Redeems Hint of pollen a sneeze or cough? Scientists have discovered nerve cells that trigger one response as opposed to another: "sneeze neurons" in the nasal passages relay sneezing signals to the brain, and separate neurons send cough messages, a study found after conducting them on mice 1.

The findings could lead to new and improved treatments for conditions such as allergies and chronic cough. That's good news because these diseases can be "incredibly frustrating" and the side effects of current treatments can be "extraordinarily problematic," says pulmonologist Matthew Drake of Oregon Health & Science University in Portland, who was not involved in the work. The study was carried out today inCellpublished.

Mucus-spewing signals

Previous work 2have Neurons in the mouse respiratory tract based on protein complexes categorized, called ion channels, which are carried on the cell surfaces.

To find out which nasal neurons cause sneezing, the researchers exposed mice to different compounds known to activate certain types of ion channels.

They hit the mark when a substance called BAM 8-22 made the mice sneeze. The compound is known to activate an ion channel called MrgprC11, which led researchers to hypothesize that neurons carrying MrgprC11 cause sneezing. In fact, the researchers found that the sick mice that had their suspected sneezing neurons deleted and then given flu were still sick but had no sneezing.

Mikrografie eines Mausnasengangs mit markierten Nies-Neuronen in Rot

Even when the sneezing neurons disappeared from the picture, the sick mice continued to have them cough-like reactions to influenza infection. Using methods similar to those that targeted the sneezing neurons, the researchers tracked the cough response to a group of neurons in the trachea that express a signaling chemical called somatostatin.

Viruses “evolve very quickly,” says neurobiologist and study co-author Qin Liu at Washington University in St. Louis, Missouri. This could explain why there are two separate systems capable of detecting and eliminating them in the airways.

Now Liu and her colleagues want to find out what happens after the sneezing and coughing neurons are triggered and send signals to the brain. She believes it is likely that their signals travel to the brain's respiratory control center, where they alter breathing patterns to produce either a cough or a sneeze.

Other sneezing neurons?

The next big challenge is to find out whether similar sets of neurons exist in humans, says neurobiologist Patrik Ernfors at the Karolinska Institutet in Stockholm. Early evidence suggests this is the case, says Liu, but more research is needed.

Some researchers suspect that there are more sneezing and coughing neurons waiting to be discovered. Most responses to sensory information are triggered by numerous categories of neurons, and sneezing and coughing are likely similar, says sensory neurobiologist Stephen Liberles at Harvard Medical School in Boston, Massachusetts.

Coughs can be so persistent that they cause people to faint, says Drake. And yet, doctors don't have good options for treating coughs. Opioids like codeine are the most powerful medications available, but they can make people extremely sleepy and are addictive.

This lack of effective medications can lead doctors to forego cough relief, says Drake. “I hope that as new therapies enter the market, the way we think about how to treat [cough] and our enthusiasm for treatment will change,” he says.