Studies on 4-benzyl-1-methyl-1,2,3,6-tetrahydropyridine, a nonneurotoxic analog of the parkinsonian inducing agent 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine

Abstract

Previous reports indicate that 4-benzyl-1-methyl-1,2,3,6-tetrahydropyridine (BMTP), the benzyl analogue of the Parkinsonian inducing neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), is not neurotoxic in the C-57 black mouse even when administered at a dose 10 times greater than the dose of MPTP required to cause an 85% depletion of neostriatal dopamine. Intrastriatal microdialysis in the rat with the corresponding 4-benzyl-1-methylpyridinium ion BMP+ for 60 min, however, causes nerve terminal destruction similar to that observed following a 15-min perfusion with the 1-methyl-4-phenylpyridinium ion MPP+, the monoamine oxidase B (MAO-B) generated metabolite derived from MPTP. With the aid of purified beef liver MAO-B and synthetic standards, we observed the efficient and quantitative conversion of BMTP to the corresponding 2,3-dihydropyridinium intermediate BMDP+, which underwent further, but incomplete, oxidation to BMP+. These MPTP-type properties point to in vivo effects, such as pharmacokinetic parameters and/or alternative metabolic pathways, to account for BMTP's lack of neurotoxicity.