Does the 'mystery of the extra glucose' during CNS activation reflect glutamate synthesis?

The hypothesis is proposed that the repeatedly demonstrated rise in local c erebral blood flow and glucose utilisation during neuronal activation, with out a corresponding increase in oxygen utilisation, may reflect glutamate f ormation from glucose, followed by complete oxidative degradation of glutam ate along complex and extended, but well described pathways, known to opera te in the brain. The former process requires large amounts of glucose but l ittle oxygen. The latter utilises oxygen but no additional glucose, is a pr olonged process and so at any one time involves only a small increase in th e rate of oxygen utilisation which is difficult to demonstrate experimental ly. (C) 1999 Elsevier Science Ltd. All rights reserved.