Abstract
1. In foetal lambs the effect of raising and lowering arterial PO2 (by varying the O2 content of the maternal inspired gas mixture) was studied in order to determine whether the systemic arterial chemoreceptors regulated the circulation.
2. From 0·7 of term relative hypoxaemia (e.g. reducing carotid PO2 from 40 to 20 mm Hg) caused a rise of arterial pressure and femoral vaso-constriction. These changes were unaffected or even increased by bilateral section of the nerves from the carotid sinus and body. They were abolished by section of the vagi or aortic nerves.
3. It is concluded that in foetal lambs during the last third of gestation the circulation is under reflex control by the aortic chemoreceptors.
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Selected References
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