Pubdate: Mon, 21 Jan 2002
Source: Winston-Salem Journal (NC)
Copyright: 2002 Piedmont Publishing Co. Inc.
Contact:  http://www.journalnow.com/
Details: http://www.mapinc.org/media/504
Author: Danielle Deaver, Journal Reporter

COCAINE ADDICTION LINKED TO SOCIAL ORDER IN MONKEYS

Dominant Ones Less Likely To Get Hooked

Monkeys higher up on the social ladder are less likely to become addicted 
to cocaine, a finding that could explain why some people are more prone to 
addiction, researchers at Wake Forest University said.

In a study that will be published in next month's Nature Neuroscience, the 
scientists put 20 macaque monkeys in small groups. After they had created a 
social ranking, the scientists allowed the monkeys to inject themselves 
with cocaine.

The monkeys that were dominant in the groups - those with better access to 
food and more able to control the other monkeys - were less likely to 
become addicted.

"The positive spin on that is environment enrichment - changes in the 
environment that enhance someone's condition - can protect them from drug 
abuse," said Michael A. Nader, an associate professor for the departments 
of physiology and pharmacology and of radiology, who conducted the study 
along with nine colleagues.

"The negative is that stressors - in this case a social stressor - can also 
impact the likelihood that a drug will have a greater potential for abuse," 
he said.

It wasn't just the stress of being on the bottom of the social scale that 
made the monkeys use more cocaine. Using Positron Emission Tomography, a 
type of scanning, the researchers found that the monkeys' brains changed 
once their social patterns were established.

After three months in the social groups, the dominant monkeys grew more 
areas in their brains where dopamine - a natural chemical in the brain that 
triggers the feeling of being high - could be absorbed.

Cocaine blocks the dopamine receptors, allowing the dopamine - and its good 
feeling - to stay around longer.

Dominant monkeys ended up with 20 percent more dopamine receptors in their 
brains than the subordinate monkeys.

That allowed them to absorb the dopamine at nearly the rate they would 
without the cocaine, so they never used enough to become addicted.

"There is a typical characteristic to how they respond. We can say that the 
drug is serving as a reinforcer. In the dominant monkeys, it was not. They 
did not press the lever very much to get the cocaine," Nader said.

The subordinate monkeys had fewer receptors, so the cocaine was able to 
block them more effectively. The dopamine stayed in their brains longer, 
and they grew to like the cocaine.

The monkeys will stay on the cocaine and will be used in other experiments, 
Nader said.

Despite being addicted to cocaine, the monkeys are all in good health, he said.

"We limit the amount of cocaine that they can get. So that there's a very, 
very small likelihood that the cocaine will have any kind of adverse affect 
on them," Nader said. "You could not walk back there and tell which monkey 
had cocaine and which didn't."
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