The emergence, localization, and maturation of neurotransmitter systems during development of the retina in xenopus laevis: II. Glycine

The high‐affinity uptake and release of glycine was studied in retinas of Xenopus laevis. In the toad and tadpole retina, ³H‐glycine was accumulated by a population of cells located predominantly in the inner nuclear layer. When retinas preloaded with ³H‐glycine were subjected to high K⁺‐concentrations, these retinas released large amounts of ³H‐glycine by a Ca⁺⁺‐dependent mechanism. The appearance and maturation of these putative glycinergic properties was followed during retinal development. Our results indicate that the high‐affinity uptake of glycine first appears around stage 33/34 whereas K⁺‐stimulated glycine release cannot be detected until stage 42.