Electroacupuncture (EA) modulates the expression of NMDA receptors in primary sensory neurons in relation to hyperalgesia in rats

Deep Sequencing Identification of Differentially Expressed miRNAs in the Spinal Cord of Resiniferatoxin-Treated Rats in Response to Electroacupuncture

Electroacupuncture (EA) is an effective treatment to relieve pain in patients with postherpetic neuralgia. However, the mechanisms of EA involved therein are still unknown. We first injected resiniferatoxin (RTX) into Sprague Dawley rats to construct the neuralgia model. One week after injection, the rats were treated with EA at the "Huantiao" (GB30) and "Yanglingquan" (GB34) acupoints for 5 weeks. Nociceptive behavioral tests were performed to analyze the changes in thermal sensitivity and mechanical allodynia after RTX induction and EA treatment. Deep sequencing was performed to identify differentially expressed miRNAs in the spinal cord of RTX-induced rats in response to EA treatment. The nociceptive behavioral tests showed that EA at the left GB30 and GB34 acupoints significantly reduced RTX-induced tactile sensitivity and increased RTX-inhibited thermal sensitivity. The sequencing data indicated that RTX resulted in one upregulated and five downregulated miRNAs, and EA treatment resulted in two upregulated miRNAs. Furthermore, seven upregulated and two downregulated miRNAs were found between rats subjected to EA and sham operation. Functional analysis suggested that the targets of differentially expressed miRNAs were enriched in many nervous system-related pathways. The pathway-gene-miRNA net analysis showed that miR-7a-5p had the most target genes. Moreover, miR-233-3p was downregulated after RTX injection and upregulated by EA treatment. We speculated that the upregulation of miR-7a-5p and miR-233-3p is involved in the analgesic effects of EA. Our analysis on the EA-induced differential expression of miRNAs provides novel insights into the mechanisms of EA analgesia in postherpetic neuralgia.

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 (β-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 β-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 Alleviated Referral Hindpaw Hyperalgesia via Suppressing Spinal Long-Term Potentiation (LTP) in TNBS-Induced Colitis Rats

Although referred pain or hypersensitivity has been repeatedly reported in irritable bowel syndrome (IBS) patients and experimental colitis rodents, little is known about the neural mechanisms. Spinal long-term potentiation (LTP) of nociceptive synaptic transmission plays a critical role in the development of somatic hyperalgesia in chronic pain conditions. Herein, we sought to determine whether spinal LTP contributes to the referral hyperalgesia in colitis rats and particularly whether electroacupuncture (EA) is effective to alleviate somatic hyperalgesia via suppressing spinal LTP. Rats in the colitis group (induced by colonic infusion of 2,4,6-trinitrobenzenesulfonic acid, TNBS), instead of the control and vehicle groups, displayed evident focal inflammatory destruction of the distal colon accompanied not only with the sensitized visceromotor response (VMR) to noxious colorectal distension (CRD) but also with referral hindpaw hyperalgesia indicated by reduced mechanical and thermal withdrawal latencies. EA at Zusanli (ST36) and Shangjuxu (ST37) attenuated the severity of colonic inflammation, as well as the visceral hypersensitivity and referral hindpaw hyperalgesia in colitis rats. Intriguingly, the threshold of C-fiber-evoked field potentials (CFEFP) was significantly reduced and the spinal LTP was exaggerated in the colitis group, both of which were restored by EA treatment. Taken together, visceral hypersensitivity and referral hindpaw hyperalgesia coexist in TNBS-induced colitis rats, which might be attributed to the enhanced LTP of nociceptive synaptic transmission in the spinal dorsal horn. EA at ST36 and ST37 could relieve visceral hypersensitivity and, in particular, attenuate referral hindpaw hyperalgesia by suppressing the enhanced spinal LTP.

Contribution of GABAergic modulation in DRGs to electroacupuncture analgesia in incisional neck pain rats

Purpose

Acupuncture therapy is effective for relieving postoperative pain. Our previous study showed that electroacupuncture (EA) at Futu (LI18) and Hegu (LI4)–Neiguan (PC6) could alleviate incisional neck pain, which was related with its effect in upregulating γ-aminobutyric acid (GABA) expression in cervical (C3–6) dorsal root ganglions (DRGs); but whether its receptor subsets GABA_Aα2R and GABA_BR1 in C3–6 DRGs are involved in EA analgesia or not, it remains unknown.

Materials and methods

Seventy-five male Sprague Dawley rats were randomized to normal control, model, LI18, LI4–PC6, and Zusanli (ST36)–Yanglingquan (GB34) groups. The incisional neck pain model was established by making a longitudinal incision along the midline of the rats’ neck, followed by repeated mechanical stimulation. EA was applied to bilateral LI18, LI4–PC6, or ST36–GB34 for 30 minutes at 4, 24, and 48 hours after operation. The thermal pain threshold of the neck was detected by a tail-flick unit, and the C3–6 DRGs were removed for assaying the immunoactivity of substance P (SP), GABA_Aα2R, glial fibrillary acidic protein (GFAP; a marker of satellite glial cells [SGCs]), and GABA_BR1 and the expression of GABA_Aα2R and GABA_BR1 mRNA and proteins using immunofluorescence, real-time PCR, and Western blotting, respectively.

Results

The cervical thermal pain threshold was significantly lower in the model group than the normal group (P<0.001), indicating hyperalgesia after neck incision, and was considerably increased in both EA-LI18 and LI4–PC6 groups (P<0.001), but not in ST36–GB34 group compared with model group (P>0.05). Immunofluorescence staining showed that GABA_Aα2 R expressed on SP⁺ neurons, and GABA_BR1 on SGCs. EA of LI18 and LI4–PC6 markedly suppressed the modeling-induced upregulation of the immunoactivity of SP (P<0.001 and P<0.01, respectively) and GFAP (P<0.01 and P<0.001, respectively) and significantly reversed neck incision–induced downregulation of the expression of GABA_Aα2R and GABA_BR1 mRNAs and proteins (P<0.05).

Conclusion

EA of LI18 and LI4–PC6 has an analgesic effect in incisional neck pain rats, which is related to its effects in upregulating GABAergic inhibitory modulation on nociceptive peptidergic neurons and SGCs in cervical DRGs.

