Toward Development of an In Vitro Model of Methamphetamine-Induced Dopamine Nerve Terminal Toxicity

• Published in: The Journal of pharmacology and experimental therapeutics 2000-05, Vol.293 (2), p.625-633
• Main Authors: Kim, S, Westphalen, R, Callahan, B, Hatzidimitriou, G, Yuan, J, Ricaurte, G A
• Format: Article
• Language: English
• Subjects: Animals; Cocaine - analogs & derivatives; Cocaine - metabolism; Dopamine - metabolism; Dopamine - physiology; Dopamine Antagonists - pharmacology; Dopamine Uptake Inhibitors - analysis; Dopamine Uptake Inhibitors - metabolism; Dopamine Uptake Inhibitors - toxicity; Dose-Response Relationship, Drug; Fenfluramine - pharmacology; Glutamic Acid - metabolism; In Vitro Techniques; Kinetics; Male; Methamphetamine - analysis; Methamphetamine - metabolism; Methamphetamine - toxicity; Neostriatum - cytology; Neostriatum - drug effects; Neostriatum - metabolism; Presynaptic Terminals - drug effects; Presynaptic Terminals - metabolism; Presynaptic Terminals - physiology; Protein Kinase C - antagonists & inhibitors; Protein Kinase C - metabolism; Rats; Rats, Sprague-Dawley; Serotonin Uptake Inhibitors - pharmacology; Synaptosomes - drug effects; Synaptosomes - metabolism; Temperature; Time Factors
• ISSN: 0022-3565; 1521-0103
• DOI: 10.1016/S0022-3565(24)39277-8

To develop an in vitro model of methamphetamine (METH)-induced dopamine (DA) neurotoxicity, striatal synaptosomes were incubated at 37°C with METH for different periods of time (10–80 min), washed once, then tested for DA transporter function at 37°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 μM) 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.