We found that adenosine, a neuromodulator with anti-nociceptive properties, was released during acupuncture in mice and that its anti-nociceptive actions required adenosine A1 receptor expression. Direct injection of an adenosine A1 receptor agonist replicated the analgesic effect of acupuncture. Inhibition of enzymes involved in adenosine degradation potentiated the acupuncture-elicited increase in adenosine, as well as its anti-nociceptive effect. These observations indicate that adenosine mediates the effects of acupuncture and that interfering with adenosine metabolism may prolong the clinical benefit of acupuncture.
The release of the adenosine was local, right at the site of the acupuncture needle, as were the anti-nociceptive effects. Local tissue damage by the needle releases the adenosine precursor purines into the extracellular fluid. Through a series of dephosphorylations ATP is converted to ADP, then to AMP and finally adenosine. Although AMP piles up, as its dephosphorylation to adenosine is the rate limiting step, the overall effect is short lived, with adenosine levels down to baseline in an hour or so. Adenosine itself dissipates quickly. (As anyone who has ever pushed adenosine to convert AVNRT knows, if you don't push fast enough, in a vein close enough to the heart, it doesn't work. In the circulating blood adenosine is gobbled up by RBCs and endothelial cells with a half life of 9 seconds). In the study, any analgesic effects were gone by a matter of hours.
Because the adenosine effect is local and transient, this study contributes little toward an explanation for the claims of acupuncture, the principal ones of which are chronic pain relief and distant effects such as improvement in hypertension, nausea, headache and the like. It also does nothing to support the claimed mechanisms involving Qi, meridians etc.