Electroacupuncture inhibits NLRP3 inflammasome activation through CB2 receptors in inflammatory pain

The therapeutic effect of electroacupuncture (EA) on inflammatory pain has been well recognized clinically. The inflammasome promotes the maturation of the inflammatory cytokines, and EA can stimulate cannabinoid CB2 receptors in inflamed tissues. In this study we investigated whether EA inhibits NLRP3 inflammasome activation through CB2 receptors and thus relieving inflammatory pain. Assay of Caspase-1 activity and western blotting revealed that complete Freund's adjuvant (CFA) injection activated the NLRP3 inflammasome in the skin tissue in rats, which was attenuated by EA treatment. Immunofluorescence labeling showed that NLRP3 inflammasome elicited by CFA in the skin macrophages were decreased by EA. Nociceptive behavioral tests demonstrated that in CB2 receptor knockout mice, the EA effects on NLRP3 inflammasomes were largely attenuated. In addition, in vitro studies in a macrophage cell line showed that CB2 receptor stimulation inhibited the NLRP3 inflammasome activation. Thus, our results suggest a novel signaling pathway through which CB2 receptors are involved in the analgesic effect of EA on inflammatory pain. Stimulation of CB2 receptors inhibits NLRP3 inflammasome activation in inflamed skin tissues. These results suggest that EA reduces the inflammatory pain by inhibiting the activation of NLRP3 inflammasome through CB2 receptors. Our findings provide novel information about the mechanisms through which EA and CB2 receptor activation reduce inflammatory pain.

The endocannabinoid system, a novel and key participant in acupuncture's multiple beneficial effects

Acupuncture and its modified forms have been used to treat multiple medical conditions, but whether the diverse effects of acupuncture are intrinsically linked at the cellular and molecular level and how they might be connected have yet to be determined. Recently, an emerging role for the endocannabinoid system (ECS) in the regulation of a variety of physiological/pathological conditions has been identified. Overlap between the biological and therapeutic effects induced by ECS activation and acupuncture has facilitated investigations into the participation of ECS in the acupuncture-induced beneficial effects, which have shed light on the idea that the ECS may be a primary mediator and regulatory factor of acupuncture's beneficial effects. This review seeks to provide a comprehensive summary of the existing literature concerning the role of endocannabinoid signaling in the various effects of acupuncture, and suggests a novel notion that acupuncture may restore homeostasis under different pathological conditions by regulating similar networks of signaling pathways, resulting in the activation of different reaction cascades in specific tissues in response to pathological insults.

Effects of electroacupuncture in a mouse model of fibromyalgia: role of N-methyl-D-aspartate receptors and related mechanisms

Objective

N-methyl-D-aspartate receptor (NMDAR) activation and downstream transduction pathways are crucial for pain signalling. Fibromyalgia (FM) is a common pain syndrome of unclear aetiology that is often drug-refractory but may benefit from treatment with electroacupuncture (EA). We examined the contributions of NMDAR signalling to FM pain and EA responses in a mouse model.

Methods

A model of FM was established by acid saline injection in 32 mice and subgroups (n=8 each) were treated with EA (2 Hz, 15 min daily for 4 days) or minimal acupuncture (MA). Expression of NMDAR subunits, calmodulin-dependent protein kinase II (CaMKII), cyclic AMP response element binding protein (pCREB) and their corresponding phospho-activated forms were measured by Western blotting and immunohistochemistry.

Results

Acid saline injection induced significant mechanical hyperalgesia (paw withdrawal threshold 2.18±0.27 g, p<0.05 vs controls), which was reversed by EA (4.23±0.33 g, p<0.05 vs FM group) but not by MA (2.37±0.14 g, p<0.05 vs EA group). Expression levels of phosphorylated N-methyl-D-aspartate receptor (pNR)1 and pNR2B were significantly increased in the dorsal root ganglion of FM model mice (132.21±14.4% and 116.69±3.22% of control values), whereas NR1 and NR2B levels were unchanged (97.31±3.79% and 97.07%±2.27%, respectively). Expression levels of pCaMKIIα and pCREB were also higher in the FM group, and these changes were reversed by EA but not by MA. Similar changes in expression were observed in spinal cord neurons.

Conclusions

Reduced NMDAR−CaMKIIα−pCREB signalling is implicated in the positive effects of EA in FM. NMDAR signalling components may represent promising therapeutic targets for FM treatment.

Dietary Plant Lectins Appear to Be Transported from the Gut to Gain Access to and Alter Dopaminergic Neurons of Caenorhabditis elegans, a Potential Etiology of Parkinson's Disease

Lectins from dietary plants have been shown to enhance drug absorption in the gastrointestinal tract of rats, be transported trans-synaptically as shown by tracing of axonal and dendritic paths, and enhance gene delivery. Other carbohydrate-binding protein toxins are known to traverse the gut intact in dogs. Post-feeding rhodamine- or TRITC-tagged dietary lectins, the lectins were tracked from gut to dopaminergic neurons (DAergic-N) in transgenic Caenorhabditis elegans (C. elegans) [egIs1(Pdat-1:GFP)] where the mutant has the green fluorescent protein (GFP) gene fused to a dopamine transport protein gene labeling DAergic-N. The lectins were supplemented along with the food organism Escherichia coli (OP50). Among nine tested rhodamine/TRITC-tagged lectins, four, including Phaseolus vulgaris erythroagglutinin (PHA-E), Bandeiraea simplicifolia (BS-I), Dolichos biflorus agglutinin (DBA), and Arachis hypogaea agglutinin (PNA), appeared to be transported from gut to the GFP-DAergic-N. Griffonia Simplicifolia and PHA-E, reduced the number of GFP-DAergic-N, suggesting a toxic activity. PHA-E, BS-I, Pisum sativum (PSA), and Triticum vulgaris agglutinin (Succinylated) reduced fluorescent intensity of GFP-DAergic-N. PHA-E, PSA, Concanavalin A, and Triticum vulgaris agglutinin decreased the size of GFP-DAergic-N, while BS-I increased neuron size. These observations suggest that dietary plant lectins are transported to and affect DAergic-N in C. elegans, which support Braak and Hawkes' hypothesis, suggesting one alternate potential dietary etiology of Parkinson's disease (PD). A recent Danish study showed that vagotomy resulted in 40% lower incidence of PD over 20 years. Differences in inherited sugar structures of gut and neuronal cell surfaces may make some individuals more susceptible in this conceptual disease etiology model.

