This creates the possibility scientists can someday develop
therapeutics to address overeating
University of Georgia
You're on a diet, but the aroma of
popcorn in the movie theater lobby triggers a seemingly irresistible craving.
Within seconds, you've ordered a tub
of the stuff and have eaten several handfuls.
Impulsivity, or responding without
thinking about the consequences of an action, has been linked to excessive food
intake, binge eating, weight gain and obesity, along with several psychiatric
disorders including drug addiction and excessive gambling.
A team of researchers that includes
a faculty member at the University of Georgia has now identified a specific
circuit in the brain that alters food impulsivity, creating the possibility
scientists can someday develop therapeutics to address overeating.
"There's underlying physiology
in your brain that is regulating your capacity to say no to (impulsive
eating)," said Emily Noble, an assistant professor in the UGA College of
Family and Consumer Sciences who served as lead author on the paper. "In
experimental models, you can activate that circuitry and get a specific
behavioral response."
Using a rat model, researchers
focused on a subset of brain cells that produce a type of transmitter in the
hypothalamus called melanin concentrating hormone (MCH).
While previous research has shown
that elevating MCH levels in the brain can increase food intake, this study is
the first to show that MCH also plays a role in impulsive behavior, Noble said.
"We found that when we activate
the cells in the brain that produce MCH, animals become more impulsive in their
behavior around food," Noble said.
To test impulsivity, researchers
trained rats to press a lever to receive a "delicious, high-fat, high-sugar"
pellet, Noble said. However, the rat had to wait 20 seconds between lever
presses. If the rat pressed the lever too soon, it had to wait an additional 20
seconds.
Researchers then used advanced
techniques to activate a specific MCH neural pathway from the hypothalamus to
the hippocampus, a part of the brain involved with learning and memory
function.
Results indicated MCH doesn't affect
how much the animals liked the food or how hard they were willing to work for
the food. Rather, the circuit acted on the animals' inhibitory control, or
their ability to stop themselves from trying to get the food."
Activating
this specific pathway of MCH neurons increased impulsive behavior without
affecting normal eating for caloric need or motivation to consume delicious
food," Noble said.
"Understanding that this circuit, which
selectively affects food impulsivity, exists opens the door to the possibility
that one day we might be able to develop therapeutics for overeating that help
people stick to a diet without reducing normal appetite or making delicious
foods less delicious."
