Dopamine transporter function assessed by antisense knockdown in the rat: Protection from dopamine neurotoxicity

The plasma membrane dopamine transporter is located on presynaptic nerve te rminals and is responsible for the termination of dopaminergic neurotransmi ssion via dopamine reuptake. The dopamine transporter may also contribute t o the pathogenesis of Parkinson disease. Dopamine transporter expression co rrelates well with susceptibility to neuronal degeneration in 1-methyl-4-ph enyl-1,2,3,6-tetrahydropyridine (MPTP)-induced parkinsonism. Recent studies have implicated the dopamine transporter in the uptake of both this neurot oxin and its metabolite, MPP+, as well as another experimental neurotoxin, 6-hydroxydopamine. In these studies we examined the role of the dopamine tr ansporter in the neurotoxicity of both MPP+ and 6-hydroxydopamine in the ra t brain using in vivo administration of phosphorothioate antisense oligonuc leotides targeting dopamine transporter mRNA. Infusion of dopamine transpor ter antisense (1 nmol/day, 7 days) into the left substantia nigra pars comp acta resulted in reduced H-3-WIN 35-428 binding in the left striatum and si gnificant levodopa and amphetamine-induced contralateral rotations. Unilate ral pretreatment with dopamine transporter antisense prior to bilateral int rastriatal infusion of either MPP+ or 6-hydroxydopamine resulted in asymmet rical striatal H-3-WIN 35-428 binding and dopamine content as well as signi ficant apomorphine-induced ipsilateral rotations, suggesting neuroprotectio n of nigrostriatal neurons on the antisense-treated side. Thus, the dopamin e transporter appears to play a critical role in determining susceptibility to the experimental neurotoxins MPP+ and 6-hydroxydopamine. In light of th is, the dopamine transporter may prove useful, both as a marker for suscept ibility to Parkinson's disease and as a target for therapeutic intervention . Synapse 37:171-178, 2000. (C) 2000 Wiley-Liss, Inc.