Scientists at Yale School of Medicine have shown that the neurons used to control appetites are also linked to an appetite for drug use like cocaine.
The scientists published their findings in the journal Nature Neuroscience¹. The neurons that control hunger are associated to overeating as well as novelty-seeking and drug addiction. In an attempt to develop treatments for metabolic disorders like obesity and diabetes, researchers have been investigating the brain’s reward mechanisms located in the midbrain. They noted that food had the potential to become a kind of drug abuse, similar to cocaine.
Using genetic approaches, they discovered that increased appetite for food can be associated with decreased novelty as well as in cocaine. Less interest in food can predict an increased interest in cocaine, states Marcelo Dietrich, lead author.
The team studied two sets of transgenic mice. In one group, they disabled a signaling molecule that controls hunger-promoting neurons in the hypothalamus. In the other, they interfered with the same neurons by eliminating the selectively during development. The mice were given non-invasive tests to measure how they responded to novelty, anxiety and how they reacted to cocaine.
Animals that have less interest in food are more interest in novelty-seeking behaviors and drugs like cocaine, states Tamas Horvath. This indicates that there are individuals with an increased drive of the reward circuitry, but who are still lean. This trait arises from the activity of the basic feeding circuits during development, which impacts the adult response to drugs, and novelty in the environment.
The team thinks that the hypothalamus, which controls vital functions like body temperature, hunger, thirst, fatigue, and sleep, is key to the development of higher brain functions. Obesity is associated with the increased drive of the reward circuitry, but this study provides a contrasting view. The reward aspect can be high, but patients can be lean. At the same time, it shows that there is a set of people who have no interest in food, but might be prone to drug addiction.
- Dietrich, M. O., et al., Nature Neuroscience 15, 1108–1110 (2012), doi: 10.1038/nn.3147