title: Dopamine-dependent compensation maintains motor behavior in mice with developmental ablation of dopaminergic neurons.
abstract: The loss of dopaminergic neurons in the substantia nigra pars compacta (SNc) and consequent depletion of striatal dopamine are known to underlie the motor deficits observed in Parkinson's disease (PD). Adaptive changes in dopaminergic terminals and in postsynaptic striatal neurons can compensate for significant losses of striatal dopamine, resulting in preservation of motor behavior. In addition, compensatory changes independent of striatal dopamine have been proposed based on PD therapies that modulate nondopaminergic circuits within the basal ganglia. We used a genetic strategy to selectively destroy dopaminergic neurons in mice during development to determine the necessity of these neurons for the maintenance of normal motor behavior in adult and aged mice. We find that loss of 90% of SNc dopaminergic neurons and consequent depletion of >95% of striatal dopamine does not result in changes in motor behavior in young-adult or aged mice as evaluated by an extensive array of motor behavior tests. Treatment of aged mutant mice with the dopamine receptor antagonist haloperidol precipitated motor behavior deficits in aged mutant mice, indicating that <5% of striatal dopamine is sufficient to maintain motor function in these mice. We also found that mutant mice exhibit an exaggerated response to l-DOPA compared with control mice, suggesting that preservation of motor function involves sensitization of striatal dopamine receptors. Our results indicate that congenital loss of dopaminergic neurons induces remarkable adaptions in the nigrostriatal system where limited amounts of dopamine in the dorsal striatum can maintain normal motor function.
authors.affiliation: Washington University Pain Center, Department of Anesthesiology, Department of Medicine, Renal Division, Hope Center for Neurological Disorders, Department of Neurology, Department of Developmental Biology, Department of Pathology and Immunology Research, Washington University School of Medicine, St. Louis, Missouri 63110, Louis Stokes Cleveland VA Medical Center, Cleveland, Ohio 44106, and Departments of Psychiatry and Neurosciences, Case Western Reserve University, Cleveland, Ohio 44106.
authors.forename: Judith P
authors.initials: JP
authors.lastname: Golden
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Demaro
authors.forename: Amanda
authors.initials: A
authors.lastname: Knoten
authors.forename: Masato
authors.initials: M
authors.lastname: Hoshi
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Pehek
authors.forename: Eugene M
authors.initials: EM
authors.lastname: Johnson
authors.forename: Robert W
authors.initials: RW
authors.lastname: Gereau
authors.forename: Sanjay
authors.initials: S
authors.lastname: Jain
mesh_terms: D000818:Animals; D004167:Diphtheria Toxin / Q000235:genetics / Q000633:toxicity; D004298:Dopamine / Q000172:deficiency / Q000378:metabolism*; D018492:Dopamine Antagonists / Q000494:pharmacology; D050483:Dopamine Plasma Membrane Transport Proteins / Q000172:deficiency / Q000235:genetics; D059290:Dopaminergic Neurons / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D005684:Gait; D006220:Haloperidol / Q000494:pharmacology; D007980:Levodopa / Q000494:pharmacology; D008636:Mesencephalon / Q000187:drug effects / Q000473:pathology; D051379:Mice; D008822:Mice, Transgenic; D009154:Mutation
chemical_list: D004167:Diphtheria Toxin; D018492:Dopamine Antagonists; D050483:Dopamine Plasma Membrane Transport Proteins; D007980:Levodopa; D006220:Haloperidol; D004298:Dopamine