Striatal D1 and D2 dopamine receptor loss in asymptomatic mutation carriers of Huntington's disease.

We have investigated striatal dopamine D1 and D2 receptor binding in asymptomatic subjects from Huntington's disease (HD) families using positron emission tomography. Nineteen adult subjects at risk of developing HD were scanned with 11C-SCH 23390 and 11C-raclopride to calculate the D1 and D2 receptor binding potential, respectively. Eight of the 19 were shown to have the HD mutation; of these, 4 subjects had significant reductions in striatal dopamine receptor binding. Abnormalities were more common in older subjects and were not correlated with the size of the HD mutation. There was a strong coefficient of correlation between individual levels of striatal D1 and D2 binding in subjects with the mutation. Of 6 other cases with a 50% risk of carrying the HD gene, 1 showed subclinical loss of caudate and putamen D2 binding. Our study suggests that both striatal D1 and D2 dopamine receptors are lost in parallel from both caudate and putamen in presymptomatic HD and that dopamine receptor binding provides a sensitive means of detecting subclinical striatal dysfunction.