Glucose deprivation potentiates toxicity of ouabain and glutamate in cortical neurons cultured for different time periods

The addition of glutamate (Glu) to culture medium for 24 hours induced the dose-dependent death of rat cortical neurons cultured for 9–10 days and did not affect neurons cultured for 4–5 days; this suggests that the later neurons are neurochemically immature. In mature cultures, glucose deprivation (GD) enhanced the toxic effect of low Glu concentrations by 15% and did not influence the toxicity of high concentrations of this neuromediator. In immature cultures, GD potentiated the Glu effect independent of the concentration of this neuromediator. Inhibition of Na+/K+ -ATPase induced the death of some of the neurons. In the presence of a normal level of glucose, ouabain decreased the viability of mature and immature neurons to 67 ± 4 % and 79 ± 5%, respectively, and its presence during GD diminished viability to 28 ± 4 % and 56 ± 3%, respectively. The toxicity of ouabain was substantially attenuated when ionotropic glutamate receptors were blocked by MK-801. GD alone caused no significant increase in the death of these cells, even after a 3-hour incubation. Thus, GD strongly increases the susceptibility of neurons to the toxicity mediated by the activation of the NMDA subtype of ionotropic Glu receptors, even in the case of neurochemically immature neurons.