Sneezing and coughing are two different ways to accomplish the same thing. One involves the nose and mucus, the other the mouth and mucus, but both are protective respiratory features designed to repel germs and irritants. Since they are so similar, doctors have generally assumed that they both involve a common set of sensory receptors and neural passageways. As new research shows, this assumption was wrong.
Indeed, in a new study published in the journal Celldoctors at Washington University School of Medicine in St. Louis, led by anesthesiologist Haowu Jiang, found that not to be the case, a discovery that could provide relief to cold and allergy sufferers in the future.
In the study, the researchers chose to initiate small, somewhat pleasant, sneezes and coughs in mice. They stimulated groups of neurons in the nasal cavity that are already known to respond to various conditions associated with sneezing, such as those dedicated to the sensation of cold or itch. That allowed them to determine exactly which sets of neurons were actually involved in triggering the sneeze. They found that, while the tissue lining the nasal passages can be activated by several different sets of neurons, tickling only one of those sets—a type of itch receptor called MrgprC11—actually triggered a sneeze.
To confirm the findings, the doctors infected the poor mice with influenza. In mice where MrgprC11 was disabled, the mice became sick and coughed, but could not sneeze. When they tried to stimulate the trachea of MrgprC11 neurons to produce a cough, they found that the trachea became irritated, but no cough appeared. Instead, the cough was connected to an entirely different set of neurons.
“At the regional level, the symptoms of sneezing and coughing are transmitted and modulated by different neuropathways,” the doctors wrote.
The research also resulted in a happy accident. Among some scientists, it seems to be a matter of debate whether mice can actually cough. Other research has argued that it can, a conclusion scientists at Washington University say they have confirmed by identifying patterns of sound and breathing in small sounds. Now we know that mice can cough, which is a good thing.
It may not seem like a big deal that sneezing and coughing are caused by different mechanisms. It’s both basically an antiseptic and some icky liquid. Jiang and his colleagues acknowledged in the study the need to determine whether the methods discovered in mice have parallels in humans. But they expressed hope that their work could lead to the development of new drugs and treatments for the symptoms of respiratory diseases and allergies.
In addition to better relief during the flu and cold season, it can reduce the side effects associated with antihistamines and corticosteroids, such as airway dryness, bleeding, and infections. As any allergy sufferer can attest, that’s not sneezing.
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