Toward development of an in vitro model of methamphetamine-induced dopamine nerve terminal toxicity.
To develop an in vitro model of methamphetamine (METH)-induced dopamine (DA) neurotoxicity, striatal synaptosomes were incubated at 37 degrees C with METH for different periods of time (10-80 min), washed once, then tested for DA transporter function at 37 degrees C. METH produced time- and dose-dependent reductions in the V(max) of DA uptake, without producing any change in K(m). Incubation of synaptosomes with the DA neurotoxins 1-methyl-4-phenyl-pyridinium ion, 6-hydroxydopamine, and amphetamine under similar conditions produced comparable effects. In contrast, incubation with fenfluramine, a serotonin neurotoxin, did not. METH-induced decreases in DA uptake were selective, insofar as striatal glutamate uptake was unaffected. Various DA transporter blockers (cocaine, methylphenidate, and bupropion) afforded complete protection against METH-induced decreases in DA uptake, without producing any effect themselves. METH's effects were also temperature dependent, with greater decreases in DA uptake occurring at higher temperatures. Tests for residual drug revealed small amounts (0.1-0.2 microM) of remaining METH, but kinetic studies indicated that decreases in DA uptake were not likely to be due to METH acting as a competitive inhibitor of DA uptake. Decreases in the V(max) of DA uptake were not accompanied by decreases in B(max) of [(3)H]WIN 35,428 binding, possibly because there is no mechanism for removing damaged DA nerve endings from the in vitro preparation Collectively, these results give good support to the development of a valid in vitro model that may prove helpful for elucidating the mechanisms underlying METH-induced DA neurotoxicity.
Kim
S
S
Department of Neurology, Johns Hopkins Bayview Medical Center, Baltimore, Maryland 21224, USA.
Westphalen
R
R
Callahan
B
B
Hatzidimitriou
G
G
Yuan
J
J
Ricaurte
G A
GA
D000818:Animals; D003042:Cocaine / Q000031:analogs & derivatives / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism / Q000502:physiology*; D018492:Dopamine Antagonists / Q000494:pharmacology; D018765:Dopamine Uptake Inhibitors / Q000032:analysis / Q000378:metabolism / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D005277:Fenfluramine / Q000494:pharmacology; D018698:Glutamic Acid / Q000378:metabolism; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D008694:Methamphetamine / Q000032:analysis / Q000378:metabolism / Q000633:toxicity*; D017072:Neostriatum / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D017729:Presynaptic Terminals / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017367:Selective Serotonin Reuptake Inhibitors / Q000494:pharmacology; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism; D013696:Temperature; D013997:Time Factors
D003042:Cocaine; D004298:Dopamine; D018492:Dopamine Antagonists; D018765:Dopamine Uptake Inhibitors; D005277:Fenfluramine; D018698:Glutamic Acid; D008694:Methamphetamine; D011493:Protein Kinase C; D017367:Selective Serotonin Reuptake Inhibitors; C021279:(1R-(exo,exo))-3-(4-fluorophenyl)-8-methyl-8- azabicyclo(3.2.1)octane-2-carboxylic acid, methyl ester