Abnormal innervation of lower limb epineurial arterioles in human diabetes.

A quantitative ultrastructural analysis was made of the terminal innervation of epineurial arterioles in the sural nerve of 6 diabetic and 6 non-diabetic patients of comparable age (mean +/- SD: 68 +/- 9 non-diabetic, 65 +/- 16 diabetic) with end stage peripheral vascular disease. The results demonstrated specific differences, identifiable morphometrically, in the pattern of innervation of epineurial vessels of diabetics compared with non-diabetics. The differences were: 1) in the diabetic group the proportion of perivascular axons found less than 7 microns from the nearest smooth muscle cell was significantly less than in the non-diabetic group (p less than 0.001); 2) the mean distance of the axons from their effector sites, the vascular smooth muscle cells, was nearly twice as far in the diabetic group compared with the non-diabetic group (p less than 0.05); and 3) the mean absolute number of axons less than 7 microns from the arteriole in the diabetic group was significantly less than in the non-diabetic group (p less than 0.01). These results demonstrate that the neuropathy associated with diabetes mellitus also involves the autonomic terminal innervation of some blood vessels. In addition, this neuropathy selectively affects the vasomotor nerves closer than 7 microns to the media.