k4 b k4 b

k3 a k3 a

k1 a b k1 a b

v v

Extracellular concentration of Acetylcholine (ACh)

Relative concentration of Acetylcholine

Extracellular concentration of β-amyloid

Production rate of ACh

Formation of β-amyloid from APP

Effect of extracellular ACh

Intracellular concentration of β-amyloid rate

a 50

Brain Constant_flux__irreversible k2

Brain Decrease_in_the_extracellular_concentration_of_beta_amyloid_0 k4 b

Brain Effect_of_extracellular_ACh_0 k3 a

Brain Loss_of_intracellular_choline_0 k1 a b