Gamma-aminobutyric acid: a substrate for oxidative metabolism of cerebral cortex

Oxygen uptake of slices of cat cerebral cortex, which have been preincubated without substrate, is supported by subsequent addition of γ-aminobutyric acid or succinic semialdehyde to an extent comparable to that by glucose or l-glutamic acid. Esterification of phosphate by cat cortex mitochondria is also supported by γ-aminobutyric acid or succinic semialdehyde, which yielded P/O ratios between 2 and 3, similar to ratios obtained with pyruvate or l-glutamic acid. The relevance of these findings to functional activity of the brain is discussed particularly in reference to seizure states, where metabolic abnormalities of glutamic acid and γ-aminobutyric acid occur, and to the physiological roles which have been proposed for γ-aminobutyric acid. It is suggested that cerebral energy metabolism may in part depend upon oxidative metabolism via the glutamic-γ-aminobutyric acid pathway, which could regulate a portion of the available energy and thus affect levels of functional activity.