STRIATAL D2 RECEPTORS IN SYMPTOMATIC AND ASYMPTOMATIC CARRIERS OF DOPA-RESPONSIVE DYSTONIA MEASURED WITH [C-11] RACLOPRIDE AND POSITRON-EMISSION-TOMOGRAPHY

We tested the hypothesis that asymptomatic carriers of dopa-responsive dystonia (DRD) have increased dopamine D2 receptors in the striatum t hat protect them from the clinical manifestations of dopaminergic defi ciency. We examined striatal D2-receptor binding in (1) symptomatic su bjects (treated and untreated) and (2) asymptomatic gene carriers. Usi ng [C-11]-raclopride PET, we found elevated striatal D2-receptor bindi ng in both groups In one of our drug-naive symptomatic subjects, 7 mon ths of treatment with levodopa/carbidopa did not affect the receptor b inding as measured on a second scan. We conclude that increased D2-rec eptor binding in DRD may be a homeostatic response to the dopaminergic deficit in subjects carrying the DRD gene, but is not the sole factor determining the clinical state of these individuals.