Sprouting and regeneration after pyramidotomy and blockade of the myelin-associated neurite growth inhibitors NI 35/250 in adult rats

After a selective unilateral lesion of the corticospinal tract (CST) at the level of the brainstem (pyramidotomy) and neutralization of the myelin associated neurite growth inhibitors NI-35/250 with the monoclonal antibody (mAb) IN-1, we had previously observed a strong behavioural recovery in parallel with an enhanced structural plasticity of the lesioned as well as the unlesioned CST. The present study focuses on the regenerative response of the cut CST axons at the lesion site in these adult rats. The results show a strong enhancement of regenerative sprouting of CST fibres by treatment with the mAb IN-1. Successful elongation of these sprouts through the pyramidal decussation and into the cervical spinal cord was also dependent on the presence of this antibody. In the spinal cord, regenerating fibres were rarely found in the position of the former CST; most of the fibres were distributed seemingly randomly over the entire lateral extent of the spinal cord.