Neurophysiological changes in the central and peripheral nervous system ofstreptozotocin-diabetic rats - Course of development and effects of insulin treatment

Diabetes mellitus can affect both the peripheral and the central nervous sy stem. However, central deficits are documented less well. than peripheral d eficits. We therefore compared the course of development of neurophysiologi cal changes in the central and peripheral nervous systems in streptozotocin -diabetic rats. Sciatic nerve conduction velocities and auditory and visual evoked potentials were measured prior to diabetes induction, and then mont hly after diabetes induction for 6 months. In addition, the effect of insul in treatment was examined. Treatment was initiated after a diabetes duratio n of 6 months and was continued for 3 months. During treatment, evoked pote ntials and nerve conduction were measured monthly. In a third experiment, c onduction velocities in ascending and descending pathways of the spinal cor d were examined after 3 and 6 months of diabetes. Impairments of sciatic ne rve conduction velocities developed fully during the first 2-3 months of di abetes, In contrast, increased latencies of auditory and visual evoked pote ntials developed only after 3-4 months of diabetes, and progressed graduall y thereafter. Insulin treatment, initiated 6 months after induction of diab etes, improved both nerve conduction velocities and evoked potential latenc ies. Conduction velocities in the spinal cord tended to be reduced after 3 months of diabetes and were significantly reduced after 6 months of diabete s. The present study demonstrates that in streptozotocin-diabetic rats the course of development of peripheral and central neurophysiological changes differs. Peripheral impairments develop within weeks after diabetes inducti on, whereas central impairments take months to develop, Insulin can reverse both peripheral and central neurophysiological alterations.