Contribution of nerve-axon reflex-related vasodilation to the total skin vasodilation in diabetic patients with and without neuropathy

OBJECTIVE- To examine the contribution of nerve-axon reflex-related vasodil ation to total acetylcholine-induced vasodilation in the skin of normal and diabetic subjects. RESEARCH DESIGN AND METHODS- The skin microcirculation was evaluated at the forearm level in 69 healthy subjects and 42 nonneuropathic diabetic patien ts and at the foot level in 27 healthy subjects and 101 diabetic patients ( 33 with neuropathy 23 with Charcot arthropathy, 32 with peripheral vascular disease and neuropathy, and 13 without complications). Two single-point la ser probes were used to measure total and neurovascular vasodilation respon se to the iontophoresis of 1% acetylcholine, 1% sodium nitroprusside, and d eionized water. RESULTS- The neurovascular response to acetylcholine was significantly high er than the response to sodium nitroprusside and deionized water (P < 0.01) . At the forearm level, the contribution of neurovascular response to the t otal response to acetylcholine was 35% in diabetic patients and 31% in cont rol subjects. At the foot level, thf contribution was 29% in diabetic patie nts without neuropathy and 36% in control subjects, while it nas significan tly diminished in the three neuropathic groups. A significantly lower nonsp ecific nerve-axon-related vasodilation was observed during the iontophoresi s of sodium nitroprusside, which does nut specifically stimulate the C noci ceptive fibers. CONCLUSIONS- Neurovascular vasodilation accounts for approximately one-thir d of thr total acetylcholine-induced vasodilation at both the forearm and f oot levels. The presence of diabetic neuropathy results in reduction of bot h the total vasodilatory response to acetylcholine and the percentage contr ibution of neurovascular vasodilation to the total response. Acetylcholine and sodium nitroprusside cause vasodilation in the skin microcirculation th rough different pathways.