Modulation of hypoxic depressions of ventilatory activity in the newborn piglet by mesencephalic mechanisms

In neonates, ventilatory responses to hypoxia are 'biphasic,' with an augme ntation followed by a decline. The hypoxia-induced augmentations in ventila tion are attenuated and the depressions are accentuated following denervati on of the peripheral chemoreceptors. Piglets that were decerebrated at a ro stral mesencephalic level exhibited these hypoxia-induced depressions. Thes e depressions were lessened following transection through the caudal mesenc ephalon. Mesencephalic mechanisms play a fundamental role in the brainstem regulation of ventilatory responses to hypoxia. (C) 1999 Elsevier Science B .V. All rights reserved.