Chapter 1 Expression of GABAA receptors in the vertebrate retina

Abstract

This chapter reviews the evidence of the distribution and localization of gamma-aminobutyric acid (GABA) receptors (GABA A ) in the vertebrate retina. In the retina, GABA has a major role in the processing of visual information and the major site of action of GABA is at GABA A receptors. Initial investigations using in vitro receptor autoradiography indicated that specific, high affinity GABA A binding sites are abundant in the inner plexiform layer (IPL). More recently, in situ hybridization and immunohistochemical approaches have demonstrated that different GABA A messenger RNAs or polypeptides are expressed by a variety of cell populations in the retina. These observations, together with molecular cloning, RNA hybridization, and biochemical and pharmacological findings—that indicate GABA A receptor heterogeneity in the nervous system—are consistent with the presence of multiple GABA A receptors in the retina. GABA A receptors are expressed by goldfish and likely by chicken photoreceptors. This observation in goldfish retina is in agreement with several electrophysiological investigations that indicate the presence of GABA A receptors on fish cone photoreceptor terminals. In mammals, to date there is no evidence for the localization of GABA A receptors at photoreceptor terminals.