Retina of the tadpole and frog: delayed dendritic development in a subpopulation of ganglion cells coincident with metamorphosis.

In this study, the morphology of tadpole retinal ganglion cells was compared to that of frogs to determine if changes in dendritic structure occur during metamorphosis. Ganglion cells were analyzed in the tadpole and frog after backfilling with horseradish peroxidase. Representative ganglion cells are present in the tadpole retina, which directly correspond to each of the 7 cell classes found in the frog. However, cells in 3 of these classes (1, 3, and 7) exist in morphologically immature states in retinas from tadpole stages St. XIV-XIX. New dendritic branches appear and the dendritic arbors of these ganglion cells expand during metamorphosis. We propose that the increased dendritic arborization may be followed by new synaptic contacts onto these cells, which contributes to the emergence of new physiological receptive field properties in the frog.