Response of laryngeal receptors to water solutions of different osmolality and ionic composition

Water-responsive laryngeal receptors with fibres in the superior laryngeal nerve were studied to characterize the specific physicochemical properties of aqueous solutions that activate these endings. The responses to water (37 degrees C) of 141 receptors were studied in 39 anaesthetized dogs breathing through a tracheostomy with the larynx functionally isolated. Of the 89 receptors stimulated by water, 53 were also challenged with isosmotic (275-315 mOsm) solutions of dextrose and sodium gluconate at 37 degrees C. Receptors that only responded to water (n = 31) with a long delay, long duration discharge were generally respiratory modulated. On the other hand, laryngeal receptors that responded to all test solutions (n = 22) with a short delay, short duration discharge were generally not respiratory modulated. We conclude that the former type of receptor responds to lower osmolality, whereas the latter responds to the lack of chloride ions in the test solutions. These two types of receptor may be responsible for the cough and bronchoconstriction induced by inhaled aerosols of different osmolalities and ionic compositions.