In the retina, several subpopulations of amacrine and cone bipolar cells have been implicated in glycinergic transmission on the basis of their ability to accumulate glycine and their endogenous glycine content. Although it is generally accepted that glycine-containing amacrine cells mediate an inhibitory response, the role of glycine in cone bipolar cells remains unclear. Furthermore, little attention has been directed towards the relationship between the role of glycine transporters in these cells and their relationship to neuronal glycine and the NMDA-type glutamate receptors. This proposal will test the hypothesis that the glycine transporter plays a major role, not only in uptake of glycine into a transmitter pool, but also in selective release of glycine for a modulatory role at NMDA receptors. Precedence for the transporter-mediated extrasynaptic release of GABA has been well-established in the retina. In this proposal, molecular biology techniques will provide the basis for generation of antisera that recognize the glycine transporter and the functional subunit of the NMDA receptor. These antisera will be employed in combined immunocytochemical studies that will compare the distributions of glycine, glycine transporters, and NMDA receptors. Nuclease mRNA protection assays and transfection studies will be used to extend the knowledge of the expression of these genes and the physiological roles of glycine transporters and NMDA receptors as they relate to glycinergic transmission in the inner retina.
