Non-displaceable binding potential changes of striatal dopamine D2 receptors in patients with first-episode major depressive disorder and the correlation with clinical features

Objective To observe non-displaceable binding potential (BPND) changes of striatal dopamine D2 receptors(SDDR) in patients with first-episode major depressive disorder (MDD) using 11C-Raclopride PET/CT, and to analyze the relationship between BPND and Hamilton rating scale for depression (HAM-D). Methods From December 2014 to December 2015, patients with first-episode MDD and age/gender-matched healthy controls underwent brain MRI and 11C-Raclopride PET/CT in this prospective study. BPND of bilateral SDDR was calculated by molecular imaging and kinetic analysis toolbox (MIAKAT). BPND changes of bilateral SDDR and their relationship with HAM-D score were analyzed. Paired t test, two-sample t test and Pearson correlation analysis were used. Results A total of 20 MDD patients (8 males, 12 females, average age: (32.80±9.76) years) and 20 healthy controls (9 males, 11 females, average age: (29.25±6.93) years) were enrolled in this study. The 11C-Raclopride uptake in brain tissue of the MDD group and control group were mainly distributed in bilateral striatum, and very few 11C-Raclopride was distributed in bilateral cerebral cortex and cerebellum. In MDD group, the BPND level of bilateral SDDR had no statistical differences(t values: 0.69, 0.35, both P>0.05), and similar results were found in the control group(t values: 0.28, 0.24, both P>0.05). Compared with the control group, however, the MDD group had lower BPND level of bilateral SDDR(t values: 3.13-4.41, all P<0.05). The BPND of bilateral caudate nucleus and/or putamen D2 receptors was correlated with HAM-D total score, anxiety/somatization factor score, cognitive impairment factor score, retardation factor score and sleep disturbance factor score(r values: from -0.688 to -0.453, all P<0.05). Conclusions The binding potential of SDDR in patients with first-episode MDD is declined, and the BPND level of SDDR is correlated with symptoms of depression. The abnormality of SDDR may be an important molecular mechanism of the abnormality of midbrain-striatal dopamine reward circuits in MDD patients. Key words: Depressive disorder; Corpus striatum; Receptors, dopamine; Positron-emission tomography; Tomography, X-ray computed; Magnetic resonance imaging; Raclopride