Peripheral motor neuropathy in spontaneously diabetic WBN/Kob rats: a morphometric and electron microscopic study

The morphology and function of peripheral motor nerves of WBN/Kob rats of the newly identified strain with late onset and long-lasting diabetes were studied in comparison with those of nondiabetic age-matched rats. The most conspicuous and frequent change seen by electron microscopy in the diabetic rats was myelinopathy, initiated by vesicle formation in granular material accumulated in the myelin lamella. Initial changes developed into myelin blebbing or distention, demyelination and remyelination. A decreased population of nerve fibers in diabetic rats of advanced age suggested that the final stage of these changes was neuronal loss resulting from complete destruction of the neurons. The myelinopathy was consistently more frequent and conspicuous in diabetic rats than in age-matched nondiabetic rats, but the difference was not significant in rats of over 28 months old, because of the age-dependent increase of the change in older rats. The conduction velocity was significantly less in diabetic rats than in age-matched nondiabetic animals at 20 months but not at 28 months of age, because at the older age nondiabetic rats also showed a reduced conduction velocity. These findings showed that male WBN/Kob rats develop diabetic motor neuropathy, but that the essential changes in diabetic neuropathy are indistinguishable morphologically and functionally from those in age-dependent neuropathy.