With six legs, wings and bulging red eyes, it would seem fruit flies have very little in common with humans. Yet, a recent study found that if you get male fruit flies drunk, they go on the prowl for sex - just like humans.
The findings, reported earlier this month in the journal PLoS One, are the first to show that alcohol leads to increased arousal and reduced inhibitions in animals. Researchers hope the findings will help make sense of human behavior under the influence of alcohol and open new areas in addiction research.
This study provides the first physiological evidence that chronic exposure to alcohol leads to arousal and disinhibition of sexual behavior,"" Kyung-An Han, assistant professor of biology at Penn State University, said. ""This was always suspected but never before shown.""
The behavior of drunken fruit flies is less than shocking given the documented sexual behavior of intoxicated humans.
""Epidemiological studies show people under the influence of alcohol are more likely to engage in risky sexual behavior,"" Han said. ""This could be due to arousal or disinhibited cognition.""
Because fruit flies rapidly produce large numbers of offspring and live only a couple of months, they are an ideal model for studying how genes influence behavior.
""The brain is so complex that it is easiest to use a simple system to dissect out how gene[s] affect [the brain],"" Han said. The fruit fly provides just the system.
Everyday life for a fruit fly in the laboratory typically involves leisurely walks along the walls of glass vial homes, eating, sleeping and sex. According to the PLoS One report, to woo a mate, a male fruit fly will flutter his wings and tap or mount a desired female until she concedes.
Under the influence of alcohol, Han said the everyday behaviors of a fruit fly begin to change. Previous studies show when a fruit fly is exposed to ethanol - the intoxicating component of alcohol - it will first appear lost, then increase walking speed before stumbling and ultimately landing on its back with legs flailing through the air and passing out.
To test how intoxicated fruit flies interact with members of the same and opposite sex, Han led a team of researchers as they coaxed groups of flies into the ""Flypub,"" a plastic container where Han treated her guests (all-male, all-females and co-ed groups) to vaporized ethanol. After the flies passed out, they were returned to their home, where they later sobered up. For six days in a row, researchers sent fruit flies back to the Flypub.
On the second day of exposure to the Flypub, researchers discovered that, in between the alcohol-induced speed walks and passing out, intoxicated male fruit flies were not only more sexually aggressive toward females but would also engage in courtship with other males. With each new visit to the Flypub, the male fruit flies sought more sex.
Females, who Han said ""typically do not chase males for sex,"" did not seek sex with males or females when exposed to alcohol.
When given equal access to both male and female flies in the co-ed pub setting, Han said male fruit flies courted females at a higher rate than males. According to Han, the willingness of drunken male fruit flies to court other males does not represent a change in sexual orientation but rather demonstrates the ability of alcohol to increase the disinhibiton of fruit flies.
""What's interesting about the fruit fly study is that we see the fruit flies expressing very human behaviors,"" said Susan Crowley, project director of UW-Madison PACE Project, a project aimed at reducing the dangers of high-risk drinking among college students. ""The [drunken] fruit flies show reduced inhibition and an easier time being part of a group.""
Unlike the drunken male fruit flies, Crowley said male and female students are equally willing to take risks under the influence of alcohol.
""Alcohol continues to be the social lubricant for students on campus,"" Crowley said. ""Students see alcohol as a way to be more comfortable with the opposite sex."" When alcohol makes students too comfortable, the benefits of momentary pleasure can outweigh perceived risks.
""In college there's a tendency for students to push the envelope and test how much they can drink while maintaining [the ability to] make willful decisions,"" Crowley said. ""When they move into another state of inebriation, that's when dangerous behaviors begin.""
The 2007 PACE Project College Alcohol Study found 24 percent of students at UW-Madison who drank reported problems with engaging in unplanned sexual activity, and 10 percent failed to use protection when having sex. In approximately 80 percent of all sexual assaults on-campus either the victim, attacker or both were reported to be intoxicated, Crowley said.
""Alcohol provides an ice-breaker for students and an excuse for risk taking,"" Crowley said. ""Under the influence of alcohol, students are more willing to engage in activities they otherwise wouldn't engage in.""
Crowley warns that such behavior often leads students to not make the connection between heavy drinking and health risks. Injury, sexually transmitted diseases, unplanned pregnancies and sexual violence may haunt students long after the alcohol-induced high wears off.
While drunken fruit flies won't offer solutions to staying safe when drinking, Han hopes to use fruit flies to better understand how the brain is functioning to support sexual arousal and disinhibiton and how the enhanced pleasure-seeking behaviors displayed by fruit flies may explain alcohol addiction.
Crowley advises students to assign a responsible friend to help moderate an evening of drinking and to step in when decision-making seems compromised.
""If you are going to drink, be with someone who knows you well, someone who can tell you 'you've had enough to drink' and 'it's time to stop,'"" Crowley said. ""When students wander off and there is no moderator present - this is when serious issues occur.""
