Dopamine D2 receptor availability and amphetamine-induced dopamine release in unipolar depression

Background: Reduced dopaminergic transmission has been implicated in the pathophysiology of major depression. The aim of the present study was to measure striatal D 2 receptor availability and amphetamineinduced dopamine release in nonpsychotic, unmedicated, unipolar patients during an episode of major depression. Methods: The striatal equilibrium specific to nonspecific partition coefficient (V 3 ″) of the D 2 receptor antagonist [ 123 I]IBZM was measured with single photon emission computerized tomography before and after amphetamine administration in 9 depressed subjects and 10 matched healthy control subjects. Results: No significant differences were observed in preamphetamine D 2 receptor availability between depressed patients (0.73 ± 0.08) and control subjects (0.78 ± 0.10, p = .23). Amphetamine-induced reduction in [ 123 I]IBZM V 3 ″ (ΔV 3 ″) was similar in depressed patients (−9.8 ± 5.5%) and control subjects (−7.8 ± 2.5%, p = .32). Amphetamine induced a transient improvement in symptomatology in depressed patients, but this improvement did not correlate with [ 123 I]IBZM ΔV 3 ″. Conclusions: This study did not replicate previously reported alterations in striatal D 2 receptor density in depressed patients and suggests that stimulant-induced dopamine release is not altered in major depression.