Marked increase in glutamate-aspartate transporter (GLAST/GluT-1) mRNA following transient retinal ischemia.

We have demonstrated the cellular localization of glutamate-aspartate transporter (GLAST/GluT-1) mRNA in the rat retina and its induction after ischemia by in situ hybridization. GLAST mRNA was expressed in the inner two-thirds of the inner nuclear layer (INL) and in sparse small cells in the inner portion of the ganglion cell layer (GCL) of the adult rat retina. GLAST mRNA was also found in about 90% of cells in the optic nerve head where more than 90% of cells express glial fibrillary acidic protein (GFAP) mRNA. Moreover, experimental occlusion of the central retinal artery followed by reperfusion for 48 h resulted in degeneration of neurons and a marked increase in GLAST mRNA expression in the INL. These findings suggest that GLAST may be expressed in Müller cells and astrocytes in the retina, and may play an important role in regulation of extracellular glutamate concentration especially under ischemic conditions.