In rat hippocampal slices, lactate serves as the primary oxidative energy substrate during neuronal activation, supporting sustained neuronal function when glucose is limited, because it can be efficiently converted to pyruvate by mitochondrial lactate dehydrogenase to fuel the tricarboxylic acid cycle and maintain ATP production.

When brain cells become active, nearby support cells produce lactate from sugar, which is sent to the active brain cells. Inside those brain cells, lactate is turned into pyruvate using a specific enzyme in the energy factories of the cell. This pyruvate then enters a cycle that makes ATP, the energy currency of the cell, keeping the brain cells working. At the same time, this process generates a molecule that neutralizes harmful chemicals produced during activity, preventing damage to the brain cells.