Wrong Theory

Mouse Tongue

The blue dots are the taste buds. Once they absorb the sweetener and the dye, they’ll start to glow green, and the sweetnessspecific taste cells will glow brighter than the others.

TASTE TEST A BETTER MOUSETRAP

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The Rodent Rig

[1] A tiny suction hose pulls out and holds the tongue of the [2] anesthetized mouse. It’s kept steady on a [3] stainless steel brace. It’s tough to watch taste buds in action—you can’t clamp a microscope onto a subject’s tongue. As a result, researchers typically study taste cells in a petri dish. But for bioengineer Myunghwan Choi and his colleagues at Harvard, a disembodied taste bud is useless. “All the micro architecture is destroyed,” Choi says. And without the microarchitecture—from taste pores to capillaries—scientists can’t fully understand how mice (and people) receive the flavor of Camembert at a molecular level.

The researcher drips a bit of artificial sweetener onto the organ in question and beams it with infrared-laser light. When a taste pore absorbs the sweetener, the surrounding taste cells attuned to sweetness start to fluoresce. (Salt has the same effect but causes different cells to glow.) It’s the first direct proof that taste cells specialize in the flavors they detect.

The laser technique Choi uses to observe tongue cells in action has already been used to observe neurons. So the next step is to use two lasermicroscope setups (and one mouse) to film the tongue and the brain at the same time, revealing the complete mechanism of taste. Perhaps science will finally discover why Cheez Whiz is so popular. —Jonathon Keats

So, to examine a live mouse tongue under a microscope, Choi’s team invented an apparatus that wouldn’t look out of place in A Clockwork Orange. First, researchers stain the mouse’s tongue with dye formulated to glow under infrared light. Then they use a tiny suction hose to pull the anesthetized rodent’s tongue out, and they steady it on a steel brace. And finally: lasers.