EFFECTS OF BRONCHOCONSTRICTION ON THE COUGH REFLEX IN THE CAT

The present study was aimed to analyse the influence of bronchoconstri ction (Carbachol, 10 mu g/kg, i.v.) on the cough response to mechanica l stimulation of the tracheal mucosa. Experiments were performed in an aesthetised and spontaneously breathing cats, using the isolated glott is technique. Airflow, pleural pressure, subglottic pressure, blood pr essure and total lung resistance mere recorded. During bronchoconstric tion, the cough response was inhibited significantly as shown by the d ecrease in the number of cough efforts (p<0.001), in maximum flow duri ng 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 pr essures. The mechanical stimulation of the tracheal mucosa evoked alwa ys a prolonged decrease of the larynx resistance, including those case s with inhibition of the cough. This study shows that the activation o f some type of receptors during bronchoconstriction can modify the cou gh response to mechanical stimulation of the tracheal mucosa. On the o ther hand, the widening of the glottis, an associated component of the cough response, can be obtained separately, suggesting that the laryn geal response is centrally integrated via different mechanisms.