Apomorphine hydrochloride-induced improvement in Huntington's chorea: stimulation of dopamine receptor.

Four patients affected by Huntington's chorea (HC) with a well defined family history of the disease were injected intramuscularly with apomorphine hydrochloride in nonemetic doses, ranging from 1 to 4 mg. Soon after treatment, all patients showed a marked decrease in abnormal involuntary movements. Pretreatment with haloperidol (2 mg intramuscularly) or sulpiride (100 mg intramuscularly) 30 minutes prior to apomorphine treatment, prevented the therapeutic effect of this compound. It is suggested that apomorphine-induced improvement in Huntington's Chorea is mediated by the stimulation of a special kind of dopamine receptor, leading to inhibition of the activity of dopaminergic neurons.