Respiratory activation of the facial nerve and alar muscles in anaesthetized dogs.

Comparisons were made of the activities of the dorsal buccal branch (d.b.b.) of the facial nerve which innervates the alae nasi and of the alar muscles themselves (alae nasi) with the activity of the phrenic nerve in eight anaesthetized, spontaneously breathing dogs during hypercapnia, end‐expiratory airway occlusion, and chest wall compression, before and after vagotomy. Nerve and muscle activities were recorded from bipolar cuff or wire electrodes respectively and processed by a moving average technique. Peak facial d.b.b., alae nasi, and phrenic activity all increased linearly with hypercapnia. Airway occlusion prolonged the duration of phrenic as well as facial d.b.b. and alae nasi activity. A comparison of electrical activity during unoccluded and occluded inspirations indicated a facilitation of phrenic activity but an inhibition of both facial d.b.b. and alae nasi activities associated with volume feed‐back. These volume‐related feed‐back effects were abolished by vagotomy. After vagotomy, peak facial d.b.b., alae nasi and phrenic activities increased during lower chest wall compression and decreased with upper chest wall compression when compared to the preceding control breath. Alae nasi and facial nerve activities, like that of the phrenic nerve, respond to respiratory chemical and reflex influences.