U OF S TEAM CREATES AGENT THAT MAY CURB ADDICTION

A University of Saskatchewan-led team has developed an agent that
could universally block a gamut of addictions, from nicotine to
alcohol to cocaine.

But don't light up a toke and start downing shots just yet --
researchers don't even know yet if the synthetic peptide is safe or
effective in humans.

In research published Sunday in the March edition of Nature Medicine,
investigators show a molecule called PTEN interacts with receptors
that in turn excite dopamine neurons -- the cells responsible for
signalling pleasure.

A synthetic peptide called Tat-3L4F interrupted that interaction and
stopped rats from being addicted to both nicotine and marijuana.

"Our finding opens up a new window for the potential use of our
peptide for the treatment of drug addiction," University of
Saskatchewan associate professor of psychiatry Dr. Xia Zhang said.

The research team also included members from the University of
Toronto and Vanderbilt University Medical Center in Tennessee.

Although only tested with nicotine and marijuana, Zhang said the
treatment could work for a range of illicit drugs because they all
act by exciting dopamine neurons in the brain's so-called ventral
tegmental area.

Since researchers can't ask the rats if they crave a joint or suffer
the munchies, they conditioned the rats with behavioural tests. Rats
were placed in a white box after receiving injections of addictive
drugs, and placed in a black box on alternate days, when they
received a placebo, or drugless, injection. Later, researchers placed
the rats between the black and white boxes and recorded how much time
they spent in each, reasoning mice who spent most of their time in
the white box were looking for a fix.

Rats who were addicted to nicotine or marijuana, but received the
special interfering peptide, spent equal time in the black and white
boxes, signalling they'd kicked their addictions.

Better yet, the peptide doesn't produce side effects like a
previously devised similar agent, which caused problems like penile
erection and anxiety.

Dr. Marvin Krank, a psychology professor at the University of British
Columbia Okanagan, warns such a drug could also stop patients from
feeling natural highs.

"They may be blocking normal natural positive rewarding things like
food and sex," Krank said. "By suppressing the reward system, some of
these drugs induce things like depression, inactivity and so on."

If researchers could design a molecule that selectively blocks drugs,
but not natural signals, it would be an "extremely powerful tool," Krank said.

"(The peptide) might block the high you get from amphetamine, but it
might make you one really unhappy person, so that you might not be
able to experience any pleasure at all," he said.

"We're a long ways a way from being able to generalize that to say,
'Here's a brand new treatment that's going to revolutionize addiction
therapy,' " he adds.

Zhang said his team has many more experiments to do, including
studying how safe and effective the peptide would be in monkeys, and
if those tests are successful, clinical trials in humans.

A 2004 survey by the Canadian Centre on Substance Abuse shows 44 per
cent of Canadians have tried cannabis in their lifetime and one in 20
Canadians has a "cannabis-related concern," like addiction.

The survey says 11.4 per cent of Canadians have tried hallucinogens,
10.6 per cent have tried cocaine and less than five per cent of the
population has tried ecstasy, inhalants or intravenous drugs like heroine.

Krank suggests one of the best cures for drug addiction is prevention.

"(What) we need to do is work more on the social and cultural end of
things," he said. "Many of the people who get drawn into this stuff,
it's because they don't have alternative outlets for finding a rewarding life."