Electromyographic responses of a nasal muscle to stimulation of the nasal vestibule in the cat.

1. The effects of nasal stimulation using an air jet or balloon on the electromyographic (e.m.g.) activity of a nasal muscle, the levator labii superioris alaeque nasi component of the quadratus labii superioris muscle, were studied in the anaesthetized cat. 2. Respiratory related nasal e.m.g. activity was recorded and this normally consisted of two components, one coinciding with the onset of inspiratory airflow and a larger component which commenced at the onset of expiratory airflow and often persisted until the onset of the following inspiratory airflow. 3. An air jet (room air, 1-8 l/min, temperature 24 degrees C) applied to the nasal vestibule by means of a small nozzle caused an increase in the amplitude of the ipsilateral spontaneous nasal e.m.g. activity. 4. The increase in nasal e.m.g. activity caused by the nasal air jet was unaffected by warming the airflow from 30 to 40 degrees C. 5. A sustained increase in nasal e.m.g. activity was caused by application of pressure to the walls of the nasal vestibule by means of a small balloon. 6. Section of the ethmoidal and infra-orbital branches of the trigeminal nerve abolished the increase in nasal e.m.g. amplitude caused by nasal stimulation with the air jet, whilst section of the facial nerve abolished the spontaneous respiratory nasal e.m.g. activity. 7. The results indicate that there are sensory receptors in the nasal vestibule which respond to nasal positive pressure and cause a reflex increase in nasal e.m.g. activity.