Ramifications of Gaba Receptor Subtypes on Retinal Information Processing
GABAergic inhibition shapes light responses in both plexiform layers of the vertebrate retina. GABA is contained in a population of horizontal cells and in about one-third of amacrine cells in the amphibian retina. Almost all second and third order neurons have GABA receptors. GABA’s influence is not only diffuse, but also diverse. Pharmacological studies, coupled with amino acid sequence analysis, have identified several subtypes of the GABA receptor, including: the classical GABAa, the GABAb, GABAρ, and GABAc receptors. We have begun investigating the role of these different receptors in information processing in the proximal retina. Although some of our results are preliminary, and our conclusions tentative, it appears that: 1) the GABAa receptor produces a strong, shunting inhibition of amacrine and ganglion cell EPSPs; 2) the GABAb receptor suppresses sustained signals while augmenting transient responses; 3) GABAρ receptors preferentially suppress transient ON responses; and 4) GABAc receptors appear to suppress sustained activity, somewhat similar to the action of GABAb receptors. Overall, GABA can modulate the retinal network through a variety of mechanisms, utilizing different receptor systems, to selectively suppress particular information pathways.
KeywordsGanglion Cell GABAa Receptor Bipolar Cell Gaba Receptor Amacrine Cell
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