Scientists discovered an interesting link between mating patterns and future behavior, while studying fruit flies. Their article, published in Science, says that given a choice, it seems that the male will be more likely to choose food soaked in alcohol, than regular food, if a female has recently rejected him. The researchers say it’s a first in terms of finding that past experience affects future behavior in fruit flies. It almost shows an emotional response.

Neuroscientist Galit Shohat-Ophir, who conducted the work at the University of California, San Francisco, but who has now moved to the Howard Hughes Medical Institute’s Janelia Farm Research Campus in Ashburn, Virginia, says she was really just messing about with ideas to see what would happen :

“This was just a wild experiment to do … We didn’t expect to see such
dramatic results.”

24 male fruit flies (Drosophila melanogaster) were divided into two groups. Half of them were put into a container with 20 females that were ready to mate; the almost 2 to 1 ratio allowing the lucky males to mate multiple times. The other half got the cold shoulder treatment from females that had already mated and were only on a 1 to 1 ratio, so the poor males repeated advances were turned away.

When all the males were then moved into a new containers after four days of mating fun or mating rejection, just as any self respecting male does when he’s feeling jilted, those from the rejected group chose to drink from the capillary of mashed food containing alcohol.

The researchers had expected all the flies to prefer the alcoholic food tube, but no so. The flies that had been mating, actively turned down the alcoholic food, preferring to keep themselves sober, perhaps in anticipation of future mating possibilities. The rejected males drank four times more alcohol than their happier counterparts.

There is actually some real science to back up the finding. It’s already known that fruit flies respond to positive experiences, with pathways in their brains showing responses to stimuli, such as alcohol and social interaction. Shohat-Ophir aimed to try to build on that with a wild card idea.

Shohat-Ophir and colleagues theorized that a chemical in the flies brain, called neuropeptide F (NPF), might play a role in the link, because NPF seems to control alcohol preferences.

They took readings of the levels of NPF in the flies’ brains after mating, or after rejection by a female. The rejected males had fifty percent less NPF in their brains than the males that had mated recently. To double-check their theory, the scientists stimulated NPF in the brains of those rejected flies, and reduced NPF in the brains of the flies that had mated. The roles quickly reversed, with the rejected flies now pumped on NPF preferring non alcoholic food and the males that had mated but been robbed of their NPF high, seeking alcohol at almost the same rate as their counterparts had done previously.

Shohat-Ophir says the conclusion to the finding is that experiences are translated into a molecular signature through levels of NPF. In turn, those NPF levels drive behavior that restores the NPF balance to normal. The process is like some kind of molecular computer in a way.

Questions still remain though, as to how the sexual experience controls the level of NPF at a molecular level, and how a reward boosts the level or a poor experience reduces it.

It’s also not understood exactly why low NPF levels trigger alcohol consumption. Nonetheless it’s an interesting concept, and one that could potentially translate into treatment for addictions and depression.

The human brain has a similar protein to NPF called neuropeptide Y (NPY). Those with depression or post-traumatic stress syndrome have been shown to have lower levels of NPY, whilst rats with low NPY show traits associated with alcoholism or addiction. The effect of social experience on NPY has not been studied. However, the results in fruit flies seem promising.

Shohat-Ophir says :

“Our results certainly don’t translate directly from flies to humans … but it does bring up questions and suggest future studies.”

Writen by Rupert Shepherd