Cough reflex and oral chemesthesis induced by capsaicin and capsiate in healthy never-smokers

Miyako Yamasaki,Motoki Yoshida,Satoru Ebihara,Shinsuke Yamanda,Shannon Freeman,Hiroyuki Arai,Takae Ebihara,Masanori Asada

doi:10.1186/1745-9974-3-9

Abstract

BackgroundMany tussive agents are components of foods, but little is known about the relationship between cough reflex and oral chemesthesis sensitivities. We investigated the relationships between cough reflex and oral chemesthesis in individuals using two transient receptor potential vanilloid 1 (TRPV1) agonists with different potencies: capsaicin and capsiate.MethodsTwenty-eight healthy never-smokers were allocated to evaluate cough and oral chemesthesis of capsinoids. Cough reflex sensitivities are estimated by the lowest concentrations generating five coughs by each TRPV1 agonist inhalation. Oral chemesthesis sensitivities are estimated by the lowest concentrations which generate a hot sensation when filter paper loaded with each TRPV1 agonist is placed on the tongue.ResultsThere were strong correlations between capsaicin- and capsiate-induced cough reflex sensitivities, and between capsaicin- and capsiate-induced oral chemesthesis sensitivities. However, there were no significant correlations between cough reflex and oral chemesthesis sensitivities induced by both capsaicin and capsiate. The cough reflex sensitivities are significantly greater in females than in males whereas there were no gender differences in oral chemesthesis.ConclusionThe results showed that the sensitivities of sensory afferents were different between cough reflex and oral chemesthesis, suggesting that TRPV1 sensitivities differ between organs within healthy individuals. Capsiate could be a tussigen for the cough challenge test.

Highlights

Many tussive agents are components of foods, but little is known about the relationship between cough reflex and oral chemesthesis sensitivities
The inhalation cough challenge is applied via the oral cavity, but little attention has been paid to the effects of tussive agents on oral sensory systems during the cough challenge test
The mean threshold concentration for capsaicin application was significantly greater in cough reflex sensitivity than that in oral chemesthesis (p < 0.03)

Summary

Introduction

Many tussive agents are components of foods, but little is known about the relationship between cough reflex and oral chemesthesis sensitivities. Many tussive agents, such as capsaicin, citric acid, and acetic acid, are components of foods, it is unknown whether these chemical stimuli stimulate sensory nerves in bronchial airways and the oral cavity. The inhalation of tussive agents as a cough challenge test is a useful method to quantify cough in a clinical setting and to assess the antitussive effects of specific therapies in a laboratory setting [1]. The inhalation cough challenge is applied via the oral cavity, but little attention has been paid to the effects of tussive agents on oral sensory systems during the cough challenge test. There is a possibility that capsaicin in the oral cavity induces bronchoconstriction the same as intranasal application of capsaicin elicits bronchoconstriction [6]

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Conclusion