Our purpose was to characterize receptors which respond to changes in uppr airway pressures. Such changes alterations in hypoglossal and phrenic nerve activities. Decerebrate, vagotomized, paralyzed and ventilated cats were prepared so that pressures could be altered within segments of upper airways. Activities of single fibers in the superior laryngeal and glossopharyngeal nerves were monitored. Most superior laryngeal receptors discharged tonically at zero transmural pressure. Discharges of approximately half decreased (A) and the rest increased (B) with pressure reductions of -7 to -8 cm H2O. Pressure increases of +7 to +28 cm H2O caused increases in Group A activities while Group B responses varied. The remaining receptors were silent, being activated by pressure decreases and/or increases. Activities of other silent receptors, similarly activated, were recorded from glossopharyngeal nerve. Tonically active glossopharyngeal receptors increased discharged after both pressure increases and decreases. Most tonically active and silent receptors, having afferents in either nerve, adapted incompletely to sustained pressures. These may have major functions in hypoglossal responses to changes in upper airway pressures.
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