3-Acetylpyridine-induced degeneration of the nigrostriatal dopamine system: an animal model of olivopontocerebellar atrophy-associated parkinsonism.

The effects of 3-acetylpyridine (3-AP) administration to rats on the mesotelencephalic dopamine system were assessed. A single 3-AP injection resulted in biochemical and immunohistochemical evidence of degeneration of the nigrostriatal dopamine system. Six weeks after 3-AP treatment decreases in both striatal dopamine content and the activity of the catecholamine biosynthetic enzyme tyrosine hydroxylase were observed. Immunohistochemical examination suggested a decreased density of striatal tyrosine hydroxylase-immunoreactive fibers and revealed the emergence of a distinctly patchy organization of the dopamine innervation to the dorsolateral striatum. While 3-AP administration resulted in biochemical and anatomical data consistent with the degeneration of nigrostriatal dopamine fibers, no significant changes in dopamine content or the density or pattern of tyrosine hydroxylase-immunoreactive fibers in the anteromedial prefrontal cortex or nucleus accumbens were seen. These data suggest that 3-AP administration may result in a relatively specific degeneration of the nigrostriatal dopamine system. Since 3-AP causes both a profound loss of the climbing fiber input to the cerebellum derived from the inferior olivary nucleus, and the degeneration of nigrostriatal dopamine neurons, 3-AP administration may provide a useful model of olivopontocerebellar atrophy-associated parkinsonism. Moreover, the differences in the neurotoxicity caused by 3-AP and that elicited by another pyridine which causes striatal dopamine depletion (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, MPTP) may offer important insights into the mechanisms of both species- and site-specific pyridine neurotoxins.