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 dopami ne 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 presynapt ic dopamine function is lower among alcoholics. Markedly low FDOPA upt ake (K-i) was observed in the left caudate of two alcoholic patients, but the mean striatal uptake values of the patient group were higher t han those of the control group. The greatest difference was observed i n the mean FDOPA intake in the left putamen, which was 28% higher in t he 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 elev ated FDOPA uptake in putamen and caudate correlated with poor Wisconsi n Card Sorting Test (WCST) performance (error %) among alcoholics (cor relation coefficients from 0.49 to 0.56), which suggests that the magn itude 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 tu rnover in type 1 alcoholism, but on the contrary indicate an increased presynaptic dopamine function. This may represent a compensatory mech anism to low postsynaptic DA function. The low presynaptic DA function observed in the left caudate of two patients suggests that type 1 alc oholism may be a heterogeneous disorder.