Glucose deprivation produces a prolonged increase in sensitivity to glutamate in cultured rat cortical neurons

Abstract

In this study we investigated whether the link between mitochondrial dysfunction and deregulation of Ca 2+ homeostasis preceding excitotoxic cell death is mediated by cellular deenergization. Glycolytic and/or mitochondrial ATP synthesis was inhibited with 2-deoxy- d -glucose (2DG) and oligomycin, respectively. Changes in cytoplasmic Ca 2+ concentration ([Ca 2+] c) and mitochondrial membrane potential were simultaneously measured in response to low (10 μM) glutamate concentrations, using the fluorescence dyes fura-2FF and rhodamine 123. 2DG, which blocks glycolysis and also inhibits mitochondrial respiration due to depletion of pyruvate, greatly increased and accelerated glutamate-induced elevation of [Ca 2+] c and mitochondrial depolarization. The 2DG-induced hypersensitivity to glutamate was observed even after 150-min washout of 2DG with glucose-containing medium, suggesting a permanent deterioration of mitochondrial function. Prior blockade of only glycolytic (2DG with pyruvate) or only mitochondrial (oligomycin) ATP synthesis did not affect neuronal sensitivity to glutamate. Collectively, these studies show that to maintain the sensitivity of neurons to glutamate at control levels at least one of the cellular sources of ATP production must be intact. Either glycolysis or oxidative phosphorylation can effectively support Ca 2+ homeostasis in cultured forebrain neurons.