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

A dopamine deficiency has been implicated in Rett syndrome, a progressive encephalopathy in girls that involves movement, tonus and cognitive disorders. To test the hypothesis that striatal D2 receptors increase in number in early stages of the disease, we measured the binding potential of I-123-lodolisuride, a specific D2 ligand, in eleven Rett children 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 neurological disorders. Regional cerebral blood flow (rCBF) was also measured with SPECT using Xe-133. The binding potential for I-123-ILIS and D2 receptors 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 higher density of D2 receptors in young patients suffering from Rett syndrome because of reduced dopaminergic neurotransmission.