A single gene may help overcome addiction

[Guest guest]

A single gene may help overcome addiction Charles Arthur

November 07 2004 at 01:37PM

 

 

http://www.iol.co.za/index.php?set_id=1 & click_id=117 & art_id=vn20041107114450378C\

196067

 

A single gene could be responsible for determining how easily people

become addicted to smoking, according to a report.

 

By tweaking a gene in the brains of mice, US researchers were able to

create a hypersensitive breed that becomes hooked at a nicotine level 50

times lower than that found in a typical smoker's blood.

 

Once addicted, the mice show the classic signs

of nicotine dependence.

 

Scientists believe the discovery could offer ways to help smokers

unable to give up.

 

 

In humans, nicotine generates a 'reward' feeling by producing a

jolt of dopamine

 

 

By producing a drug that somehow targets the neurons in the brain with

the nicotine sensitivity, scientists could help reduce the four million

smoking-related deaths each year.

 

The results, reported in the journal Science, showed that people's

ability to give up smoking - which, as Mark Twain quipped, can be done

" hundreds of times " - depends strongly on the chemical structure of a

particular neuron in the brain called the alpha-4 nicotinic acetylcholine

receptors.

 

Receptors are like chemical locks in the brain which react to

particular molecular keys.

 

In humans, nicotine generates a " reward " feeling by producing a jolt

of dopamine, a calming chemical, when it is taken up by the appropriate

brain receptors.

 

Addiction occurs when the nicotine " parks " in the receptors, which are

intended for a different chemical transmitter, acetylcholine.

 

But continued exposure to nicotine means the receptors become less

sensitive, which leads to the smoker's need for a regular " fix " .

 

Henry Lester, a biology professor at the California Institute of

Technology, where the work was done, said that the mice showed classic signs

of being addicted - including choosing nicotine before a food such as salt,

and frenetic activity.

 

" Dependence-related behaviours, including reward, tolerance, and

sensitisation, occur strongly and at remarkably low nicotine doses " in the

mice, the research team wrote.

 

Stephen Dewey, a scientist at Brookhaven National Laboratory, who has

studied epilepsy drugs to treat nicotine addiction, said: " The power lies in

the ability to be so specific. In being so specific, you can treat the cause

without the ramifications of the side-effects. "

 

But Daniel McGehee, a neurobiologist at the University of Chicago who

specialises in nicotine receptors, warned that interfering with nicotine's

effect on the brain might also dull such experiences as eating food or

drinking water.

 

" That (receptor) pathway is not there to promote tobacco use. It's

there to promote healthy behaviours that lead to the survival of our

species, " McGehee said.

 

Tampering with it " may interfere with our ability to find pleasure and

joy in normal, healthy things. "

 

Lester said: " What we have done is to show that a particular molecule

is not only necessary for nicotine addiction, but is sufficient for nicotine

addiction.

 

" When the particular alpha receptor is activated by nicotine - and no

other receptors - that is sufficient to produce some of the effects

associated with addiction. " - The Independent

 

 

 

a.. Related Stories More Medical Stories

a.. Gruesome exhibition shows effects of abuse

b.. Passive smoking: it's worse than you think

c.. Smoking can shave 10 years off your life

d.. Norway says no way to smoking in bars

e.. Smoking ban linked to drop in heart attacks

f.. Another cigarette myth goes up in smoke

 

 

This article was originally published on page 17 of Sunday Argus

on November 07, 2004