Striatal dopamine D1 and D2 receptors in burning mouth syndrome

&NA; Animal studies have indicated that the nigrostriatal dopaminergic system is involved in central pain modulation. In a recent positron emission tomography (PET) study, we demonstrated presynaptic dysfunction of the nigrostriatal dopaminergic pathway in burning mouth syndrome, which is a chronic pain state. The objective of the present study was to examine striatal dopamine D1 and D2 receptors in these patients. We used 11C‐NNC 756 and 11C‐raclopride to study D1 and D2 receptor binding in a PET study in ten burning mouth patients and 11 healthy controls. Patients underwent a structured psychiatric evaluation and an electrophysiological test for the excitability of the blink reflex. The striatal uptake of 11C‐NNC 756 did not differ between patients and controls. In a voxel‐level analysis, the uptake of 11C‐raclopride was statistically significantly higher in the left putamen in burning mouth patients (corrected P‐value 0.038 at cluster‐level). In the region of interest analysis, the D1/D2 ratio was 7.7% lower in the right putamen (0.64±0.04 vs. 0.69±0.04, P=0.01) and 6.4 % lower in the left putamen (0.65±0.05 vs. 0.70±0.05, P=0.05) when compared to controls. Increased 11C‐raclopride uptake and the subsequent decrease in the D1/D2 ratio may indicate a decline in endogenous dopamine levels in the putamen in burning mouth patients.