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Male fruit flies rejected by females in a lab experiment were more likely to go on an alcohol 'bender' than flies who were successful in wooing females into sex.
The frustrated flies were found to consume more offered food laced with alcohol than the sexually sated flies.
Scientists found that the rejected males who drank more had a lowered level of a chemical called neuropeptide F (NPF) while the successful males had a higher level.
It is possible the alcohol stimulates a 'reward' system in the fly's brain in the same way as sexual conquest and that levels of the chemical can control behaviour.
Because humans have a similar - but much more complicated and efficient brain - to the fly, the behaviour may offer an insight into how we behave.
Dr Galit Shohat-Ophir, the lead author of the report and now of the Howard Hughes Medical Institute in Virginia, US said:
"It is thought that reward systems evolved to reinforce behaviours that are important for the survival of both individuals and species, like food consumption and mating,.
"Drugs of abuse kind of hijack the same neural pathways used by natural rewards, so we wanted to use alcohol - which is an extreme example of a compound that can affect the reward system - to get into the mechanism of what makes social interaction rewarding for animals."
Dr Shohat-Ophir and colleagues subjected a number of flies to different tests in the laboratory of Ulrike Heberlein at the University of California, San Francisco.
In one set of experiments, revealed in the journal Science male flies were put in a box with five virgin females, which were receptive to the males' advances. In another, males were locked up with females that had already mated and which thus roundly rejected the males' attempts at sex.
Offered either their normal food slurry or a version charged with 15% alcohol, the mated males avoided the alcohol, whereas the sexually deprived males went on a comparative bender.
The team then searched for a chemical that connected the two sides of the story and came upon NPF.
They found that the heavy-drinking rejected males had a lowered level of the chemical, and sated, mated males had an elevated level.
"What we think is that these NPF levels are some kind of 'molecular signature' to the experience," Dr Shohat-Ophir explained.
To show that the NPF is actually responsible for the change rather than just associated with it, the researchers actively manipulated just how much NPF was in the flies' brains.
Those with depressed levels acted like the rejected males, and those with elevated levels behaved like the mated males.
"What this leads us to think is that the fly brain - and presumably also other animals' and human brains - have some kind of a system to control their level of internal reward, that once the internal reward level is down-regulated it will be followed by behaviour that will restore it back," Dr Shohat-Ophir said.
But in a note of caution in the same Journal, Troy Zars of the University of Missouri wrote that "anthropomorphising the results from flies is difficult to suppress, but the relevance to human behaviour is obviously not yet established".
Nevertheless, he suggested that the work linked "a rewarding social interaction with a lasting change in behaviour". {Via} - Murali Sridharan
