Pubdate: Wed, 23 Jan 2002
Source: Orange County Register (CA)
Copyright: 2002 The Orange County Register
Author: Will Dunham, Reuters


Social Standing Is Key In Determining Who's Susceptible To Drug Use,
Study Concludes.

WASHINGTON -- Social standing - being dominant or subordinate - plays a 
vital role in susceptibility to drug use, scientists said Tuesday in a 
study of monkeys that may shed light on human addiction.

Researchers at Wake Forest University in Winston-Salem, N.C., found that 
macaque monkeys deemed to be subordinate in small groups were much more 
likely to give themselves doses of cocaine in a laboratory setting than 
dominant monkeys.

Brain chemistry linked to social rank explains the phenomenon, the 
scientists said in a study published in the journal Nature Neuroscience.

Where an individual monkey stands on the simian totem pole is reflected in 
the brain chemical dopamine, which is closely linked with cocaine and other 
types of substance abuse, they found.

The dominant monkeys experienced an increase in a type of dopamine receptor 
known to be involved in brain pathways for reward processing, and were less 
vulnerable to cocaine abuse than their wallflower laboratory companions. 
Michael Nader, who led the study, said the research showed that 
environmental changes can have a profound impact on brain chemistry 
relating to sensitivity to a given addictive drug - a finding that could 
have parallels in people.

Cocaine acts on the brain by raising levels of dopamine in synapses - gaps 
between nerve cells - with elevated dopamine levels corresponding to the 
"high" experienced by the user. Dopamine, categorized as a 
neurotransmitter, is released in normal nerve-impulse transmissions in the 

Nader and his colleagues studied 20 male monkeys. The researchers looked at 
their hormonal activity and behavior, then used a sophisticated imaging 
technique to measure activity in the brain.

A change in living arrangements was then imposed. The monkeys were moved 
into groups of four. In the ensuing social interaction over three months, 
dominant monkeys emerged in the five groups, and a hierarchy was established.

The researchers then introduced cocaine to the monkeys, allowing them to 
self-administer doses. The top monkeys were far less likely to do so than 
the others.

Brain scans revealed that the dominant monkeys - those that were the most 
aggressive and least submissive toward others - experienced major changes 
relating to dopamine starting after the group-housing arrangement was imposed.

Because the changes were not seen when the monkeys lived by themselves, the 
scientists said the changes in brain chemistry resulted from the process of 
becoming dominant.

"The environmental consequences of those social hierarchies resulted in 
these changes," Nader said in an interview. "And the changes were in the 
dominant animals and not in the subordinate animals. So the positive spin 
on that is that environmental enrichment can produce rapid changes in the 
brain that, in this particular case, protected the individual from drug 
abuse. And that is the applicability (to people)."

Nader said the findings involving these monkeys should not be interpreted 
to mean that, in people, those at the top of the social ladder are the 
least susceptible to substance abuse.

"I don't think it's the social subordination vs. the CEO that's the main 
point. It's that environmental enrichment ... can produce rapid and robust 
changes in the brain."
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