Abstract: Acupuncture-induced analgesia depends on the activation of endogenous pain modulation pathways. In this study, we asked whether ascending nociceptive control (ANC), a form of
pain-induced analgesia, contributes to the antinociceptive effect of acupuncture. To answer this
question, we...

Abstract: Acupuncture-induced analgesia depends on the activation of endogenous pain modulation pathways. In this study, we asked whether ascending nociceptive control (ANC), a form of
pain-induced analgesia, contributes to the antinociceptive effect of acupuncture. To answer this
question, we tested the ability of procedures that block ANC-induced analgesia, at peripheral, spinal,
nucleus accumbens and rostral ventral medulla levels, to block acupuncture-induced analgesia.
Acupuncture at ST36 (Zusanli), a widely used acupoint located in the hind limb, induced potent
heterosegmental antinociception in the orofacial formalin test. The magnitude of this antinociceptive
effect was similar to that induced by an intraplantar injection of capsaicin, a procedure classically
used to activate ANC. The antinociceptive effect of acupuncture was blocked by sciatic C-fibers
depletion (1% perineural capsaicin), spinal administration of a m-opioid (Cys2,Tyr3,Orn5,Pen7amide,
.2 mg) or of a GABAA (bicuculline, .3 mg) receptor antagonist, intra–nucleus accumbens administration
of a m-opioid receptor antagonist (Cys2,Tyr3,Orn5,Pen7amide, 1 mg), or intrarostral ventral medulla
administration of a nicotinic acetylcholine receptor antagonist (mecamylamine, .6 mg). In addition,
acupuncture at ST36 and/or upper lip formalin induced c-Fos expression in the nucleus accumbens
and in rostral ventral medulla. On the basis of these results, we propose that ANC contributes to
the antinociceptive effect of acupuncture.
Perspective: This article presents a novel mechanism of acupuncture analgesia, contributing to the
understanding of its scientific basis. Because ANC is a pain modulation pathway activated by
peripheral noxious stimulation that ascends to supraspinal regions, it could be the link between
acupoint stimulation and the central mechanisms underlying acupuncture analgesia

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