Page 172 - The Memory Program How to Prevent Memory Loss and Enhance Memory Power

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From age forty to ninety, the nucleus basalis of Meynert gradually and progressively loses up to
half its cholinergic nerve cells.
This loss of cholinergic nerve cells causes a delay in the brain's ability to process information
quickly and accurately, which is why aging leads to slower reactions as well as to mild memory
loss.
In Alzheimer's disease, the nucleus basalis is nearly wiped out within a few years after clinical
onset of the illness, causing severe memory loss.

Cholinergic nerve cells release acetylcholine into a narrow cleft or space called the synapse. This
acetylcholine molecule races across the synapse and latches onto a receptor in the next neuron, called
the postsynaptic neuron. The postsynaptic receptor is specially configured for the acetylcholine
molecule, the way a keyhole receives a key. Attachment to this receptor triggers a series of
biochemical and physiologic events in the postsynaptic or receiving neuron, leading to a change in
brain function that involves improved mental arousal and memory. Once acetylcholine completes its
job, it is either sucked back by the nerve cell that released it, ready to fight another day, or it is
broken down by the enzyme acetylcholinesterase in the synaptic cleft.

Different Ways to Boost Acetylcholine

Cholinesterase inhibitors are compounds that inhibit the action of this enzyme, acetylcholinesterase.
Treatment with cholinesterase inhibitors indirectly raises the level of acetylcholine by preventing its
breakdown, thereby leading to improved attention, mental arousal, learning, and memory. In fact,
cholinesterase inhibitors have now reached the forefront of treatment in Alzheimer's disease, and
memory loss more broadly.

If you step back for a moment and think about the issue, this indirect approach does seem a bit
odd. Why not directly increase the amount of acetylcholine by pouring it directly into the synapse, or
administer a substance (precursor) that is converted to acetylcholine in the brain? Well, these
strategies have been tried with compounds like choline and lecithin.