RESPIRATORY-RELATED CONTROL OF PALATOGLOSSUS AND LEVATOR PALATINI MUSCLE-ACTIVITY

Route of respiration [nasal (NR) vs. oral (OR)] is determined by the p osition of the soft palate. Despite this, little is known about the re spiratory-related activity of palatal muscles. We investigated the act ivity of two palatal muscles: palatoglossus (PG) and levator palatini (LP). Eight normal male subjects were studied during wakefulness with intramuscular electrodes placed in the PG and LP. The electromyograms (EMGs) of the PG and LP were measured during both NR and OR under 1) q uiet basal respiration, 2) inspiratory resistive loading (25 cmH(2)O.1 (-1).s), and 3) progressive hypercapnia. The PG consistently demonstra ted inspiratory phasic activity during NR with greater inspiratory and expiratory EMGs (P < 0.05) during basal NR compared with basal OR [3. 3 +/- 0.2 (SE), 1.1 +/- 0.1, 2.3 +/- 0.4, and 1.0 -1 0.2 arbitrary uni ts for PG nasal inspiratory, PG oral inspiratory, PG nasal expiratory, and PG oral expiratory, respectively]. During OR, the LP was inspirat ory phasic in 4 subjects and expiratory phasic in 4 subjects, with gre ater inspiratory and expiratory EMGs during basal OR compared with bas al NR (5.5 +/- 1.1, 2.1 +/- 0.4, 6.8 +/- 1.5, and 1.8 +/- 0.4 arbitrar y units for LP oral inspiratory, LP nasal inspiratory, PG oral expirat ory, and PG nasal expiratory, respectively). Both muscles demonstrated significantly increased activity during both inspiratory resistive lo ading and hypercapnia. However, their route-specific activation patter n continued during such stimulated breathing. We conclude that 1) the route of respiration is influenced by the complex interaction of the P G and LP and 2) the response of these muscles to respiratory stimuli i s dependent on the route of respiration.