Evidence for retrograde axonal transport of MPP+ in the rat

Three to 24 h after injecting radioactive 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine ([3H]MPTP) into the rat striatum, a considerable number of neuronal perikarya were retrogradely radiolabeled in the dorsal raphe, substantia nigra pars compacta and selected regions of the substantia nigra pars reticulata, leaving cells in the ventral tegmental area unlabeled. Pretreatment with tranylcypromine prevented such radiolabel accumulation, indicating that 1-methyl-4-phenylpyridine (MPP+) (but not MPTP) undergoes selective uptake and subsequent retrograde transport in these specific striatal afferent systems.