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Title: Development of the mammalian retinofugal pathways
Author: Chan, Sun-On
ISNI:       0000 0001 3527 0877
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 1991
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The retinofugal pathways in the rat and the ferret have been studied in order to understand how the decussation pattern at the chiasm and the retinotopic maps in the targets are developed. By using Dil as a anterograde marker, it was found that fibres from one eye are arranged in a quadrant-specific order in the developing rat optic stalk. This order decays as the fibres approach the brain and is eventually lost at the chiasm. Thereafter, the fibres are arranged in another order which may predict the dorsoventral axis of their target termination. There is no obvious difference in the arrangement of fibres when the albino and normally pigmented optic pathways are compared, indicating that the misrouting of fibres at the chiasm of albino rats is not due to a change in gross fibre topography in the stalk. By using Dil as a retrograde marker, it was found that the earliest uncrossed axons come exclusively from the central retina of rats, the axons from the temporal crescent arise later during prenatal development. The uncrossed fibres are found intermingling in the stalk with the crossed fibres at all ages studied, indicating that a non-chiasmatic cue must be involved in setting up the decussation pattern. It was also shown that only the temporal crescent but not the central ipsilateral component is abnormal in the albino rat during early stages of development, suggesting that the albino gene may act specifically on the cells in the retina. By removing one eye prenatally in rats and ferrets, either pigmented or albino, the uncrossed pathway of the remaining eye is reduced at birth. This indicates that the axons require an interaction with fibres from the other eye to select an uncrossed path at the chiasm. The decussation line of the pigmented enucleates is not altered, indicating that the early enucleation does not produce an albino-like uncrossed pathway. Further, it has been shown in ferrets that the temporal crescent can be abolished after an early monocular enucleation, indicating that the binocular fibre interaction at the chiasm is crucial for the development of the temporal crescent.
Supervisor: Guillery, R. W. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Retina ; Neural networks (Neurobiology) ; Rats as laboratory animals