Functional importance of the astrocytic glycogen-shunt and glycolysis for maintenance of an intact intra/extracellular glutamate gradient.

It has been proposed that a considerable fraction of glucose metabolism proceeds via the glycogen-shunt consisting of conversion of glucose units to glycogen residues and subsequent production of glucose-1-phosphate to be metabolized in glycolysis after conversion to glucose-6-phosphate. The importance of this as well as the significance of ATP formed in glycolysis versus that formed by the concerted action of the tricarboxylic acid (TCA) cycle processes and oxidative phosphorylation for maintenance of glutamate transport capacity in astrocytes is discussed. It is argued that glycolytically derived energy in the form of ATP may be of particular functional importance in this context.