Electroacupuncture decreases Netrin-1-induced myelinated afferent fiber sprouting and neuropathic pain through µ-opioid receptors.

Purpose: We determined whether electroacupuncture (EA) reduces Netrin-1-induced myelinated primary afferent nerve fiber sprouting in the spinal cord and pain hypersensitivity associated with postherpetic neuralgia (PHN) through activation of µ-opioid receptors. Methods: PHN was induced by systemic injection of resiniferatoxin (RTX) in rats. Thirty-six days after RTX injection, a µ-opioid receptor antagonist, beta-funaltrexamine (ß-FNA) or a κ-opioid receptor antagonist, nor Binaltorphimine (nor-BNI), was injected intrathecally 30 mins before EA, once every other day for 4 times. Mechanical allodynia was tested with von Frey filaments. The protein expression level of Netrin-1 and its receptors (DCC and UNC5H2) were quantified by using western blotting. The myelinated primary afferent nerve fiber sprouting was mapped with the transganglionic tracer cholera toxin B-subunit (CTB). Results: Treatment with 2 Hz EA at "Huantiao" (GB30) and "Yanglingquan" (GB34) decreased the mechanical allodynia at 22 days and the myelinated primary afferent nerve fiber preternatural sprouting into the lamina II of the spinal dorsal horn at 42 days after RTX injection. Also, treatment with 2 Hz EA reduced the protein levels of DCC and Netrin-1 and promoted the expression of UNC5H2 in the spinal dorsal horn 42 days after RTX injection. Furthermore, the µ-opioid receptor antagonist ß-FNA, but not the κ-opioid receptor antagonist nor-BNI, reversed the effect of EA on neuropathic pain caused by RTX. In addition, morphine inhibited the Netrin-1 protein level induced by RTX in SH-SY5Y cells. Conclusions: Through activation of µ-opioid receptors, treatment with EA reduces the expression level of DCC and Netrin-1 and changes a growth-permissive environment in spinal dorsal horn into an inhibitory environment by increasing UNC5H2, thus decreasing RTX-caused primary afferent nerve sprouting in the spinal dorsal horn and neuropathic pain.

Electroacupuncture potentiates peripheral CB2 receptor-inhibited chronic pain in a mouse model of knee osteoarthritis.

PURPOSE: Knee osteoarthritis (KOA) is a highly prevalent, chronic joint disorder, with chronic pain as its typical symptom. Although studies have shown that an activated peripheral CB2 receptor can reduce acute pain, whether the CB2 receptor is involved in electroacupuncture (EA) inhibiting chronic pain and the involved mechanism remains unclear. The aim of this study was to investigate whether EA may strengthen peripheral CB2 receptor-inhibited chronic pain in a mouse model of KOA. MATERIALS AND METHODS: KOA was induced by intra-articular injection of monosodium iodoacetate (MIA) into the left knee joint of mice. Thermal hyperalgesia was tested with the hot plate test, and mechanical allodynia was quantified using von Frey filaments. The expression of CB2 receptor and IL-1ß were quantified by using immunofluorescence labeling. RESULTS: EA treatment at 2 Hz+1 mA significantly increased the expression of CB2 receptor in fibroblasts and decreased the expression of IL-1ß in the menisci compared with that in the KOA group. However, EA had no effect on the expression of IL-1ß in CB2-/- mice. At 2 Hz+1 mA, EA significantly increased mechanical threshold, thermal latency, and weight borne after KOA modeling. However, knockout of the CB2 receptor blocked these effects of EA. After 2 Hz+1 mA treatment, EA significantly reduced the Osteoarthritis Research Society International (OARSI) score after KOA modeling. However, EA had no significant effect on the OARSI score in CB2-/- mice. CONCLUSION: EA reduced the expression of IL-1ß by activating the CB2 receptor, thus inhibiting the chronic pain in the mouse model of KOA.

[Stimulating Frequency-dependent Analgesic Effect of Electroacupuncture via Down-regulating Expression of VEGF in Dorsal Horns of Lumbar Spinal Cord in Post Herpetic Neuralgia Rats].

