MAOB and Alzheimer disease: MAO-B (but not MAO-A) activity is elevated in the hippocampus of AD patients [45], and the levels of several neuroamines (noradrenaline, serotonin, taurine, and dopamine), but not of other common neurotransmitters, such as glutamate, are reduced in the brain of people with DS [46, 47], consistent with an elevation in brain MAO activity in DS.