DOPAMINERGIC D2 RECEPTOR SPECT IMAGING IN RETT-SYNDROME - INCREASE OFSPECIFIC BINDING IN STRIATUM

A dopamine deficiency has been implicated in Rett syndrome, a progress ive encephalopathy in girls that involves movement, tonus and cognitiv e disorders. To test the hypothesis that striatal D2 receptors increas e in number in early stages of the disease, we measured the binding po tential of I-123-lodolisuride, a specific D2 ligand, in eleven Rett ch ildren aged 4-15 yr (7.9 +/- 3.5 yr) (mean +/- s.d.) and eight control subjects aged 3.5-13 yr (8.1 +/-3.8 yr) who exhibited other neurologi cal disorders. Regional cerebral blood flow (rCBF) was also measured w ith SPECT using Xe-133. The binding potential for I-123-ILIS and D2 re ceptors was significantly higher in Rett (0.45) than in controls (0.23 ) (p < 0.01). An increase in I-123-ILIS binding due to increased rCBF in patents' striata was excluded. Our results are consistent with a hi gher density of D2 receptors in young patients suffering from Rett syn drome because of reduced dopaminergic neurotransmission.