Researchers looking at a set of neurons in the part of the brain that controls hunger have found that mice with an increased appetite for food had less interest in cocaine, while those less interested in food were more interested in cocaine and other novelty-seeking behaviors.
In attempting to develop treatments for metabolic disorders such as obesity and diabetes, scientists have paid increasing attention to the reward circuits located in the mid-brain.
The idea is that in these patients, food may become a “drug of abuse” similar to cocaine.
But the study from researchers at the Yale School of Medicine flips the common wisdom on its head, according to Marcelo Dietrich, Ph.D., a postdoctoral associate.
“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 Dietrich.
The research team studied two sets of mice. In one set, they knocked out a signaling molecule that controls hunger-promoting neurons in the hypothalamus.
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.
The Yale researchers believe that the hypothalamus, which controls body functions such as temperature, hunger, thirst, fatigue and sleep, 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 behaviors,” said Tamas Horvath, Ph.D., a professor of biomedical research and chair of comparative medicine at Yale School of Medicine.
“There is this contemporary view that obesity is associated with the increased drive of the reward circuitry, but here we provide a contrasting view: That the reward aspect can be very high, but subjects can still be very lean. At the same time, it indicates that a set of people who have no interest in food might be more prone to drug addiction.”
The study is published online in Nature Neuroscience.
Source: Yale University