Of meridians and mice
On a shelf next to the desk in my office there is a model of a dog. This is not just any old model, but is a model showing acupuncture points on the dog, and it came with a list of the points and what each point is associated with. When I first got the model I was concerned about a point on the tail called Wei Jan, which is used to treat stroke, sunstroke and gastroenteritis. The reason I was worried is that some dogs are born without tails (and until recently some of them had their tails cut off to comply with fashion), but I found that losing this point is not a problem as there are several other points which can treat stroke and sunstroke. Gastroenteritis is treated by needling or smoking Hou San Li (on the rear leg), which provides the added advantage of also being useful for posterior paralysis, neuralgia, paralysis of pelvic limb, intestinal spasm and colic, arthritis, febrile symptoms and dyspepsia, as well as preventing diseases and making the dog strong and healthy. I am not making this up.
You might think that there is little scientific evidence for the efficacy of acupuncture on dogs or any other animal (some would say including humans), but research published recently in Nature Neuroscience suggested that acupuncture could have an analgesic effect on mice. Yes, mice. Researchers found that needling a certain point on a mouse's leg caused the reaction time to a painful stimulus to increase.
The method was to partially cripple the mice and then insert a needle in a point below the knee (known in humans as the Zusanli Point). For about an hour after insertion the mice showed a slower reaction to the paw at the end of the leg being placed on a hot surface. The objective was to find out whether the pain-relieving effect of acupuncture was caused by the release of the chemical adenosine, and when the researchers examined the areas where needles had been inserted they found both tissue damage and adenosine. So far, so good. It seems that acupuncture can help mice produce the chemical response necessary to reduce the sensation of pain.
The research does, however, raise some questions. The first is whether it is legitimate to assume that acupuncture points on humans can be applied to mice. I know that the points on my dog model don't exactly map to the points on a human acupuncture model that sits on the next shelf, so maybe mice have different points again. According to an acupuncture manual I have the ST-36 Zusanli Point on humans is "Below the knee, 3 cun inferior to Dubi ST-35, one fingerbreadth lateral to the anterior crest of the tibia" and these distances will be very small when scaled from a human leg to a mouse leg. Using the point is appropriate, however, as it "Activates the channel and alleviates pain". In addition it "Harmonises the Stomach, Fortifies the Spleen and resolves dampness, Supports the correct qi and fosters the original qi, Tonifies qi and nourishes blood and yin, Clears fire and calms the spirit, Revives the yang and restores consciousness". I am still not making this up.
Getting serious for a moment, the matter of scale is important. The researchers found visible tissue damage in the mice legs, and we already know that adenosine is produced in response to tissue damage and has an effect on pain perception. It is reasonable to assume that sticking and twirling a needle in a mouse's knee will have a much larger effect on the mouse than doing the same thing with the same needle to a human. If someone hits you on the knee with a baseball bat you might not respond as quickly as usual to a mildly painful stimulus to the corresponding foot for a while, but I'm not about to try bat-to-knee therapy for my peripheral neuropathy any time soon.
This research is typical of much that goes on in the alternative medicine world. It starts off by assuming that something works (in this case acupuncture for pain relief), adds more assumptions that seem to come from thin air (the existence of qi, meridians and acupuncture points), piles on assumptions that something is already known without testing (certain acupuncture points have the same, already known, effect when needled regardless of the physiology or size of the "patient"), pours on a quantity of existing but not novel knowledge (adenosine is produced when tissues are damaged and has an effect on pain perception, and agonists to adenosine receptors will have a similar effect to adenosine itself) and loops back to declare the original assumption proven. Perhaps I should quote the last sentence of the research paper's abstract: "These observations indicate that adenosine mediates the effects of acupuncture and that interfering with adenosine metabolism may prolong the clinical benefit of acupuncture".
Further research in humans is called for. I have a baseball bat. I need some volunteers.
This article was published as the Naked Skeptic column in the September/October 2010 edition of Australasian Science
