is pain [7]. The literature indicates that the dopaminergic system may be involved
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