Explaining the "Munchies" by Looking at the Brain's Response to Marijuana

Neurons in the brain that normally suppress appetite can trigger the “munchies” — the urge to eat – after using marijuana, according to research published in Nature.

Researchers from Yale University used mice models to demonstrate that marijuana use can trigger increased hypothalamic pro-opiomelanocortin (POMC) neuron activity. Typically, these neurons suppress and regulate appetite, but the researchers showed the chemical promotion of cannabinoid receptor 1 (CB1R) increases feeding and the activity of POMC cells. The researchers aimed to examine the effects that marijuana has on brain circuits by selectively manipulating transgenic mice’s cellular pathways.

“By observing how the appetite center of the brain responds to marijuana, we were able to see what drives the hunger brought about by cannabis and how that same mechanism that normally turns off feeding becomes a driver of eating,” lead author Tamas Horvath explained in a press release. “It’s like pressing a car’s brakes and accelerating instead. We were surprised to find that the neurons we thought were responsible for shutting down eating were suddenly being activated and promoting hunger, even when you are full. It fools the brain’s central feeding system.”

Beyond explaining untimely cravings, Horvath continued, these findings can provide other benefits such as helping cancer patients who often lose their appetite during various cycles of treatment. Prior research has demonstrated the use of cannabis has a substantial effect on appetite, even when the users are full. It is also understood that CB1R can contribute to over eating.

“This event is key to cannabinoid receptor driven eating,” explained Horvath, who continued by saying that this eating behavior that is driven by the POMC neurons is just one type of action that can trigger increased CB1R signaling. “More research is needed to validate these findings,” he concluded.

Another thing Horvath hopes to investigate in the near future is whether this primitive brain mechanism is the key to getting high on cannabis.

“These processes involve mitochondrial adaptations that, when blocked, abolish CB1R induced cellular responses and feeding,” the authors concluded in the study. “Together, these results uncover a previously unsuspected role of POMC neurons in the promotion of feeding by cannabinoids.”