( The tongue's ability to differentiate b...)Bitter or sweet? The same taste bud can tell the difference

The study explains the discovery of a chemical messenger called neuropeptide Y (NPY) in taste bud cells. Though researchers have long known that NPY is active in the brain and gut, this is the first study to show that it is also active in taste bud cells.

That finding gives scientists a deeper understanding of how the human brain may distinguish between different types of tastes, said Scott Herness, the study's lead author and a professor of oral biology and neuroscience at Ohio State University .

The current study builds on previous work by Herness and his colleagues. A few years ago, the team found that another chemical messenger, cholecystokinin (CCK), is active in some taste bud cells. They think that these two peptides ?small proteins that let cells talk to one another ?have different effects in the same cells.

The researchers report their findings in this week's online edition of the Proceedings of the National Academy of Sciences.

CK may send opposite signals to the brain, depending on what kind of substance is on the tongue. Given the current findings, Herness thinks that CCK tells the brain that something bitter is on the tongue, while NPY sends a message that something sweet is being eaten.

"We were surprised to see that NPY had the exact opposite action of CCK," he said. "But this would ensure that the brain gets a clear message of what kind of taste is on the tongue."

Taste buds are really clusters of 50 to 100 cells. Nerve fibers connect each bud to the brain, but only a few of the cells in each taste bud touch these fibers. The prevailing thought was that cells that don't have a connection to a nerve fiber must have some way of sending a signal to that fiber. But researchers weren't sure how that happened.

"We knew that many taste bud cells that have receptors f
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Source:Ohio State University