Changes in Skin Blood Flow and Skin Sympathetic Nerve Activity in Response to Manual Acupuncture Stimulation in Humans

Abstract

To determine the effects of manual acupuncture stimulation (MAS) on skin sympathetic nerve activity (SSNA), SSNA and skin blood flow (SBF) were measured during a resting period and during MAS. Twelve healthy male subjects were divided into an acupuncture group ( n = 7) and a control group ( n = 5). SSNA was recorded from the left median nerve at the elbow using microneurography, while SBF was recorded using laser Doppler flowmeter. In the acupuncture group, MAS was delivered to LI 4 point in the right thenar muscle. The acupuncture needle was retained for 2 minutes before being removed. SSNA and SBF recordings were performed for a total of 12 minutes, from 5 minutes prior to MAS until the end of the trial. In the control group, the 2-minute period of acupuncture was replaced by 2 minutes of rest. During the first minute of MAS, we observed an increase in SSNA accompanied by a reduction in SBF. In the acupuncture group, these parameters returned to baseline values in the second minute of MAS. Parameters in the control group were unchanged throughout the experimental procedure. A significant negative correlation was observed between changes in SSNA and SBF during the first minute of MAS. In addition, a negative correlation was demonstrated between the basal value of SSNA and the change in SSNA in response to MAS. These results suggest that MAS elicited a transient increase in SSNA and that this increase is dependent on the baseline of SSNA.