title: Primary role of respiratory afferents in sustaining breathing rhythm.
abstract: We studied the effects on breathing rhythm of suppressing the major respiratory stimuli (wakefulness, vagal, peripheral and central chemoreceptors) in healthy, unanesthetized dogs. Respiratory frequency (f) was obtained with a pneumotachograph; the state of wakefulness (W) or sleep was determined by EEG and behavioral criteria. During quiet W, f averaged 17 breaths/min and minute volume of ventilation (VI), 8.4 l/min. In slow-wave sleep (SWS), f slowed to 14 breaths/min, and VI decreased to 6.8 l/min. Afferent vagal blockade during SWS slowed f to 4 breaths/min, due primarily to prolongation of expiratory duration (Te) to 13.3 s, and decreased VI to 4.8 l/min. One breath of 100% O2 prolonged Te further to 27.4 s. Central chemoreceptor sensitivity was then reduced by inducting a metabolic alkalosis that combined with SWS, vagal blockade, and hyperoxia prolonged Te to as long as 57 s and reduced f to as low as 1 breath/min. The results demonstrate that afferent respiratory stimuli are essential for sustaining adequate ventilation.
mesh_terms: D000818:Animals; D002245:Carbon Dioxide; D002628:Chemoreceptor Cells / Q000502:physiology; D004285:Dogs; D010100:Oxygen; D012119:Respiration; D012890:Sleep / Q000502:physiology; D012895:Sleep, REM / Q000502:physiology; D014630:Vagus Nerve / Q000502:physiology*; D014851:Wakefulness / Q000502:physiology
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen