The development of drugs and other treatments for specific symptoms or conditions relies heavily on either serendipity (the chance finding of a beneficial effect) or on an understanding of underlying mechanisms. In pain, for example, there are limited ways in which we can block pain signals – such as activating opiate receptors, or inhibiting prostaglandins. There are only so many ways in which you can interact with these systems. The discovery of a novel mechanism of modulating pain is therefore most welcome, and has the potential of leading to entirely new treatments that may have a better side effect profile than existing treatments and also have an additive clinical effect.<\/p>\n
A recent study by Nana Goldman et. al.<\/a>, published in Nature Neuroscience, adds to our understanding of pain relief by identifying the role of adenosine in reducing pain activity in the peripheral nervous system. The researchers, in a nice series of experiments, demonstrated that producing a local painful stimulus in mice causes the local release of ATP (adenosine triphosphate) that peaks at about 30 minutes. This correlates with a decreased pain response in the mice. Further, if drugs are given that prolong the effect of adenosine, the analgesic effect itself is prolonged.<\/p>\n Also, if drugs are given that activate the adenosine A1 receptor, the observed analgesic effect is replicated. When these experiments are replicated in knockout mice that do not have the gene for the adenosine A1 receptor, there is no observed analgesic effect.<\/p>\n Together these experiments are fairly solid evidence that local pain results in the local release of adenosine that in turn binds to the adenosine A1 receptor inhibiting the pain response. This is potentially very exiting – it should lead to further investigation of the adenosine A1 receptor and the effects of activating and inhibiting it. This may lead to the development of drugs or other interventions that activate these receptors and may ultimately be a very useful addition to our ability to treat acute and chronic pain.<\/p>\n Now Comes the Spin<\/strong><\/p>\n In a rational science-based world the above would be the end of this blog entry. But that is not the world we currently live in. In this study the chosen method of provoking pain was the insertion of an acupuncture needle into the “Zusanli point” of the lower extremity and rotating it. This allowed the authors of this study to spin the results as if they were validation for acupuncture itself – and the mainstream press dutifully followed suit.<\/p>\n The introduction to this study is an apology for acupuncture itself, and sets the tone for the rest of the paper as well as the press release and comments to follow:<\/p>\n Acupuncture is a procedure in which fine needles are inserted into an individual at discrete points and then manipulated, with the intent of relieving pain. Since its development in China around 2,000 B.C., acupuncture has become worldwide in its practice. Although Western medicine has treated acupuncture with considerable skepticism, a broader worldwide population has granted it acceptance. For instance, the World Health Organization endorses acupuncture for at least two dozen conditions and the US National Institutes of Health issued a consensus statement proposing acupuncture as a therapeutic intervention for complementary medicine. Perhaps most tellingly, the U.S. Internal Revenue Service approved acupuncture as a deductible medical expense in 1973.<\/p><\/blockquote>\n That this paragraphs appears in a high impact peer-reviewed journal is very curious (to put it mildly). It is full of misinformation and logical fallacies. Acupuncture is used for more than pain relief, and so making statements about the efficacy of “acupuncture” go way beyond the scope of this study, which only involves pain. The authors should have specifically pointed out that this study cannot be used to explain any indication for acupuncture that does not involve local pain relief. Acupuncture as it was practiced in China 4000 years ago bears little resemblance to what is practiced today, and may have been more of a form a bloodletting<\/a>.<\/p>\n The authors then make a false dichotomy between “Western medicine” and, presumably, “Eastern medicine” – which is an anti-scientific and culturally bigoted point of view. This is followed by an argument from popularity, and a particularly bizarre argument from authority – noting that the IRS accepts acupuncture as a medical expense. I was unaware that the IRS is a scientific medical organization.<\/p>\n The authors also fail to put this study into its proper context by reviewing existing evidence – the more traditional use of the introduction to peer-reviewed research. The clinical research on acupuncture, which is quite extensive, finds that any measured symptomatic effect is almost certainly due mostly or entirely to placebo effects. Further, it does not matter where you stick the acupuncture needle, nor even if you do stick the need through the skin. Twisting toothpicks against the skin in random locations has the same effect.<\/p>\n My interpretation of the research is that acupuncture (placing needles at specific acupuncture points to manipulate chi) does not work. There may, however, be non-specific physiological responses to the mechanical stimulation of sticking needles at random locations, or just poking toothpicks. This study, if anything, supports this interpretation – it, if fact, has identified a local mechanism of analgesia that can help explain a non-specific response to acupuncture, sham acupuncture, or placebo acupuncture and therefore is consistent with the clinical evidence showing no difference among these interventions.<\/p>\n