The incidence of breathing movements of fetal sheep in normoxia and hypoxia after peripheral chemodenervation and brain-stem transection.
The incidence of fetal breathing movements and low voltage electrocortical activity was measured in three groups of fetal sheep, at 123-137 days gestation. The first group (transected & denervated) had the brainstem transected at the level of the colliculi and also had peripheral arterial chemodenervation. The second group (denervated) had a sham brain-stem transection and peripheral arterial chemodenervation. The third group (sham-operated) had sham brain-stem transection and sham peripheral chemodenervation. No differences were observed in the incidence of fetal breathing movements or low voltage electrocortical activity between the sham-operated and the denervated groups in normoxia, or in hypoxia when all these fetuses became apnoeic. There were however differences between these 2 groups and the transected & denervated group, in which fetal breathing movements where dissociated from electrocortical activity and which in some fetuses were continuous. During isocapnic hypoxia 3 of 8 transected & denervated fetuses made fetal breathing movements. We discuss the problems of interpreting data from brain-stem transected fetuses, but conclude that the evidence reveals no tonic influence of the peripheral arterial chemoreceptors on fetal breathing movements.
Moore
P J
PJ
Department of Biochemistry & Physiology, University of Reading, Whiteknights, U.K.
Parkes
M J
MJ
Nijhuis
J G
JG
Hanson
M A
MA
D000818:Animals; D001933:Brain Stem / Q000502:physiology / Q000601:surgery; D002628:Chemoreceptor Cells / Q000502:physiology*; D005260:Female; D005311:Fetal Hypoxia / Q000503:physiopathology*; D005333:Fetus / Q000502:physiology*; D011247:Pregnancy; D012119:Respiration; D012756:Sheep; D013563:Sympathectomy, Chemical