That's because the receptors that get activated are located in the smelling center of the brain. And sense of smell is known to be a key factor driving appetite.

In case you're wondering, the mice didn't toke up. The researchers injected the rodents with THC, the active ingredient in marijuana.

Of course, mice aren't men — especially when it comes to smelling. The little rodents spend much more of their lives sniffing out yummy food than we do. And they devote much more of their brain power to the activity.

But there are some hints that a similar mechanism may also be at work in people.

We didn't make this up: The scientists who performed the study on how cannabis triggers the munchies through the sense of smell commissioned an artist to put this illustration together. Image: Charlie Padgett/Courtesy of Giovanni Marsicano

When you skip a meal or fast, your brain creates compounds, called endocannibinoids — appropriate, right? — that look and act similarly to THC. And not surprisingly, these chemicals drive you to eat.

But hunger also makes you more sensitive to food aromas.

So Marsicano and his team thought perhaps the two processes — that burning desire to eat (i.e., munchies) and enhanced smelling — were linked. So he and his team went hunting for receptors in mouse brains that controlled both.

They hit the jackpot when they looked in the mice's olfactory bulbs.

That part of the brain was packed with receptors that bind THC and ramp up the rodents' appetite — both when they'd been fasting and when they were high.

These receptors also made the mice more sensitive to odors when their tummies were empty or their brains were stoned.

The data suggest that the major way marijuana triggers the munchies — at least in mice — is through olfaction, Marsicano and his team write in the study.

As for humans? We're a more complicated lot, and there's more than just the sense of smell at play when we get the munchies (from hunger or high). For starters, our "cannabinoid" receptors are located not just in our brains but in other parts of the body.

Copyright 2014 NPR.

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The Science Of Munchies: Why The Scent Of A Burger Gives Us A High