Greater availability of dopamine transporters in patients with major depression - A dual-isotope SPECT study

In order to explore the neuropathology of the pre- and post-synaptic dopamine neurons of patients with major depression, we examined striatal D₂/D₃ receptor uptake and dopamine transporter (DAT) availability simultaneously in drug-free depressed patients using a dual-isotope single photon emission computed tomography (SPECT) imaging technique. Ten unmedicated patients with unmediated depression and ten healthy controls were recruited. The striatal dopamine D₂/D₃ receptor availability was measured using SPECT and [¹²³I] IBZM, while DAT was measured using SPECT and [^99mTc] TRODAT-1. The symptom changes of the drug-free patients were reassessed after a 4-week antidepressant treatment. DAT binding in the patient group were significantly higher than in control group. That was not the case, however, for striatal D₂/D₃ receptor availability. Pre-treatment striatal DAT availability correlated only marginally with changes in the Hamilton Depression Rating Scale after 4 weeks of treatment. Central dopamine functions may be altered in patients with major depression, particularly in the pre-synaptic sites.