LOWER-STATUS MONKEYS MORE LIKELY TO TAKE COCAINE

NEW YORK - The alpha male in a group of monkeys gets
the best banana, doesn't have to fight--and is less likely than
subordinate monkeys to use cocaine, scientists have observed.

Dr. Michael Nader of Wake Forest University in Winston-Salem, North
Carolina and colleagues found that animals who became dominant after
moving from solitary housing to social housing showed changes in brain
chemistry that made them less likely to use drugs. But monkeys who
were subordinate after the move showed no brain chemistry changes.

The findings suggest that environmental changes can affect the brain
and, perhaps, the success or failure of treatment for drug addiction,
the researchers conclude.

In the study, 20 monkeys that had been living alone in separate cages
for 18 months were moved into social housing, with four monkeys to a
cage.

One monkey in each group became dominant. In some groups, another
monkey eventually claimed the No. 1 rank, but there was always a
dominant monkey. During 3 months of living in small groups, the
animals were occasionally given access to cocaine.

At the beginning of the study and again during social housing, Nader
and his colleagues scanned the monkeys' brains and measured the volume
of dopamine D2 receptors.

These receptors interact with the ``feel-good'' brain chemical
dopamine, which is part of the brain's ``reward system'' and plays
what is thought to be a key role in mood and motivation.

Previous research has suggested that people who are vulnerable to
addiction may have fewer-than-normal brain receptors for dopamine. The
theory is that this pushes them to make up the difference by using
substances--including alcohol and other drugs--that elevate dopamine
levels in the body.

In monkeys that were dominant in their groups at the time of the brain
scan, the volume of dopamine D2 receptors increased 22% during the
course of the study.

Conversely, in subordinate monkeys, the volume of receptors did not
change appreciably, the research team reports in the January 22nd
online edition of Nature Neuroscience.

Furthermore, subordinate monkeys were more likely to give themselves
cocaine than to choose water. Dominant monkeys didn't avoid cocaine
altogether, but their intake was significantly lower than that of
their subordinates.

``So there was something about the social environment and being the
dominant monkey that resulted in this large change in D2 receptors,''
Nader said. Previous studies have shown that ''environmental
enrichment''--like moving from solitary to social housing--can
increase dopamine receptor numbers, he added.

``When you enhance the environment of the individual, you decrease the
propensity to abuse drugs,'' Nader explained.

``What we're thinking is that being the dominant male in that
environment is very enriching,'' he added. ``They have access to all
the food, they get groomed the most, no other monkey aggresses toward
the most dominant monkey--so they live a pretty nice life.''

The study results also suggest that drug abuse ``is not a life
sentence,'' Nader said. It may be that when an individual seeks
treatment, ``changes in the environment can impact the brain and that
can ultimately impact their success rate.''