Getting over a breakup is not easy; rejection is even more awful. Many people turn to alcohol to drown out their sorrow. In an attempt to study this seemingly unreasonable human behavior, scientists found that, surprisingly, humans are not the only ones who seek consolation from alcohol. In a recent article published in Science, Shohat-Ophir et al. revealed a case of alcohol dependence behavior in Drosophila Melanogaster, commonly known as fruit flies. They found that when fruit flies get unlucky in love, they are more likely to go for booze and become “drunken” flies.
As discussed in an earlier post by Kate, addictive drugs can alter the natural reward pathway and “hard-wire” a habitual drug-seeking behavior. Shohat-Ophir’s research group took this idea further and investigated the mechanism of artificial drugs’ disruption of the natural reward pathways. In their study, they observed the behavior of the fruit flies in response to a particular kind of social interaction: mating.
The Shohat-Ophir research team placed one group of male flies in the company of virgin female flies that were receptive to courtship efforts. A second group of male flies was placed with female flies that had mated previously and had no interest in mating. Naturally, these “experienced” female flies rejected the courtship attempts by these male flies. After the encounter with the female flies, both groups of male flies were given the choice of consuming normal food or food that contained alcoholic substances. The sexually rejected flies preferentially consumed alcohol, drinking four times more alcohol than the mated male flies. The research team concluded that alcohol became a compensatory reward for the unrequited physical desire of the rejected male flies. Perhaps the alcohol did soothe their loneliness and help mend their broken hearts!
Shohat-Ophir’s research team hypothesized that a chemical in the brain called neuropeptide F (NPF), which is called NPY in humans, might be linked to this addictive behavior, as it has been shown previously to mediate alcohol preference. Indeed, they found that the mated flies had higher levels of NPF than the sexually rejected flies.
Using genetic tools, the research team manipulated the expression level of NPF in the mated male flies. A low level of NPF triggered the mated flies to binge on alcohol—a behavior that was previously only seen in the sexually rejected flies. Conversely, increasing the expression level of NPF in virgin male flies, which usually have a high preference for alcohol, caused their alcohol-seeking behavior to disappear!
Although it may take time to extrapolate from the behavior of fruit flies to human behavior, this study established a link between NPF/Y and addictive behavior, which is a novel finding that can lead to further research on the role of NPF/Y in the reward system and the mechanism of substance addiction. Future studies that unravel the “hard-wiring” of reward-based addiction can guide us to new treatment for addictions, but scientists are definitely far from developing treatments for a broken heart!Shohat-Ophir G., Kaun K.R., Azanchi R., Mohammed H. & Heberlein U. (2012). Sexual Deprivation Increases Ethanol Intake in Drosophila, Science, 335 (6074) 1351-1355. DOI: 10.1126/science.1215932 Images adapted from Craig Robinson/moodboard/Corbis y Tetra Images/Corbis.