title: Vagal denervation inhibits the increase in pulmonary blood flow during partial lung aeration at birth.
abstract: Lung aeration at birth significantly increases pulmonary blood flow, which is unrelated to increased oxygenation or other spatial relationships that match ventilation to perfusion. Using simultaneous X-ray imaging and angiography in near-term rabbits, we investigated the relative contributions of the vagus nerve and oxygenation to the increase in pulmonary blood flow at birth. Vagal denervation inhibited the global increase in pulmonary blood flow induced by partial lung aeration, although high inspired oxygen concentrations can partially mitigate this effect. The results of the present study indicate that a vagal reflex may mediate a rapid global increase in pulmonary blood flow in response to partial lung aeration.
  
  
  
  Air entry into the lungs at birth triggers major cardiovascular changes, including a large increase in pulmonary blood flow (PBF) that is not spatially related to regional lung aeration. To investigate the possible underlying role of a vagally-mediated stimulus, we used simultaneous phase-contrast X-ray imaging and angiography in near-term (30 days of gestation) vagotomized (n = 15) or sham-operated (n = 15) rabbit kittens. Rabbits were imaged before ventilation, when one lung was ventilated (unilateral) with 100% nitrogen (N2), air or 100% oxygen (O2), and after all kittens were switched to unilateral ventilation in air and then ventilation of both lungs using air. Compared to control kittens, vagotomized kittens had little or no increase in PBF in both lungs following unilateral ventilation when ventilation occurred with 100% N2or with air. However, relative PBF did increase in vagotomized animals ventilated with 100% O2, indicating the independent stimulatory effects of local oxygen concentration and autonomic innervation on the changes in PBF at birth. These findings demonstrate that vagal denervation inhibits the previously observed increase in PBF with partial lung aeration, although high inspired oxygen concentrations can partially mitigate this effect.
authors.affiliation: The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, Australia.|Department of Obstetrics and Gynaecology, Monash University, Melbourne, Australia.
authors.forename: Justin A R
authors.initials: JA
authors.lastname: Lang
authors.affiliation: Monash Biomedical Imaging Facility and Department of Physiology, Monash University, Melbourne, Australia.|Australian Synchrotron, Melbourne, Australia.|Department of Cardiac Physiology, National Cerebral and Cardiovascular Centre Research Institute, Osaka, Japan.
authors.forename: James T
authors.initials: JT
authors.lastname: Pearson
authors.affiliation: The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, Australia.|Department of Obstetrics and Gynaecology, Monash University, Melbourne, Australia.|Medical University of Graz, Austria.
authors.forename: Corinna
authors.initials: C
authors.lastname: Binder-Heschl
authors.affiliation: The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, Australia.|Department of Obstetrics and Gynaecology, Monash University, Melbourne, Australia.
authors.forename: Megan J
authors.initials: MJ
authors.lastname: Wallace
authors.affiliation: The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, Australia.|Department of Obstetrics and Gynaecology, Monash University, Melbourne, Australia.
authors.forename: Melissa L
authors.initials: ML
authors.lastname: Siew
authors.affiliation: School of Physics and Astronomy, Monash University, Melbourne, Australia.
authors.forename: Marcus J
authors.initials: MJ
authors.lastname: Kitchen
authors.affiliation: Department of Pediatrics, Leiden University Medical Centre, Leiden, Netherlands.
authors.forename: Arjan B
authors.initials: AB
authors.lastname: Te Pas
authors.affiliation: Medical Imaging and Radiation Sciences, Monash University, Melbourne, Australia.|Department of Medical Imaging, University of Saskatchewan, Saskatoon, Canada.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Lewis
authors.affiliation: The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, Australia.|Department of Obstetrics and Gynaecology, Monash University, Melbourne, Australia.
authors.forename: Graeme R
authors.initials: GR
authors.lastname: Polglase
authors.affiliation: Department of Cardiac Physiology, National Cerebral and Cardiovascular Centre Research Institute, Osaka, Japan.
authors.forename: Mikiyasu
authors.initials: M
authors.lastname: Shirai
authors.affiliation: The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, Australia.|Department of Obstetrics and Gynaecology, Monash University, Melbourne, Australia.
authors.forename: Stuart B
authors.initials: SB
authors.lastname: Hooper
mesh_terms: D000792:Angiography; D000818:Animals; D003714:Denervation; D008168:Lung / Q000000981:diagnostic imaging / Q000502:physiology; D011651:Pulmonary Artery / Q000502:physiology; D011652:Pulmonary Circulation / Q000502:physiology*; D011817:Rabbits; D012121:Respiration, Artificial; D014628:Vagotomy; D014630:Vagus Nerve / Q000502:physiology* / Q000601:surgery
keywords: angiography; newborn; perfusion; pulmonary blood flow; vagotomy; ventilation