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B. B. Thomas, T. Matsuda, D. Cholakian, F. Yong, S. R. Sadda, M. S. Humayun, J. D. Weiland; Morphologic Evaluation of the Superior Colliculus in a Retinal Degenerate Rat Model. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1429.
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© ARVO (1962-2015); The Authors (2016-present)
To examine whether retinal degeneration-induced visual deprivation causes alterations in the neurons of the higher visual areas of the brain, morphologic evaluation was performed in the superior colliculus (SC) of retinal degenerate (RD) S334 ter-line-3 rats, a model comparable to some forms of human retinitis pigmentosa.
Morphological evaluation of the SC neurons was performed in ten RD rats (500-600 day old) and five age matched controls (normal Copenhagen rats). Left and right SC were extracted from the golgi-impregnated brain. Vibratome sections were stained and imaged under a Nikon FXA microscope. SC from three of the RD animals and two of the controls were used for Hematoxylyn and Eosin (H&E) based evaluations performed in a 100 square µm area within the SC surface.
Morphological data suggested that in RD rats, differences can be observed in the dendritic arborization pattern in the superficial SC (within 200 µm from the SC surface). Several neuronal types were present in the superficial SC of normal control Copenhagen rats, but absent in RD animals, including multipolar widefield and dorsoventrally oriented cylindrical (widefield and narrow field) neurons. On the other hand, many undefined neuronal types (not observed in normal control animals) were observed in the superficial SC of line-3 RD rats. H&E staining- based observations suggested that significant differences exist between normal and RD rats in the mean nuclear count (p<0.0001, student t-test). In line-3 RD rats, the mean nuclear count in the superficial SC was 22.08±0.47/100 square µm SC area, whereas, in normal Copenhagen rats, the value was 34.750±0.99/100 square µm SC area. Morphometric evaluation revealed no apparent differences between the two groups in the mean nuclear diameter and internuclear material density values.
This study suggests that in S334ter-line-3 retinal degenerate rats, morphological alterations takes place in the SC due to prolonged visual deprivation. Such changes may affect the properties of the visual responses reaching the surface of the SC, and may have implications for therapeutic strategies such as retinal cell replacement or retinal prosthetics.
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