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 ass ociated neurite growth inhibitors NI-35/250 with the monoclonal antibody (m Ab) IN-1, we had previously observed a strong behavioural recovery in paral lel with an enhanced structural plasticity of the lesioned as well as the u nlesioned CST. The present study focuses on the regenerative response of th e 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 wit h the mAb IN-1. Successful elongation of these sprouts through the pyramida l decussation and into the cervical spinal cord was also dependent on the p resence of this antibody. In the spinal cord, regenerating fibres were rare ly found in the position of the former CST; most of the fibres were distrib uted seemingly randomly over the entire lateral extent of the spinal cord.