Mechanisms of Vasodilation in Skin during Lumbar Transcutaneous Spinal Cord Stimulation

Abstract

The changes in blood flow in shin skin were analyzed by laser Doppler flowmetry during transcutaneous electrical spinal cord stimulation (TSCS) by subthreshold bipolar pulses with a frequency of 30 Hz in 12 healthy subjects. It was shown that TSCS in the area of the T₁₁ and L₁ vertebrae led to a significant increase in skin blood flow. With a stimulus intensity of 90% of the motor threshold, the microcirculation rate increased by more than 85% compared to the baseline. The findings indicate that the stimulation of blood flow in skin by TSCS is mainly due to the antidromic stimulation of sensory nerve fibers. Nitric oxide (NO) is an important mediator contributing to vasodilation and increased cutaneous blood flow in TSCS; NO is of mostly endothelial origin. It was shown that high-conductivity Ca²⁺-sensitive K⁺ channels are involved in the process of vasodilation in skin during TSCS. The interaction between NO- and Ca-mediated mechanisms in shin skin was observed during TSCS, resulting in increased vasodilation and blood flow.