ARCHITECTURAL CHANGES OF THE CORTICOSPINAL SYSTEM IN THE DYSTROPHIN DEFECTIVE MDX MOUSE

The mutant mdx mice which lack the protein dystrophin are an animal model of Duchenne muscular dystrophy. We studied the organization of the cortico-spinal (CS) system in mdr mice using the horseradish peroxidase retrograde tracing technique. Tracer injections were placed in the cervical spinal cord of mutant and control mice. The tangential and radial distribution of CS labeled neurons were similar in mdx and normal mice. Conversely, the absolute number and the cell packing density of labeled CS neurons were considerably lower in mdr than in controls. In mdr, the average size of CS cells was smaller while the perikaryal sizes displayed a normal distribution. In addition, CS neurons of mdr appeared round-shaped compared to the pyramidal cells labeled in control animals. The structural modifications described here should prompt a reconsideration of the involvement of central nervous system in the dystrophin deficient mdr mice.