• The sedative effectiveness of apomorphine in a newly developed animal model of Huntington's disease was examined. The motor responses of rats with kainic acid lesions of the neostriatum to a sedative dose of apomorphine (50 μg/kg) was similar to that observed in intact controls. In contrast, compared to controls, a marked potentiation of the motor stimulant effects of dextroamphetamine was confirmed in the kainic acid-lesioned group. We suggest that the pathological changes underlying the symptoms observed in this animal model and in Huntington's disease do not include abnormalities in presynaptic dopamine receptors in the neostriatum.