Much like males of our own species, male fruit flies, when spurned by females, drink to numb the pain of rejection. According to a study outlined in the New York Times, fruit flies who are unable to mate prefer food laced with alcohol to regular food.
Humans may like to think that our urge to have a drink is the product of a complex mix of age-old societal and psychological drives, but in fact, according to a study published in the journal Science, even common, lowly fruit flies want a drink after they've had a hard day.
The study, conducted by a group of researchers led by neuroscientist Galit Shohat-Ophir, placed 24 male fruit flies (Drosophila melanogaster) into one of two situations. Half of the flies were places in glass tubes with females who were ready to mate, while the others were placed in tubes with females who had recently mated and were therefore unresponsive to the male flies' advances.
After four days of "repeated mating or rejection," the male flies were placed in new containers with set amounts of food, half containing alcohol and half without. When the flies were later removed, scientists measured how much of the food had been consumed.
Researchers expected to find that all flies prefer food soaked in alcohol, which opens their brains' "reward" passageways, making the experience pleasurable, much as it does in humans. What they actually found was that the mated males have an aversion to the alcohol-containing food. Dr. Shohat-Ophir told Science, "And the rejected males have a high preference to that food with alcohol." On average, the rejected males drank four times more alcohol than the mated ones.
The dramatic results were unexpected, but according to Dr. Markus Heilig, the clinical director of the National Institute on Alcohol Abuse and Alcoholism and the National Institute on Drug Abuse, "Reading this study is like looking back in time, to see the very origins of the reward circuit that drives fundamental behaviors like sex, eating and sleeping."
Heilig told the New York Times that these findings are congruent with new findings about alcoholism and treatments for alcohol abuse.
Shohat-Ophir's team said that a brain chemical called Neuropeptide F (NPF) plays a role in moderating alcohol consumption in fruit flies. The flies who had faced repeated rejections, when tested, had less than half the amount of NPF in their brains as recently mated flies.
The findings suggest that NPF levels can drive behavior as the brain seeks to restore its reward system to normal. In humans, a chemical called Neuropeptide Y (NPY) may serve a similar function. NPY has been shown to regulate drug and alcohol consumption in rats, and according to Science, studies show that people with depression or who have undergone trauma have reduced levels of NPY.
Whether or not social experiences and rewards can influence a person's levels of NPY has yet to be studied. "Our results certainly don't translate directly from flies to humans," said Shohat-Ophir, "but it does bring up questions and suggest future studies."
(image copryright via Shutterstock)