快猫短视频

HITTING the bottle a little too often? In the future, your doctor may
prescribe a dose of extra brain receptors.

Researchers in the US have drastically reduced the intake of alcoholic rats
by giving them extra genes for a brain receptor that picks up pleasure signals.
The finding could lead to treatments for alcoholism.

Previous studies have shown that chronic alcoholics have reduced levels of
the D2 receptor, which binds to dopamine. Since dopamine is linked to feelings
of pleasure and is released when people drink or take drugs, it could mean that
people with fewer D2 receptors consume more and more drugs to get the same
effect.

So Panayotis Thanos of the Brookhaven National Laboratory in Upton, New York,
and his team decided to see if increasing D2 levels could restore the pleasure
response and reduce the need for alcohol. They injected a virus carrying the
gene for the D2 receptor directly into the brains of two groups of rats. One
group was addicted to alcohol, while the other generally preferred water to
booze.

Brain studies showed that this gene therapy increased the number of D2
receptors. And there was a definite effect on behaviour. 鈥淲ithin a matter of
three to four days we saw a very startling difference,鈥� says Thanos. The fluid
intake of the alcoholic animals dropped from 80 to 90 per cent alcohol to 20 per
cent or less. As for the other group, they became near teetotallers.

The effects only lasted about eight days, since D2 levels returned to normal
as the extra genes were broken down. But the researchers were able to recreate
the effect on the same rats days later.

鈥淭his research is very exciting,鈥� says Ellen Witt of the National Institute
on Alcohol Abuse and Alcoholism near Washington DC. But both she and Robert
Karp, programme director for genetics at NIAAA, are cautious about the
implications.

鈥淧eople hearing about this research might get very excited and think that we
are on the road to gene therapy for alcoholism,鈥� Karp says. 鈥淚 think that鈥檚
going to be science fiction for a long time.鈥� Instead, drugs that raise the
activity or the level of D2 receptors are a more likely first step, he says.
鈥淚t鈥檚 an exciting lead for therapy.鈥�

Jeffery Wickens鈥檚 team at the University of Otago in Dunedin, New Zealand,
has also shown how important dopamine is in addictive behaviour. In studies on
rats, published last week in Nature (vol 413, p 67), Wickens鈥檚 team
showed that when dopamine is released as a reward for certain behaviour, it
physically reinforces the connections between the neurons responsible for that
behaviour. If dopamine receptors are blocked, no changes occur in the strength
of the connections.

Giving people a dopamine blocker won鈥檛 reverse addiction, Wickens says. But
he thinks such drugs could be useful during treatment programmes. 鈥淩educing the
reinforcing effect of dopamine might provide some protection in the event of a
momentary relapse,鈥� he says.