The Role of Capsaicin-sensitive C-fibre Afferent Nerves in the Cough Reflex

While airway rapidly adapting receptors can mediate the cough reflex, much evidence suggests that bronchial C-fibre receptors are also involved in guinea-pigs and man. In man local and systemic C-fibre stimulants have a potent tussive action, which is blocked by low doses of local anaesthetics which leave the reflex bronchoconstriction intact. In guinea-pigs destruction of airway C-fibre receptors by large doses of capsaicin abolishes the cough reflex due to capsaicin and citric acid. Thus there may be subpopulations of airway C-fibres responsible for the different reflexes such as apnoea, cough and bronchoconstriction. The evidence for the role of C-fibre receptors in cough is described and discussed.