Effects of B vitamins on glutamate-induced neurotoxicity in retinal cultures

The effects of B vitamins on glutamate-induced neurotoxicity were examined using primary cultures obtained from the rat retina. Cell viability was markedly reduced by a brief exposure to glutamate followed by incubation with glutamate-free media for 1 h. Glutamate cytotoxicity was reduced in the cultures that had been maintained in thiamine-, pyridoxine- or nicotinamide-containing medium before the exposure to glutamate. Glutamate cytotoxicity was also reduced by chronic application of thiamine pyrophosphate and pyridoxal phosphate, which are active coenzyme forms of thiamine and pyridoxine, respectively. By contrast, chronic application of riboflavin, pantothenate, biotin, folic acid and inositol did not affect glutamate cytotoxicity. None of the B vitamins tested had any effect on glutamate cytotoxicity when added only during the exposure to glutamate. These findings suggest that chronically applied thiamine, pyridoxine and nicotinamide protect retinal neurons against glutamate cytotoxicity.