Secondary transneuronal degeneration: cortical changes induced by peripheral nerve section in neonatal rats

Secondary transneuronal degeneration of the cortico-spinal tract (CST) has been induced after sciatic nerve section in newborn rats. Observations made 21-60 days after the lesion showed a considerable decrease in number of myelinated and unmyelinated fibres of the CST ipsilateral to the lesion and of horseradish peroxidase-labelled nerve cells in the somato-sensorimotor cortex of the contralateral cerebral hemisphere. This phenomenon which has never been observed in spite of the frequent studies of experimental peripheral nerve lesions, may be significant in normal and pathological development.