EFFECTS OF LOCAL HYPERTHERMIA ON THE SENSITIVITY OF RAT SCIATIC-NERVE FROM DIABETIC RATS

The effect of local hyperthermia on the sciatic nerve from diabetic rats was investigated. Diabetes mellitus was induced by streptozotocin. Twelve weeks after induction a 5 mm segment of the nerve was locally heated at a temperature of 45-degrees-C (5-30 min). Loss of motor function was assessed by means of the toe-spreading test, 24 h post heating. The calculated ED50 for nerves from diabetic rats was significantly (p < 0.01) smaller than the ED50 for control nerves; 9.1 +/- 1.1 min vs 16.3 +/- 1.1 min. This indicates that nerves from diabetic rats are more sensitive to heat than nerves from control rats. Histopathological investigation of nerves from normal rats and nerves from diabetic rats confirmed this difference. Edema, vascular damage and degenerative changes of axons and myelin sheaths were present at lower heat doses when compared to control nerves. Recovery studies showed that recovery from heat induced motor function loss was delayed in diabetic rats compared to control rats.