Negative pressure effects on mechanically opposing pharyngeal muscles in awake and sleeping goats

Our aim was to investigate the effects of the negative pressure reflex on m echanically opposing pharyngeal muscles during wakefulness, slow-wave sleep (SWS), and rapid eye movement (REM) sleep. In four goats with isolated upp er airways, we measured tracheal airflow and electrical activity of the thy ropharyngeus (TP; constricting), the stylopharyngeus (SP; dilating), and th e diaphragm (Dia). In the wakefulness state in response to negative pressur e tests, TP decreased (65%), SP increased (198%), and tidal volume (V-T) (6 6%) and rate of rise of Dia (Dia(slope), 69%) decreased (P< 0.02). Similarl y, during SWS, the negative pressure response of TP (31%), V-T (61%), and D ia(slope) (60%) decreased, whereas SP (113%) increased, relative to SWS con trol (P< 0.02). In REM sleep, the negative pressure response by TP and SP w ere small, whereas both V-T (38%) and Dia(slope) (24%) were greatly decreas ed (P< 0.02) compared with REM control. Inspiratory duration remained uncha nged in response to negative pressure tests in all states. These data provi de evidence that mechanically opposing inspiratory and expiratory pharyngea l muscles are reciprocally controlled and their response to negative pressu re are state dependent.