Researchers have zeroed in on a set of nerve cells (neurons) in the brain's hypothalamus that is not only linked with hunger and overeating, but also drives drug addiction.

Researchers focused attention on the brain's reward circuits located in the midbrain to develop treatments for metabolic disorders such as obesity and diabetes.

"Using genetic approaches, we found that increased appetite for food can actually be associated with decreased interest in novelty as well as in cocaine, and on the other hand, less interest in food can predict increased interest in cocaine," said Marcelo O. Dietrich, postdoctoral associate at the Yale School of Medicine.

Dietrich conducted the research with Tamas L. Horvath, professor of biomedical research at the Yale School and his team, studying two sets of transgenic mice, the journal Nature Neuroscience reports.

In one set, they knocked out a signalling molecule that controls hunger-promoting neurons in the hypothalamus, which regulates vital functions such as body temperature, hunger, thirst fatigue and sleep, according to an Yale statement.

In the other set, they interfered with the same neurons by eliminating them selectively during development using diphtheria toxin. The mice were given various non-invasive tests that measured how they respond to novelty, and anxiety, and how they react to cocaine.

"We found that animals that have less interest in food are more interested in novelty-seeking behaviours and drugs like cocaine," said Horvath. "This suggests that there may be individuals with increased drive of the reward circuitry, but who are still lean."

"This is a complex trait that arises from the activity of the basic feeding circuits during development, which then impacts the adult response to drugs and novelty in the environment," added Horvath.

Horvath and his team argue that the hypothalamus, is key to the development of higher brain functions.

"These hunger-promoting neurons are critically important during development to establish the set point of higher brain functions, and their impaired function may be the underlying cause for altered motivated and cognitive behaviours," he said.