Nasal mechanoreceptors in guinea pigs.

The characteristics of nasal mechanoreceptors in the ethmoidal nerve (EN) of guinea pigs were clarified by electrophysiological identification of their responsiveness to transmural pressure, i.e., the inspiratory effort induced by tracheal occlusion and probing of the nasal cavity, vestibule or alae nasi of the nose. A total of 73 mechanoreceptors were recorded from 18 guinea pigs breathing through the nose or a tracheostomy with an isolated nasal airway. Six receptors (6/22) in nasal-breathing animals were stimulated by upper airway occlusion, and 18 receptors (18/22) in tracheostomy-breathing animals were stimulated by maintained negative pressure in the nose. Mechanoreceptors responding to probing to the nose were found in both experimental set-ups. The mean threshold of 'pressure'-responsive receptors to negative pressure was very high (-3.87 +/- 0.95 kPa). Most of the receptors were also examined for response to ammonia vapour or instillation of distilled water; only three 'touch'-responsive receptors could be stimulated by ammonia and/or distilled water. These results suggest low sensitivity to pressure changes and noxious chemical stimuli of mechanoreceptors in the EN of guinea pigs.