Redistribution of axoplasm in the motor root in experimental diabetes

Early experimental diabetes is associated with a reduction in axonal caliber. To elucidate the changes of nerve caliber further, we investigated the proximal and distal regions of the anterior root of rats after 5 weeks of streptozocin-induced diabetes. After vascular perfusion fixation, the fifth lumbar motor root was excised and two 3-mm segments were isolated, one at the level of the spinal cord and one at the dorsal root ganglion. The areas of myelinated fibers and their axons were measured by point counting. Axons from diabetic mice were enlarged proximally as compared to the controls, and reduced distally. It has been hypothesized that the reduction in axonal caliber is caused by an impairment of axonal transport of structural proteins rather than by osmotic shrinkage. Our findings indicate a redistribution of axoplasm in the nerves of the diabetic mice and support the hypothesis that changes in the axonal transport of neurofilaments are responsible for the structural changes seen in early diabetes. Similar changes could also play a role in the development of neuropathy in man.