Relative roles of irritant, type-J and pulmonary stretch receptors in lung reflexes.

Bilateral anodal block of both cervical vagus nerves of anaesthetized rabbits has been used to assess the relative role of afferent pathways with myelinated fibres (primarily from lung irritant receptors) and with nonmyelinated fibres (from J-receptors) in respiratory responses to some lung conditions. With inhalation of histamine aerosol the increase in breathing frequency is due to myelinated afferent fibres from irritant receptors. The similar response with inhalation of halothane is due to non-myelinated fibres from J-receptors. The reflex breathing response in lung oedema involves both pathways, but in the experimental conditions the myelinated pathway plays the larger part. The interaction of these two mechanisms, and the possible role of pulmonary stretch receptors, is discussed.