Platelet [3H]dopamine uptake is differentially affected by neuroleptic drug treatment in schizophrenia and schizophreniform disorder

1. The uptake of [³H]dopamine was measured using platelet-rich plasma (PRP) from neuroleptic- free subjects and again, in some cases, after the subject had been treated with neuroleptic drugs. 2. There were no differences in [³H]dopamine uptake by PRP in subjects who were or were not mentally ill. 3. After treatment with neuroleptic drugs the Km for platelet [³H]dopamine uptake had increased in 76% of subjects with schizophrenia and 87% of subjects with schizophreniform disorder. Similarly, the Vmax for platelet [³H]dopamine uptake had increased in 81% of the subjects with schizophrenia and 86% of the subjects with schizophreniform disorder. 4. By contrast, the Km for platelet [³H]dopamine uptake had decreased in 94% of subjects who had a psychoses associated with an illness other than schizophrenia or schizophreniform disorder whilst the Vmax for platelet [³H]dopamine uptake also decreased by 94% in these subjects. 5. In subjects with psychoses, platelet [³H]dopamine uptake is differentially altered during euroleptic drug treatment depending on diagnosis.