Effects of LI⁺ on the metabolism in brain of glutamate, glutamine, aspartate and gaba from [1-¹⁴C]acetate in vitro

Guinea pig brain slices were incubated in media in which Li⁺ replaced part of the Na⁺. Leakage of glutamic acid, glutamine, aspartic acid and GABA into the media were increased markedly; glutamic acid was most affected. The uptake of [1-¹⁴C]acetate was decreased in the presence of Li⁺. Of the amino acids related to the citric acid cycle the labeling of glutamine was most affected. The presence of 100% O₂ counteracts in part the Li⁺ effects. The results were interpretable on the basis of the compartmentation of citric acid cycle metabolism in brain. It is suggested that the pool of 'transmitter' glutamate is related to the small pool of glutamate which actively labels glutamine.