“Tony” did everything he could to get the pretty red-eyed girl. He chased her into the corner, tapped her abdomen with his forelegs, serenaded her with his single-winged song, and even licked her genitalia. Despite a perfect performance of this hard-wired mating dance, he was rejected.
Like any good cowboy in a sad country song, Tony turned to the bottle. But unlike most cowboys, Tony is a fly.
New research shows that humans aren’t the only species to turn to alcohol after social or sexual rejection. The paper Sexual Deprivation Increases Ethanol Intake in Drosophila, published last month in Nature, explores the influence of reward pathways on sex, drugs and social interactions — and gives a whole new meaning to the term “barfly.”
The brain’s reward system is designed to reinforce behaviors necessary for survival. Both natural “highs” and highs that result from drug intake can trigger this reward system. Abnormal regions within reward pathways are often associated with addiction.
To study these pathways, researchers from the Austin drug and alcohol addiction programs subjected flies to two separate scenarios. One group of male flies (dubbed “rejected-isolated”) experienced 1-hour sessions of sexual rejection three times a day for four days (they were exposed to females that already had mated). These males responded by showing suppressed courtship behavior in future interactions with receptive (virgin) females. No surprise there. The second group — the “mated-grouped” — mated with multiple receptive virgin females for 6 hours a day for 4 days.
Flies from each group were then given a choice between alcohol-free food, and food containing 15% ethanol. The results? The mated group preferred alcohol-free food, and the social and sexual rejects preferred the alcohol.