title: Functional expression of the norepinephrine transporter in cultured rat astrocytes.
abstract: We assessed the functional expression of the norepinephrine (NE) transporter (NET) in cultured rat cortical astrocytes. Specific [3H]NE uptake increased in a time-dependent manner, and this uptake involves temperature- and Na+-sensitive mechanisms. The Na+-dependent [3H]NE uptake was saturable, and the Km for the process was 539.3 +/- 55.4 nm and the Vmax was 1.41 +/- 0.03 pmol/mg protein/min. Ouabain, a Na+-K+ ATPase inhibitor, significantly inhibited Na+-dependent [3H]NE uptake. The selective NE uptake inhibitor nisoxetine, the tricyclic antidepressants desipramine and imipramine, and the serotonin and NE reuptake inhibitor (SNRI) milnacipran very potently inhibited Na+-dependent [3H]NE uptake. On the other hand, GBR-12935 (a selective dopamine uptake inhibitor), fluvoxamine (a selective serotonin reuptake inhibitor), venlafaxine (a SNRI) and cocaine had weaker inhibitory activities. RT-PCR demonstrated that astrocytes expressed mRNA for the cloned NET protein, which was characterized as neuronal NET. Western blots indicated that anti-NET polyclonal antibody recognized a major band of 80 kDa in astrocytes. These data indicate that the neuronal NET is functionally expressed in cultured rat astrocytes. Glial cells may exert significant control of noradrenergic activity by inactivating NE that escapes neuronal re-uptake in sites distant from terminals, and are thus cellular targets for antidepressant drugs that inhibit NE uptake.
authors.affiliation: Department of Pharmacology, and Intractable Diseases Research Center, Tokyo Medical University, Shinjuku, Shinjuku-ku, Tokyo, Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Inazu
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Takeda
authors.forename: Teruhiko
authors.initials: T
authors.lastname: Matsumiya
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000378:metabolism*; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D008996:Monoamine Oxidase Inhibitors / Q000494:pharmacology; D009638:Norepinephrine / Q000037:antagonists & inhibitors / Q000493:pharmacokinetics; D050484:Norepinephrine Plasma Membrane Transport Proteins; D010042:Ouabain / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012964:Sodium / Q000502:physiology; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors; D027981:Symporters / Q000235:genetics / Q000378:metabolism*; D013696:Temperature; D013997:Time Factors
chemical_list: D004791:Enzyme Inhibitors; D008996:Monoamine Oxidase Inhibitors; D050484:Norepinephrine Plasma Membrane Transport Proteins; D012333:RNA, Messenger; C493226:Slc6a2 protein, rat; D027981:Symporters; D010042:Ouabain; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D009638:Norepinephrine