Dr. Roberta Palmour

PHOTO: CLAUDIO CALLIGARIS

Drunken monkeys hold a clue

TIM HORNYAK | Locals on the sleepy Caribbean island of St. Kitts call her the "Monkey Doctor," but geneticist Roberta Palmour doesn't monkey around when it comes to her research.

Palmour spends about three months a year at the island's Behavioural Sciences Foundation getting vervet monkeys drunk in order to unravel the mysteries of human alcoholism.

The small, omnivorous vervets, also known as African green monkeys or Cercopithecus aethiops, are one of the few animal species that will voluntarily imbibe alcohol if it is offered to them.

Originally imported as pets from west Africa to the islands of St. Kitts, Nevis and Barbados during the late 17th century, wild vervets were later said to be caught by slaves using a mixture of rum and molasses in coconut shells. The monkeys would drink themselves into a stupor, and could then be simply picked up.

Thanks to their affinity for booze, the vervets are now providing Palmour and colleagues such as McGill psychiatrist Frank Ervine, who founded the vervet colony 30 years ago, with new insights into the biochemical and genetic underpinnings of human drinking.

"The remarkable thing that we have learned about alcohol consumption in these monkeys is how similar it is to the range of alcohol consumption that we see in people," says Palmour.

"We have the whole range of different patterns. We have monkeys that don't drink at all, that are real teetotallers, monkeys that drink in a very social kind of way, and -- of greatest interest to me because I'm interested in genes that increase vulnerability to psychiatric disorders -- the alcohol-abusing animals."

Roughly consistent with the prevalence of serious human alcohol abuse, only about 12 per cent of the colony's 1,000 vervet monkeys voluntarily drink over five grams of ethanol per kilogram per day, while less than five per cent consume everything available to them, usually over eight grams of ethanol, repeatedly drinking themselves into a coma.

Palmour calls the first group steady drinkers, and the second group binge drinkers. They differ more from each other in terms of their drinking patterns than in the amounts of alcohol they consume.

"If you allow them to have unrestricted access to alcohol, the binge drinkers will kill themselves in two or three months by drinking so much that they'll develop either liver damage or cardiomyopathy," says Palmour.

"The steady drinkers do very well in social groups, and many make very good alpha males. They run troops well, they keep order well, and they're very dominant. This is sort of contrary to what some of the human studies suggest. This kind of alcoholic monkey is a very functional animal."

In the past, scientific conventional wisdom held that primates didn't drink alcohol. The vervets, however, will drink anything from laboratory alcohol to St. Kitts rum, which they prefer because of the familiar smell of the island's sugar cane, which ferments naturally. Unlike the vervets, most primate species will not naturally drink alcohol unless they are specifically taught or manipulated by researchers.

While monkeys that are social drinkers prefer their alcohol sweetened, the steady and binge drinkers like drinking only alcohol and water, at about the same concentration as a whiskey and soda, roughly 20 per cent.

"Our monkeys are always given a choice of drinking alcohol or water," says Palmour. "We never give them only alcohol, and we have not used any kinds of behavioural manipulations to increase alcohol consumption."

Because of their alcoholic predisposition, and the fact that vervet monkeys share about 96 per cent of their genetic composition with humans, Palmour hopes that her team's upcoming map of the vervet genome will yield more clues in the study of genetic-likelihood alcoholism and other complex disorders such as hypertension and anxiety.

Alcoholism is one of the most common psychiatric disorders in Canada, and one of the most costly. In 1985, Statistics Canada reported that it accounted for over $2 billion per year in direct health costs, and a loss of over $5 million in productivity.

Before the 1960s, alcoholism was thought to be purely learned behaviour, the result of environmental factors. Palmour, however, joined McGill in 1982 to work on the growing evidence of a genetic vulnerability, which can be promoted or inhibited by the environment.

"In doing this monkey work, one of the things that is inescapable is that a part of alcoholism is biological," says Palmour. "These monkeys are not under social stress, they live in a beautiful tropical paradise, they don't have economic problems or deprivation. And yet they drink. So we hope that by knowing more about what those biological components are, we'll have better ways of intervening and, ideally, preventing problems before they occur in potential human alcoholics."

Though not as addictive as nicotine, alcohol may cause irreversible changes to the central nervous system. Due to awareness of the possible causes of overdrinking, many people from alcoholic families modify their drinking habits to limit their liability, says Palmour, who has helped identify some candidate genes that may increase vulnerability to alcoholism in the vervet population. Biochemical studies from the St. Kitts colony also indicate that the neurotransmitters dopamine and serotonin in steady and binge drinkers have altered functions, which may be exaggerated by chronic alcohol abuse.

"We tend to think that chemicals like nicotine and alcohol have reversible effects on the brain," says Palmour. "Once your brain has had a lot of experience with nicotine, it may not be the same brain that it was before.

"So teenage drinking binges are not necessarily something to laugh at. Some can't grow out of them to become normal, productive adults."