Figure 4.

Top row: average oxygen partitioning among the three cell types in the three different steady states, each computed from a sample of 100,000 configurations. In the two steady states, ES and AS, characterized by assigning a target rate of glutamate efflux, glutamatergic neurons uptake the majority of oxygen, 75% of the total in ES and 67% in AS, with the remaining almost equally split between astrocytes and GABAergic neurons. This is in agreement with the understanding that neurons are the major sites of oxidative rephosphorylation of ATP (Gjedde, 2007). In inhibitory steady state, the largest uptake of oxygen, 45%, is by astrocyte, in agreement with Hertz et al (2007) and Öz et al (2004), who reported a sustained astrocytic oxidative activity. Bottom row: histograms of oxygen glucose index (OGI) for each cell type in the three steady states. The OGI values for each cell type, which are the ratios of oxygen to glucose uptake, are computed from a 100,000 sample for each steady-state configuration. In ES, the OGI distribution in neuron can be up to 20 times higher than in astrocyte, in accordance with Gjedde (2007). GABA, gamma aminobutyric acid; ES, excitatory steady state; AS, awake steady state.