[Experimental changes in BDNF- and NT-3-like immunoreactivities in the spinal cord following its transection]

Brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) are neurotrophic factors involved in the neurotrophin family. However, while their biological activities on cultured neurons and their distribution have been reported, their functions in the central nervous system including the spinal cord are still unknown. We have recently developed antibodies to BDNF and to NT-3 synthetic peptides with different amino acid sequences as tools to visualize these molecules in in vivo tissue. Each antibody was specific to either BDNF or NT-3. Using these antibodies, we investigated the distribution of BDNF- or NT-3-like immunoreactivities (LI) in the spinal cord following transection in rats. In Group with an uninjured spinal cord as control, both BDNF-LI and NT-3-LI were localized in the gray matter, and particularly in the motor neurons of the ventral horn, and in some axons and glial cells of the white matter. In Group after transection of the spinal cord as a model of spinal injury, the motor neurons in the spinal cord, were strongly stained by anti-NT-3 antibodies and less strong by anti-BDNF antibodies at 3 weeks after injury. In the gray matter at 4 weeks after injury, astrocyte-like cells were markedly stained with anti-BDNF antibodies These findings indicate that in the spinal cord after injury, the biosynthesis of BDNF was upregulated in a different manner from that of NT-3 and that BDNF and NT-3 were both involved in the repair mechanisms, directing the amelioration of the spinal cord injury.