title: Methamphetamine-induced rapid and reversible changes in dopamine transporter function: an in vitro model.
abstract: This laboratory has demonstrated that a single methamphetamine (METH) injection rapidly and reversibly decreases the activity of the dopamine transporter (DAT), as assessed ex vivo in synaptosomes prepared from treated rats. This decrease does not occur because of residual drug introduced by the original injection or nor is it associated with a change in binding of the DAT ligand WIN35428. The purpose of this study was to elucidate the mechanism or mechanisms of this METH effect by determining whether direct application of this stimulant to synaptosomes causes changes in DAT similar to those observed ex vivo. Similar to the ex vivo effect, incubation of striatal synaptosomes with METH decreased DAT activity, but not WIN35428 binding: the effect on activity was not eliminated by repeated washing of synaptosomes. Also, as observed ex vivo, incubation with 3,4-methylenedioxymethamphetamine, but not cocaine or methylphenidate, caused a METH-like reduction in DAT function. The rapid and reversible METH-induced diminution in DAT activity did not occur because of a change in membrane potential, as assessed in vitro and ex vivo by [(3)H]tetraphenylphosphonium accumulation. However, the METH-related decline in DAT function may be attributed to phosphorylation because NPC15437, a protein kinase C inhibitor, attenuated the METH-induced decline in DAT function. Similarities between previously reported effects ex vivo of a single METH injection on serotonin and norepinephrine transporter function and effects of direct METH application in vitro were also found. Together, these data demonstrate that the in vitro incubation model mimics the rapid and reversible effects observed after a single METH injection.
authors.affiliation: Department of Pharmacology and Toxicology, University of Utah, Salt Lake City, Utah 84112, USA.
authors.forename: V
authors.initials: V
authors.lastname: Sandoval
authors.forename: E L
authors.initials: EL
authors.lastname: Riddle
authors.forename: Y V
authors.initials: YV
authors.lastname: Ugarte
authors.forename: G R
authors.initials: GR
authors.lastname: Hanson
authors.forename: A E
authors.initials: AE
authors.lastname: Fleckenstein
mesh_terms: D015104:3,4-Methylenedioxyamphetamine / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002352:Carrier Proteins / Q000378:metabolism*; D003042:Cocaine / Q000031:analogs & derivatives* / Q000494:pharmacology; D003342:Corpus Striatum / Q000737:chemistry; D004298:Dopamine / Q000493:pharmacokinetics; D050483:Dopamine Plasma Membrane Transport Proteins; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D008562:Membrane Glycoproteins; D008564:Membrane Potentials / Q000187:drug effects; D026901:Membrane Transport Proteins; D008694:Methamphetamine / Q000138:chemical synthesis / Q000494:pharmacology*; D008774:Methylphenidate / Q000494:pharmacology; D008954:Models, Biological; D009419:Nerve Tissue Proteins; D009638:Norepinephrine / Q000493:pharmacokinetics; D009861:Onium Compounds / Q000378:metabolism; D009943:Organophosphorus Compounds / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000493:pharmacokinetics; D013574:Synaptosomes / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D050483:Dopamine Plasma Membrane Transport Proteins; D004791:Enzyme Inhibitors; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D009861:Onium Compounds; D009943:Organophosphorus Compounds; C493216:Slc6a3 protein, rat; D008774:Methylphenidate; D012701:Serotonin; D008694:Methamphetamine; D015104:3,4-Methylenedioxyamphetamine; C021279:(1R-(exo,exo))-3-(4-fluorophenyl)-8-methyl-8- azabicyclo(3.2.1)octane-2-carboxylic acid, methyl ester; D011493:Protein Kinase C; D003042:Cocaine; C013289:tetraphenylphosphonium; D004298:Dopamine; D009638:Norepinephrine