Dendritic morphology of identified retinal ganglion cells in Xenopus laevis: a comparison between the results of horseradish peroxidase and cobaltic-lysine retrograde labelling.

Following the application either of cobaltic-lysine complex or a 30% solution of horseradish peroxidase (HRP) in a sealed tube to the cut end of the optic nerve of young adult Xenopus frogs, the dendritic morphology of large ganglion cells was studied in retinal wholemount preparations, and compared with that in animals of the same size as revealed by the short time administration of HRP crystals. In the former two groups of animals, after 24 h survival, the size of the dendritic arborization of characterized ganglion cell types, Types I and III, were found to be significantly larger (61-79% and 180-187%, respectively) than those which survived 3 days after the administration of HRP crystals. These findings suggest that the very fine dendritic branches of large ganglion cells may remain unlabelled after a short-time exposure to HRP.