Molecular mechanisms underlying the effects of acupuncture on neuropathic pain

Acupuncture has been used to treat neuropathic pain for a long time, but its mechanisms of action remain unknown. In this study, we observed the effects of electroacupuncture and manual acu-puncture on neuropathic pain and on ephrin-B/EphB signaling in rats models of chronic constriction injury-induced neuropathic pain. The results showed that manual acupuncture and elec-puncture significantly reduced mechanical hypersensitivity following chronic constriction injury, es-pecially electroacupuncture treatment. Real-time PCR results revealed that ephrin-B1/B3 and EphB1/B2 mRNA expression levels were significantly increased in the spinal dorsal horns of chronic constriction injury rats. Electroacupuncture and manual acupuncture suppressed the high sion of ephrin-B1 mRNA, and elevated EphB3/B4 mRNA expression. Electroacupuncture signifi-cantly enhanced the mRNA expression of ephrin-B3 and EphB3/B6 in the dorsal horns of neuro-pathic pain rats. Western blot results revealed that electroacupuncture in particular, and manual acupuncture, significantly up-regulated ephrin-B3 protein levels in rat spinal dorsal horns. The re-sults of this study suggest that acupuncture could activate ephrin-B/EphB signaling in neuropathic pain rats and improve neurological function.

Effect of electro-acupuncture stimulation of Ximen (PC4) and Neiguan (PC6) on remifentanil-induced breakthrough pain following thoracal esophagectomy

The clinical analgesic effect of electro-acupuncture (EA) stimulation (EAS) on breakthrough pain induced by remifentanil in patients undergoing radical thoracic esophagectomy, and the mechanisms were assessed. Sixty patients (ASAIII) scheduled for elective radical esophagectomy were randomized into three groups: group A (control) receiving a general anesthesia only; group B (sham) given EA needles at PC4 (Ximen) and PC6 (Neiguan) but no stimulation; and group C (EAS) electrically given EAS of the ipsilateral PC4 and PC6 throughout the surgery. The EAS consisting of a disperse-dense wave with a low frequency of 2 Hz and a high frequency of 20 Hz, was performed 30 min prior to induction of general anesthesia and continued through the surgery. At the emergence, sufentanil infusion was given for postoperative analgesia with loading dose of 7.5 μg, followed by a continuous infusion of 2.25 μg/h. The patient self-administration of sufentanil was 0.75 μg with a lockout of 15 min as needed. Additional breakthrough pain was treated with dezocine (5 mg) intravenously at the patient's request. Blood samples were collected before (T1), 2 h (T2), 24 h (T3), and 48 h (T4) after operation to measure the plasma β-EP, PGE2, and 5-HT. The operative time, the total dose of sufentanil and the dose of self-administration, and the rescue doses of dezocine were recorded. Visual Analogue Scale (VAS) scores at 2, 12, 24 and 48 h postoperatively and the incidence of apnea and severe hypotension were recorded. The results showed that the gender, age, weight, operative time and remifentanil consumption were comparable among 3 groups. Patients in EAS group had the lowest VAS scores postoperatively among the three groups (P<0.05). The total dose of sufentanil was 115±6.0 μg in EAS group, significantly lower than that in control (134.3±5.9 μg) and sham (133.5±7.0 μg) groups. Similarly, the rescue dose of dezocine was the least in EAS group (P<0.05) among the three groups. Plasma β-EP levels in EAS group at T3 (176.90±45.73) and T4 (162.96±35.00 pg/mL) were significantly higher than those in control (132.33±36.75 and 128.79±41.24 pg/mL) and sham (136.56±45.80 and 129.85±36.14 pg/mL) groups, P<0.05 for all. EAS could decrease the release of PGE2. Plasma PGE2 levels in EAS group at T2 and T3 (41±5 and 40±5 pg/mL respectively) were significantly lower than those in control (64±5 and 62±7 pg/mL) and sham (66±6 and 62±6 pg/mL) groups. Plasma 5-HT levels in EAS group at T2 (133.66±40.85) and T3 (154.66±52.49 ng/mL) were significantly lower than those in control (168.33±56.94 and 225.28±82.03) and sham (164.54±47.53 and 217.74±76.45 ng/mL) groups. For intra-group comparison, plasma 5-HT and PGE2 levels in control and sham groups at T2 and T3, and β-EP in EAS group at T3 and T4 were significantly higher than those at T1 (P<0.05); PGE2 and 5-HT levels in EAS group showed no significant difference among the different time points (P>0.05). No apnea or severe hypotension was observed in any group. It was concluded that intraoperative ipsilateral EAS at PC4 and PC6 provides effective postoperative analgesia for patients undergoing radical esophagectomy with remifentanil anesthesia and significantly decrease requirement for parental narcotics. The underlying mechanism may be related to stimulation of the release of endogenous β-EP and inhibition of inflammatory mediators (5-HT and PGE2).

P2X4 receptor in the dorsal horn partially contributes to brain-derived neurotrophic factor oversecretion and toll-like receptor-4 receptor activation associated with bone cancer pain

Previous studies have suggested that the microglial P2X7 purinoceptor is involved in the release of tumor necrosis factor-α (TNFα) following activation of toll-like receptor-4 (TLR4), which is associated with nociceptive behavior. In addition, this progress is evoked by the activation of the P2X4 purinoceptor (P2X4R). Although P2X4R is also localized within spinal microglia in the dorsal horn, little is known about its role in cancer-induced bone pain (CIBP), which is in some ways unique. With the present rat model of CIBP, we demonstrate a critical role of the microglial P2X4R in the enhanced nociceptive transmission, which is associated with TLR4 activation and secretion of brain-derived neurotrophic factor (BDNF) and TNFα in the dorsal horn. We assessed mechanical threshold and spontaneous pain of CIBP rats. Moreover, P2X4R small interfering RNA (siRNA) was administered intrathecally, and real-time PCR, Western blots, immunofluorescence histochemistry, and ELISA were used to detect the expression of P2X4R, TLR4, OX-42, phosphorylated-p38 MAPK (p-p38), BDNF, and TNFα. Compared with controls, intrathecal injection of P2X4R siRNA could prevent nociceptive behavior induced by ATP plus lipopolysaccharide and CIBP and reduce the expression of P2X4R, TLR4, p-p38, BDNF, and TNFα. In addition, the increase of BDNF protein in rat microglial cells depended on P2X4 receptor signaling, which is partially associated with TLR4 activation. The ability of microglial P2X4R to activate TLR4 in spinal cord leading to behavioral hypersensitivity and oversecretion of BDNF could provide an opportunity for the prevention and treatment of CIBP.

