Shedding light on restoring respiratory function after spinal cord injury

Trauma at the cervical level is one of the most common types of spinal cord injury (SCI). Injuries at this level are particularly devastating since this results in disruption of the bulbospinal projections to the phrenic nucleus (PN), which is composed of motor neurons that directly innervate the diaphragm. In the laboratory, the model of choice for investigating cervical SCI and its resulting respiratory defi cits has been the C2 hemisection. In this model the cervical SC is exposed and hemisected from the midline all the way to the lateral most aspect of the cord. With the emergence of new and powerful tools from molecular neuroscience, new therapeutically relevant alternatives to these approaches have become available, including expression of light sensitive proteins called channelrhodopsins.

• 1
  Pharmacological intervention which can increase central respiratory drive might be a potential way to induce recovery of the ipsilateral hemidiaphragm following C2 hemisection – without contralateral phrenicotomy.
• 2
  Following expression in both mammalian and non-mammalian tissue, it can be induced by photostimulation to depolarize neurons, fi re action potentials and control activity of neurons independent of any kind of pre-synaptic input
• 3
  After restoring breathing activity with long light stimulation and then allowing the animal to recover for 1 day, we found that restored diaphragm function persisted for at least 24 h.