BRAIN STUDY OFFERS ADDICTION CLUES

Scientists believe they are closer to understanding why alcohol and drugs
exert an addictive effect on the brain. A study of rats suggests that part
of the brain linked to addiction produces a strong supply of morphine-like
substances called endorphins in response to alcohol, cocaine or amphetamine.

These endorphins could be the means by which the brain becomes trained to
crave, says the researchers.

The study, carried out at two US universities and published in the Journal
of Neuroscience, is thought to be the first to show the increased presence
of endorphins in this area under such circumstances.

The researchers gave the rats injections of alcohol, cocaine, amphetamine,
nicotine and an inactive salt solution.

They then measured endorphin levels in brain fluids removed from awake and
active rats.

They found a significant increase in endorphins in rats given the first
three substances.

Despite the fact that scientists have been studying the brain pathways of
addiction for more than a decade, they are still not fully understood.

About 15 years ago, it was discovered that in a region of the brain called
the nucleus accumbens, "drugs of abuse" caused an elevation of the brain
chemical dopamine.

Addiction jigsaw

The discovery that there may also be an increase in endorphins - which can
lock into receptors in the nucleus accumbens - sheds more light on the
process of addiction.

Dr Clyde Hodge, from the University of North Caroline at Chapel Hill, said:
"We hypothesize that this drug-induced release of endorphins may contribute
to the positive reinforcing and motivating properties of alcohol and
psycho-stimulant drugs.

"We did not find this same boost in endorphins in this brain region with
nicotine, but we don't know why.

"It could be that the dose of nicotine we used was too low or that nicotine
does not cause this same effect and instead acts in some other way."

Professor David Balfour, an expert in psychopharmacology from the
University of Dundee, said: "The dopamine hypothesis of dependence has been
around for the last 25 years.

"But what has become clear is that it isn't enough to explain the complete
biology of dependence.

"What these findings are doing is giving us another part of the jigsaw -
it's beginning to fit together."