Tuesday, 20 March 2012

Sexually frustrated flies get drunk

Male fruit flies that have been sexually rejected are more likely to turn to alcohol, research recently published in the journal ‘Science’ shows. This is the first discovery that social experiences can have long-lasting effects on the behaviour of fruit flies.


Male flies that have been sexually rejected consume
more alcohol (right).
Credit: G. Shohat-Ophir, taken from
http://news.sciencemag.org

The study created two different cohorts of flies: the rejected cohort was mixed with female flies that had already been mated and therefore refused to mate with the males. The males were rejected during one-hour sessions, three times a day for four days. The male flies in the mated cohort were mixed with receptive unmated females for 6-hour mating sessions, also for four days. The flies from each cohort were then given the choice between regular food and food containing 15% ethanol. The male flies in the rejected cohort consistently chose the ethanol containing food!

The researchers also uncovered some of the mechanisms responsible for the alcoholic behaviour observed in the rejected male flies. A neuropeptide called neuropeptide F (NPF, homologue to the mammalian neuropeptide Y) is responsible for alcohol consumption in fruit flies. When the heads of the flies were compared, it was found that the rejected males had significantly lower levels of NPF. In the next phase of the experiment, the NPF neurons were artificially activated which led to the conclusion that there may be a causal relationship between sexual experience, NPF levels and preference for alcohol. Further testing also showed that both sex and alcohol are rewarding behaviours (meaning that they are likely to be “pleasurable” experiences) for the flies. The authors of the study suggest that sexual deprivation leads to lower levels of NPF that make the flies look for rewards such as alcohol.

Reference:
Shohat-Ophir G, Kaun KR, Azanchi R, Heberlein U. Sexual Deprivation Increases Ethanol Intake in Drosophila. Science. 2012;335:1351-5.

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