News in Science

Jilted fruit flies turn to alcohol

Drowning sorrow Frustrated male fruit flies, whose sexual advances are rejected by females, turn to alcohol to drown their sorrows, a new study reveals.

Scientists at the University of California, San Francisco have discovered that a low amount of neuropeptide F molecule in the brains of sex-starved fruit flies pushes them to drink far more than their sexually satisfied counterparts.

The results have led scientists to speculate that their work could shed light on brain mechanisms behind human addiction.

A similar human molecule - neuropeptide Y - may also link social triggers to behaviours such as heavy drinking and drug abuse, according to the study published in journal Science.

"If neuropeptide Y turns out to be the transducer between the state of the psyche and the drive to abuse alcohol and drugs, one could develop therapies to inhibit neuropeptide Y receptors," says lead researcher Dr Ulrike Heberlein, a professor of anatomy and neurology at UCSF.

She says clinical trials were underway to determine whether neuropeptide Y can alleviate anxiety and other mood disorders as well as obesity.

For the experiment, male fruit flies were placed in a container with females flies, including both virgins and some that had already mated.

Virgin females were receptive to courting males and readily mated, but females flies who had mated lost interest in sex for a time because of sex peptide, a substance that males inject with sperm during the encounter.

Rejected males then stopped trying to mate, even when placed in the same cage as virgin flies.

But when they were placed by themselves in another container that had two straws - one containing plain food and the other containing food with 15 per cent alcohol - the rejected males binged on the alcohol.

Reward switch

The scientists say the behaviour was predicted by the levels of neuropeptide F in their brains.

"It's a switch that represents the level of reward in the brain and translates it into reward-seeking behaviour," says lead author Dr Galit Shohat-Ophir of the Howard Hughes Medical Institute Janelia Farm Research Center in Virginia.

Rejected flies had lower levels of neuropeptide F and sought an alternative reward through intoxication.

The scientists found that they could induce the same behaviours in the flies by genetically manipulating the levels of neuropeptide F in their brains.

Activating neuropeptide F production in the brains of virgin male flies caused them to behave as though they were sexually satisfied, and thus they were less keen to drink.

And lowering the levels of the molecule in sexually satisfied flies made them behave as though they were rejected, inciting them to drink more.