FIGURE 3.

Low-dose IH elicits spinal respiratory motor plasticity

For example, a single presentation of acute intermittent hypoxia (AIH: 3–10 episodes, 5-min duration, 5-min intervals) elicits phrenic (and diaphragm), long-term facilitation (3, 118). Similar, but greater relative effects are observed in the inspiratory intercostal nerves/muscles (34a). These forms of respiratory motor plasticity can be harnessed to recover lost breathing capacity by exposing rats with cervical spinal injuries to daily AIH (7 days; Ref. 68). Similar motor plasticity is also observed in limb function (68, 119), demonstrating that IH elicits plasticity in diverse motor systems. Understanding mechanisms giving rise to respiratory motor plasticity may guide development of novel therapies to treat motor impairment in diverse clinical disorders, including spinal cord injury and ALS.