Effects of bronchoconstriction on the cough reflex in the cat

The present study was aimed to analyse the influence of bronchoconstriction (Carbachol, 10 micrograms/kg, i.v.) on the cough response to mechanical stimulation of the tracheal mucosa. Experiments were performed in anaesthetised and spontaneously breathing cats, using the isolated glottis technique. Airflow, pleural pressure, subglottic pressure, blood pressure and total lung resistance were recorded. During bronchoconstriction, the cough response was inhibited significantly as shown by the decrease in the number of cough efforts (p < 0.001), in maximum flow during inspiratory (p < 0.001) and expiratory (p < 0.001) movements and in the change of the expiratory (p < 0.01) and inspiratory (p < 0.01) pleural pressures. The mechanical stimulation of the tracheal mucosa evoked always a prolonged decrease of the larynx resistance, including those cases with inhibition of the cough. This study shows that the activation of some type of receptors during bronchoconstriction can modify the cough response to mechanical stimulation of the tracheal mucosa. On the other hand, the widening of the glottis, an associated component of the cough response, can be obtained separately, suggesting that the laryngeal response is centrally integrated via different mechanisms.