Semaphorin and neuropilin expression in motoneurons after intraspinal motoneuron axotomy.

We have examined mRNA and protein distribution for the axon guidance molecules semaphorin3A, 3F, 4F and semaphorin receptors neuropilin-1 and 2, 1-21 days after intramedullary axotomy of rat lumbar spinal cord motoneurons. We show that semaphorin3A mRNA and protein are up-regulated in the scar and in motoneurons from 3 days and upto 3 weeks after injury. Neuropilin-1 mRNA showed no changed expression in axotomized motoneurons. Semaphorin3F mRNA expression was found in ventral roots after ventral funiculus lesion (VFL) and neuropilin-2 mRNA was found in affected motoneurons from 1 day after injury throughout the examined period. Semaphorin4F mRNA was first found in motoneurons 3 weeks after lesion. These results suggest semaphorin/neuropilin involvement in the injury response of intramedullary axotomized motoneurons.