Retinofugal pathways in normal and albino axolotls.

The retinofugal pathways of normal and albino axolotls have been studied by tracing the transport of radioactive materials after tritiated proline was injected into one eye. The pathways demonstrated by this method include crossed projections to the diencephalon, pretectum, and tectum, and a small component that goes to the midbrain tegmentum in the basal optic root. Ipsilaterally, radioactive label was found in all of the same cerebral regions, but in much smaller quantities. Although on the basis of earlier fiber degeneration studies most of the label could be interpreted as evidence for direct retinofugal pathways, some of the label, especially that in the ipsilateral tectum, does not correspond to a known pathway and may represent a small new component or have been produced by transneuronal transport mechanisms. The pattern of labeling was the same in the albino as in the normally pigmented axolotls. Thus, it appears that the abnormality of the chiasmatic pathway, which has been found in albinos of many different mammalian species, does not occur in axolotls.