Major metabolic fluxes (μmol/g tissue/min) in neuron-astrocyte coupling for resting conditions. The fluxes were calculated with the objective of maximizing the glutamate/glutamine/GABA cycle fluxes between the two cell types with subsequent minimization of Euclidean norm of fluxes, using the uptake rates given in Table 1 as constraints. Thick arrows show uptake and release reactions. Dashed arrows indicate shuttling of metabolites between the two cell types. Only key pathway fluxes are represented here for simplicity. The flux distributions for all the reactions listed in Additional File 1 are given in Additional File 4:Supplementary Table 3.