Study carried out on male fruit flies show that those that have been rejected by females drink significantly more alcohol than those that have mated freely, the BBC reports. This is because the brain’s reward systems reinforce behaviors required for species survival, including sex, food consumption, and social interaction. Drugs of abuse co-opt these neural pathways, which can lead to addiction.

The work points to a brain chemical called neuropeptide F, which seems to be regulated by the flies' behavior.

Human brains have a similar chemical, which may react in a similar way.

The connection between alcohol and this chemical has already been noted in studies involving hard-drinking mice.

The new work explores the link between such reward-seeking and the study of social interactions

In one set of experiments, 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. Later it was found out that the heavy-drinking rejected males had a lowered level of the chemical, and sated, mated males had an elevated level suggesting the NPF levels are some kind of 'molecular signature' to the experience.

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.

This led the scientist to think 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 behavior that will restore it back..

It is tempting, given that humans share a similar brain chemical, to imagine that NPF drives human behavior as well.

Do you think heavy drinking in humans has anything to do with sexual deprivation?