Red nucleus inhibits breathing during hypoxia in neonates.

Conscious, anaesthetized and decerebrate young mammals respond to acute hypoxia with an initial increase in breathing followed by a fall to, or to below, pre-hypoxic levels--the biphasic ventilatory response. The ventilatory rise is due to sustained hypoxic stimulation of the peripheral chemoreceptors. We present evidence from brain stem and peripheral chemoreflex studies supporting the concept that, in addition to the peripheral chemoreceptors, hypoxia also activates brain stem pathways that inhibit ventilation. A key part of the inhibitory pathway is an area within the red nucleus. Destruction of this area in young decerebrate rabbits abolishes the ventilatory fall during hypoxia, yet has no effect on respiratory control during normoxia and does not affect arterial blood pressure changes in hypoxia. In support of this hypothesis, we report that there are neurones within the red nucleus that increase their discharge in hypoxia. The role of higher brain stem/hypothalamic function in central respiratory control during hypoxia in the fetus and neonate are considered.