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Kim, et al. (2004). Electroacupuncture effect on allodynia in rat neuropathic pain model

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    Kim, et al. (2004). Electroacupuncture effect on allodynia in rat neuropathic pain model

    • Kim JH, Min BI, Na HS and Park DS (2004). Relieving effects of electroacupuncture on mechanical allodynia in neuropathic pain model of inferior caudal trunk injury in rat: mediation by spinal opioid receptors. Brain Res. 998: 230-6. Department of East-West Medicine, Graduate School, Kyung Hee University, Seoul, South Korea. The relieving effects of electroacupuncture (EA) on mechanical allodynia and its mechanism related to the spinal opioid system were investigated in a rat model of neuropathic pain. To produce neuropathic pain in the tail, the right superior caudal trunk was resected between the S1 and S2 spinal nerves. Two weeks after the surgery, EA stimulation (2 or 100 Hz, 0.3 ms, 0.2-0.3 mA) was delivered to Zusanli (ST36) for 30 min. The degree of mechanical allodynia was evaluated quantitatively by touching the tail with von Frey hair (2.0 g) at 10 min intervals. These rats were then subjected to an i.t. injection with one of the three specific opioid agonists in successive ways: the mu agonist (DAMGO 25, 50 and 100 pmol), the delta agonist (DADELT II 0.5, 1 and 2 nmol), and the kappa agonist (U50488H 5, 10 and 20 nmol) separated by 10 min in cumulative doses. During 30 min of EA stimulation, specific opioid antagonists were subjected to i.t. injection: the mu antagonist (beta-FNA 5, 10 and 20 nmol), the delta antagonist (naltrindole 5, 10 and 20 nmol), and the kappa antagonist (nor-BNI 3, 6 and 12 nmol) separated by 10 min in cumulative doses. As a result, EA reduced the behavioral signs of mechanical allodynia. Two Hz EA induced a robust and longer lasting effect than 100 Hz. All three opioid agonists also showed relieving effects on mechanical allodynia. However, nor-BNI could not block the EA effects on mechanical allodynia, whereas beta-FNA or naltrindole significantly blocked EA effects. These results suggest that the mu and delta, but not kappa, opioid receptors in the spinal cord of the rat, play important roles in mediating relieving effects on mechanical allodynia induced by 2 Hz EA.



    I posted this paper for three reasons. First, it is one of the few rigorous studies of acupuncture effects in an animal pain model. Second, they used electrical stimulation placed at specific acupuncture points on the rats, finding that the 2 Hz stimulation was better than 100 Hz stimulation in producing robust and lasting effects. Third, they used opioid receptor antagonists to block the effect of the acupuncture, showing that only specific opioid receptor antagonists blocked the acupuncture effects. These data strongly support a role of opioids in acupuncture effects.

    These results are surprising in several respects. The effects of electrical acupuncture appears to be frequency specific. At 2 Hz, the electrical stimulation is relatively slow. Only mu and delta receptor antagonists prevented the acupuncture effects but mu, delta, and kappa receptor agonists (stimulators) were able to relieve the pain. This suggests that the electical acupuncture may be working through activation of neurons that have receptors for mu and delta opioid receptors. A number of endogenous opioids activate these receptors but the finding that kappa receptor blockers do not prevent the efects of electrical acunpuncture rules out several endogenous opioid ligands including dynorphin and thyrotropin releasing hormone. This information is of interest because it suggests some possible pharmaceutical and electrical acupuncture approaches to the treatment of neuropathic pain.


    [This message was edited by Wise Young on 05-23-04 at 03:18 PM.]


      they use some type of electrical stim on the needles on me, will have to print this and check what it is
      cauda equina