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 D2 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 (V3″) of the D2 receptor antagonist [123I]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 D2 receptor availability between depressed patients (0.73 ± 0.08) and control subjects (0.78 ± 0.10, p = .23). Amphetamine-induced reduction in [123I]IBZM V3″ (ΔV3″) 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 [123I]IBZM ΔV3″. Conclusions: This study did not replicate previously reported alterations in striatal D2 receptor density in depressed patients and suggests that stimulant-induced dopamine release is not altered in major depression.