Animals quickly learn to avoid most foods with a bitter taste because these often contain dangerous toxins. Bitterness "is a signal telling us that something is quite wrong in the food we've ingested," says Enrique Rozengurt of the University of California, Los Angeles School of Medicine.
It's a handy protective mechanism, and animals may depend on more than their tongues to detect bitter substances, Rozengurt and his colleagues find. In the Feb. 19 Proceedings of the National Academy of Sciences, they report that parts of the rodent gastrointestinal tract harbor the same bitter-taste receptors as tongues do. They further reveal that a lab-grown line of cells derived from a rat's small intestine makes these receptors and reacts to bitter substances in a manner similar to taste buds.