LOCALIZATION OF THE GLUTAMATE TRANSPORTER PROTEIN GLAST IN RAT RETINA

Glutamate is a neurotransmitter in retina. Glutamate transporter prote ins keep the resting extracellular glutamate concentration low. This i s required for normal neurotransmission and prevents the extracellular concentration of glutamate from reaching toxic levels. Here we descri be the light and electron microscopic localization of the glutamate tr ansporter protein GLAST in rat retina using an antibody raised and aff inity purified against a peptide corresponding to amino acid residues 522-541. The strongest immunocytochemical labelling was observed in th e outer plexiform layer, ganglion cell layer, and optic disc. GLAST wa s found in Muller cell processes in all retinal layers, notably enshea thing the photoreceptor terminals in the outer plexiform layer, and in astrocytes close to vessels in the inner retina and optic disc. No la belling was observed in neurons. The electrophoretic mobility of GLAST in retina was similar to that in cerebellum. In conclusion, the findi ngs are in agreement with those reported by Derouiche and Rauen [7], e xcept that we did not detect any GLAST in the retinal pigment epitheli um.