Time course of schizophrenia and platelet 5-HT level.

The concentration of platelet serotonin (5-HT) and the simultaneous uptake of 5-HT into platelets have been investigated in schizophrenic patients with (A) intermittent time course of illness (complete remission), (B) chronic time course (partial remission and residual symptoms), and (C) intermittent-chronic time course (good remission at the beginning of illness with gradual progression to chronic stage). An increased platelet 5-HT concentration (i.e., hyperserotoninemia) of unknown etiology was observed, especially in the group with chronic time course of disease as compared to the normal controls. At the same time, kinetic constants Km and Vmax of 5-HT uptake into platelets were unchanged in all patients. Neuroleptic treatment did not produce any significant change either in platelet 5-HT level or in the uptake of 5-HT. These results provide further support for the possible 5-HT dysfunction in schizophrenia.