An interesting study by Paulson & Shay (2013) confirms that Acupuncture activates the sympathetic nervous system during and after treatment.
Their single blinded randomised descriptive study showed that those who received acupuncture to the forearm muscles (on one side) after a bout of fatiguing wrist extension exercises measured a bilateral decrease in skin resistance and distal skin temperature. There was a significant difference in outcome measures when compared to sham acupuncture or no treatment. The fact that the changes were measured bilaterally suggests central control changes, probably at the level of the hypothalamus.
The acupuncture group also measured an increase in perfusion (blood flow) but on the side of treatment only, which the authors suggest is likely to be due to a local circulatory versus central/systemic control change.
These findings suggest an increase in sympathetic tone in the short term i.e. during and immediately after acupuncture, which may be related not only to the needle but perhaps the anticipation and context of the acupuncture process itself.
It would have been interesting to have data from longer term follow up to determine if a general decrease in sympathetic tone when compared to baselines measures had occurred. Clinically we find that acupuncture in the longer term, over a course of treatment decreases sympathetic tone and this is supported in the literature (White et al, 2008). This effect may account for many of the positive effects we see with Acupuncture, especially when treating those with more centrally driven pain, likely to be involving autonomic deregulation and an increased sympathetic drive such as Fibromyalgia and Tension Type Headache for example.
The results of this study, also confirm that when it comes to affecting autonomic change, it may not be as relevant where the needle is placed given the central mechanisms likely to be at play which can result in bilateral changes in outcome measures of sympathetic function. Where more local needling may be of benefit is to enhance the local perfusion effects which may influence healing via axon reflex activity.
Overall, more research is needed to quantify this potentially very valuable physiological effect of Acupuncture.