Fetal breathing, sleep state and cardiovascular adaptations to anaemia in sheep.
1. In unanaesthetized fetal sheep (greater than 0.8 term) prolonged anaemia initially reduced the incidences of low-voltage electrocortical activity, rapid eye movements and breathing activity; but the incidence of each returned to normal within 4-7 h. 2. Anaemia induced a persistent rise in fetal heart rate and plasma concentrations of adrenaline, noradrenaline and cortisol. 3. After 16 h the fetal haematocrit was returned to normal. Isocapnic hypoxia induced less than 1 h later also inhibited eye and breathing activity. 4. After 1 h fetal arterial PO2 (Pa,O2) was returned to normal. This rise in O2 tension was associated with an elevation in the incidence of low-voltage electrocortical activity, eye movements and breathing. Breathing movements also occurred during high-voltage electrocortical activity. 5. It is concluded that the brain PO2 set-point for hypoxic inhibition adapts rapidly to alterations in O2-carrying capacity and is probably due to changes in the concentration and/or receptor affinity of a central neuromodulator. Secondly, a rise in brain PO2 at birth may contribute to the onset of continuous breathing.
Matsuda
K
K
Department of Physiology, School of Medicine, Loma Linda University, CA 92324.
Ducsay
C
C
Koos
B J
BJ
D000222:Adaptation, Physiological / Q000502:physiology*; D000740:Anemia / Q000196:embryology* / Q000503:physiopathology; D000818:Animals; D002319:Cardiovascular System / Q000196:embryology*; D004594:Electrophysiology; D004837:Epinephrine / Q000097:blood; D005133:Eye Movements / Q000502:physiology; D005260:Female; D005312:Fetal Blood / Q000737:chemistry; D005311:Fetal Hypoxia / Q000503:physiopathology; D006340:Heart Rate, Fetal / Q000502:physiology; D006854:Hydrocortisone / Q000097:blood; D009068:Movement / Q000502:physiology*; D009638:Norepinephrine / Q000097:blood; D011247:Pregnancy; D012119:Respiration / Q000502:physiology*; D012756:Sheep / Q000196:embryology* / Q000502:physiology; D012890:Sleep / Q000502:physiology*
D006854:Hydrocortisone; D009638:Norepinephrine; D004837:Epinephrine