Q. A 3-year-old girl with a history of arginase deficiency is brought to the emergency department by her parents. They report that she has been showing signs of confusion and irritability over the past few days. On examination, the girl appears lethargic and disoriented. Laboratory tests reveal hyperammonemia. In this child, hyperammonemia is most likely to result in which of the following changes in brain neurotransmitter levels?