Acute Sympathetic Responses Elicited by Acupuncture Are Pain-Related and Non-Specific

Abstract

In a randomized, single-blind study the effects of acupuncture or non-acupuncture point needling on sympathetic reflexes (fingertip cutaneous microcirculation measured by laser Doppler flowmetry and photoplethysmography, laser Doppler flux in nasal mucosa, skin temperature of fingertip, nose bridge and glabella measured by means of infrared thermography and thermistor, heart rate and skin conductance) were studied in the same healthy volunteers. There were acute, transient sympathetic reflex responses (flux in finger skin and nasal mucosa, blood volume in finger skin, temperature of fingertip and nose bridge skin and finger skin conductance) to acupuncture and non-acupuncture point needling but no differences between them. Because both acupuncture and placebo needling caused pain, we investigated whether the observed responses were pain-related. Painless low-level laser stimulation, a treatment suggested to have similar therapeutic effects as acupuncture, at an acupuncture point had no effects on the sympathetic responses analysed. Moreover, administration of a local anaesthetic, lidocaine, to abolish pain resulted in reduced sympathetic responses to acupuncture. Finally, acupuncture of the insensitive legs of paraplegics had no effect on sympathetic responses. These results suggest that the acute, transient sympathetic reflexes elicited by needling were pain-related and thus not specific to stimulation at acupuncture points.