Increased response to glutamate in small diameter dorsal root ganglion neurons after sciatic nerve injury

Glutamate in the peripheral nervous system is involved in neuropathic pain, yet we know little how nerve injury alters responses to this neurotransmitter in primary sensory neurons. We recorded neuronal responses from the ex-vivo preparations of the dorsal root ganglia (DRG) one week following a chronic constriction injury (CCI) of the sciatic nerve in adult rats. We found that small diameter DRG neurons (<30 µm) exhibited increased excitability that was associated with decreased membrane threshold and rheobase, whereas responses in large diameter neurons (>30 µm) were unaffected. Puff application of either glutamate, or the selective ionotropic glutamate receptor agonists alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and kainic acid (KA), or the group I metabotropic receptor (mGluR) agonist (S)-3,5-dihydroxyphenylglycine (DHPG), induced larger inward currents in CCI DRGs compared to those from uninjured rats. N-methyl-D-aspartate (NMDA)-induced currents were unchanged. In addition to larger inward currents following CCI, a greater number of neurons responded to glutamate, AMPA, NMDA, and DHPG, but not to KA. Western blot analysis of the DRGs revealed that CCI resulted in a 35% increase in GluA1 and a 60% decrease in GluA2, the AMPA receptor subunits, compared to uninjured controls. mGluR1 receptor expression increased by 60% in the membrane fraction, whereas mGluR5 receptor subunit expression remained unchanged after CCI. These results show that following nerve injury, small diameter DRG neurons, many of which are nociceptive, have increased excitability and an increased response to glutamate that is associated with changes in receptor expression at the neuronal membrane. Our findings provide further evidence that glutamatergic transmission in the periphery plays a role in nociception.

Mechanisms of acupuncture-electroacupuncture on persistent pain

In the last decade, preclinical investigations of electroacupuncture mechanisms on persistent tissue injury (inflammatory), nerve injury (neuropathic), cancer, and visceral pain have increased. These studies show that electroacupuncture activates the nervous system differently in health than in pain conditions, alleviates both sensory and affective inflammatory pain, and inhibits inflammatory and neuropathic pain more effectively at 2 to 10 Hz than at 100 Hz. Electroacupuncture blocks pain by activating a variety of bioactive chemicals through peripheral, spinal, and supraspinal mechanisms. These include opioids, which desensitize peripheral nociceptors and reduce proinflammatory cytokines peripherally and in the spinal cord, and serotonin and norepinephrine, which decrease spinal N-methyl-D-aspartate receptor subunit GluN1 phosphorylation. Additional studies suggest that electroacupuncture, when combined with low dosages of conventional analgesics, provides effective pain management which can forestall the side effects of often-debilitating pharmaceuticals.

Anti-inflammatory effect of glycosaminoglycan derived from Gryllus bimaculatus (a type of cricket, insect) on adjuvant-treated chronic arthritis rat model

Anti-inflammatory effects of glycosaminoglycan (GAG) derived from cricket (Gryllus bimaculatus, Gb) were investigated in a complete Freund's adjuvant (CFA)-treated chronic arthritic rat model. This GAG produced a significant anti-edema effect as evidenced by inhibition of C-reactive protein (CRP) and rheumatoid factor, and interfered with atherogenesis by reducing proinflammatory cytokine levels of (1) vascular endothelial growth factor (VEGF) production in human umbilical vein endothelial cells (HUVEC), (2) interleukin-6, (3) prostaglandin E2-stimulated lipopolysaccharide in RAW 264.7 cells, and (4) tumor necrosis factor (TNF)-α production in normal splenocytes, in a dose-dependent manner. This GAG was also found to induce nitric oxide (NO) production in HUVEC cells and elevated endothelial nitric oxide synthase (eNOS) activity levels. Histological findings demonstrated the fifth lumbar vertebrae (LV) dorsal root ganglion, which was linked to the paw treated with Gb GAG, was repaired against CFA-induced cartilage destruction. Further, combined indomethacin (5 mg/kg)-Gb GAG (10 mg/kg) inhibited more effectively CFA-induced paw edema at 3 h and 2 or 3 d after treatment to levels comparable to only the anti-inflammatory drug indomethacin. Ultraviolet (UV)-irritated skin inflammation also downregulated nuclear factor κB (NFκB) activity in transfected HaCaT cells. Data suggest that the anti-inflammatory effects of GAG obtained from cricket (Gb) may be useful for treatment of inflammatory diseases including chronic arthritis.

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.

Electroacupuncture alleviates stress-induced visceral hypersensitivity through an opioid system in rats

AIM: To investigate whether stress-induced visceral hypersensitivity could be alleviated by electroacupuncture (EA) and whether EA effect was mediated by endogenous opiates.

METHODS: Six to nine week-old male Sprague-Dawley rats were used in this study. Visceral hypersensitivity was induced by a 9-d heterotypic intermittent stress (HIS) protocol composed of 3 randomly stressors, which included cold restraint stress at 4 °C for 45 min, water avoidance stress for 60 min, and forced swimming stress for 20 min, in adult male rats. The extent of visceral hypersensitivity was quantified by electromyography or by abdominal withdrawal reflex (AWR) scores of colorectal distension at different distention pressures (20 mmHg, 40 mmHg, 60 mmHg and 80 mmHg). AWR scores either 0, 1, 2, 3 or 4 were obtained by a blinded observer. EA or sham EA was performed at classical acupoint ST-36 (Zu-San-Li) or BL-43 (Gao-Huang) in both hindlimbs of rats for 30 min. Naloxone (NLX) or NLX methiodide (m-NLX) was administered intraperitoneally to HIS rats in some experiments.

