Acupuncture at distant myofascial trigger spots enhances endogenous opioids in rabbits: a possible mechanism for managing myofascial pain.

BACKGROUND AND AIM: Acupuncture applied at myofascial trigger points (MTrPs) of distant anatomical regions, to reduce pain in a patient's area of primary complaint, is one strategy that is available to manage myofascial pain. However, the endogenous opioid-mediated analgesic mechanism of distant acupuncture associated with pain control is still unclear. This aims of this study were to evaluate the changes in enkephalin and ß-endorphin in serum, spinal cord, dorsal root ganglion (DRG) and muscle induced by acupuncture at distant myofascial trigger spots (MTrSs, similar to human MTrPs) in rabbits, to explore its underlying remote analgesic mechanism. METHODS: Acupuncture at MTrSs of a distant muscle (gastrocnemius) was performed either for one session or five daily sessions in rabbits. The levels of enkephalin and ß-endorphin in proximal muscle (biceps femoris), serum, DRGs and spinal cords (L5-S2) were then determined by immunoassay immediately and 5 days after treatment. RESULTS: Immediately after treatment, acupuncture comprising both one dose and five doses significantly enhanced spinal enkephalin expression and serum ß-endorphin levels (p<0.05). However, only five-dose acupuncture significantly enhanced the ß-endorphin levels in the biceps femoris and DRGs (p<0.05), while 1-dose acupuncture did not (p>0.05). Furthermore, 5 days after treatment, significantly increased levels of spinal enkephalin and serum ß-endorphin persisted in animals that received 5-dose acupuncture (p<0.05). CONCLUSIONS: This study demonstrates that interactions within the endogenous opioid system may be involved in the remote effects of acupuncture treatment and could be a potential analgesic mechanism underlying MTrP pain management.

Remote dose-dependent effects of dry needling at distant myofascial trigger spots of rabbit skeletal muscles on reduction of substance P levels of proximal muscle and spinal cords.

BACKGROUND: Dry needling at distant myofascial trigger points is an effective pain management in patients with myofascial pain. However, the biochemical effects of remote dry needling are not well understood. This study evaluates the remote effects of dry needling with different dosages on the expressions of substance P (SP) in the proximal muscle, spinal dorsal horns of rabbits. METHODS: Male New Zealand rabbits (2.5-3.0 kg) received dry needling at myofascial trigger spots of a gastrocnemius (distant muscle) in one (1D) or five sessions (5D). Bilateral biceps femoris (proximal muscles) and superficial laminaes of L5-S2, T2-T5, and C2-C5 were sampled immediately and 5 days after dry needling to determine the levels of SP using immunohistochemistry and western blot. RESULTS: Immediately after dry needling for 1D and 5D, the expressions of SP were significantly decreased in ipsilateral biceps femoris and bilateral spinal superficial laminaes (P < .05). Five days after dry needling, these reduced immunoactivities of SP were found only in animals receiving 5D dry needling (P < .05). CONCLUSIONS: This remote effect of dry needling involves the reduction of SP levels in proximal muscle and spinal superficial laminaes, which may be closely associated with the control of myofascial pain.