Serum nitric oxide metabolite levels and the effect of antipsychotic therapy in schizophrenia

BACKGROUND: Recently it was proposed that nitric oxide metabolites (NO) may have a role in the pathophysiology of schizophrenia and major depressive disorders. The present study was performed to assess changes in serum nitric oxide metabolite levels in schizophrenic patients compared with healthy controls. Our secondary aim was to further evaluate the impact of psychopharmacologic treatment on circulating NO levels not assessed previously. METHODS: Serum NO levels of patients with schizophrenia (n=20) before and after 6 weeks of treatment were compared with those of healthy controls (n=20). Severity of schizophrenia and response to treatment were assessed with positive and negative symptoms of schizophrenia. NO levels were estimated by Griess method in serum samples. RESULTS: In patients with schizophrenia, pre-treatment serum NO levels were higher than those of control subjects (39.15 +/- 18.24 vs. 25.40 +/- 5.83 micromol/L, p=0.036) and also of post-treatment values (34.41 +/- 16.35 vs. 25.40 +/- 5.83 micromol/L, p=0.049), respectively. However, no significant difference was found between serum NO levels in pre- and post-treatment values. CONCLUSIONS: Our findings of increased serum NO levels in schizophrenic patients confirmed the role of NO in the pathophysiology of schizophrenia. However, we found that antipsychotic drugs do not reveal significant effects on serum levels of NO in schizophrenia in a 6-week treatment regimen. Further studies with longer therapy periods may suggest some new clues for novel treatment strategies employing antioxidants and NOS inhibitors in schizophrenia.