Does early monocular enucleation in a marsupial affect the surviving uncrossed retinofugal pathway?

摘要

Monocular enucleations have been done during early stages (postnatal days 3 to 9) of visual system development of Monodelphis domestica, in order to determine whether in this marsupial, as in several eutherian mammals, there are any interactions between the pathways from the two eyes in establishing the uncrossed retinofugal projection. We have examined the distribution and the number of retrogradely labelled ganglion cells that project to the same side of the brain from the surviving eyes shortly after the uncrossed pathway is first formed in normal development (postnatal days 14 to 28). Even at these early stages of development the surviving uncrossed pathway shows no significant reduction, confirming earlier observations of adult marsupials and showing that at no stage in development is there any evidence that the crossed pathway from one eye influences the navigation of axons that will form the uncrossed pathway from the other eye. This is in sharp contrast to observations of mice, rats and ferrets and is in accord with expectations based on the difference of the chiasmatic structure in marsupials as compared with eutherians.