Peripheral neuropathy in selectively-inbred spontaneously diabetic rats: Electrophysiological, morphometrical and freeze-replica studies.

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Abstract
Function and structure of peripheral nerves in selectively-inbred spontaneously diabetic rats (SDR) were quantitatively examined in order to clarify the relationship between these 2 changes. Electrophysiologically, SDR showed a significant decrease in motor nerve conduction velocity of the tail by 2 mo. of age. Thereafter, the conduction velocity was constantly lower in SDR than in age-matched control rats. Morphometrical analysis of peripheral nerves from light micrographs and EM could not yield any definite structural differences, except for a reduction in caliber of unmyelinated axons, between 2 mo.-old and age-matched controls, whereas an endoneurial space was widened in 3 mo.-old SDR as compared with those of controls. Loss of myelinated nerve fibers, a reduction in nerve fiber size and axonal size was apparent in 6 mo.-old SDR. By freeze-replica studies, neither any qualitative changes of intramembrane faces nor any quantitative differences in the density of intramembranous particles of internodal myelin and Schwann cell membranes were detected in 2 mo.-old SDR when compared with those in controls. The delayed nerve conduction velocity was probably most related to diabetic dysmetabolism and independent of the structural changes of peripheral nerves being in the course of distal axonopathy.