PURPOSE. TO determine whether low concentrations of glutamate induce cell death in purified rat retinal ganglion cells (RGCs). METHODS. Rat retinal ganglion cells were purified from dissociated retinal cells by a modified two-step panning method and were cultured in serum-free medium containing neurotrophic factors and forskolin. Survival of RGCs after exposure to glutamate, with or without glutamate receptor antagonists, was measured by calcein-acetoxymethyl ester staining after 3 days in culture. To visualize calcium signals, RGCs were loaded with the calcium indicator dye, fluo-3 acetoxymethyl ester, and fluorescence was measured by laser scanning confocal microscope. Electrophysiological properties of RGCs were examined by using the whole-cell, patch-clamp technique. RESULTS. The application of increasing concentrations (5-500 μM) of glutamate caused a dose-dependent increase in RGC death after 3 days in culture. Neurotoxic effects of low doses of glutamate were totally blocked by a specific α-amino-3-dihydro-5- methyl-isoxazol-4-propionic acid-kainate (AMPA-KA) receptor antagonist, 6,7- dinitroquinoxaline-2,3-dione (DNQX), but not by a specific N-methyl-D- aspartate receptor antagonist, 2-amino-5-phosphonovalerate (APV). In addition, calcium imaging and patch-clamp recordings showed that intracellular calcium accumulation and glutamate-evoked inward currents were completely blocked by DNQX but not by APV. CONCLUSIONS. LOW doses of glutamate can activate AMPA-KA receptors in RGCs, which causes increases in intracellular calcium and decreases in cell survival. This is the first report to show the functional role of calcium-permeable AMPA-KA receptors in cultured RGCs.
|Original language||English (US)|
|Number of pages||10|
|Journal||Investigative Ophthalmology and Visual Science|
|State||Published - May 1998|
All Science Journal Classification (ASJC) codes
- Sensory Systems
- Cellular and Molecular Neuroscience