RESULTS: HIS rats displayed an increased sensitivity to colorectal distention, which started from 6 h (the first measurement), maintained for 24 h, and AWR scores returned to basal levels at 48 h and 7 d after HIS compared to pre-HIS baseline at different distention pressures. The AWR scores before HIS were 0.6 ± 0.2, 1.3 ± 0.2, 1.9 ± 0.2 and 2.3 ± 0.2 for 20 mmHg, 40 mmHg, 60 mmHg and 80 mmHg distention pressures, respectively. Six hours after termination of the last stressor, the AWR scores were 2.0 ± 0.1, 2.5 ± 0.1, 2.8 ± 0.2 and 3.5 ± 0.2 for 20 mmHg, 40 mmHg, 60 mmHg and 80 mmHg distention pressures, respectively. EA given at classical acupoint ST-36 in both hindlimbs for 30 min significantly attenuated the hypersensitive responses to colorectal distention in HIS rats compared with sham EA treatment [AWRs at 20 mmHg: 2.0 ± 0.2 vs 0.7 ± 0.1, P = 4.23 711 E-4; AWRs at 40 mmHg: 2.6 ± 0.2 vs 1.5 ± 0.2, P = 0.00 163; AWRs at 60 mmHg: 3.1 ± 0.2 vs 1.9 ± 0.1, P = 0.003; AWRs at 80 mmHg: 3.6 ± 0.1 vs 2.4 ± 0.2, P = 0.0023; electromyographic (EMG) at 20 mmHg: 24 ± 4.7 vs 13.8 ± 3.5; EMG at 40 mmHg: 60.2 ± 6.6 vs 30 ± 4.9, P = 0.00 523; EMG at 60 mmHg: 83 ± 10 vs 39.8 ± 5.9, P = 0.00 029; EMG at 80 mmHg: 94.3 ± 10.8 vs 49.6 ± 5.9, P = 0.00 021]. In addition, EA at the acupuncture point BL-43 with same parameters did not alleviate visceral hypersensitivity in HIS rats. EA in healthy rats also did not have any effect on AWR scores to colorectal distention at distention pressures of 20 and 40 mmHg. The EA-mediated analgesic effect was blocked by pretreatment with NLX in HIS rats [AWR scores pretreated with NLX vs normal saline (NS) were 2.0 vs 0.70 ± 0.20, 2.80 ± 0.12 vs 1.50 ± 0.27, 3 vs 2.00 ± 0.15 and 3.60 ± 0.18 vs 2.60 ± 0.18 for 20 mmHg, 40 mmHg, 60 mmHg and 80 mmHg; P = 0.0087, 0.0104, 0.0117 and 0.0188 for 20, 40, 60 and 80 mmHg, respectively]. Furthermore, EA-mediated analgesic effect was completely reversed by administration of m-NLX, a peripherally restricted opioid antagonist (EMG pretreated with m-NLX vs NS were 30.84 ± 4.39 vs 13.33 ± 3.88, 74.16 ± 9.04 vs 36.28 ± 8.01, 96.45 ± 11.80 vs 50.19 ± 8.28, and 111.59 ± 13.79 vs 56.42 ± 8.43 for 20 mmHg, 40 mmHg, 60 mmHg and 80 mmHg; P = 0.05 026, 0.00 034, 0.00 005, 0.000 007 for 20 mmHg, 40 mmHg, 60 mmHg and 80 mmHg, respectively).

CONCLUSION: EA given at classical acupoint ST-36 alleviates stress-induced visceral pain, which is most likely mediated by opioid pathways in the periphery.

Differences in neural-immune gene expression response in rat spinal dorsal horn correlates with variations in electroacupuncture analgesia

Background

Electroacupuncture (EA) has been widely used to alleviate diverse pains. Accumulated clinical experiences and experimental observations indicated that significant differences exist in sensitivity to EA analgesia for individuals of patients and model animals. However, the molecular mechanism accounting for this difference remains obscure.

Methodology/Principal Findings

We classified model male rats into high-responder (HR; TFL changes >150) and non-responder (NR; TFL changes ≤0) groups based on changes of their pain threshold detected by tail-flick latency (TFL) before and after 2 Hz or 100 Hz EA treatment. Gene expression analysis of spinal dorsal horn (DH) revealed divergent expression in HR and NR after 2 Hz/100 Hz EA. The expression of the neurotransmitter system related genes was significantly highly regulated in the HR animals while the proinflammation cytokines related genes were up-regulated more significantly in NR than that in HR after 2 Hz and 100 Hz EA stimulation, especially in the case of 2 Hz stimulation.

Conclusions/Significance

Our results suggested that differential regulation and coordination of neural-immune related genes might play an important role for individual variations in analgesic effects responding to EA in DH. It also provided new candidate genes related to EA responsiveness for future investigation.

Brain-derived neurotrophic factor modulates N-methyl-D-aspartate receptor activation in a rat model of cancer-induced bone pain

Brain-derived neurotrophic factor (BDNF) released within the spinal cord induces phosphorylation of N-methyl-D-aspartate (NMDA) receptors on the spinal cord neurons. This process is necessary for maintaining pain hypersensitivity after nerve injury. However, little is known about the role of BDNF and NMDA receptors in cancer-induced bone pain (CIBP), whose features are unique. This study demonstrates a critical role of the BDNF-modulated NMDA subunit 1 (NR1) in the induction and maintenance of behavioral hypersensitivity in a rat model of CIBP, both in the spinal cord and in the dorsal root ganglia (DRG). We selectively suppressed BDNF expression by RNA interference (RNAi) using intrathecal administration of BDNF small interfering RNA (siRNA). Then, we assessed mechanical threshold and spontaneous pain in CIBP rats. Real-time PCR, Western blotting, and fluorescent immunohistochemical staining were used to detect BDNF or NR1 both in vivo and in vitro. BDNF and phospho-NR1 were expressed under CIBP experimental conditions, with expression levels peaking at day 6 (BDNF) or 9 (NR1). Intrathecal BDNF siRNA prevented CIBP at an early stage of tumor growth (days 4-6). However, at later stages (days 10-12), intrathecal BDNF siRNA only attenuated, but did not completely block, the established CIBP. BDNF-induced NMDA receptor activation in the spinal cord or DRG leads to central sensitization and behavioral hypersensitivity. Thus, BDNF might provide a targeting opportunity for alleviating CIBP.

