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J Physiol Vol 445 pp 713-723
Copyright © 1992 by The Physiological Society
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Fetal breathing, sleep state and cardiovascular adaptations to anaemia in sheep.

K Matsuda, C Ducsay and B J Koos

Department of Physiology, School of Medicine, Loma Linda University, CA 92324.

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.




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Am. J. Physiol. Regul. Integr. Comp. Physiol.Home page
B. J. Koos and A. Chau
Fetal cardiovascular and breathing responses to an adenosine A2a receptor agonist in sheep
Am J Physiol Regulatory Integrative Comp Physiol, January 1, 1998; 274(1): R152 - R159.
[Abstract] [Full Text] [PDF]




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