title: Inhibition of brain vesicular monoamine transporter (VMAT2) enhances 1-methyl-4-phenylpyridinium neurotoxicity in vivo in rat striata.
abstract: Dopamine neurons from various animal species differ in sensitivity to the neurotoxicity of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) or 1-methyl-4-phenylpyridinium (MPP(+)). Compared with striatal vesicles isolated from mice, those from rats have a higher density of the brain vesicular monoamine transporter (VMAT2) and a greater ability to sequester MPP(+), suggesting a larger storage capacity for MPP(+) in rat vesicles. In the present study, we examined whether striatal VMAT2-containing vesicles might provide protection against the neurotoxic effects of MPP(+) in vivo. Dose-response curves for striatally infused MPP(+) were determined in animals pretreated with or without a VMAT2 inhibitor. Ro 4-1284 administration (10 mg/kg i.p.; VMAT2 inhibitor) produced a 5-fold leftward shift in the MPP(+) dose-response curve and a significant lowering of the EC(50) concentration for MPP(+)-induced damage. These findings provide evidence for a substantial accumulation of MPP(+) in VMAT2-containing vesicles in vivo in the rat striatum and support the hypothesis that MPP(+) sequestration in vesicles can provide protection against its toxic actions. In mice, VMAT2 inhibition did not reliably enhance toxicity produced by a striatal infusion of MPP(+) or by systemic administration of MPTP. These data suggest that vesicular sequestration of MPP(+) may be of less importance in mice than in rats as relates to protection from the toxin. The present results also reveal that although VMAT2 inhibition enhanced striatal MPP(+) toxicity in the rat, the potency of MPP(+) in the rat striatum was less than that in mouse striatum. This implies that there are other factors that either exacerbate MPP(+) toxicity in the mouse or attenuate MPP(+) toxicity in rats.
authors.affiliation: Department of Neurology, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854-4535, USA.
authors.forename: R G
authors.initials: RG
authors.lastname: Staal
authors.forename: P K
authors.initials: PK
authors.lastname: Sonsalla
mesh_terms: D015655:1-Methyl-4-phenylpyridinium / Q000633:toxicity*; D012369:2H-Benzo(a)quinolizin-2-ol, 2-Ethyl-1,3,4,6,7,11b-hexahydro-3-isobutyl-9,10-dimethoxy- / Q000494:pharmacology; D000818:Animals; D001923:Brain Chemistry / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D008297:Male; D008562:Membrane Glycoproteins / Q000037:antagonists & inhibitors*; D026901:Membrane Transport Proteins; D051379:Mice; D017551:Microdialysis; D017072:Neostriatum / Q000187:drug effects / Q000378:metabolism*; D009479:Neuropeptides; D009498:Neurotoxins / Q000633:toxicity*; D018377:Neurotransmitter Agents / Q000037:antagonists & inhibitors*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013045:Species Specificity; D013572:Synaptic Vesicles / Q000187:drug effects / Q000378:metabolism; D013997:Time Factors; D050492:Vesicular Biogenic Amine Transport Proteins; D050493:Vesicular Monoamine Transport Proteins
chemical_list: D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009479:Neuropeptides; D009498:Neurotoxins; D018377:Neurotransmitter Agents; C493453:Slc18a2 protein, mouse; C493454:Slc18a2 protein, rat; D050492:Vesicular Biogenic Amine Transport Proteins; D050493:Vesicular Monoamine Transport Proteins; D012369:2H-Benzo(a)quinolizin-2-ol, 2-Ethyl-1,3,4,6,7,11b-hexahydro-3-isobutyl-9,10-dimethoxy-; D015655:1-Methyl-4-phenylpyridinium