Dopamine, serotonin and alpha-adrenergic receptor blocking activities in serum and their relationships to prolactin level in schizophrenic patients receiving long-term chlorpromazine treatment.

The clinical application of a dopamine radioreceptor assay for neuroleptics has been proposed. Simultaneous monitoring of serum antidopaminergic (anti-DA), antiserotonergic (anti-5HT) antiadrenergic (anti-NA) activities may provide a better understanding of clinical effects of neuroleptics. Serum anti-DA and anti-5HT activities were estimated by competition for 3H-spiperone binding to dopamine and serotonin receptors in rat brain, respectively, and anti-NA activity by competition for 3H-WB-4101 binding to alpha-receptors. Thirty-one patients receiving maintenance doses of chlorpromazine (CPZ) chronically were studied. Serum activities varied among patients receiving the same dose, but correlated significantly with dose. Anti-DA activity also correlated with both anti-5HT anti-NA activities, and the average ratio of anti-5HT or anti-NA to anti-DA activity was slightly reduced by metabolism of CPZ. However, some patients had a different spectrum of serum activities from that of in vitro activities. Serum prolactin (PRL) correlated weakly with all the serum activities. The serum PRL anti-DA activity ratio appeared to be independent of anti-5HT or anti-NA activity, suggesting the predominant involvement of anti-DA activity in the stimulation of PRL release.