Brain mechanism behind ‘the munchies’ discovered in new study
By giving mice vaporized cannabis, researchers have uncovered a brain mechanism that causes the drug’s appetite-stimulating effects, known as ‘the munchies’. The findings could pave the way for therapeutics to treat appetite disorders like anorexia and obesity and to improve the appetite of patients undergoing cancer treatment.
Many would be familiar with the munchies, the ravenous hunger that often follows cannabis use. While scientists have known about the phenomenon for a long time, what happens in the brain to cause it remained up for debate.
Now, a study by researchers from Washington State University (WSU) has uncovered one of the brain mechanisms that stimulated appetite in mice after they inhaled cannabis.
The researchers exposed mice to vaporized Cannabis sativa plant matter (7.8% THC, 0.5% CBD) to see how their brain cells reacted. Using calcium imaging, which is similar to an MRI, they found that the inhalation of cannabis activated a significant number of neurons in the mediobasal hypothalamus (MBH), a part of the brain important to the control of food intake, when the mice entered the food-containing zone, where a palatable high-fat diet was consistently offered. Importantly, the number of active MBH neurons remained nearly constant when the mice were anticipating eating and while they were eating.
“When the mice are given cannabis, neurons come on that typically are not active,” said Jon Davis, the study’s corresponding author. “There is something important happening in the hypothalamus after vapor cannabis.”
Within the MBH, Agouti-related protein (AgRP)-expressing neurons are key to promoting hunger and the motivation to obtain food. Notably, the sensory terminals of AgRP neurons express cannabinoid type-1 receptors (CB1R), which are thought to contribute to the appetite-stimulatory properties of Cannabis sativa. Using chemogenetics, which acts like a molecular switch, the researchers found that CB1R controlled the activity of AgRP neurons. When these neurons were switched off, cannabis no longer stimulated appetite in the mice.
“We now know one of the ways that the brain responds to recreational-type cannabis to promote appetite,” Davis said.
The study is the first to detail the in vivo effects of inhaled cannabis on neuronal activity in the appetite-regulatory region of the brain and suggests that MBH neurons may play a strong regulatory role for feeding behaviors stimulated by the drug.
The researchers say their findings could pave the way for therapeutics to treat appetite disorders like anorexia and obesity and to improve the appetite of patients undergoing cancer treatment.
The study was published in the journal Scientific Reports.