title: GDNF improves dopamine function in the substantia nigra but not the putamen of unilateral MPTP-lesioned rhesus monkeys.
abstract: Microdialysis measurements of dopamine (DA) and DA metabolites were carried out in the putamen and substantia nigra of unilateral 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned rhesus monkeys that received intraventricular injections of vehicle or glial-derived neurotrophic factor (GDNF, 300 microg) 3 weeks prior to the microdialysis studies. Following behavioral measures in the MPTP-lesioned monkeys, they were anesthetized with isoflurane and placed in a stereotaxic apparatus. Magnetic resonance imaging (MRI)-guided sterile stereotaxic procedures were used for implantations of the microdialysis probes. Basal extracellular levels of DA and the DA metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), were found to be decreased by >95% in the right putamen of the MPTP-lesioned monkeys as compared to normal animals. In contrast, basal DA levels were not significantly decreased, and DOPAC and HVA levels were decreased by only 65% and 30%, respectively, in the MPTP-lesioned substantia nigra. Significant reductions in d-amphetamine-evoked DA release were also observed in the MPTP-lesioned substantia nigra and putamen of the monkeys as compared to normal animals. A single intraventricular administration of GDNF into one group of MPTP-lesioned monkeys elicited improvements in the parkinsonian symptoms in these animals at 2-3 weeks post-administration. In addition, d-amphetamine-evoked overflow of DA was significantly increased in the substantia nigra but not the putamen of MPTP-lesioned monkeys that had received GDNF. Moreover, post-mortem brain tissue studies showed increases in whole tissue levels of DA and DA metabolite levels primarily within the substantia nigra in MPTP-lesioned monkeys that had received GDNF. Taken together, these data support that single ventricular infusions of GDNF produce improvements in motoric behavior in MPTP-lesioned monkeys that correlate with increases in DA neuronal function that are localized to the substantia nigra and not the putamen.
authors.affiliation: Departments of Psychiatry and Pharmacology, University of Colorado Health Sciences Center, 4200 E. Ninth Avenue, Campus Box C268-71, Denver, CO, USA. greg.gerhardt@uchsc.edu
authors.forename: G A
authors.initials: GA
authors.lastname: Gerhardt
authors.forename: W A
authors.initials: WA
authors.lastname: Cass
authors.forename: P
authors.initials: P
authors.lastname: Huettl
authors.forename: S
authors.initials: S
authors.lastname: Brock
authors.forename: Z
authors.initials: Z
authors.lastname: Zhang
authors.forename: D M
authors.initials: DM
authors.lastname: Gash
mesh_terms: D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D000818:Animals; D001481:Basal Metabolism; D003913:Dextroamphetamine / Q000494:pharmacology; D004298:Dopamine / Q000378:metabolism / Q000502:physiology*; D015259:Dopamine Agents / Q000633:toxicity*; D005260:Female; D007839:Functional Laterality; D051100:Glial Cell Line-Derived Neurotrophic Factor; D006719:Homovanillic Acid / Q000378:metabolism; D020267:MPTP Poisoning; D008253:Macaca mulatta; D017551:Microdialysis; D009414:Nerve Growth Factors / Q000494:pharmacology*; D009419:Nerve Tissue Proteins / Q000494:pharmacology*; D011699:Putamen / Q000187:drug effects* / Q000378:metabolism; D013378:Substantia Nigra / Q000187:drug effects* / Q000378:metabolism
chemical_list: D015259:Dopamine Agents; D051100:Glial Cell Line-Derived Neurotrophic Factor; D009414:Nerve Growth Factors; D009419:Nerve Tissue Proteins; D015102:3,4-Dihydroxyphenylacetic Acid; D003913:Dextroamphetamine; D004298:Dopamine; D006719:Homovanillic Acid