Autonomic neuropathy in the alloxan-diabetic rat

This study was designed to correlate functional and ultrastructural examination of the innervation of the atria and vas deferens of rats with long-term alloxan-induced diabetes mellitus. After 7-8 months of diabetes the responses of preparations in vitro to nerve stimulation and to exogenous autonomic transmitter were compared with those from age-matched controls. Right atria from controls and diabetics were equally responsive to noradrenergic nerve stimulation and to exogenous noradrenaline. Left atria from diabetic rats were supersensitive to both noradrenaline and acetylcholine. The left atria gave normal inotropic responses to noradrenergic nerve stimulation but responses to cholinergic nerve stimulation were absent. The vasa deferentia from both groups gave similar responses to noradrenergic nerve stimulation and to noradrenaline. The electron microscope revealed many abnormal, degenerate noradrenergic nerve profiles in both right atria and vas deferens. No cholinergic terminals were found in the right atria. These findings indicate that this form of experimental diabetes causes parasympathetic denervation of the heart with some indications of degeneration of sympathetic nerves.