1‐Methyl‐4‐Phenylpyridinium Uptake by Human and Rat Striatal Synaptosomes

Abstract
1‐Methyl‐4‐phenylpyridinium (MPP+) was taken up into human and rat striatal synaptosomes by a saturable system, similar to that for dopamine, with Km values of 0.24 and 0.17 μM, respectively, and similar Vmax values. Uptake of MPP+ and dopamine into both rat and human synaptosomes was inhibited by cocaine and amfonelic acid, with the latter being five to 10 times more potent than the former. MPP+ uptake was potently inhibited by dopamine in preparations from both species. In general, the characteristics of human and rat synaptosomal MPP+ uptake were very similar. It seems unlikely that species differences in toxicity to 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine or reaction to dopamine uptake blockers stem from this system.