Adrenergic innervation in the tibial and vagus nerves of rats with streptozotocin-induced diabetes

Adrenergic innervation of tibial and vagus nerves was studied after 1-16 weeks duration of streptozotocin (STZ)-induced diabetes in rats. Sucrose-phosphate glyoxylic acid (SPG) histochemistry and the formaldehyde-induced fluorescence (FIF) method were used to demonstrate adrenergic nerve fibers in the epi-perineurial and endoneurial compartments. Densities of innervation were quantitated with fluorescence microscopy. The density of periarteriolar adrenergic innervation in the epi-perineurium of the tibial and vagus nerves was increased 5 and 12 weeks after STZ injections as compared with control. At 16 weeks, mean densities of periarteriolar innervation in epi-perineurium had returned to or below control levels in both nerve types. In the endoneurium, however, the mean density of adrenergic nerve fibers decreased gradually at 5 weeks after induction of diabetes in both nerves, and was totally absent at 12 weeks. At 16 weeks no sign of recovering innervation in the endoneurium was seen. In conclusion, adrenergic innervation goes through similar pathological alterations both in tibial and vagus nerves shortly after the induction of streptozotocin diabetes. These changes may contribute to diabetic peripheral neuropathy by impairing the regulation of nerve blood flow.