Reduced dopamine transporter density in the ventral striatum of patients with Parkinson's disease and pathological gambling

Pathological gambling (PG) represents a behavioral side effect of dopamine replacement therapy in a minority of patients with Parkinson's disease (PD). Using striatal dopamine transporter (DAT) with single photon emission tomography we assessed presynaptic dopaminergic function in 8 PD patients with PG, 21 matched PD control subjects, and 14 healthy subjects. Statistical Parametric Mapping was applied for image analysis. The analysis of variance (ANOVA) revealed that the three groups differed in dorsal and ventral striata bilaterally. The post-hoc analysis displayed a reduced tracer binding in the ventral striatum of PD patients with PG compared to PD controls, possibly reflecting either a reduction of mesolimbic projections or, alternatively, a lower membrane DAT expression on presynaptic terminals. The latter hypothesis is most likely given that the functional reduction of presynaptic reuptake would be more consistent with the increased dopamine levels in the ventral striatum recently reported in PD gamblers.