Platelet 5-HT2A receptors in schizophrenic patients with and without neuroleptic treatment

It has been suggested that abnormal function of the serotonergic system may be implicated in the pathophysiology of schizophrenia. In order to examine the role of this system in schizophrenia, we have determined 5-HT2A recept ors on human platelets of 20 control subjects and 37 schizophrenic patients by using [H-3]spiperone and ketanserin. The data showed that the maximum n umber (B-max) of 5-HT2A receptors for schizophrenic patients without neurol eptic therapy was significantly higher than that for control subjects. The B-max values for [H-3]spiperone binding to platelets of schizophrenic patie nts on butyrophenone, phenothiazine, benzisosazole and thioxanthene therapi es were significantly lower than those obtained from the drug-free group, b ut were comparable to control values. The effect of various medication peri ods on platelet 5-HT2A receptors was also examined. We found that after 2-4 weeks, 1-4 months, 4-12 months and more than 1 year of neuroleptic treatme nts, the B-max values were significantly decreased when compared with value s in the drug-free group. The present results indicate that treatment with various types of neuroleptics decreases the hypersensitivity of platelet 5- HT2A receptors. Significant clinical improvements occurred in all types of neuroleptic-treated groups and for all different treatment durations in thi s study. The precise mechanisms of how neuroleptics achieve their therapeut ic effects still need to be further delineated. (C) 2000 Elsevier Science I reland Ltd. All rights reserved.