So THAT’s why you get the munchies…

Chowing down. Image courtesy of Joel Telling under a creative commons license.
Chowing down. Image courtesy of Joel Telling under a creative commons license.

While not the actual title or tag-line on a recent Nature Neuroscience paper, it is certainly a punchline that first comes to mind upon reading the title “The endocannabinoid system controls food intake via olfactory processes”. The endocannabinoid system responds to the active components in marijuana among other signaling molecules in the body including endocannabinoids made by the body. However, even if you’re not partaking of marijuana, this system is active in regulating how your body responds when it begins to get hungry.

When you starve a mouse for 24 hours, it will normally respond by eating much more than usual when you give back its food dish. If you starve a mouse that has had its cannabinoid receptor gene deleted, it will not eat more than usual when food is returned to the cage. It turns out that cannabinoid receptors are necessary for this behavior and if you activate the receptors by giving mice THC  even mice that shouldn’t be hungry at all, are very interested in food. These receptors are on groups of brain cells that connect with the main olfactory bulb (the large group of cells that are involved in the processing of different smells).

This connection leads to a “turning up” of scent sensitivity when the cannabinoid receptors are activated. It’s not entirely clear whether this tuning up makes food smells more attractive than usual, or increases the motivation to identify the source of a particular smell. And while many people focus on this in terms of a recreational curiosity, understanding this system and the regulation of hunger and eating can be relevant in understanding other food-related conditions like anorexia or obesity.

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