RESEARCH LINKS DRUG ADDICTION TO SOCIAL STATUS

Lab monkeys who enjoy the exalted position of leader of the pack are
less likely to take cocaine than subordinates, a study by North
Carolina researchers shows.

Not only that, scientists found brain function in the dominant
primates actually changed after they attained their exalted social
status, the group from Wake Forest University reported yesterday in
the journal Nature Neuroscience.

"For monkeys, there's nothing better than being the top dog," said
neuropharmacologist Michael Nader, lead author of the report. Some
benefits include first dibs on treats, not to mention constant
grooming from inferiors. "They get access to all the resources that
are in there, they're No. 1 on the list and, for whatever reason, that
resulted in changes in the brain."

The point of the study was to examine whether environment -- in this
case, social status -- can help explain why some cocaine users become
addicted to the drug while others do not, said Dr. Nader, professor of
physiology and pharmacology at Wake Forest's medical school.

In this study, male monkeys were raised alone in cages for about 10
months on average before they were housed together in five groups of
four.

After three months, scientists ranked the monkeys based on how much
aggression they displayed and how many times other monkeys bowed to
their will. No. 1 was the most dominant, No. 4 was submissive and the
other two fell somewhere in between.

Brain scans before and after the social housing showed the dominant
monkeys in each of the five groups had 22 per cent more activity in D2
receptors, the part of the neuron that helps regulate the flow of
dopamine, the feel-good brain chemical. In subordinate monkeys, there
was essentially no change.

When the monkeys were trained to self-administer cocaine through an
intravenous shunt, subordinate monkeys would often take the maximum 30
doses offered in each hour-long session (about the equivalent to a
human dose). Although dominant monkeys did not avoid cocaine
altogether, they took the drug more infrequently and at lower doses.

The research is significant because it suggests that environment can
reduce vulnerability to drug use.

"That's encouraging, that the environment can produce such an effect,"
Dr. Nader said. "Irrespective of what the genetic predisposition [to
drug use] was, the environment overcame that in a positive way."

Frank Ervin, a psychiatry professor at McGill University in Montreal
who is also scientific director of a primate laboratory on the
Caribbean island of St. Kitts, said the research reminds us that
social structure makes a whole lot of difference to brain function, in
this case how the D2 receptors work.

But Dr. Ervin thought throwing four male monkeys together for three
months was not enough time for a stable social relationship to evolve
and questioned whether the so-called dominant monkeys were really No.
1.

"What they describe is a bully hierarchy," he said, noting the
researchers defined the dominant monkey as one who displayed the most
aggressive behaviour. "In a good social troop, the alpha is not the
one who shows aggression."

He thinks the caged monkeys not showing a lot of aggression were
likely not natural leaders but stressed out beta males.

The other problem with the animal model is it does not take into
account one of the most important determining factors in drug or
alcohol abuse: the genetic predisposition to addiction.