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Intranuclear rodlets in the rabbit retina following treatment with MPTP
Abstract:
Retinas from pigmented rabbits treated with N-methyl-4-phenyl-1,2,3,6- tetrahydropyridine (MPTP, a chemical inducer of Parkinsonism in man and monkeys) were studied using light- and electron microscopy. The nuclei of many cells in the inner nuclear layer and the ganglion cell layer of the treated retinas contained crystalloids (intranuclear rodlets) of varying length (0.5-8 microns) which were composed of bundles of 12 nm filaments and which were seen only rarely in untreated retinas. The induced rodlets are oval to round cylinders, 15-20 filaments across (although they are smaller in untreated retinas). Similar intranuclear inclusions have been described under varying conditions in neurons and glia in the central nervous system of several animal species. In rabbits injected acutely with MPTP, most of the affected cells are in the inner nuclear layer in the position of bipolar cells, while in the chronically injected animals, clearly identifiable amacrine cells, and the nuclei of some cells in the ganglion cell layer also contained the inclusions. Evidence is presented that the rodlet-containing cells in the ganglion cell layer include both ganglion cells and displaced amacrine cells. These anatomic findings are relevant to understanding the physiological and biochemical effects of the drug on the retina which we reported previously (Wong, Ishibashi, Tucker and Hamasaki, 1985).
Insights
N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) induced intranuclear rodlets in rabbit retinas. These inclusions, composed of filaments, appeared in bipolar, amacrine, and ganglion cells, offering insights into MPTP
Area of Science:
- Neuroscience
- Ophthalmology
- Toxicology
Background:
- N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is a neurotoxin known to induce Parkinsonism.
- The effects of MPTP on the retina are not fully understood, though previous studies have explored its physiological and biochemical impacts.
Purpose of the Study:
- To investigate the ultrastructural changes in rabbit retinas following MPTP treatment.
- To identify the specific cell types affected by MPTP within the retinal layers.
Main Methods:
- Light and electron microscopy were used to examine retinal tissues from MPTP-treated and control rabbits.
- Histological analysis focused on identifying and characterizing intranuclear inclusions.
Main Results:
- MPTP treatment induced the formation of intranuclear crystalloids (rodlets) in retinal cells.
- These rodlets, composed of 12 nm filaments, were observed in the inner nuclear layer (bipolar cells) and ganglion cell layer (ganglion cells and displaced amacrine cells).
- Rodlet formation varied between acute and chronic MPTP exposure, with amacrine cells being more affected in chronic cases.
Conclusions:
- MPTP induces significant anatomical changes in the rabbit retina, specifically the formation of intranuclear rodlets.
- The affected cell populations (bipolar, amacrine, and ganglion cells) provide a cellular basis for understanding MPTP's retinal toxicity.
- These findings contribute to the broader understanding of MPTP's neurotoxic effects and their relevance to Parkinsonism.