Smell Receptors in the Tongue?

Chemical Sense, June 2019.

Olfactory receptors, the ones that that permit us to detect odors in the nose, are also in the taste cells of our tongues. It appears that the interactions between smell and taste, both of which comprise flavor, may actually begin on the tongue and not in the brain as previously thought.  This provides a more solid scientific framework that helps explain how odor molecules modulate our perception of how something tastes.

Consider this: we can recognize that something smells like strawberries, even though a strawberry doesn’t appear to have much of a smell when you sniff them. This is one example of how our sense of smell helps create a flavor.

The sense of taste handles sweet, salty, sour, bitter, and umami (savory) molecules on the tongue. A pear and an apple taste pretty much the same if you hold your nose while eating. What our brains do when we eat something is to combine taste and smell, alongside information from other senses, to create what we perceive as flavor.

It has generally been believed that information pathways from taste and smell remain separate until reaching the brain. Researchers found that this assumption remained somewhat unchallenged but were stimulated to reconsider it all in thinking about how snakes extend their tongues so that they can “smell” or sense their environment.

After developing techniques that would allow them to create and maintain cultures of taste cells, researchers found many of the molecules present in human olfactory receptors. Then employing molecular imaging, they demonstrated these cells responded to odor molecules in a manner similar to olfactory receptor cells. Additional experiments by the scientists demonstrated that a single taste cell can contain both taste and olfactory receptors, which supports the present findings.

These kind of basic science revelations may have important translational impact. Better understanding how smell and taste interact could also better inform us about either of those senses individually. It is interesting that we do not know what compounds activate the vast majority of the 400 types of functional human olfactory receptors. The cells cultured by the team, which respond to odors, could be used to screen molecules that bind to such receptors.

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