MPP+ depletes retinal dopamine and induces D-1 receptor supersensitivity.

Intraocular administration of 1-methyl-4-phenylpyridinium ion (MPP+) to mice resulted in a dose-dependent depletion of retinal dopamine (DA) and 3,4-dihydroxyphenylacetic acid. Pretreatment with benztropine partially prevented the MPP+-induced depletion. 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) was less active than MPP+ for depleting DA when administered by the same route and pretreatment with deprenyl partially prevented the depletion. Supersensitivity of retinal D-1 receptors resulted following MPP+-induced DA depletion.