Abstract
Acupuncture is an alternative treatment for wide spectrum chronic pain. However, its validity remains controversial due to the disputed efficacy assessed in various clinical studies. Moreover, variability amongst individuals complicates the predictability of outcome, which impedes the integration of acupuncture into mainstream pain management programs. In light of our previous finding that the analgesic effect of acupuncture is mediated by adenosine A1 receptor activation at the acupuncture point, we here report that in acute and chronic animal pain models, oral intake of caffeine, a potent adenosine receptor antagonist, interferes with acupuncture analgesia, even at a low dose. Local administration of caffeine at the acupuncture point was sufficient to eliminate the analgesic effect, dismissing the systemic action of caffeine. Such interference was reversible, as caffeine withdrawal fully restored the efficacy of acupuncture by the next day, and long-term exposure to caffeine did not alter A1 receptor expression at the acupuncture point. Combined, these data indicate that a trace amount of caffeine can reversibly block the analgesic effects of acupuncture, and controlling caffeine consumption during acupuncture may improve pain management outcomes.
Highlights
Analgesia is one of the most widely accepted effects of acupuncture
Unlike various clinical studies where placebo effects play a major role in overall efficacy of acupuncture treatment, the animals in our experiements had no prior expectations toward the possible outcomes of the procedures
Our animal models are free from complications in interpreting the effect of caffeine on anlagesia, which can arise from various side effects associated with changes in caffeine consumption in humans
Summary
Analgesia is one of the most widely accepted effects of acupuncture. acupuncture’s efficacy beyond the placebo effect still remains controversial, primarily because of an incomplete understanding of its biological basis. The A1 receptors responsible for mediating analgesia are localized in the vicinity of the acupuncture point rather than at distant central nervous system This is evident since local administration of the A1 receptor agonist, 2-Chloro-N6-cyclopentyladenosine (CCPA), at the acupuncture point resulted in analgesia, while acupuncture applied to the contralateral leg to the site of pain failed to reduce pain[1]. Such a transient adenosine increase was present with acupuncture in humans[2]. The same acupuncture treatment failed to reduce pain in mice receiving the drinking water supplemented with caffeine (0.3 and 0.6 mg/ml). Displayed are means ± S.E.M. in B–G
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