Central depletion of dopamine in rats by 1-methyl-4-phenylpyridine.

Effects of 1-methyl-4-phenylpyridine(MPP+), a putative neurotoxic metabolite of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine(MPTP), on the contents of dopamine were examined in the various regions of the rat brain. Under anesthesia with pentobarbital sodium and flunitrazepam, MPP+ 150 micrograms/rat was intracerebroventricularly infused for 5 hours, at 30 micrograms/100 microliters/hr. Seven days later, the contents of dopamine, but not those of noradrenaline and activities of choline acetyl transferase in the brain were found to be significantly decreased, as compared to findings in the respective controls. The MPP+-induced depletion of dopamine was most evident in the striatum (38% of control). Contents of dopamine in the substantia nigra and ventral tegmental area were not significantly affected by MPP+. These results are interpreted to mean that intracerebroventricular continuous infusion of MPP+, in a relatively low concentration, induces a moderate but relatively specific disruption of central dopaminergic nerve terminals in rats, presumably by the selective accumulation of this neurotoxic agent into these nerve terminals.