Needling Adenosine

Acupuncture’s reputed pain-easing benefits appear to derive from the neurotransmitter adenosine and not just from a placebo effect, according to Maiken Nedergaard of the University of Rochester Medical Center and colleagues (Nat. Neurosci., DOI: 10.1038/nn.2562). Studying mice with discomfort induced in one paw, Nedergaard’s team found that acupuncture enhanced the release of adenosine triphosphate. ATP release occurred only if the acupuncture needle was twirled after insertion to cause minor tissue damage, a process that mimics needle manipulation during acupuncture treatment. The researchers determined that the released ATP rapidly degraded to adenosine, a natural painkilling compound that also suppresses inflammation and promotes sleep. The neurotransmitter activated adenosine A1 receptors on pain-transmitting nerve fibers, thereby reducing the nerves’ activity. The team found that the same pain suppression occurred in the absence of acupuncture when the receptors were activated with an injection of 2-chloro-N-cyclopentyladenosine. Furthermore, acupuncture had no effect on pain levels in mice lacking the receptors. The researchers also showed that the leukemia drug deoxycoformycin, which inhibits AMP deaminase and adenosine deaminase, two enzymes that reduce adenosine levels, more than tripled the time that acupuncture’s beneficial effects lasted.