OBJECTIVE: To observe the effect of different frequencies of electroacupuncture (EA) stimulation on pain threshold (PT) and expression of vascular endothelial growth factor (VEGF) in dorsal horns (DHs) of the lumbar spinal cord in resiniferatoxin (RTX)-induced post-herpetic neuralgia (PHN) rats, so as to reveal its mechanism in alleviating PHN. METHODS: Male SD rats were randomized into control, model, 2 Hz-EA, 15 Hz-EA, 100 Hz-EA and sham EA groups (n=16 in each). The PHN model was induced by a single intraperitoneal injection of RTX (250 µg/kg), and rats of the control group received intraperitoneal injection of the same dose of vehicle (10% Tween 80, 10% alcohol and 0.9% NaCl). Rats of EA treatment groups received EA stimulation (2 Hz, 15 Hz or 100 Hz, 1 mA) at the left "Huantiao" (GB 30) and "Yanglingquan" (GB 34) for 30 min, once every other day for 35 days, starting from 1 week after RTX injection. For sham control, acupuncture needles were inserted ipsilaterally into GB 30 and GB 34 for 30 min without electrical stimulation or manual needle manipulation. The mechanical allodynia was quantified with Von Frey filaments. The expression of mRNA and protein of VEGF in the DHs of lumbar spinal cord 4-6 segments (sampled under light microscope) was detected by quantitative polymerase chain reaction (qPCR) and Western blot, respectively. RESULTS: A single RTX injection gradually induced tactile allodynia (significant reduction of the mechanical PT) within 3 weeks relevant to the control group (P<0.01). EA applied to GB 30 and GB 34 at 2 Hz and 15 Hz, but not 100 Hz, significantly decreased the tactile allodynia after the treatment (2 Hz from 2 weeks on and 15 Hz from 3 weeks on) in RTX-treated rats (P<0.05). RTX administration increased the mRNA and protein expression of VEGF in the lumbar spinal cord compared with the control group (P<0. 05). Moreover, 2 Hz, but not 15 Hz and 100 Hz EA significantly reduced VEGF mRNA and protein expression(P<0.05). The expression of both VEGF mRNA and protein was negatively correlated with mechanical PT in RTX-induced PHN rats. CONCLUSION: EA at 2 Hz can significantly reduce VEGF expression in the lumbar spinal cord DHs of PHN rats, which is possibly in part related to its effect in alleviating the mechanical allodynia. Our study suggests that 2 Hz EA is the best stimulation frequency for relieving PHN.

Electroacupuncture Potentiates Cannabinoid Receptor-Mediated Descending Inhibitory Control in a Mouse Model of Knee Osteoarthritis.

Knee osteoarthritis (KOA) is a highly prevalent, chronic joint disorder, which can lead to chronic pain. Although electroacupuncture (EA) is effective in relieving chronic pain in the clinic, the involved mechanisms remain unclear. Reduced diffuse noxius inhibitory controls (DNIC) function is associated with chronic pain and may be related to the action of endocannabinoids. In the present study, we determined whether EA may potentiate cannabinoid receptor-mediated descending inhibitory control and inhibit chronic pain in a mouse model of KOA. We found that the optimized parameters of EA inhibiting chronic pain were the low frequency and high intensity (2 Hz + 1 mA). EA reversed the reduced expression of CB1 receptors and the 2-arachidonoylglycerol (2-AG) level in the midbrain in chronic pain. Microinjection of the CB1 receptor antagonist AM251 into the ventrolateral periaqueductal gray (vlPAG) can reversed the EA effect on pain hypersensitivity and DNIC function. In addition, CB1 receptors on GABAergic but not glutamatergic neurons are involved in the EA effect on DNIC function and descending inhibitory control of 5-HT in the medulla, thus inhibiting chronic pain. Our data suggest that endocannabinoid (2-AG)-CB1R-GABA-5-HT may be a novel signaling pathway involved in the effect of EA improving DNIC function and inhibiting chronic pain.

Efficacy of Acupuncture in Children with Nocturnal Enuresis: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.

Background. Nocturnal enuresis (NE) is recognized as a widespread health problem in young children and adolescents. Clinical researches about acupuncture therapy for nocturnal enuresis are increasing, while systematic reviews assessing the efficacy of acupuncture therapy are still lacking. Objective. This study aims to assess the effectiveness of acupuncture therapy for nocturnal enuresis. Materials and Methods. A comprehensive literature search of 8 databases was performed up to June 2014; randomized controlled trials which compared acupuncture therapy and placebo treatment or pharmacological therapy were identified. A meta-analysis was conducted. Results. This review included 21 RCTs and a total of 1590 subjects. The overall methodological qualities were low. The results of meta-analysis showed that acupuncture therapy was more effective for clinical efficacy when compared with placebo or pharmacological treatment. Adverse events associated with acupuncture therapy were not documented. Conclusion. Based on the findings of this study, we cautiously suggest that acupuncture therapy could improve the clinical efficacy. However, the beneficial effect of acupuncture might be overstated due to low methodological qualities. Rigorous high quality RCTs are urgently needed.

Efficacy of Acupuncture in Itch: A Systematic Review and Meta-Analysis of Clinical Randomized Controlled Trials.

