Elevated plasma nitrate levels in depressive states

Background: Previous studies have shown that nitric oxide (NO) synthase inhibitors show preclinical antidepressant-like properties, suggesting that NO is involved in the pathogenesis of depression. The purpose of this study is to examine whether or not NO production increases in depressed patients. Methods: Plasma nitrate concentrations, an index of NO production, were measured by high-performance liquid chromatography in depressed patients (n=17) and compared with patients suffering anxiety (n=6) and with healthy controls (n=12). Results: Plasma nitrate concentrations were significantly higher in depressed patients than in patients with an anxiety disorder (P<0.05) or in controls (P<0.01). Limitations: The study group was small. The source of the surplus production of NO in patients with major depressive episode remains unclear. Conclusions: These results suggest that NO production is increased in depression.