A comparative study of irritant and type J receptors in the cat

Abstract

Activity was recorded from irritant and type J afferent vagal fibres in cats with open chests and the response of the receptors to a variety of respiratory and chemical stimuli was investigated. Conduction velocities for the type J and irritant fibres were 0.9–2.1 and 9.1–25.0 m/sec, respectively. Any spontaneous discharge from type J receptors was sparse, whereas most irritant receptors displayed a prominent spontaneous discharge which was related, sometimes inconsistently, to the respiratory cycle. Whereas inflation stimulated both types of receptors, deflation affected only the irritant receptors. Phenyl diguanide and capsaicin affected both types of endings but the pattern of the response was different in the two fibre types; the evoked discharge in type J fibres was not inhibited when the lung was inflated with pressures of up to 20 cm H 2O. Histamine and ammonia affected both types of ending. The nomenclature of the small diameter intrapulmonary fibres as “type J” fibres is discussed and the limitations of this term, as at presently used, are outlined.