Reduction of Alamar Blue, a novel redox indicator, is dependent on both the glycolytic and oxidative metabolism of glucose in rat cultured neurons

Recently, it has been hypothesized that neurons mainly utilize lactate produced by astrocytes to generate energy (i.e. ATP). Regardless of numerous studies, whether lactate rather than glucose fuels neurons in vivo remains a matter of controversy. In the present study we have examined the substrate-preference of the reduction of Alamar Blue, a novel redox indicator, by cultured rat astroglia and neurons. Alamar Blue reduction is dependent on cellular reducing equivalents. Therefore, the substrate-preference of Alamar Blue reduction could reflect that for cellular energy production. Rates of Alamar Blue reduction by 2 mM glucose were two-fold higher in astroglia than those in neurons. Alamar Blue reduction induced by 2 mM lactate was 78% of that by 2 mM glucose in neurons while only 20% in astroglia. Nevertheless, glucose elicited larger Alamar Blue reduction than lactate both in astroglia and neurons. These results indicate that neuronal energy production in vivo depends on both the glycolytic and oxidative metabolism of glucose even though astroglia rely on glycolysis as has been reported.