Bitter Taste

This information was in the Bee this morning, and I thought it - odd:

Most people aren't wild about things that taste bitter, and there may be an evolutionary reason for that: bitter taste receptors on the tongue may have developed to help warn people away from eating toxic plants. So imagine the surprise when a group of researchers from the University of Maryland School of Medicine discovered bitter taste receptors on human lungs. What's more, rather than causing prompt constriction of the airway when exposed to bitter substances, these taste receptors resulted in a swift and thorough relaxation of lung muscles allowing for freer breathing.

...The Boston Globe reported:

When they exposed the receptors to bitter tastes, the lungs relaxed instead of tightening. Working with mice engineered to have a human form of asthma, they found that aerosolized bitter substances, such as quinine and saccharin (for its bitter aftertaste), opened up airways much more than the asthma medication albuterol did in similar mice.

It was the opposite of what the researchers expected; they assumed the bitter aerosols would lead to airway constriction in order to prevent the inhalation of potentially toxic substances. But in tests in mice and in sections of human airways taken from cancer patients, the team found that stimulation of the bitter receptors caused airways to expand to 90% of their original volume. (More on Time.com: Survey —

Liggett and his team theorize in their paper that humans could have evolved this response to ease recovery from upper respiratory conditions like pneumonia and bronchitis. The bacteria associated with these conditions secrete bitter compounds; in response, lung muscles relax and open airways, which allows people to cough up and expel mucus and other bacteria-containing fluid, speeding recovery.