Fig. 3.

Diverse proposed models of neural energy metabolism. At least four models of neural energy metabolism have been proposed based on the current evidence. The first model (①) is the ANLS hypothesis, which proposes that neuronal activity augments astrocytic glycolysis and lactate secretion and feeds neurons with lactate as an energy substrate. The second model (②) suggests that the lactate shuttle noted above occurs only under resting rather than stimulated conditions. The third model (③) postulates the direct uptake of glucose by neurons from the interstitium. The last model (④) states that lactate is transported from astrocytes to oligodendrocytes through gap junctions and that oligodendrocytes nurture and recharge axons with lactate.