The interrelationships between electrical stimulation, the environment surrounding the vascular endothelial cells of the skin, and the role of nitric oxide in mediating the blood flow response to electrical stimulation.

Background: Electrical stimulation (ES) is a commonly used modality in physical therapy for treating wounds such as diabetic ulcers and pressure sores but the mechanism of its effect on skin blood flow (BF) has not been determined.

Material/methods: Ten subjects were examined during ES of the skin above the quadriceps muscle with biphasic sine wave stimulation at a frequency of 30 Hertz, pulse width 250 microseconds. BF was measured between the electrodes with a Laser Doppler Flow meter. In one series of experiments, N-Nitro-L-Arginine Methyl Ester (L-NAME) was infused to determine the effect of blocking nitric oxide production on the blood flow response to ES. In another series, acetylcholine and epinephrine were infused to determine the effects of the initial blood flow prior to stimulation on the magnitude of the BF response to ES.

Results: The apparent mechanism of the increase in blood flow during electrical stimulation seems to be mediated by nitric oxide since the increase in blood flow as a result of stimulation was blocked by L-NAME. Modulation of the vasoconstrictor or vasodilator tone of the skin blood vessels altered the magnitude of the BF response to electrical stimulation; epinephrine blocked the response and acetylcholine increased the response.

Conclusions: The BF response to ES is caused by NO and can be modulated by changing the environment of the vascular endothelial cell.