EMD 23,448: effects of a putative dopamine autoreceptor agonist in chorea.

A novel dopamine agonist, which stimulates presynaptic dopamine receptors in the experimental animal, was administered acutely to four patients with chorea. Abnormal involuntary movements worsened, plasma prolactin levels fell, and plasma growth hormone concentrations increased in all patients tested. These effects resemble those associated with a postsynaptic rather than presynaptic dopamine agonist, and thus raise some question about the ability of conventional dopaminomimetic screens to predict clinical activity.