Background: Nitric oxide (NO) is synthesized by neuronal and endothelial NO synthase (NOS), and has multiple functions in brain circuits and plasticity, neuroprotection and neurotoxicity, and behavior. We evaluated plasma levels of NO metabolite in patients with schizophrenia. Method: Plasma levels of NO metabolites, nitrite and nitrate, were measured in 45 male schizophrenics and 45 male normal controls. The severity of schizophrenia and response to treatment were assessed with the positive and negative syndrome scale. Plasma NO metabolite levels were estimated by Griess method in plasma samples. Results: Plasma levels of the NO metabolites were significantly lower in schizophrenics than in normal controls (t = 2.841, df = 88, p = 0.006). There were no significant correlations between plasma NO metabolites and PANSS scores in schizophrenics. Conclusions: Our study suggests that decreased plasma NO metabolite level is associated with schizophrenia. This finding supports the hypothesis of a NO system reduction in schizophrenics.
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