Control of genioglossal muscle activity in the anesthetized piglet: The role of vagal afferents

We examined genioglossal muscle electromyogram activity during room air breathing and hyperoxic hypercapnia in 10 anesthetized (halothane) newborn piglets before and after bilateral midcervical vagotomy. With vagal afferents intact, genioglossal activity was absent during room air breathing in 10/10 study animals and was recruited in only 4/10 piglets during carbon dioxide breathing. After vagotomy, genioglossal activity remained absent in 9/10 study animals during room air breathing but was recruited in 10/10 piglets during the hypercapnic gas exposure at arterial CO₂ tensions comparable to prevagotomy levels. We conclude that vagal afferent feedback modulates genioglossal activity in anesthetized newborn piglets and exerts an inhibitory influence on the activity of this muscle during hyperpnea induced by carbon dioxide breathing.