Axoplasmic transport of noradrenaline in the sciatic nerves of spontaneously diabetic mice

Abstract

The intraaxonal transport of noradrenaline and tyrosine hydroxylase was studied in the sciatic nerves of diabetic, obese and appropriate control mice. Noradrenaline and tyrosine hydroxylase accumulated proximal to a constriction applied to the nerves. Noradrenaline concentration in the non-constricted sciatic nerves did not differ significantly in nondiabetic and diabetic mice (0.67±0.04 and 0.58±0.01 ng/cm respectively); in obese mice and lean littermates the noradrenaline concentration was 0.47±0.05 ng/cm and 0.46±0.01 ng/cm. After nine hours of constriction the concentration of noradrenaline increased in the axons of nondiabetic (1.15±0.06 ng/cm), in obese (0.90±0.08 ng/cm) and lean mice (1.10±0.07 ng/cm) but remained low (0.68±0.07 ng/cm) in diabetic mice. — Administration of insulin (10 U/kg/day) to diabetic mutants completely reversed the decrease in NA accumulation. NA accumulated only in the nerve segment proximal (1 cm) to a constriction and was transported distally at an apparent velocity of 0.75 mm/hr in control axons. The difference of NA accumulation between diabetic and nondiabetic control indicate a reduced rate of axoplasmic flow in the noradrenergic axons of diabetic animals.