Role of carotid sinus and aortic nerves in respiratory control of infant rats.

The roles of carotid sinus (CSN) and aortic depressor nerves (ADN) in the maintenance of rhythmic respiration and in the response to airway occlusion were investigated in 8- to 10-day-old infant rats. Cutting the CSN led to a periodic loss of rhythmic respiration with arrhythmic low-amplitude waveforms, frequent end-expiratory pauses, and occasional apneas observed in unanesthetized unrestrained pups studied in their home cage nests by impedance pneumography. Cutting the ADN alone did not have this effect. Sinoaortic denervation (SAD) in which both nerves were cut, produced a more severe disturbance that was not relieved by tracheostomy, indicating that it was not due to upper airway obstruction. Tracheal pressure recordings from anesthetized SAD infants in response to short periods of external airway obstruction showed reduced respiratory efforts and prolonged recovery times, deficits that may play a role in the mortality previously reported after SAD in infant rats.