SUBCELLULAR-DISTRIBUTION OF GABA RECEPTORS IN BOVINE RETINA

Two synaptosomal fractions were isolated from bovine retina and analyzed for GABA receptors using a [3H]GABA binding assay. Two receptor sites were identified: one with an affinity constant of 345 nm, which was uniformly distributed between the two fractions, and a second site with an affinity constant of 38 nm, which was primarily associated with the synaptosomal fraction enriched in photoreceptor cell terminals. Both sites demonstrated a high degree of pharmacologic specificity. The GABA receptor agonist, muscimol, was a more potent displacer than imidazolacetic acid or bicuculline; uptake blockers, diaminobutyric acid and β-alanine were poor displacers. These data provide further support for the role of GABA as a neurotransmitter in retina. It also suggests the presence of a significant GABAnergic system in the outer plexiform layer of the bovine retina. © 1979.