Depletion of norepinephrine in mouse heart by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mimicked by 1-methyl-4-phenylpyridinium (MPP+) and not blocked by deprenyl

A single dose of MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) in mice caused 75-87% depletion of heart norepinephrine (NE) concentration 24 hrs later. MPP+ (1-methyl-4-phenylpyridinium) caused similar depletion of heart NE. The effect of MPTP was not blocked by pretreatment with deprenyl, an inhibitor of type B monoamine oxidase (MAO-B). Also, deprenyl pretreatment did not prevent the depletion of heart NE after 4 daily doses of MPTP, even though in the same mice deprenyl pretreatment did prevent depletion of dopamine in the striatum and of NE in the frontal cortex. Apparently the depletion of heart NE by MPTP, unlike the depletion of brain catecholamines, does not require that MPTP be metabolized by MAO-B and can be mimicked by systemic injection of MPP+.