Preliminary Evidence of Reduced Combined Output of Dopamine and Its Metabolites in Chronic Schizophrenia

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Abstract
• The mean combined total body excretion of dopamine (DA) and its metabolites, measured by summing the molar excretion of DA and its metabolites in 24-hour urine samples (Sum DA), was reduced in 20 patients with schizophrenia who had not been receiving medication for at least two weeks. These patients were relatively resistant to treatment, as they were unable to live independently outside institutional settings despite conventional neuroleptic therapy. In contrast, sum norepinephrine (Sum NE), measured by summing the molar excretion of NE and its metabolites, was not reduced. These results are highlighted by expressing the data in terms of the ratio of Sum DA/Sum NE. Patients with schizophrenia had a significantly lower ratio. Treatment with haloperidol normalized the low ratio. Urinary excretion of 5-hydroxyindoleacetic acid was normal in the schizophrenic patients. These results suggest that chronic schizophrenia is more likely to be associated with a low rather than a high state of DA activity.