Characteristics of spike rate of peripheral sympathetic nervous signal in streptozotocin-induced diabetic rats

Although streptozotocin-administered (STZ) rats were widely used as an experimental diabetic neuropathy model, sympathetic nerve activity (SNA) in STZ rats has not been microneurographically evaluated so far. In the present study, we investigated the multi-unit, compound sympathetic signal from the sciatic nerve of rats 3 weeks after the administration of streptozotocin, and compared the signal with that of normal (control) rats. After obtaining the sympathetic signal, glucose was intravenously administered to make a transient increase in the blood glucose level to cause SNA change. The sympathetic burst rate did not show any statistical difference between groups at steady state. Even after the glucose administration, it changed little in each group. On the other hand, the firing rate of action potentials (AP-rate) in STZ group was significantly lower than that in control group before glucose administration (p < 0.05). In addition, AP-rate was increased in control animals after glucose administration, but not in STZ rats. The results suggest a lower sympathetic tone and poorer response to glucose load under high blood glucose and low plasma insulin condition, and that the AP-rate may be useful for the evaluation of microneurographically measured, peripheral sympathetic activity.