The Journal of comparative neurology
-
Spinal cord injury (SCI) induces retrograde cell death in descending pathways, which can be prevented by long-term intrathecal infusion of neurotrophins (Novikova et al. [2000] Eur J Neurosci 12:776-780). The present study investigates whether the same treatment also leads to improved regeneration of the injured tracts. After cervical SCI in adult rats, a peripheral nerve graft was attached to the rostral wall of the lesion cavity. ⋯ In comparison with untreated controls, the latter treatment also caused 35% reduction in axonal sprouting of descending pathways rostral to the lesion site and 72% reduction in the number of spinal cord neurons extending axons into the nerve graft. Local and short-term treatments neither prevented retrograde cell death nor enhanced regeneration of descending tracts, but induced robust regeneration of spinal cord neurons into the nerve graft. These results indicate that the signal pathways promoting neuronal survival and axonal regeneration, respectively, in descending tracts after SCI respond differently to neurotrophic stimuli and that efficient rescue of axotomized tract neurons is not a sufficient prerequisite for regeneration.