Postnatal changes in O₂ and CO₂ sensitivity in rodents

In rodents, the ventilatory responses to hypoxia (low O₂) and hypercarbia (high CO₂) change significantly over postnatal development. In hypoxia, most adult rodents increase ventilation and decrease metabolism to some degree. Hypercarbia, however, leads to an increase in ventilation with little, to no change in metabolism. Neonates, on the other hand, respond to hypoxia with a profound metabolic depression, and a severely attenuated ventilatory response. In hypercarbia, they exhibit a strong ventilatory response early in development that blunts, reaches a nadir, and then rises back to the adult-like response, thus, stabilizing postnatally. In this review we discuss how the O₂ and CO₂ ventilatory responses develop in rodents, the possible mechanisms that drive these postnatal changes, and how being raised in a burrow, an environment putatively low in O₂ and high in CO₂, may affect the development of O₂ and CO₂ sensitivity in rodents.