Postnatal maturation of vagal respiratory reflexes in preterm and full-term lambs.
The postnatal development of ventilatory reflexes originating from bronchopulmonary receptors was assessed in preterm vs. full-term lambs. Ventilation and arterial pressure were repeatedly measured in 10 preterm (gestational age, 132 days) and 7 full-term lambs without sedation from day 1 to day 42. The Hering-Breuer inhibitory reflex (slowly adapting stretch receptors) was assessed by the increase in expiratory time during end-inspiratory occlusion. The pulmonary chemoreflex (C-fiber endings) was assessed by the initial apnea + bradycardia + systemic hypotension and the secondary tachypnea after capsaicin intravenous injection. Results show the following. 1) Premature birth did not modify the maturation of the Hering-Breuer reflex. 2) Whereas a classic pulmonary chemoreflex was observed in the very first hours of life in preterm lambs, the tachypneic component of this reflex was weaker than in full-term lambs on day 1. 3) Premature birth led to a reversed postnatal maturation of this tachypneic response (tendency to increase with postnatal age). Our findings suggest that premature birth in lambs modifies postnatal maturation of the pulmonary chemoreflex.
Arsenault
Julie
J
Respiratory Research Unit, Department of Public Health, Faculty of Medicine, University of Sherbrooke, Sherbrooke, Quebec, Canada J1H 5N4, USA. Jp.Praud@USherbrooke.ca
Moreau-Bussiere
Francois
F
Reix
Philippe
P
Niyonsenga
Theophile
T
Praud
Jean-Paul
JP
D000375:Aging / Q000502:physiology; D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D001784:Blood Gas Analysis; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D002211:Capsaicin / Q000494:pharmacology; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D008168:Lung / Q000254:growth & development / Q000502:physiology; D036421:Nerve Fibers, Unmyelinated / Q000502:physiology; D011661:Pulmonary Stretch Receptors / Q000502:physiology; D012018:Reflex / Q000187:drug effects / Q000502:physiology*; D015656:Respiratory Mechanics / Q000187:drug effects / Q000502:physiology*; D012756:Sheep; D013268:Stimulation, Chemical; D013990:Tidal Volume / Q000187:drug effects / Q000502:physiology; D014630:Vagus Nerve / Q000187:drug effects / Q000254:growth & development* / Q000502:physiology*
D002211:Capsaicin