Branching of Myelinated and Unmyelinated Fibers During Nerve Regeneration

Nerve cells projecting into peripheral nerves are usually depicted as having an axon which runs straight towards its target. In certain conditions, however, the axons branch within the nerve trunk. Ramon Y Cajal (1928) observed extensive branching of nerve fibers in regenerated nerves. The branchings occurred at the site of injury, and repeated branchings were produced when the nerve was sectioned at multiple sites. Electron microscopic data are scarce. Bray and Aguayo (1974) counted unmyelinated axons in the crushed cervical trunk of rat at different levels and found that, distal to the crush, the number of axons transiently increased by several 100% but then returned to normal. In the present study branching of myelinated and unmyelinated fibers in crushed peroneal and soleus nerves was investigated. The advantage of using the soleus nerve was that all fibers could be assessed which eliminated the error inherent to sampling procedures.