Updates:
Glucose versus lactate in immature brain slices
Brain metabolism updates: Sweet and sour recipes for the brain
Astrocyte-neuron lactate transport is required for long-term memory formation – F1000.com evaluation

The primacy of glucose as a mature brain fuel has been questioned and lactate was suggested to be a substrate that active neurons prefer over glucose (1). Lactate has long been considered to be a potentially damaging end-metabolite of anaerobic glycolysis (conversion of glucose to pyruvate when little  or no oxygen is available). Since the original report by Pellerin & Magistretti, it has been widely assumed that lactate production takes place in astrocytes. Pellerin & Magistretti (2) proposed that lactate may not be a metabolic dead-end product but rather the dominant oxidative substrate for neurons.

“Over the past decade scientists have passionately debated whether the activated brain burns glucose completely to water or incompletely to lactate,” said Karl Kasischke, a researcher in the Cornell University, Ithaca, NY (3). “Our results unify existing contradictory opinions and should be a win-win situation for both factions,” said Kasischke.

On the other hand there are opponents of the hypothesis discussing the theoretical background and critically reviewing the experimental evidence  (e.g., 4)

Sources

1. Magistretti PJ. 1999. Brain energy metabolism. (In) Fundamental neuroscience New York, Academic Press New York, Academic Press (pp) 389−413.

2. Pellerin, L. and Magistretti, P. J. (1994). Glutamate uptake into astrocytes stimulates aerobic glycolysis: a mechanism coupling neuronal activity to glucose utilization. Proc. Natl. Acad. Sci. USA 91, 10625-10629

3. Karl A. Kasischke, Harshad D. Vishwasrao, Patricia J. Fisher, Warren R. Zipfel, Watt W. Webb. Neural Activity Triggers Neuronal Oxidative Metabolism Followed by Astrocytic Glycolysis. Science 2 July 2004: Vol. 305. no. 5680, pp. 99 – 103

4. Ching-Ping Chih, Eugene L Roberts Jr.. Energy Substrates for Neurons During Neural Activity: A Critical Review of the Astrocyte-Neuron Lactate Shuttle Hypothesis. J Cerebral Blood Flow & Metabolism (2003) 23, 1263–1281;