title: Aging-related changes in the nigrostriatal dopamine system and the response to MPTP in nonhuman primates: diminished compensatory mechanisms as a prelude to parkinsonism.
abstract: Aging is the most prominent risk factor for Parkinson's disease. Yet, consensus of how advancing age may predispose the dopamine (DA) system to parkinsonism is lacking. Three age ranges of female rhesus monkeys, 8-9, 15-17, and 21-31 years, received unilateral DA depletion with intracarotid 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Morphological and biochemical analyses of DA-depleted and intact hemispheres revealed three primary findings: (1) The intact striatum exhibited age-related declines in dopamine (DA) and homovanillic acid (HVA) that were present by middle age; (2) In the MPTP-treated striatum, the compensatory increase in DA activity was absent in old monkeys; and (3) Age-associated morphological changes included declines in the density of tyrosine hydroxylase (TH) positive fibers in striatum, decreased nigral soma size, and optical density of TH, but no significant loss of neurons. These findings suggest that aging produces changes in the nigrostriatal DA system that approach the threshold for expression of parkinsonian features, and that progressive impairment of plasticity may be central to the role of aging in development of parkinsonism.
authors.affiliation: Department of Neurology, University of Cincinnati, PO Box 670525, 265 Albert Sabin Way, Cincinnati, OH 45267, USA. timothy.collier@uc.edu
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Collier
authors.forename: Jack
authors.initials: J
authors.lastname: Lipton
authors.forename: Brian F
authors.initials: BF
authors.lastname: Daley
authors.forename: Stephane
authors.initials: S
authors.lastname: Palfi
authors.forename: Yaping
authors.initials: Y
authors.lastname: Chu
authors.forename: Caryl
authors.initials: C
authors.lastname: Sortwell
authors.forename: Roy A E
authors.initials: RA
authors.lastname: Bakay
authors.forename: John R
authors.initials: JR
authors.lastname: Sladek
authors.forename: Jeffrey H
authors.initials: JH
authors.lastname: Kordower
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology; D001921:Brain / Q000473:pathology; D002851:Chromatography, High Pressure Liquid; D004298:Dopamine / Q000378:metabolism / Q000502:physiology*; D005260:Female; D007150:Immunohistochemistry; D020267:MPTP Poisoning / Q000473:pathology* / Q000523:psychology; D008253:Macaca mulatta; D009043:Motor Activity / Q000187:drug effects; D017072:Neostriatum / Q000254:growth & development* / Q000473:pathology*; D010302:Parkinson Disease, Secondary / Q000139:chemically induced* / Q000473:pathology* / Q000523:psychology; D013378:Substantia Nigra / Q000254:growth & development* / Q000473:pathology*; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism
chemical_list: D014446:Tyrosine 3-Monooxygenase; D004298:Dopamine