Non-invasive tests of neurovascular function: reduced responses in diabetes mellitus.

Painful transcutaneous electrical nerve stimulation (TENS) of the foot dorsum evoked axon reflex vasodilatation, measured by laser Doppler flowmetry. In addition, acetylcholine (ACh) and sodium nitrite (NaNO2) were iontophoresed to cause vasodilatation by endothelium dependent and independent mechanisms, respectively. Compared with healthy volunteers, diabetic patients with clinically diagnosed neuropathy showed reduced electrical axon reflex flare and ACh responses, but not NaNO2 responses. Such reduced cutaneous nocifensor functions may contribute to some symptoms and complications of diabetes mellitus.