MONKEY COCAINE STUDY LINKS STATUS, ADDICTION

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
brain.

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."