Abstract
Diabetic neuropathy was studied histologically in alloxanized diabetic rats, with the method of motor nerve conduction velocity (MCV) and with the quantitation of myelinated nerve fibers.
The MCV was measured in the tail nerve with needle electrodes. Biopsy specimens were collected from the proximal portion (peroneal-proximal) and distal portion (peroneal-distal) of the peroneal nerve, the proximal portion (sural-proximal) and distal portion (sural-distal) of the sural nerve, and the motor root (motor-root) and sensory root (sensory-root) of the sciatic nerve.
On the transverse section of these nerves, the density of the total number of myelinated nerve fibers (number of nerve fibers/mm2) was calculated, and histograms of myelinated nerve fibers according to a diameter were made.
Diabetic rats were divided into five groups according to the course: before, and 1, 2, 3 and 4 weeks after administration of alloxan. The results from these groups were compared with those from untreated control groups. The MCV in the diabetic rats of the 2, 3 and 4 week groups was significantly lower than that in the untreated control groups. A significant decrease of the density of total myelinated nerve fibers was observed in the sural-proximal and sural-distal in the 3-week groups as well as in the peroneal-proximal, peroneal-distal, sural-proximal, sural-distal and sensory-root in the 4 week group in the diabetic rats. A significant decrease in the number of myelinated nerve fibers and disappearance of the peak in the myelinated nerve fibers of large diameter were observed in the peroneal and sural nerve, especially in the sural-distal in the 2, 3 and 4 week groups in the diabetic rats. There was no change in the motor-root, on the other hand, in the sensory-root, decrease of myelinated nerve fibers of large diameter was characteristic, although the number of myelinated nerve fibers of the small diameter remained unchanged in the diabetic rats.
It is considered that these findings are valid for investigating the pathogenesis of human diabetic neuropathy.