Efeitos da eletroacupuntura, aquapuntura e farmacopuntura em cadelas anestesiadas com isofluorano e submetidas à ovário-histerectomia

Avaliaram-se os efeitos analgésicos da eletroacupuntura, aquapuntura e farmacopuntura com morfina nos acupontos VB41 e TA5 de 24 cadelas hígidas submetidas à ovário-histerectomia. Os animais foram distribuídos em quatro grupos (G) de igual número - GDest, GMorf, GElet e GC - e anestesiados com acepromazina, propofol e isofluorano. Após a estabilização do plano anestésico, os animais do GDest receberam 0,5mL de água destilada em cada acuponto; os do GMorf receberam 0,1mg/kg de morfina distribuído nos quatro acupontos; os do GElet foram submetidos à eletroacupuntura; e os do GC, acupuntura em pontos sham. Os animais do GC receberam, após o término do procedimento cirúrgico e antes do início da avaliação pelas escalas de dor, 2,0mg/kg de tramadol. Foram avaliadas: frequências cardíaca e respiratória, temperatura retal e glicemia. A dor foi avaliada por duas escalas, uma de analogia numérica e outra contagem variável, por três observadores. A avaliação iniciou-se imediatamente após a extubação e foi realizada a cada 15 minutos, durante duas horas. Não houve diferença entre os tratamentos em todas as variáveis. Pode-se concluir que eletroacupuntura, aquapuntura e farmacopuntura com morfina resultaram em analgesia similar ao tramadol no pós-operatório imediato de cadelas submetidas à ovário-histerectomia eletiva.

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

BACKGROUND

Electroacupuncture (EA) can produce analgesia by increasing the β-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 β-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 β-endorphin were quantified by real-time PCR and Western blotting, respectively. The β-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 β-funaltrexamine significantly attenuated the antinociceptive effect produced by them. AM1241 or EA significantly increased the mRNA level of POMC and the protein level of β-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 β-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.

Electroacupuncture attenuates mechanical and warm allodynia through suppression of spinal glial activation in a rat model of neuropathic pain

Neuropathic pain remains one of the most difficult clinical pain syndromes to treat. It is traditionally viewed as being mediated solely by neurons; however, glial cells have recently been implicated as powerful modulators of pain. It is known that the analgesic effects of electroacupuncture (EA) are mediated by descending pain inhibitory systems, which mainly involve spinal opioid, adrenergic, dopaminergic, serotonergic, and cholinergic receptors. However, studies investigating the suppressive effects of EA on spinal glial activation are rare. In the present study, we assessed the cumulative analgesic effects of EA on mechanical and warm allodynia in a rat model of neuropathic pain. We investigated the clinical efficacy of EA as long-term therapy and examined its effects on spinal glia, matrix metalloproteinase (MMP)-9/MMP-2, proinflammatory cytokines and serum immunoglobulin G (IgG) concentration. Rats were randomly divided into four groups as follows: the operation group (OP), operation with EA-non acupoint (EA-NA), operation with EA-ST36 acupoint (EA-ST36), and sham operation (shamOP). Following neuropathic or sham surgery, repeated EA was performed every other day after the behavioral test. On day 53 after the behavioral test, rats were perfused for immunohistochemistry and Western blot analysis to observe quantitative changes in spinal glial markers such as OX-42, astrocytic glial fibrillary acidic protein (GFAP), MMP-9/MMP-2, and proinflammatory cytokines. Allodynia and OX-42/GFAP/MMP-9/MMP-2/tumor necrosis factor (TNF)-α/interleukin (IL)-1β activity in the EA-ST36 group was significantly reduced, compared to the OP and EA-NA groups, and IgG in EA-ST36 rats significantly increased. Our results suggest that the analgesic effect of EA may be partly mediated via inhibition of inflammation and glial activation and repeated EA stimulation may be useful for treating chronic pain clinically.

A randomized controlled trial of auricular transcutaneous electrical nerve stimulation for managing posthysterectomy pain

Background. A patient- and assessor-blinded randomized controlled trial was conducted to examine the effectiveness of auricular transcutaneous electrical nerve stimulation (TENS) in relieving posthysterectomy pain. Method. Forty-eight women who had undergone a total abdominal hysterectomy were randomly assigned into three groups (n = 16 each) to receive either (i) auricular TENS to therapeutic points (the true TENS group), (ii) auricular TENS to inappropriate points (the sham TENS group), or (iii) 20 minutes of bed rest with no stimulation (the control group). The intervention was delivered about 24 hours after the operation. A visual analogue scale was used to assess pain while resting (VAS-rest) and upon huffing (VAS-huff) and coughing (VAS-cough), and the peak expiratory flow rate (PEFR) was assessed before and at 0, 15, and 30 minutes after the intervention. Result. As compared to the baseline, only the true TENS group reported a significant reduction in VAS-rest (P = .001), VAS-huff (P = .004), and VAS-cough (P = .001), while no significant reduction in any of the VAS scores was seen in the sham TENS group (all P > .05). In contrast, a small rising trend was observed in the VAS-rest and VAS-huff scores of the control group, while the VAS-cough score remained largely unchanged during the period of the study. A between-group comparison revealed that all three VAS scores of the true TENS group were significantly lower than those of the control group at 15 and 30 minutes after the intervention (all P < .02). No significant between-group difference was observed in PEFR at any point in time. Conclusion. A single session of auricular TENS applied at specific therapeutic points significantly reduced resting (VAS-rest) and movement-evoked pain (VAS-huff, VAS-cough), and the effects lasted for at least 30 minutes after the stimulation. The analgesic effects of auricular TENS appeared to be point specific and could not be attributed to the placebo effect alone. However, auricular TENS did not produce any significant improvement in the performance of PEFR.

