Ruthenium red protects against glutamate-induced neuronal death in cerebellar culture

Intracytosplasmic concentration of calcium dramatically increases after glutamate exposure in cultured neurons. Here, we investigated the effects of glutamate (100 mu M, 15 min) on the intramitochondrial calcium homeostasis using Ca-45 as a radioactive tracer. Calcium content increased in both cytoplasmic and mitochondrial fractions during the first 15 min following glutamate exposure. Whereas calcium content declined in the cytosolic fraction during the next 45 min, it remained elevated in the mitochondrial fraction. We next investigated the effects of ruthenium red, a mitochondrial calcium uptake blocker, on calcium homeostasis and neuronal viability after glutamate. Ruthenium red (100 mu M) fully protected granule cells from glutamate exposure when performed in low sodium-chloride solution. Furthermore, ruthenium red substantially lessened calcium accumulation in mitochondrial fraction after glutamate exposure.