MAOA and Alzheimer disease: Interestingly though, a more robust displacement of the binding signals of the three tracers was noted when adding 1 μM harmine (another reversible inhibitor selective for MAO-A that is also known to inhibit protein kinase DYRK1A and tau phosphorylation at multiple AD-related sites [16]) to the blocking solution (Fig. 6); our interpretation of this result is discussed further below.