Background. Itch (pruritus) is a sensitive state that provokes the desire to scratch. It is not only a common symptom of skin diseases but it also occurs in some systemic diseases. Clinical studies on the efficacy of the acupuncture therapy in alleviating itch are increasing, while systematic reviews assessing the efficacy of acupuncture therapy are still lacking. Objective. This systematic review aims to assess the effectiveness of acupuncture therapy for itch. Materials and Methods. A comprehensive literature search of eight databases was performed up to June 2014, and randomized controlled trials which compared acupuncture therapy and placebo acupuncture or no treatment group were identified. Accordingly, a meta-analysis was conducted. Results. This review included three articles of randomized controlled trials (RCTs) from a total of 2530 articles. The results of Meta-analysis showed that acupuncture therapy was effective to alleviate itch compared with placebo acupuncture and no treatment group. Conclusion. Based on the findings of this systematic review, we cautiously suggest that acupuncture therapy could improve the clinical efficacy of itch. However, this conclusion needs more studies on various ethnic samples to confirm our final conclusion.

Electroacupuncture improves thermal and mechanical sensitivities in a rat model of postherpetic neuralgia.

BACKGROUND: Electroacupuncture (EA) is effective in relieving pain in patients with postherpetic neuralgia (PHN). However, the mechanism underlying the therapeutic effect of EA in PHN is still unclear. Systemic injection of resiniferatoxin (RTX), an ultrapotent analog of TRPV1 agonist, in adult rats can reproduce the clinical symptoms of PHN by ablating TRPV1-expressing sensory neurons. In this study, we determined the beneficial effect of EA and the potential mechanisms in this rat model of PHN. METHODS: PHN was induced in rats by a single injection of RTX. Thermal hyperalgesia was tested with a radiant heat stimulus, and mechanical allodynia was quantified with von Frey filaments. TRPV1 receptors were shown by using immunofluorescence labeling. The ultrastructural changes of the sciatic nerve were assessed by electron microscopic examination. The sprouting of myelinated primary afferent terminals into the spinal dorsal horn was mapped by using the transganglionic tracer cholera toxin B-subunit (CTB). RESULTS: RTX injection diminished thermal sensitivity and gradually induced tactile allodynia within 3 weeks. EA applied to GB30 and GB34 at 2 and 15 Hz, but not 100 Hz, significantly increased the thermal sensitivity 4 weeks after treatment and decreased the tactile allodynia 2 weeks after treatment in RTX-treated rats. EA treatment at 2 and 15 Hz recovered the loss of TRPV1-positive dorsal root ganglion neurons and their central terminals of afferent fibers in the spinal superficial dorsal horn of RTX-treated rats. Moreover, EA significantly reduced the loss of unmyelinated fibers and the damage of the myelinated nerve fibers of RTX-treated rats. Furthermore, EA at 2 and 15 Hz inhibited the sprouting of myelinated primary afferent terminals into the spinal lamina II of RTX-treated rats. CONCLUSIONS: EA treatment improves thermal perception by recovering TRPV1-positive sensory neurons and nerve terminals damaged by RTX. EA Also reduces RTX-induced tactile allodynia by attenuating the damage of myelinated afferent nerves and their abnormal sprouting into the spinal lamina II. Our study provides new information about the mechanisms of the therapeutic actions of EA in the treatment of PHN.

Cannabinoid CB2 receptors contribute to upregulation of ß-endorphin in inflamed skin tissues by electroacupuncture.

BACKGROUND: Electroacupuncture (EA) can produce analgesia by increasing the ß-endorphin level and activation of peripheral µ-opioid receptors in inflamed tissues. Endogenous cannabinoids and peripheral cannabinoid CB2 receptors (CB2Rs) are also involved in the antinociceptive effect of EA on inflammatory pain. However, little is known about how peripheral CB2Rs interact with the endogenous opioid system at the inflammatory site and how this interaction contributes to the antinociceptive effect of EA on inflammatory pain. In this study, we determined the role of peripheral CB2Rs in the effects of EA on the expression of ß-endorphin in inflamed skin tissues and inflammatory pain. RESULTS: Inflammatory pain was induced by injection of complete Freund's adjuvant into the left hindpaw of rats. Thermal hyperalgesia was tested with a radiant heat stimulus, and mechanical allodynia was quantified using von Frey filaments. The mRNA level of POMC and protein level of ß-endorphin were quantified by real-time PCR and Western blotting, respectively. The ß-endorphin-containing keratinocytes and immune cells in the inflamed skin tissues were detected by double-immunofluorescence labeling. The CB2R agonist AM1241 or EA significantly reduced thermal hyperalgesia and mechanical allodynia, whereas the selective µ-opioid receptor antagonist ß-funaltrexamine significantly attenuated the antinociceptive effect produced by them. AM1241 or EA significantly increased the mRNA level of POMC and the protein level of ß-endorphin in inflamed skin tissues, and these effects were significantly attenuated by pretreatment with the CB2R antagonist AM630. AM1241 or EA also significantly increased the percentage of ß-endorphin-immunoreactive keratinocytes, macrophages, and T-lymphocytes in inflamed skin tissues, and these effects were blocked by AM630. CONCLUSIONS: EA and CB2R stimulation reduce inflammatory pain through activation of µ-opioid receptors. EA increases endogenous opioid expression in keratinocytes and infiltrating immune cells at the inflammatory site through CB2R activation.