title: Involvement of tissue plasminogen activator-plasmin system in depolarization-evoked dopamine release in the nucleus accumbens of mice.
abstract: Tissue plasminogen activator (tPA), a serine protease, catalyzes the conversion of plasminogen to plasmin. In the present study, we investigated the role of the tPA-plasmin system in depolarization-evoked dopamine (DA) and acetylcholine (ACh) release in the nucleus accumbens (NAc) and hippocampus, respectively, of mice, by using in vivo microdialysis. Microinjection of either tPA or plasmin significantly potentiated 40 mM KCl-induced DA release without affecting basal DA levels. In contrast, plasminogen activator inhibitor-1 dose-dependently reduced 60 mM KCl-induced DA release. The 60 mM KCl-evoked DA release in the NAc was markedly diminished in tPA-deficient (tPA-/-) mice compared with wild-type mice, although basal DA levels did not differ between the two groups. Microinjections of either exogenous tPA (100 ng) or plasmin (100 ng) into the NAc of tPA-/-mice restored 60 mM KCl-induced DA release, as observed in wild-type mice. In contrast, there was no difference in either basal or 60 mM KCl-induced ACh release in the hippocampus between wild-type and tPA-/-mice. Our findings suggest that the tPA-plasmin system is involved in the regulation of depolarization-evoked DA release in the NAc.
authors.affiliation: Laboratory of Neuropsychopharmacology, Division of Life Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan.
authors.forename: Mina
authors.initials: M
authors.lastname: Ito
authors.forename: Taku
authors.initials: T
authors.lastname: Nagai
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kamei
authors.forename: Noritaka
authors.initials: N
authors.lastname: Nakamichi
authors.forename: Toshitaka
authors.initials: T
authors.lastname: Nabeshima
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Takuma
authors.forename: Kiyofumi
authors.initials: K
authors.lastname: Yamada
mesh_terms: D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D004298:Dopamine / Q000378:metabolism*; D005341:Fibrinolysin / Q000378:metabolism*; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009714:Nucleus Accumbens / Q000187:drug effects / Q000378:metabolism*; D017395:Plasminogen Activator Inhibitor 1 / Q000494:pharmacology; D010959:Tissue Plasminogen Activator / Q000172:deficiency / Q000378:metabolism*
chemical_list: D017395:Plasminogen Activator Inhibitor 1; D010959:Tissue Plasminogen Activator; D005341:Fibrinolysin; D000109:Acetylcholine; D004298:Dopamine