Properties of 'irritant' receptors in canine lung

Activity was recorded from 48 vagal afferent fibers arising from what appeared to be rapidly adapting receptors in the lungs of open-chest dogs. Most of these receptors were stimulated by hyperinflation, forced deflation and reinflation of the lungs, and their mean conduction velocity was 23.3 m/sec (n = 41) compared with 32.3 m/sec (n = 100) for pulmonary stretch receptors. Activity in the receptors was increased most frequently by histamine given by aerosol or intravascularly, only occasionally by ammonia vapor and cigarette smoke, and was essentially unchanged by ether vapor, CO₂ and phenyl diguanide. The importance of locating presumed pulmonary receptors in the lungs is emphasized, as responses of receptors in the esophagus and pulmonary artery to ventilatory and chemical stimuli were similar to those of rapidly adapting bronchopulmonary receptors. The properties of these canine bronchopulmonary receptors are compared with those of similar receptors in other species. The lack of effect of inhaled irritants on most rapidly adapting receptors in dog lung indicates that the term 'irritant receptor' may be inappropriate.