The effects of hypoxia and CO2 on the sleep-waking pattern of the potoroo (Potorous tridactylus apicalis)

Four male potoroos (Potorous tridactylus apicalis) breathed 21% and 7% O₂ with and without the addition of 5% CO₂. The effects of these gas mixtures on the potoroo's sleeping-waking pattern (SWP) were studied. The SWP while breathing 21% O₂/5%CO₂ was unchanged when compared with that of breathing ambient air (21% O₂). While breathing 7% O₂, the SWP was severely disrupted: total sleep time (TST) and slow wave sleep (SWS) increased markedly. Brain temperature fell substantially. Paradoxical sleep (PS) was almost abolished and wakefulness (W) decreased. The addition of 5% CO₂ to the O₂ deficient gas mixture, i.e., 7% O₂/5% CO₂, restored the SWP to that obtained while breathing ambient air. It is concluded that CO₂ neutralizes the disruptive effect which hypoxia has on the potoroo's SWP. It is hypothesized that this constitutes a homeostatic mechanism for stabilizing the SWP and is carried over from pouch life.