Electroacupuncture increases CB2 receptor expression on keratinocytes and infiltrating inflammatory cells in inflamed skin tissues of rats

Endogenous cannabinoids and peripheral cannabinoid CB2 receptors (CB2Rs) are involved in the antinociceptive effect of electroacupuncture (EA) on inflammatory pain. However, it remains unclear about how EA affects the expression and distribution patterns of peripheral CB2Rs in inflamed skin tissues. To study this, inflammatory pain was induced by local injection of complete Freund's adjuvant into the hindpaw of rats. The mRNA and protein levels of CB2Rs were quantified by using RTPCR and Western blotting, respectively. The distribution of CB2Rs on keratinocytes and immune cells recruited to the inflamed skin tissues was determined by using double-immunofluorescence labeling. Induction of tissue inflammation significantly increased the mRNA and protein levels of CB2Rs in the skin tissue. Also, both 2 Hz and 100 Hz EA, applied to GB30 and GB34, significantly increased the mRNA and protein levels of CB2Rs in inflamed tissues compared to the sham EA group. CB2Rimmunoreactivities were mainly distributed in keratinocytes, macrophages, and T-lymphocytes in the epidermis and dermis of the inflamed skin tissue. Inflammation caused a significant increase in the number of CB2R-immunoreactive keratinocytes, macrophages, and T-lymphocytes. Furthermore, compared to the sham EA group, EA at 2 or 100 Hz significantly increased the number of keratinocytes, macrophages, and T-lymphocytes with CB2R-immunoreactivity in the inflamed skin tissue. Therefore, our findings suggest that EA is associated with upregulation of local CB2Rs in the inflamed skin tissue. EA primarily potentiates the expression of CB2Rs on keratinocytes and infiltrating inflammatory cells at the site of inflammation.

PERSPECTIVE

This study shows that electroacupuncture increases the CB2 receptor expression on keratinocytes and infiltrating inflammatory cells in inflammatory skin tissues. This finding provides new evidence showing the potential role of CB2 receptors in the analgesic effect of acupuncture on inflammatory pain.

Tibia tumor-induced cancer pain involves spinal p38 mitogen-activated protein kinase activation via TLR4-dependent mechanisms

Molecular mechanisms underlying bone cancer pain are poorly understood. Recently, p38 mitogen-activated protein kinase (MAPK) activation was shown to play a major role not only in the production of proinflammatory cytokines but also in the progression of inflammatory and neuropathic pain. We have demonstrated that tactile allodynia and spontaneous pain of female rats with tibia tumors were correlated with the increase of both phosphorylated-p38MAPK (p-p38MAPK) and proinflammatory cytokines (IL-1beta and TNF-alpha) in the spinal cord 6 days after Walker 256 cells' inoculation. This change was specific to bone cancer pain because rats without tibia tumors failed to show such an increase. On the other hand, a 3-day administration [4 microg/rat/day, intrathecally (i.t.)] of 4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)1H-imidazole (SB203580), an inhibitor of p38MAPK, could suppress tactile allodynia and spontaneous pain of the bone cancer pain rats and decrease the phosphorylation of p38 as well as the expression of IL-1beta and TNF-alpha. To characterize the cellular events upstream of p38MAPK, we have examined the role of the toll-like receptor 4 (TLR4), which had been suggested to be involved in pain hypersensitivity. We found that prolonged knockdown of TLR4 during the 3-day administration of TLR4 small interfering RNA (siRNA; 2 microg/rat/day, i.t.) could attenuate hyperalgesia developed by Walker 256 cells' inoculation and decrease the phosphorylation of p38 as well as the increase of IL-1beta and TNF-alpha expression. These results demonstrate that TLR4-dependent phosphorylation of p38MAPK in spinal cord of rats might contribute to the development and maintenance of bone cancer pain, and p38MAPK and TLR4 would possibly be the potential targets for pain therapy.

Trigeminal expression of N-methyl-D-aspartate receptor subunit 1 and behavior responses to experimental tooth movement in rats

OBJECTIVE

To test the hypothesis that peripheral N-methyl-D-aspartate (NMDA) receptors play a role in pain induced by experimental tooth movement.

MATERIALS AND METHODS

Male Sprague-Dawley rats weighing between 200 g and 300 g were used in this study. Expression of NMDA receptors subunit 1 (NMDAR1) in the mandibular portion of the trigeminal ganglion (TG) was determined by Western blotting 4 hours and 1, 2, 3, 5, 7, and 14 days after tooth movement. Changes in the time taken by the rats on nocifensive behavior then effects of NMDA receptor antagonist MK-801 and force magnitude on these changes in behavior and NMDAR1 expression were evaluated.

RESULTS

Experimental tooth movement led to a statistically significant increase in NMDAR1 expression at protein level from day 1 to 7 after force application initiating tooth movement. Time spent on nocifensive behavior dramatically increased from day 1 to 7. The rhythm in NMDAR1 expression in the TG and behavioral activities correlated well with the initial orthodontic pain responses. The magnitude of the nocifensive behavior and NMDAR1 expression were both force magnitude dependent and could be reduced by peripheral NMDA receptor antagonist MK-801.

CONCLUSIONS

The hypothesis is accepted. Peripheral NMDA receptors are modulated by experimental tooth movement and involved in the development of tooth movement pain.

Electroacupuncture suppresses capsaicin-induced secondary hyperalgesia through an endogenous spinal opioid mechanism

Central sensitization, caused either by tissue inflammation or peripheral nerve injury, plays an important role in persistent pain. An animal model of capsaicin-induced pain has well-defined peripheral and central sensitization components, thus is useful for studying the analgesic effect on two separate components. The focus of this study is to examine the analgesic effects of electroacupuncture (EA) on capsaicin-induced secondary hyperalgesia, which represents central sensitization. Capsaicin (0.1%, 20 microl) was injected into the plantar side of the left hind paw, and foot withdrawal thresholds in response to von Frey stimuli (mechanical sensitivity) were determined for both primary and secondary hyperalgesia in rats. EA (2 Hz, 3 mA) was applied to various pairs of acupoints, GB30-GB34, BL40-BL60, GV2-GV6, LI3-LI6 and SI3-TE8, for 30 min under isoflurane anesthesia and then the effect of EA on mechanical sensitivity of paw was determined. EA applied to the ipsilateral SI3-TE8, but to none of the other acupoints, significantly reduced capsaicin-induced secondary hyperalgesia but not primary hyperalgesia. EA analgesic effect was inhibited by a systemic non-specific opioid receptor (OR) antagonist or an intrathecal mu- or delta-OR antagonist. EA analgesic effect was not affected by an intrathecal kappa-OR antagonist or systemic adrenergic receptor antagonist. This study demonstrates that EA produces a stimulation point-specific analgesic effect on capsaicin-induced secondary hyperalgesia (central sensitization), mediated by activating endogenous spinal mu- and delta-opioid receptors.

