Pubdate: Mon, 13 Feb 2006
Source: StarPhoenix, The (CN SN)
Copyright: 2006 The StarPhoenix
Contact:  http://www.canada.com/saskatoon/starphoenix/
Details: http://www.mapinc.org/media/400
Author: Janet French

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."
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MAP posted-by: Beth Wehrman