Striatal presynaptic dopamine function in type 1 alcoholics measured with positron emission tomography

Recent in vivo studies have shown low dopamine D-2 receptor and dopamine transporter densities among late onset (type 1) alcoholics. We have now studied 6-[F-18]-FDOPA (FDOPA) uptake in 10 type 1 alcoholics and eight matched controls to test the hypothesis that striatal presynaptic dopamine function is lower among alcoholics. Markedly low FDOPA uptake (K-i) was observed in the left caudate of two alcoholic patients, but the mean striatal uptake values of the patient group were higher than those of the control group. The greatest difference was observed in the mean FDOPA intake in the left putamen, which was 28% higher in the patient group (t=3.00, P=0.008, d.f.=16, independent samples t-test), and in the right caudate (difference 36%, t=2.87, P=0.01). The elevated FDOPA uptake in putamen and caudate correlated with poor Wisconsin Card Sorting Test (WCST) performance (error %) among alcoholics (correlation coefficients from 0.49 to 0.56), which suggests that the magnitude of presynaptic dopamine function alteration correlates with the degree of disability to modify one's behavior. The results do not give support to the hypothesis of generally decreased striatal dopamine turnover in type 1 alcoholism, but on the contrary indicate an increased presynaptic dopamine function. This may represent a compensatory mechanism to low postsynaptic DA function. The low presynaptic DA function observed in the left caudate of two patients suggests that type 1 alcoholism may be a heterogeneous disorder.