Reduced dopamine turnover in the basal ganglia of depressed suicides

We have measured the concentrations of dopamine, and the dopamine metabolites homovanillic acid (HVA) and dihydroxyphenylacetic acid (DOPAC), in five brain regions from suicide victims with a firm retrospective diagnosis of depression, and matched controls. The suicides were divided into those free of antidepressant drugs and those in whom prescription of antidepressant drugs was clearly documented. DOPAC concentrations were significantly lower in caudate, putamen and nucleus accumbens of antidepressant-free suicides compared to controls. In antidepressant-treated suicides, lower concentrations of DOPAC were observed in the basal ganglia, reaching statistical significance in caudate. Lower DOPAC concentrations were largely restricted to those suicides who died by non-violent methods. There were no significant differences in dopamine and HVA concentrations in either suicide group compared to controls, although there was a trend for HVA concentrations to be lower in suicides. This study provides evidence for reduced dopamine turnover, as judged from reduced DOPAC levels, in depressed suicides, although we cannot exclude the possibility that this may be due to ingestion of toxic agents.