Fruit flies that develop homosexual tendencies when drunk may help
reveal how alcohol loosens human sexual inhibitions, claim researchers.

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Kyung-An Han
and her colleagues at Pennsylvania State University in University Park
used a voyeuristic chamber dubbed the "Flypub" to observe the influence
of alcohol on the sexual behaviour of male Drosophila fruit flies.

The
researchers got the flies drunk on the fumes of an ethanol-doused
cotton pad placed at the base of the chamber, and filmed them using a
camera held above the Flypub’s transparent ceiling.

Male Drosophila
will normally only court females, following them and vibrating their
wings in a courtship "song", before attempting to copulate.

The
first time they were exposed to alcohol, groups of male flies became
noticeably intoxicated but kept themselves to themselves. But with
repeated doses of alcohol on successive days, homosexual courtship
became common.

From the third day onwards, the flies were forming "courtship chains" of amorous males.

Blocked reward

Han
argues that the drunken flies provide a good model to explore how
alcohol affects human sexual behaviour. While the ability of alcohol to
loosen human inhibitions is well known, it is difficult for scientists
to study.

Han’s
team used flies that were genetically modified so they cannot release
dopamine in the brain unless the temperature exceeds 30 ºC, to test if
the effects of alcohol were dependent on this brain chemical. Indeed
they did show that the effect of alcohol on sexual behaviour depends on
the presence of this neurotransmitter.

That
makes sense, says Ulrike Heberlein, who studies the genetics of
alcohol-induced behaviour at the University of California, San
Francisco. She says dopamine is central to the neural reward circuits
that evolved to motivate animals to seek food and sex, but which are
also stimulated by drugs of abuse.

But
do fruit flies really provide a good model for what happens in the
inebriated human brain? Heberlein, who works on both flies and mice,
believes they do. "What is cool is that there is such a similarity,"
she says. "I am surprised by the parallels."

Via New Scientist