Aporphines 16 Action of aporphine alkaloids on locomotor activity in rats with 6-hydroxydopamine lesions of the nucleus accumbens

(-)-Apomorphine and (±)-N-n-propylnorapomorphine ((±)-NPA) produce stereotypy but not locomotor activity in normal rats. In rats with selective bilateral lesions of dopamine terminals in the nucleus accumbens induced by microinjection of 6-hydroxydopamine both compounds produced a marked stimulation of locomotor activity (±)-NPA was considerably more potent than (-)-apomorphine. The maximal intensity of stimulation produced by the two drugs was, however, similar. The locomotor stimulant effects of (-)-apomorphine were inhibited by (+)-bulbocapnine (20 mg/kg) or pimozide (0.5 mg/kg). (±)-N-n-Propylnorapocodeine also produced a long-lasting stimulation of locomotor activity. (±)-Aporphine, (±)-isoapomorphine, (-)-1,2-dihydroxyaporphine, and (-)-nuciferine were all inactive in stimulating locomotor activity.