- [Voiceover] Scientists and physicians continue to learn
more and more about Alzheimer's disease and dementia
in general, but unfortunately, they still haven't
found a cure.
With that said, though, there are medications
that can help lesson the symptoms of dementia,
like memory loss and confusion.
Currently, all the medications approved
by the Food and Drug Administration or the FDA
are aimed at either one of two neurotransmitters:
acetylcholine or glutamate.
The first class of drugs are cholinesterase inhibitors.
Acetylcholine is a really important neurotransmitter
in our brain and nervous system.
Even though it has important functions in other parts
of our body, in our brain, it helps our neurons communicate.
And it's this communication of our neurons
that allows our brain to think and do things
like sustain attention, sense things, learn
and remember things.
Okay, so, say we have these two neurons here
that are trying to communicate,
one transmitting neuron and one receiving neuron.
The transmitting neuron releases
the neurotransmitter acetylcholine, which then binds
to an acetylcholine receptor on the receiving neuron.
And this is how these two neurons communicate, right?
To sort of regulate this process, though, you have this
enzyme that constantly breaks down the acetylcholine
that's being released and this sort of makes sure
that too much doesn't build up.
And this guy is called acetylcholinesterase,
and it breaks acetylcholine down into acetic acid
and choline.
Think of acetylcholinesterase like Pac-Man
and all of these acetylcholines as the little dots
that he eats.
He's constantly going around eating the dots,
but some of them may get by to communicate
between the neurons.
So, it's like this balance, right, of some of the dots
being eaten and some communicating.
Acetylcholinesterase is a type of cholinesterase.
So, if we throw a cholinesterase inhibitor into the mix,
like the ghost in Pac-Man, then we inhibit or stop
our Pac-Man from doing his job of eating the dots, right?
Which means more of these dots build up,
and we tilt the balance in favor of the dots
or acetylcholine.
Now, patients with Alzheimer's disease, though,
already have decreased levels of dots in the first place.
So, with Pac-Man there, they have even less.
But if we inhibit Pac-Man, then we have less dots
being eaten, right?
And so, we end up with more active acetylcholine.
And by doing this, by stopping the enzyme that breaks
down acetylcholine, we can help neurons communicate
in people with Alzheimer's disease.
And this medication can help delay worsening
of dementia symptoms for about six to 12 months
on average, for about half of the patients that take them.
And although they're usually pretty well tolerated,
some side effects can include nausea, vomiting,
and loss of appetite.
All right, so that's the first type of medication
for Alzheimer's disease.
The second type targets the neurotransmitter glutamate,
and is called memantine.
Just like acetylcholinesterase inhibitors,
memantine is prescribed to help patients with symptoms
related to memory, attention, reasoning,
and language skills.
Instead of acetylcholine, though, now we focus
on this neurotransmitter called glutamate.
Glutamate, when at normal levels, actually helps
our learning and memory, and is considered
an excitatory neurotransmitter.
When glutamate levels get too high, though,
it's actually toxic to the cell.
And we use the word called excitotoxicity,
where the cell gets actually too stimulated and may die
as a result.
Having too much glutamate is thought to be one
possible way that people with Alzheimer's disease
lose nerve cells and therefore have problems
with learning and remembering new things.
So, again, we've got our two neurons transmitting
and receiving, right?
And we have this receptor on the receiving neuron
called the NMDA receptor, which is also like this channel
or gateway that lets in ions to the receiving cell.
Now, this gateway lets them in when glutamate binds to it.
So, if there's too much glutamate and this gateway
is always open, then the receiving neuron can suffer
from excitotoxicity, because it's like always
being stimulated.
Now, memantine blocks this receptor for glutamate,
so it keeps this channel closed more.
And when it's closed more, we bring down the stimulation
to normal levels and avoid killing the cell
by overstimulating it.
Think of glutamate like this key that opens the door
to this party down here, letting all the ions in.
If too many get in, though, the party gets too big
and too crowded and out of control.
If we put a different lock on the door,
memantine, then the key won't open it,
and the party stays at reasonable levels.
Now, memantine is used most often to treat moderate
to severe Alzheimer's disease, and will often be taken
alongside cholinesterase inhibitors.
Some side effects can be things like headache,
confusion, and dizziness.
So, switching gears a little bit, other forms of treatment
often target behavioral symptoms, like agitation,
irritability, aggression, and anxiety.
Usually, it's preferred to focus on treatments
that don't use medications for these, though,
like behavioral modification,
since a lot of medications intended to treat
behavioral symptoms can actually increase confusion
and can even be associated with increased mortality.