Researchers probe overeating, dopamine receptors

A new Yale study suggests that a certain type of neuron in the front of the brain might be to blame for the popularity of National Chocolate Cake Day, which was celebrated across the country on Monday.

Researchers at the Yale School of Medicine demonstrated that stimulating a class of dopamine-receptor neurons in mice causes them to eat more, while the mice ate less after the neurons were inhibited.

While the finding holds potential for development of obesity treatments in the future, it should more immediately inform basic neuroscientific research, said Benjamin Land, study lead author and postdoctoral associate in psychiatry at the Yale School of Medicine. The study was published in the journal Nature Neuroscience on Jan. 19.

“We were interested in how the prefrontal cortex controls food intake,” Land said. “Nobody has ever really shown that before and there are no published studies on it.”

Though previous studies have suggested that the prefrontal cortex and other executive function regions of the brain play a role in regulating feeding, this study is the first to elucidate the precise circuitry. The study also showed that dopamine receptor neurons — a class that expresses the D1 family of receptors — are involved in a dopamine-signaling circuit that includes the amygdala, one of the brain’s most primitive regions.

According to Ronald Duman, professor of neurobiology at the Yale School of Medicine who was not involved in the study, past research has suggested that the amygdala is involved in eating, but it was not clear from those studies that this region was so closely linked to neurons in the prefrontal cortex. While eating behavior is typically associated with lower-level brain regions, the finding connected this behavior to the dopamine receptor neurons in the prefrontal cortex, an area of the brain responsible for higher-order functions like decision-making, Duman said.

For Duman, though there is still more information needed to understand the neurobiology of eating, this study lays groundwork for researching overeating disorders. By further understanding specific circuits and brain regions, Duman said scientists are getting closer to developing strategies to control such diseases.

“Eating disorders are clearly having a major impact on society and culture and this kind of work helps us to understand what controls normal and abnormal eating behavior,” he said.

Ivan de Araujo, a professor of psychiatry at the Yale School of Medicine not involved with the study, said he agreed that the study may lead to treatments for eating disorders such as obesity, adding that the study adds the prefrontal cortex as a new target for researchers investigating the neurobiology of obesity.

For Marina Picciotto, a professor of psychiatry at the Yale School of Medicine not involved in the study, the study enriches both the academic and clinical understanding of overeating.

“Understanding the neurobiology is important because it tells you how the brain is organized to take care of complex behaviors, in this case food seeking and working for food,” she said. “But in terms of therapeutics, when you identify these new pathways, it gives you new ways to potentially intervene.”

According to the Center for Disease Control and Prevention, more than one third of U.S. adults are obese.

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