title: Novel neuroprotective mechanisms of pramipexole, an anti-Parkinson drug, against endogenous dopamine-mediated excitotoxicity.
abstract: Parkinson disease is characterized by selective degeneration of mesencephalic dopaminergic neurons, and endogenous dopamine may play a pivotal role in the degenerative processes. Using primary cultured mesencephalic neurons, we found that glutamate, an excitotoxin, caused selective dopaminergic neuronal death depending on endogenous dopamine content. Pramipexole, a dopamine D2/D3 receptor agonist used clinically in the treatment of Parkinson disease, did not affect glutamate-induced calcium influx but blocked dopaminergic neuronal death induced by glutamate. Pramipexole reduced dopamine content but did not change the levels of total or phosphorylated tyrosine hydroxylase, a rate-limiting enzyme in dopamine synthesis. The neuroprotective effect of pramipexole was independent of dopamine receptor stimulation because it was not abrogated by domperidone, a dopamine D2-type receptor antagonist. Moreover, both active S(-)- and inactive R(+)-enantiomers of pramipexole as a dopamine D2-like receptor agonist equally suppressed dopaminergic neuronal death. These results suggest that pramipexole protects dopaminergic neurons from glutamate neurotoxicity by the reduction of intracellular dopamine content, independently of dopamine D2-like receptor activation.
authors.affiliation: Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Kyoto University, 46-29 Yoshida-shimoadachi-cho, Sakyo-ku, Kyoto 606-8501, Japan.
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Izumi
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Sawada
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Yamamoto
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Kume
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Katsuki
authors.forename: Shun
authors.initials: S
authors.lastname: Shimohama
authors.forename: Akinori
authors.initials: A
authors.lastname: Akaike
mesh_terms: D000818:Animals; D000978:Antiparkinson Agents / Q000494:pharmacology*; D052160:Benzothiazoles / Q000494:pharmacology*; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004298:Dopamine / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D018698:Glutamic Acid / Q000633:toxicity; D007150:Immunohistochemistry; D008636:Mesencephalon / Q000166:cytology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D018696:Neuroprotective Agents / Q000494:pharmacology*; D010300:Parkinson Disease / Q000378:metabolism* / Q000473:pathology; D000077487:Pramipexole; D051381:Rats
chemical_list: D000978:Antiparkinson Agents; D052160:Benzothiazoles; D018696:Neuroprotective Agents; D018698:Glutamic Acid; D000077487:Pramipexole; D004298:Dopamine