PLATELET SEROTONIN-2 RECEPTORS IN SCHIZOPHRENIA - EFFECTS OF ILLNESS AND NEUROLEPTIC TREATMENT

To examine the role of serotonin2 (5-hydroxytryptamine2, 5-HT2) recept ors in schizophrenia, we determined the binding indices of 5-HT2 recep tors using I-125-lysergic acid diethylamide (LSD) as the radioligand i n platelets obtained from 40 normal control subjects and 42 drug-free schizophrenic patients. We also examined the effect of neuroleptic dru g treatment on the binding parameters (B(max) and K(d)) of 5-HT2 recep tors in platelets of schizophrenic patients. We observed that the B(ma x) of I-125-LSD binding in platelets of schizophrenic patients was sig nificantly higher than in platelets of normal subjects. There was no s ignificant difference, however, between the K(d) of I-125-LSD binding in platelets of schizophrenic patients and normal control subjects. Fu rthermore, we found no correlation between Brief Psychiatric Rating Sc ale scores and either B(max) or K(d) of I-125-LSD binding at the end o f the drug washout period. We also observed that neither treatment wit h haloperidol nor treatment with thiothixine caused significant change s in B(max) and K(d) of I-125-LSD binding in platelets of schizophreni c patients. However, both fluphenazine and trifluoperazine did signifi cantly increase the B(max) of I-125-LSD binding without any significan t change in the K(d) values in platelets of schizophrenic patients. Ou r results thus suggest that platelet 5-HT2 receptors are increased in schizophrenia and that chronic treatment with fluphenazine and trifluo perazine, but not haloperidol or thiothixine, further increases the 5- HT2 receptor binding sites in platelets of schizophrenic patients.