SMOKING ALTERS BRAIN 'LIKE DRUGS'

Smoking cigarettes causes the same changes to the brain as using
illicit drugs like cocaine, a study suggests.

US researchers compared post-mortem brain tissue samples from
smokers, former smokers and non-smokers.

Their findings, published in Journal of Neuroscience, suggested
smoking causes changes to the brain which are evident years after
someone has quit.

A UK expert said the changes might explain why smokers found it hard
to stop - and why they then relapsed.

The researchers from the National Institute on Drug Abuse (Nida)
looked at samples of human brain tissue from the nucleus accumbens
and the ventral midbrain - brain regions that play a part in
controlling addictive behaviours.

Eight samples were taken from people who had smoked until their
deaths, eight from people who had smoked for up to 25 years before
their death and eight non-smokers.

All died of causes unrelated to smoking.

Relapse

The scientists looked at levels of two enzymes - protein kinase A and
adenylate cyclase. Both translate chemical signals, such as dopamine,
which exist outside the cells, into a form that can be understood inside.

It would be surprising if taking large doses of a drug such as
nicotine many times a day over many years did not result in lasting
changes in the brain Dr John Stapleton, National Addictions Centre

Smokers were found to have higher levels of these enzymes in the
nucleus accumbens, a part of the brain that processes information
related to motivation and reward, which virtually all illicit drugs act upon.

But levels of both enzymes were also found to be high in the area of
the midbrain that responds to dopamine, which acts as a "reward
chemical" in smokers and former smokers.

The same changes had previously been seen in the brains of rats given
repeated injections of cocaine and morphine.

Writing in the Journal of Neuroscience, the team led by Dr Bruce
Hope, said: "The present study confirms that drug-induced
neuroadaptations [brain changes] observed in animals can also be
observed in humans."

The researchers suggest that the differences seen in both smokers'
and non-smokers' brains "may contribute to long-lasting alterations
in nicotine-induced reward and addiction in humans".

The researchers say this suggests that the changes persist long after
smoking has ceased and could contribute to drug relapse.

Dr John Stapleton, of the National Addictions Centre at King's
College London, said: "It would be surprising if taking large doses
of a drug such as nicotine many times a day over many years did not
result in lasting changes in the brain.

"The new results may take us closer to understanding these changes.

"The key question remains as to whether such changes are partly
responsible for the intractable nature of smoking and relapse after
many months or years of stopping."