Selective Depression by Ethanol of Upper Airway Respiratory Motor Activity in Cats

We studied the effects of systemically administered ethyl alcohol on the respiratory motor activity of the phrenic, hypoglossal and recurrent laryngeal nerves in unanesthetized, decerebrate cats. Some of the cats were studied after carotid sinus nerve section. In addition, parallel studies were done in intact, awake cats with chronic electromyographic electrodes in the diaphragm, genioglossus, and posterior cricoarytenoid (PCA) muscles. In decerebrate animals, alcohol induced a significant reduction of hypoglossal and recurrent laryngeal nerve activities at doses that had little or no effect on the phrenic nerve discharge. Similar changes were observed in chemodenervated cats. In awake animals, genioglossal and PCA muscle activities were depressed by alcohol, whereas diaphragm activity showed no consistent change. Alcohol caused a significant increase in respiratory frequency in awake cats and reduced the responses of genioglossal and PCA muscle activities to hypercapnia and normocapnic hypoxia. We conclude that alcohol induces a selective reduction in upper airway respiratory motor activity by an action that does not require intact suprapontile structures, vagal afferents, or peripheral chemoreceptors. This reduction may contribute to the alcohol-induced exacerbation of obstructive sleep apnea.