In a healthy, non-diseased brain, the small amount of extracellular Ab is degraded by microglia and astrocytes.
•Aβ is generated at high levels in the normal brain as a consequence of synaptic activity
•Aβ is present in the brain at 50-100 fold higher levels than in plasma
•Aβ is synthesized at a rate of 7.6%/hr
•Aβ is cleared from the brain at a rate of 8.3%/hr
(Bateman et al. NatMed 12:856, 2006)
Perturbations in clearance will result in accumulation of Aβ in the brain