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 whether dopamine dysregulation involving the D-2/D-3 receptor occurs in GTS, we performed single slice dynamic single photon emission computed tomography (SPECT) with (123)iodo-6-methoxybenzamide (I-123-IBZM) in 15 GTS patients (eight unmedicated) and six healthy volunteers. After intravenous administration of 5 mCi (185 MBq) of I-123-IBZM, dynamic SPECT (5 minutes per slice) studies were performed at the level of the basal ganglia for 55 minutes. The mean activity per pixel in the basal ganglia was compared with the mean activity per pixel in the visual cortex. Unmedicated GTS patients showed no differences from control subjects. However, GTS patients taking D-2 blocking medications had significantly decreased I-123-IBZM binding compared with control subjects in both the right and left basal ganglia. Thus, D-2/D-3 receptor availability, as measured by I-123-IBZM SPECT, is not abnormal in GTS.