Astrocytes are 'good scouts': being prepared also helps neighboring neurons.

Recognition of glycogen as an active participant in the energetics of brain activation is replacing the long-held concept of glycogen as an emergency energy reserve, but the functional roles of glycogen and the cellular utilization of glycogen carbon are unresolved issues. Metabolic modeling by DiNuzzo et al, in this issue predicts that mobilization of glycogen during brain activation provides fuel for activated astrocytes and increases product inhibition of hexokinase thereby reducing astrocytic utilization of blood-borne glucose and increasing glucose availability for activated neurons. Glucose buffering and glucose channeling (not lactate shuttling to neurons) are proposed to be the consequences of glycogenolysis.