Researchers at Rockefeller University have discovered a set of brain cells that may be the key to limiting how much we want to eat. While exploring the hippocampus region of the brain in mice, the team identified neurons that act as an appetite suppressant.
The hippocampus is involved in memory, and previous studies have shown that defects in this region can disrupt feeding behavior. This suggests that, somehow, the hippocampus influences an animal’s impulse to eat based on past experiences with food.
With this in mind, postdoctoral research associate Estefania Azevedo pinpointed a group of hippocampal cells, known as hD2R neurons, which become activated whenever a mouse begins to eat. The team found that the mice ate less when hD2R neurons were stimulated, and ate more when their activity was turned off.
Ultimately, the experts determined that hD2R neurons react to food by deterring animals from eating it. Azevedo explained that even though animals usually benefit from eating, it is useful to exercise restraint in some cases. For example, if an animal has just eaten, it would be unnecessarily risky to go out searching for more food.
“These cells keep an animal from overeating,” said Azevedo. “They appear to make eating less rewarding and, in that sense, are tuning the animal’s relationship to food.”
Experiments with mice showed that hDR2 activation diminished memories that linked food to particular locations.
“Mental connections between food and location are important for survival, and the strength of these connections is regulated by how rewarding an experience is,” said Azevedo. “Because hD2R neurons affect an animal’s relationship with food, it also ends up affecting these connections.”
The researchers also discovered a previously unidentified brain circuit in which hD2R neurons receive input from a part of the brain that processes sensory information before sending output to a brain region involved in feeding. According to the researchers, this suggests that the neurons promote a healthy balance between sensing food and eating it.
The research also indicates that the brain has complex ways of controlling appetite, which may lead to the development of therapies to curb overeating.
“Our study shows that brain areas involved in cognitive processing and memory formation affect feeding behavior,” said Azevedo. “So it is possible that, with training, people may be able to learn to change their relationship to food.”
The study is published in the journal Neuron.
By Chrissy Sexton, Earth.com Staff Writer