Scientists at the University of California, San Francisco (UCSF) have discovered that sexually deprived male fruit flies drink far more than sexually satisfied male flies. The researchers discovered that a tiny molecule in the fly's brain called neuropeptide F governs this behavior. As the levels of the molecule change in their brains, the flies' behavior changes as well.
The experiments began with male fruit flies placed in a container with either virgin female flies or female flies that had already mated. While virgin females readily mate and are receptive toward courting males, once they have mated, females flies lose their interest in sex for a time because of the influence of a substance known as sex peptide, which males inject along with sperm at the culmination of the encounter. This causes them to reject the advances of the male flies. The rejected males then gave up trying to mate altogether. Even when placed in the same cage as virgin flies, they were not as interested in having sex.
Their drinking behavior also changed. When the flies were placed by themselves in a new container and presented with two straws, one containing plain food and the other containing food supplemented with 15% alcohol, the sexually rejected flies binged on the alcohol, drinking far more than the sexually satisfied flies whose advances were never spurned. The drinking behavior was predicted by the levels of neuropeptide F in their brains.
Galit Shohat-Ophir, PhD, the first author of the new study, says, "It's a switch that represents the level of reward in the brain and translates it into reward-seeking behavior."
The new work may help shed light on the brain mechanisms that cause human addiction. The researchers say a similar human molecule, called neuropeptide Y, may also connect social triggers to behaviors like excessive drinking and drug abuse. Adjusting the levels of neuropeptide Y in people may help alter their addictive behavior - which is what the researchers observed in the experiments with fruit flies. The researchers say clinical trials are underway to test whether delivery of neuropeptide Y can alleviate anxiety and other mood disorders in people.
, "Sexual Deprivation Increases Ethanol Intake in Drosophila" by Shohat-Ophir, K. R. Kaun, R. Azanchi and U. Heberlein appears in the March 16 issue of the journal Science
Photo: Galit Shohat-Ophir