DOPAMINE-RECEPTOR AVAILABILITY IN TOURETTES-SYNDROME

A large body of evidence suggests that abnormal dopaminergic activity is present in Gilles de la Tourette Syndrome (GTS). To investigate whe ther dopamine dysregulation involving the D-2/D-3 receptor occurs in G TS, we performed single slice dynamic single photon emission computed tomography (SPECT) with (123)iodo-6-methoxybenzamide (I-123-IBZM) in 1 5 GTS patients (eight unmedicated) and six healthy volunteers. After i ntravenous administration of 5 mCi (185 MBq) of I-123-IBZM, dynamic SP ECT (5 minutes per slice) studies were performed at the level of the b asal ganglia for 55 minutes. The mean activity per pixel in the basal ganglia was compared with the mean activity per pixel in the visual co rtex. Unmedicated GTS patients showed no differences from control subj ects. However, GTS patients taking D-2 blocking medications had signif icantly decreased I-123-IBZM binding compared with control subjects in both the right and left basal ganglia. Thus, D-2/D-3 receptor availab ility, as measured by I-123-IBZM SPECT, is not abnormal in GTS.