Clinical effects of acupuncture after surgical operation in patients with prolapse of the lumbar intervertebral disc

OBJECTIVE

To investigate the clinical effects of acupuncture after surgical operation in patients with prolapse of the lumbar intervertebral disc (PLID).

METHODS

Sixty-nine patients in this series, who had undergone the removal of nucleus pulposus and the intervertebral fusion as well, were randomly divided into a treatment group of 35 cases and a control group of 34 cases. The former was treated by acupuncture and conventional rehabilitation therapy, and the latter only by the rehabilitation therapy. The therapeutic effects were evaluated according to the scoring system stipulated by Japanese Orthopedics Association (JOA).

RESULTS

In the treatment group, the average functional recovery rates in 3-month, 6-month and one-year periods were respectively 49.93%, 90.31% and 95.08%; while the rates were repesctively 26.24%, 63.42% and 71.36% in the control group, showing statistically significant difference between the two groups (P<0.05).

CONCLUSIONS

Acupuncture can confirmatively promote the functional recovery for'patients with prolapse of the lumbar intervertebral disc after surgical removal of nucleus pulposus and with intervertebral fusion.

Neural mechanism underlying acupuncture analgesia

Acupuncture has been accepted to effectively treat chronic pain by inserting needles into the specific "acupuncture points" (acupoints) on the patient's body. During the last decades, our understanding of how the brain processes acupuncture analgesia has undergone considerable development. Acupuncture analgesia is manifested only when the intricate feeling (soreness, numbness, heaviness and distension) of acupuncture in patients occurs following acupuncture manipulation. Manual acupuncture (MA) is the insertion of an acupuncture needle into acupoint followed by the twisting of the needle up and down by hand. In MA, all types of afferent fibers (Abeta, Adelta and C) are activated. In electrical acupuncture (EA), a stimulating current via the inserted needle is delivered to acupoints. Electrical current intense enough to excite Abeta- and part of Adelta-fibers can induce an analgesic effect. Acupuncture signals ascend mainly through the spinal ventrolateral funiculus to the brain. Many brain nuclei composing a complicated network are involved in processing acupuncture analgesia, including the nucleus raphe magnus (NRM), periaqueductal grey (PAG), locus coeruleus, arcuate nucleus (Arc), preoptic area, nucleus submedius, habenular nucleus, accumbens nucleus, caudate nucleus, septal area, amygdale, etc. Acupuncture analgesia is essentially a manifestation of integrative processes at different levels in the CNS between afferent impulses from pain regions and impulses from acupoints. In the last decade, profound studies on neural mechanisms underlying acupuncture analgesia predominately focus on cellular and molecular substrate and functional brain imaging and have developed rapidly. Diverse signal molecules contribute to mediating acupuncture analgesia, such as opioid peptides (mu-, delta- and kappa-receptors), glutamate (NMDA and AMPA/KA receptors), 5-hydroxytryptamine, and cholecystokinin octapeptide. Among these, the opioid peptides and their receptors in Arc-PAG-NRM-spinal dorsal horn pathway play a pivotal role in mediating acupuncture analgesia. The release of opioid peptides evoked by electroacupuncture is frequency-dependent. EA at 2 and 100Hz produces release of enkephalin and dynorphin in the spinal cord, respectively. CCK-8 antagonizes acupuncture analgesia. The individual differences of acupuncture analgesia are associated with inherited genetic factors and the density of CCK receptors. The brain regions associated with acupuncture analgesia identified in animal experiments were confirmed and further explored in the human brain by means of functional imaging. EA analgesia is likely associated with its counter-regulation to spinal glial activation. PTX-sesntive Gi/o protein- and MAP kinase-mediated signal pathways as well as the downstream events NF-kappaB, c-fos and c-jun play important roles in EA analgesia.

Are reviews based on sham acupuncture procedures in fibromyalgia syndrome (FMS) valid?

In recent reviews regarding the efficacy of acupuncture in fibromyalgia syndrome (FMS) it has been concluded that acupuncture has no specific effect since the control procedure (superficial needling and/or needling away from 'specific' points) had similar effects. These conclusions may be questioned since superficial needling and/or needling away from specific trigger points is not inert. Also, manual acupuncture or mild electroacupuncture (EA) may not be sufficient to activate the endogenous pain inhibiting system. Patients with FMS suffer from allodynia, fatigue and muscle ache, which is partly explained by peripheral and central sensitisation. Sensitisation results in augmented and altered stimulus responses whereby light stimulation of the skin has as strong an effect as regular needling on the pain inhibitory system in FMS. Central sensitisation in FMS is also associated with expanded receptive fields of central neurons resulting in a larger topographic distribution of the pain. This would suggest that control procedures using needling away from the 'specific site' might have as strong an effect as needling within the most painful area. Also, repeated nociceptive input from muscles (as obtained by de qi) results in expansion of receptive fields which in turn may result in activation of descending pain inhibition outside the stimulated myotome. Sensitisation to pain, such as in FMS, may also be related to abnormalities in descending efferent pathways. As there is likely to be an imbalance between excitatory and inhibitory systems in FMS, stronger stimulation may therefore be needed to activate the descending pain inhibitory system. In studies using mild manual acupuncture or weak EA stimulation optimal pain inhibition may therefore not have been obtained. When conducting studies on acupuncture, the clinical condition or syndrome needs to be taken into account and the control procedure designed accordingly.

Non-pharmacological techniques for pain management in neonates

Significant progress in understanding the physiology, clinical correlates, and consequences of neonatal pain have resulted in greater attention to pain management during neonatal intensive care. A number of nonpharmacological therapies have been investigated, including nonnutritive sucking, with and without sucrose use, swaddling or facilitated tucking, kangaroo care, music therapy, and multi-sensorial stimulation. Although the efficacy of these approaches is clearly evident, they cannot provide analgesia for moderate or severe pain in the neonate. Further, some of these therapies cannot be effectively applied to all populations of critically ill neonates. Acupuncture, an ancient practice in Chinese medicine, has gained increasing popularity for symptom control among adults and older children. Acupuncture may provide an effective nonpharmacological approach for the treatment of pain in neonates, even moderate or severe pain, and should be considered for inclusion in a graduated multidisciplinary algorithm for neonatal pain management.