Autoradiographic studies of [3H]-glycine, [3H]-GABA, and [3H]-muscimol uptake in the mudpuppy retina.

Autoradiographic studies showed selective accumulation of [3H]-glycine, [3H]-GABA, and the GABA agonist [3H]-muscimol by neurons of the mudpuppy retina. [3H]-Glycine was taken up by bipolar cells, amacrine cells, and displaced amacrine or ganglion cells. Both [3H]-GABA and [3H]-muscimol were also accumulated by bipolar cells, amacrine cells and ganglion layer cells. However, the [3H]-GABA uptake pattern differed from that of [3H]-muscimol in showing labeling of horizontal cells, an increased percentage of cells in the ganglion cell layer, and a band in the most proximal portion of the inner plexiform layer. Variations in grain density suggested the presence of multiple subpopulations of [3H]-glycine- and [3H]-GABA-labeled amacrine cells. The labeled cells may play a role in inhibitory pathways in the inner retina.