Your nose knows: First study on mammals finds nose tip smells harsh odors

William Atkins
Wednesday, 05 March 2008 19:22

Science - Biology

U.S. researchers have found for the first time where humans first sense irritating odors such as rotten eggs, chlorine, and gasoline. It’s at the tip of your nose.          

Thomas E. Finger, of the Cellular and Development Biology department at the University of Colorado Health Sciences Center (Aurora), was one of the authors conducting this pioneering study.

Their results might add scientific merit to the common response of people when they crinkle their noses immediately after coming across nasty smells?

They found that the cells at the tip of the nose sense bad smells and they warn the brain of possible danger. In fact, the brain may react by stopping breathing for a few seconds in order to allow the person to run away from the irritating smell.

Finger’s team stated that scientists already knew that these solitary chemosensory cells (SCCs) are found on most aquatic vertebrates (such as sharks). Scientists assumed these cells are also present on all mammals.

However, before this study, scientists did not know where they were located on humans. They thought the chemosensory cells might be positioned on nerve endings within the nose.

Therefore, to learn where these chemosensory cells are located, the team studied mice. They measured changes in the chemosensory cells of mice as they exposed them to low and high levels of various chemical odors.

The researchers found that special cells at the tip of the nose sense the odors and, then, send that information to the brains of the mice.

According to the abstract to their paper, “Together, our data demonstrate that the TRPM5-expressing cells respond to a variety of chemicals at high exposure levels typical of irritants and are positioned in the nasal cavity appropriately to monitor inhaled air quality.” (TRPM5 is an abbreviation for transient receptor potential channel M5.)

The scientists announced their discovery on Tuesday, March 4, 2008. The result of their study (“TRPM5-expressing solitary chemosensory cells respond to odorous irritants”) appears in the December 2007 issue of the Journal of Neurophysiology.

Besides Finger, the researchers also included Diego Restrepo (Colorado Health Sciences Center, Aurora), Weihong Lin (University Of Maryland, Baltimore), Tatsuya Ogura (University Of Maryland, Baltimore), and Robert F. Margolskee (Mount Sinai School of Medicine, New York City).