DIFFERENTIAL EXPRESSION OF 3 GLUTAMATE TRANSPORTER SUBTYPES IN THE RAT RETINA

The immunocytochemical distribution of the three excitatory amino acid transporter subtypes GLT-1, GLAST-1 and EAAC-1 was studied in the rat retina using antibodies raised against synthetic peptides correspondi ng: to the C-terminus of each transporter subtype (Rothstein et al. 19 94). A comparative immunoblot analysis of rat cortex, cerebellum and r etina membrane proteins suggested the following rank order of glutamat e transporter subtype expression in retina: GLAST-1 greater than or eq ual to EAAC-1>GLT-1. GLAST-1 immunoreactivity was seen in Muller cells and astrocytes. EAAC-1 was found in horizontal cells, in amacrine and displaced amacrine cells, and in ganglion cells. A minority of bipola r cells also expressed EAAC-1. GLT-1 was preferentially expressed by d ifferent types of bipolar cells; however, it was also found in some am acrine cells. The functional role of this differential distribution of glutamate transporters in the retina is discussed.