Which intermediate of citric acid cycle is used in detoxification of ammonia in brain?

When ammonia is present in body in large amount (hyperammonemia), then this alpha-ketoglutarate of TCA combines with one amino group to form glutamate Fuher glutamate combines with the second amino group to form glutamine Glutamine is a safe form of ammonia storage & transpo. Alpha-ketoglutarate is depleted, which affects TCA cycle. That's why brain is affected as the first organ (Brain is highly aerobic tissue).