Primary role of respiratory afferents in sustaining breathing rhythm

• Published in: Journal of applied physiology: respiratory, environmental and exercise physiology Vol. 45; no. 1; p. 11
• Main Authors: Sullivan, C E, Kozar, L F, Murphy, E, Phillipson, E A
• Format: Journal Article
• Language: English
• Published: United States 01.07.1978
• Subjects: Animals; Carbon Dioxide; Chemoreceptor Cells - physiology; Dogs; Oxygen; Respiration; Sleep - physiology; Sleep, REM - physiology; Vagus Nerve - physiology; Wakefulness - physiology
• ISSN: 0161-7567
• DOI: 10.1152/jappl.1978.45.1.11

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.