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Drunk Monkeys Mirror People

By Jennifer Viegas, Discovery News

May 9, 2006—Monkeys drink more alcohol when housed alone, and some
like to end a long day in the lab with a boozy cocktail, according to
a new analysis of alcohol consumption among members of a rhesus
macaque social group.

These and other observed behaviors strongly correspond with human
patterns of alcohol use. Researchers attribute a predisposition to
alcohol abuse in some monkeys and people to a combination of genetic
and environmental factors.

In the study subjects, "blood alcohol levels often exceeded the .08
percent level, which is the legal limit for most states in the U.S.,"
said Scott Chen, one of the study's authors and a researcher at the
National Institutes of Health Animal Center in Maryland.

The study, recently published in the journal Methods, also found that
booze affects monkeys much the same way it affects people.

"It was not unusual to see some of the monkeys stumble and fall, sway,
and vomit," Chen added. "In a few of our heavy drinkers, they would
drink until they fell asleep."

For the initial experiment, 21 females gained access to an
aspartame-sweetened ethanol concoction during a group "happy hour."
Neck collars registered the amount of fluid consumed, and each monkey
received a blood alcohol level test at the end of the period.

In a follow-up experiment, 10 monkeys were housed individually during
the "happy hour."

"The singly housed monkeys certainly drank more than the socially
housed monkeys- at least two to three-fold more," Chen told Discovery
News. "With the socially housed monkeys, there are a number of factors
that can potentially compete with access to alcohol, such as social
status or dominance ranking."

Lower-ranked monkeys and males tended to drink more overall, but
certain individuals consistently drank more than others, regardless of
status or housing conditions.

"Similar to humans, rhesus macaques have individual differences in
taste preference, stress levels, drug tolerance and genetic background
that lead to differences in alcohol intake," explained Chen.

In yet another study, the scientists gave a group of male monkeys
24-hour access to the beverage dispensers. According to the
researchers, a spike in consumption immediately followed the
facility's working hours.

"Like humans, monkeys are more likely to drink after stressful
periods, such as soon after the daily 8-5 testing hours and after a
long week of testing," said Chen.

Judy Cameron, a professor and senior scientist at Oregon Health &
Science University, told Discovery News, "The fact that different
animals consume very different amounts of ethanol suggests that the
neural systems in the brain that govern alcohol consumption differ in
macaques as they do in humans."

"Monkeys show highly individual responses in their choice to drink
alcohol excessively," agreed Kathleen Grant, a senior scientist at the
Oregon National Primate Research Center. "There are important
parallels to human alcoholism."

Since the monkeys appeared to go through withdrawal, Chen and his team
hope to investigate drugs that may help prevent related symptoms,
which often result in relapse in human alcoholics.