Neonatal stress disrupts laryngeal chemoreflex function in anesthetized rat pups

Abstract

In preterm infants, the presence of liquids or solids in the airways stimulates the laryngeal chemoreflex (LCR) that results in apneas with potentially life threatening consequences. Because neonatal stress interferes with respiratory control development, we tested the hypothesis that neonatal maternal separation (NMS) compromises LCR function in rat pups. Experiments were performed on 10 to 15 days old male pups that were undisturbed (controls) or subjected to NMS (3h/day each day beginning at P3 to P13). Pups were anesthetized (chloralose, 20 mg/kg + urethane, 1 mg/kg) and maintained at 35°C. Following tracheotomy, a water filled catheter was placed near the larynx. Breathing was monitored with intercostal EMG electrode. O2 saturation and heart rate were monitored with pulse oxymetry. Following baseline measurements, each pup received 10 μL injection of water near the larynx. This procedure was repeated 3 times with a 5 min recovery period between injections. In NMS rats, apnea duration tended to increase following each stimulation; this was not observed in controls. LCR‐related O2 desaturations and bradycardias were more important in NMS pups than controls. The mortality rate observed in NMS pups (83%) was greater than controls (33%). We conclude that neonatal stress compromises LCR function in young rats and could contribute to respiratory disorders in infants. This research was supported by CIHR.