Barflies (12.31.02) - Drunk flies are helping geneticists understand alcoholism.
Buzzed Brain (05.13.03) - Scientists may have identified what actually regulates the craving for alcohol in the brain, which could lead to new therapies for alcoholics.
You've heard the advice—don't drink on an empty stomach. Now scientists studying drunken fruit flies have discovered that the hormone insulin, which surges after we eat, may make the brain less sensitive to alcohol intoxication. This ScienCentral News video has more.
Bar Flies
Could a drunk Drosophila (aka a fruit fly) lead scientists find a new way to treat alcoholism in people? Since we share about two-thirds of our genes with fruit flies, researchers hope to discover genetic pathways that control our brains' response to alcohol by measuring flies' sensitivity to intoxication.
"In humans, the relationship between sensitivity and alcoholism is such that the less sensitive you are to alcohol, the more likely you are to become an alcoholic later in life," says Ulrike Heberlein, professor of anatomy at the University of California, San Francisco.
Heberlein has shown in previous research that behavior-wise, drunk flies have a lot in common with drunk humans—more active at first, then poor coordination, then sluggishness, and eventually, passing out. She and her colleagues use a device they call an "inebriometer," in which flies are placed at the top of a four-foot high column and exposed to ethanol vapor. "When flies become intoxicated they lose their posture and they fall through the column and we measure how long it takes for the flies to come out of the column," says Heberlein.
The researchers set out to find which regions in the flies' brains regulate sensitivity to alcohol intoxication. "We did this in an unbiased way by going into the fly brain using genetic tools and inactivating one brain region at a time," Heberlein explains. "And then we asked what happens to the behavior of the fly in the inebriometer."
They reported in the journal Nature Neuroscience that the flies that dropped the quickest had defects in brain cells that make insulin. "When you have a reduction in the amount of insulin that is produced, you have an increased sensitivity to the intoxicating effects of alcohol," says Heberlein.
When flies become drunk, they fall through the columns.
When the team then disrupted signaling molecules that respond to insulin in the brains of normal flies, they saw the same result. "What this essentially told us is that it's not just the cells that make insulin that are involved, but the response of the whole brain to insulin…is important in alcohol intoxication," she says.
Insulin is well-known for its role in regulating blood sugar levels in the body, and recent research has revealed that in the brain, insulin is involved in regulating food intake by acting on the molecular pathway that transports the brain chemical dopamine, which is associated with the pleasure people get from eating, sex, and drugs. So, Heberlein says, it makes sense that insulin might also be involved in alcohol or drug rewards. "It's a whole new role for insulin in regulating how the brain responds to drugs of abuse," she says. "I think it will hopefully entice people to take a much closer look at what this pathway does, insulin and its pathway do, in regulating the rewarding properties of drugs of abuse."
If the finding in these barflies is eventually confirmed in people, the researchers say it could be a big clue in helping prevent or treat addiction in people, perhaps with drugs that control insulin activity. But Heberlein says the next step is to study insulin's role in drug and alcohol responses in mammals.
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