Plasma levels of dopamine metabolite correlate with mismatch negativity in patients with schizophrenia

Aim Mismatch negativity (MMN) deficit is one of the most robust and replicable findings in schizophrenia, and primarily reflects deficient functioning of the N‐methyl‐D‐aspartate (NMDA) receptor system. Although the dopamine receptor is known not to modulate MMN over the short term, it is unclear whether the dopamine system affects MMN in the long term. Methods We explored correlations between MMN and levels of plasma dopamine and serotonin metabolites in 18 patients with schizophrenia psychiatrically evaluated with the Positive and Negative Syndrome Scale (PANSS). Results A significant negative correlation exists between MMN amplitude and plasma levels of dopamine metabolites. Plasma serotonin metabolite levels were not correlated with MMN. The PANSS total score and Negative score also showed negative correlations with MMN amplitude. Conclusion The usual strong therapeutic blockade of dopamine receptors applied in cases of schizophrenia may reduce MMN over the long term.