Scientists have discovered a protein molecule¹ on the surface of nerve cells that makes us cough when irritated.

科学家发现人们恼怒的时候，是神经细胞表面的蛋白质分子引起的。

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Chronic cough affects about 10% of the UK population

They hope the findings could lead to new drugs to treat chronic（长期的，慢性的） cough, which affects about 10% of the UK population.

Coughing is the symptom for which medical advice is most commonly sought and it accounts for over half of new patient consultations³ to a GP.

The University of Hull⁴ study was presented to a British Pharmacological Society meeting.

Lead researcher Professor Alyn Morice said: "Chronic cough can be socially isolating⁵ and disabling and people come from all over Europe to my cough clinic because the cough is ruining their lives, yet current treatment options are limited with remedies little better than honey and lemon."

Research has already focused on protein receptors（受容器，感觉器官） which sit on the surface of nerve cells, and enable them to pass on signals.

One particular receptor - TRPV1 - generated excitement after it was shown to produce a cough reflex when stimulated⁶ by capsaicin（辣椒素）, an extract of chilli peppers.

A number of companies produced potential drugs to block the receptor, which helps the body to sense heat, and to register pain.

However, their work was stymied⁷（被侵袭的） by the revelation（揭露，泄露） that patients in which the receptor was blocked not only had an impaired⁸ ability to detect heat, but also developed a higher body temperature.

Cinnamon（肉桂） extract

The Hull group instead focused on a different type of receptor, called TRPA1, which is more concerned with the ability to sense coldness.

They showed it produced a cough reflex when it was stimulated by a cinnamon extract.

They went on to clone the receptor in order to study its chemistry more closely.

Professor Morice said it would take several years for his work to yield new drugs to block cough, even if the work proceeded well.

But he said: "The TRPA1 receptor that we have identified as a cough receptor and recently cloned is more interesting because it is set off by a much wider range of substances."

The Hull team is carrying out large-scale patient studies to try to identify agents to block the newly-identified receptor.

Their goal is to restore the cough reflex to normal levels, rather than to stop it completely.

Professor Morice said: "When people have a cough they have a heightened sensitivity.

However, we don't want to eliminate cough in patients because it is vital to keeping people well - it stops us getting pneumonia⁹（肺炎） - so a return to normal sensitivity is the goal.

British Lung Foundation vice-president Dr Keith Prowse described the study as interesting.

"We now need to find out what exactly stimulates¹⁰ this receptor and how it can be blocked," he said.

"If a successful blocker of this new receptor can be developed, it would be an excellent treatment for coughs which affects millions people in the UK and especially those with respiratory diseases（呼吸道疾病） such as chronic obstructive pulmonary disorder¹¹ (COPD) and asthma¹²（哮喘）."