Responses of the pigmented rabbit retina to NMPTP, a chemical inducer of parkinsonism.

The electrophysiological and neurochemical effects of N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (NMPTP), a chemical inducer of Parkinsonism in man and monkeys, on the pigmented rabbit retina were determined under both chronic and acute conditions. The implicit time, the oscillatory potentials, and the amplitude of the b-wave of the rabbit electroretinogram were affected; both dopamine and dihydroxyphenylalanine (DOPA) levels were depressed. Ultrastructural analysis of acute and chronic retinas showed the occurrence of an intranuclear filamentous inclusion in the nucleus of some cells in the inner nuclear and ganglion cell layer of chronic samples. The effects of the neurotoxin NMPTP on the retina suggest that dopaminergic metabolism is impaired, which then affects the components of the electroretinogram attributed to both bipolar and amacrine cells. In addition, the retina may provide a model in which to study the bichemical and pharmacological mechanisms of NMPTP toxicity.