Box 3 | Glial inhibition in evolution

From the following article:

Glial inhibition of CNS axon regeneration

Glenn Yiu and Zhigang He

Nature Reviews Neuroscience 7, 617-627 (August 2006)

doi:10.1038/nrn1956

Why have such diverse mechanisms evolved to limit axon regeneration in the adult CNS? Unlike most higher vertebrates, primitive organisms such as newts and salamanders can regenerate after spinal cord injury. Regeneration also occurs in some mammals such as opossums, but only in the days immediately following birth127. Assuming that ontogeny recapitulates phylogeny, an analogy can be drawn with the increased ability of the embryonic nervous system to regenerate when compared with adults. This evidence suggests that the loss of CNS regeneration might have resulted from recent evolutionary adaptations, and is not hard-wired into the nervous system. Therefore, although glial inhibition is still likely to be crucial for preserving higher-order processes, removing these inhibitory influences after injury could potentially recover some basic, more primitive functions in the clinical setting, such as the ability to breathe without a respirator or improved bowel or bladder control.