Sports Medicine Research: In the Lab & In the Field: A Neural Mechanism May Explain How Electroacupuncture Reduces Ankle Sprain Pain (Sports Med Res)
Monday, May 2, 2011

A Neural Mechanism May Explain How Electroacupuncture Reduces Ankle Sprain Pain

Electroacupuncture reduces the evoked responses of the spinal dorsal horn neurons in ankle sprained rats.

Kim JH, Kim HY, Chung K, Chung JM. J Neurophysiol. 2011 Mar 9. [Epub ahead of print]

Over the past 20 years, the use of acupuncture to treat musculoskeletal pain (including ankle sprain pain) has increased in the United States but the therapeutic benefits and underlying mechanisms remain unclear. To gain a better understanding of how electroacupuncture influences ankle sprain pain the authors used a rat model of ankle sprains (equivalent to a grade 1 or 2 ankle sprain) to evaluate the effect of electroacupuncture on pain and dorsal horn neuron activity to ankle movements. The animals were divided into two groups: normal and acute ankle sprained (left hind limb). Pain severity was assessed by evaluating the amount of weight-bearing force on the hind limbs during walking. Electroacupuncture was applied to the opposite forelimb at the SI-6 acupoint by trains of electrical pulses (10 Hz, 1 ms pulse width, 2 mA intensity for 30 minutes; among these animals this protocol was shown to be most effective). Neuron activity in the dorsal horn (where sensory information enters the spinal cord) of the lumbar spine was also evaluated in response to 3 types of mechanical stimuli: plantarflexion, inversion, and compression. In brief, the electroacupuncture decreased pain and abnormal dorsal horn activity. The study reports some very interesting findings but I included some highlights. Up to 4 hours after electroacupuncture treatment (the longest follow-up time) weight-bearing forces of the sprained ankle were improved compared to before treatment. Animals with ankle sprains had abnormal hyperactivity of dorsal horn neurons compared to normal rats but the hyperactivity was reduced after electroacupuncture. Using two receptor blockers, which can selectively block the two pathways (opioid system and non-opioid system) that may be involved in the treatment benefits of electroacupuncture, the authors determined a possible mechanism for how electroacupuncture influences pain. Based on these findings the authors suggest that there is a neural mechanism for electroacupuncture induced pain relief.

This study is important to clinicians because it demonstrates a possibly underlying mechanism for electroacupuncture. The authors demonstrated that electroacupuncture at SI-6 (on the opposite forelimb) was able to reduce ankle sprain pain in rats and a different set of rats demonstrated a physiologic mechanism for the treatment response. As acupuncture becomes more popular it is helpful to see research like this providing important insight about the underlying mechanisms. It will also be interesting to see more human trials with musculoskletal injuries/pain. What are your experiences with patients that receive acupuncture?

Written by: Jeffrey Driban
Reviewed by: Stephen Thomas

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