MPTP alters central catecholamine neurons in addition to the nigrostriatal system.
The present studies were undertaken to determine if MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) treatment in mice alters catecholamine or serotonin systems of the brain in addition to reported effects on the dopaminergic nigrostriatal system. Male Swiss-Webster mice were injected with 30 mg/kg MPTP daily for three days. Treated and control animals were sacrificed 10 and 24 days after the last injection, and brains were prepared for serotonin immunocytochemistry and catecholamine histofluorescence. MPTP treatment resulted in a reduced number of neurons and a reduced intensity of the fluorescence in the remaining cell bodies of substantia nigra pars compacta. A reduced presence of catecholamine varicosities in the medullary raphe nuclei and the ventromedial reticular formation of the medulla was observed. Immunocytochemical studies revealed no alteration in the number of serotonin positive cell bodies in the dorsal and median raphe nuclei. We suggest that MPTP treatment selectively alters some non-nigrostriatal catecholamine systems of the brain stem in addition to its toxic effects on the dopaminergic nigrostriatal system, while leaving other non-nigrostriatal catecholamine systems intact.