Capsaicin sensitive sensory neurons mediate the response to nasal irritation induced by the vapour phase of cigarette smoke

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Cigarette-smoke exposure in awake guinea-pigs induced reproducible nose wipings with the fore-paws. This behaviour was used as a model to study the mechanisms underlying the irritant effect of cigarette smoke. The nose wipings upon smoke exposure were abolished after local anaesthesia of the nasal mucosa, which indicates that this response was due to activation of nasal protective reflexes. Removal of the particulate phase of the smoke including nicotine using a Cambridge filter only slightly reduced the wiping response, and nicotine-free cigarette also induced marked irritation. This suggests that irritant chemicals in the vapour phase of the smoke caused this effect. Systemic capsaicin pretreatment, which is known to cause a functional impairment of chemosensitive C-fibre afferents, abolished the nose wiping behaviour seen upon smoke exposure. Local pretreatment of the nasal mucosa with capsaicin also significantly reduced the number of smoke-induced nose wipings. It is concluded that smoke-induced irritation, as indicated by nose wipings, is primarily due to activation of capsaicin-sensitive sensory nerves in the nasal mucosa by vapour-phase components.