title: The nigrostriatal dopamine system of aging GFRalpha-1 heterozygous mice: neurochemistry, morphology and behavior.
abstract: Given the established importance of glial cell line-derived neurotrophic factor (GDNF) in maintaining dopaminergic neurotransmitter systems, the nigrostriatal system and associated behaviors of mice with genetic reduction of its high-affinity receptor, GDNF receptor (GFR)alpha-1 (GFRalpha-1(+/-)), were compared with wild-type controls. Motor activity and the stimulatory effects of a dopamine (DA) D1 receptor agonist (SKF 82958) were assessed longitudinally at 8 and 18 months of age. Monoamine concentrations and dopaminergic nerve terminals in the striatum and the number of dopaminergic neurons in the substantia nigra (SN) were assessed. The results support the importance of GFRalpha-1 in maintaining normal function of the nigrostriatal dopaminergic system, with deficits being observed for GFRalpha-1(+/-) mice at both ages. Motor activity was lower and the stimulatory effects of the DA agonist were enhanced for the older GFRalpha-1(+/-) mice. DA in the striatum was reduced in the GFRalpha-1(+/-) mice at both ages, and tyrosine hydroxylase-positive cell numbers in the SN were reduced most substantially in the older GFRalpha-1(+/-) mice. The combined behavioral, pharmacological probe, neurochemical and morphological measures provide evidence of abnormalities in GFRalpha-1(+/-) mice that are indicative of an exacerbated aging-related decline in dopaminergic system function. The noted deficiencies, in turn, suggest that GFRalpha-1 is necessary for GDNF to maintain normal function of the nigrostriatal dopaminergic system. Although the precise mechanism(s) for the aging-related changes in the dopaminergic system remain to be established, the present study clearly establishes that genetic reductions in GFRalpha-1 can contribute to the degenerative changes observed in this system during the aging process.
authors.affiliation: Department of Neurosciences, Medical University of South Carolina, Charleston, SC 29425, USA. zamanv@musc.edu
authors.forename: Vandana
authors.initials: V
authors.lastname: Zaman
authors.forename: Heather A
authors.initials: HA
authors.lastname: Boger
authors.forename: Ann-Charlotte
authors.initials: AC
authors.lastname: Granholm
authors.forename: Baerbel
authors.initials: B
authors.lastname: Rohrer
authors.forename: Alfred
authors.initials: A
authors.lastname: Moore
authors.forename: Mona
authors.initials: M
authors.lastname: Buhusi
authors.forename: Greg A
authors.initials: GA
authors.lastname: Gerhardt
authors.forename: Barry J
authors.initials: BJ
authors.lastname: Hoffer
authors.forename: Lawrence D
authors.initials: LD
authors.lastname: Middaugh
mesh_terms: D000375:Aging / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D003342:Corpus Striatum / Q000166:cytology / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism*; D018491:Dopamine Agonists / Q000494:pharmacology; D051100:Glial Cell Line-Derived Neurotrophic Factor / Q000378:metabolism*; D051097:Glial Cell Line-Derived Neurotrophic Factor Receptors / Q000235:genetics*; D006579:Heterozygote; D051379:Mice; D018345:Mice, Knockout; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D009410:Nerve Degeneration / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology; D009434:Neural Pathways / Q000166:cytology / Q000378:metabolism; D010300:Parkinson Disease / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology; D017729:Presynaptic Terminals / Q000187:drug effects / Q000378:metabolism; D017447:Receptors, Dopamine D1 / Q000819:agonists / Q000378:metabolism; D013378:Substantia Nigra / Q000166:cytology / Q000378:metabolism*
chemical_list: D018491:Dopamine Agonists; C494988:Gfra1 protein, mouse; D051100:Glial Cell Line-Derived Neurotrophic Factor; D051097:Glial Cell Line-Derived Neurotrophic Factor Receptors; D017447:Receptors, Dopamine D1; D004298:Dopamine