The curse of addiction must have existed since ancient
times.  It did not take long for primitive humans to discover
that certain plants have properties that contribute to the “well-
being” of a person.  The plants in question were either chewed,
eaten, or smoked.

Having never experimented with drugs, I can only speculate
as to the reasons people start using them and eventually getting
hooked.  Some possibilities:  Under peer pressure, at a young
age, trying a drug(s); escaping an emotionally taxing situation;
or simply boredom.  The brain has 40 to 50 billion neurons, the
number of connections (synapses) between these neurons defy
compilation (we’re probably talking of trillions).  There is
constant firing of neurons, endless chattering.  As long as we
are awake, the brain is incredibly active.  Active doing what?
Well, that’s exactly the point, the brain need to be constantly
“fed.”  What food?  Knowledge, challenges, intelligent activity.
We either keep ourselves meaningfully occupied, or we shush our
brain – with drugs.  But there is a price to pay.

According to recent research, psychoactive drugs can modify
the epigenetic code of our brain cells.  Recent findings throw
some light that might help to explain how transient changes in
the brain (the presence of drugs) result in long-term alterations
to the connections (between neurons) that can ultimately lead to
addiction.

The brain learns by constantly linking events with results
until associative memories are formed.  Drugs that produce a
“high” or a good feeling impact this learning circuit:  It seems
that, in addiction, the reward-related learning system goes into
pathological overdrive leading to compulsion.  Regular drug use
further reinforces the “good” memory and sets the stage for a
vicious circle: the more you use a drug, the more you need it;
the more you need it, the more you consume; and you start anew
with the situation getting progressively worse.

At a physical level, learning promotes the strength of
connections and enhances communications between neurons.  It is
not clear how this happens at the molecular level.  It is
believed that it involves the switching on of genes that control
changes in the structure of the connections.

A number of genes are switched on in brain cells following
consumption of a drug; new research shows that this switch
mechanism involves epigenetics modifications – chemical changes
to either the DNA or the histones.

I will remind the reader that epigenetics changes do not
affect the DNA code itself, but rather, make – or does not make –
the code available for transcribing and eventually synthesizing a
protein.

Depending upon the mode of consumption, genes are impacted
in three ways.  Let’s use cocaine as an example.  Certain genes
are switched on by infrequent (acute) administration of cocaine,
while others are switched on only after chronic use.  Finally,
some are switched on by both.  The gene activated by acute
consumption, get their associated histone H4 proteins acetylated,
while gene switched on by chronic drug use get their associated
H3 proteins acetylated.  Finally, genes that are activated by
both types of drug usage, show H4 acetylation when cocaine is
first used, and then switch to H3 acetylation as the consumption
becomes chronic.  One more point, H3 acetylation persists long
after cocaine withdrawal; this would explain why breaking an
addiction is such a difficult thing.

No doubt you’re reading this difficult and technical part in
the hope that I will tell you that there is on the horizon a
possible cure for addiction.  Is there?  It seems so, although we
are not there yet.

The same genes that are activated by cocaine can also be
switched on by other addictive drugs.  If it turns out that these
other drugs are also acting epigenetically and with long-lasting
effect, then researching how to erase the epigenetics changes in
specific areas of the brain could possibly lead to a treatment of
addiction.

Source

Addiction:  the epigenetic effect
Ruth Williams
September 2006
http://epigenome.eu/en/1,37,0

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