We describe a two-component positive-feedback system that could
account for the large reduction of acetylcholine that is characteristic
of patients with Alzheimer's disease (AD). One component is
ß-amyloid-induced apoptosis of cholinergic cells,
leading to a decrease in acetylcholine. The other component
is an increase in the concentration of ß-amyloid in
response to a decrease in acetylcholine. We describe each mechanism
with a differential equation, and then solve the two equations
numerically. The solution provides a description of the time
course of the reduction of acetylcholine in AD patients that
is consistent with epidemiological data. This model may also
provide an explanation for the significant, but lesser, decrease
of other neurotransmitters that is characteristic of AD.
