Fink-Heimer/Nauta demonstration of regenerating axons in the rat spinal cord.

Six months after complete spinal cord transection, regenerated descending motor axons can be found by electrophysiologic testing and can also be demonstrated anatomically using the Fink-Heimer/Nauta technique. Regeneration was found in all animals, treated or control, but statistically significant increased regeneration as measured by the Fink-Heimer/Nauta technique was found in animals treated with a single injection of 75 mg/kg of cyclophosphamide 24 hours after the original spinal cord transection. This result is similar to those of another study using the orthograde axonal transport of tritiated proline as a measure of axonal regeneration. The mode of action of cyclophosphamide may be by its immunosuppressive properties because this drug is most effective when administered 24 hours after cord transection, a time when its effects as an immunosuppressant would be maximal.