Background: There is an increasing interest in the role of nitric oxide (NO) and pterines in the pathophysiology of neuropsychiatric disorders. The results so far show an inconsistent pattern. Methods: In the present study, neopterin and a measure of NO synthesis in plasma of symptomatic and euthymic bipolar affective patients were compared to those of patients with a major depression and healthy controls. As an index of NO synthesis, the ratio of the amino acids citrul-line and arginine (Cit-Arg ratio) was calculated. Neopterin is a bypass product in the synthesis of tetrahydrobiopterin, which is a cofactor of NO synthase. Results: The results indicate that both neopterin and the Cit-Arg ratio are decreased in bipolar affective patients, irrespective of their symptomatic status. In addition, an association between the values of the Cit-Arg ratio and the neopterin level was observed, which is suggestive for a low tetrahydrobiopterin activity. Conclusion: NO formation may be endangered in bipolar affective disorder. Copyright

Arginine, Bipolar disorder, Citrulline, Major depression, Neopterin, Nitric oxide, Tetrahydrobiopterin,
Department of Psychiatry

Hoekstra, R, Fekkes, D, Pepplinkhuizen, L, Loonen, A.J.M, Tuinier, S, & Verhoeven, W.M.A. (2006). Nitric oxide and neopterin in bipolar affective disorder. Neuropsychobiology, 54(1), 75–81. doi:10.1159/000096042