Abstract
The modification of cough reflex by contraction and relaxation of the peripheral airway was investigated in anesthetized dogs. For administration of the drugs directly into the peripheral airway, an arterial cannula was chronically implanted in the right bronchial artery via the right intercostal artery. The cough reflex was induced by electrical stimulation of the upper tracheal mucosa by means of an electrode-cannula. Evaluation of the cough response was made by changes in frequency and amplitude of coughs. Drug solutions were infused for 5 min at a rate of 0.17 ml/min into the right bronchial artery. Intraarterial infusion of isoproterenol, 1-3 μg/min, reduced the amplitude, but had no effect on the frequency of coughs, while that of histamine, 3-10 μg/min, increased the frequency and amplitude of coughs. Atropine, 100 μg/min, caused no significant changes in amplitude and frequency, respectively. Benzonatate, 0.85 mg/min, reduced the frequency, but had no effect on the amplitude. Thus, the tonus of the peripheral airway, in particular the airway contraction, may the increase the frequency of cough reflex by lowering the threshold of the airway receptors.
