Axonal sprouting following incomplete spinal cord injury: an experimental model

Recovery of function following incomplete spinal cord injury may in part result from growth of new connections by spared descending pathways. It has been difficult to demonstrate such anatomical reorganization with traditional anatomic techniques. This study utilizes an immunocytochemical method to demonstrate axonal growth cones within the lumbar spinal cord in rats recovering from an incomplete midthoracic spinal cord injury. Adult rats underwent subtotal section of the midthoracic cord sparing the left lateral funiculus and a portion of the left ventral funiculus. Light microscope immunocytochemistry was performed on sections of lumbar spinal cord with antibodies to identify sprouting axons. These antibodies were used to determine the distribution of growth cones on both sides of the lumbar spinal cord in experimental and control animals. Growth cones were first observed three days after the spinal cord lesion. Specific labeling, similar in appearance to previous reports of growth cone identification, was apparent within the immediate gray and ventral horns on both sides of the cord. These data support the hypothesis of collateral sprouting distal to the lesion site following incomplete spinal cord injury. It further supports the idea that recovery of function following incomplete spinal cord injury is, in part, mediated by spared descending pathways.