Electroacupuncture Promotes Nerve Regeneration and Functional Recovery Through Regulating lncRNA GAS5 Targeting miR-21 After Sciatic Nerve Injury.

Although the benefits of electroacupuncture (EA) for peripheral nerve injury (PNI) are well accepted in clinical practice, the underlying mechanism remains incompletely elucidated. In our study, we observed that EA intervention led to a reduction in the expression of the long non-coding RNA growth-arrest-specific transcript 5 (GAS5) and an increased in miR-21 levels within the injured nerve, effectively promoting functional recovery and nerve regeneration following sciatic nerve injury (SNI). In contrast, administration of adeno-associated virus expressing GAS5 (AAV-GAS5) weakened the therapeutic effect of EA. On the other hand, both silencing GAS5 and introducing a miR-21 mimic prominently enhanced the proliferation activity and migration ability of Schwann cells (SCs), while also inhibiting SCs apoptosis. On the contrary, inhibition of SCs apoptosis was found to be mediated by miR-21. Additionally, overexpression of GAS5 counteracted the effects of the miR-21 mimic on SCs. Moreover, SCs that transfected with the miR-21 mimic promoted neurite growth in hypoxia/reoxygenation-induced neurons, which might be prevented by overexpressing GAS5. Furthermore, GAS5 was found to be widely distributed in the cytoplasm and was negatively regulated by miR-21. Consequently, the targeting of GAS5 by miR-21 represents a potential mechanism through which EA enhances reinnervation and functional restoration following SNI. Mechanistically, the GAS5/miR-21 axis can modulate the proliferation, migration, and apoptosis of SCs while potentially influencing the neurite growth of neurons.

Therapeutic effects of cinnamon bark oil on sciatic nerve injury in rats.

OBJECTIVE: The aim of this study was to investigate the effects of cinnamon bark essential oil (CBO) on analgesia, motor activity, balance, and coordination in rats with sciatic nerve damage. MATERIALS AND METHODS: Rats were divided into three groups as simply randomized. The right sciatic nerve (RSN) of the Sham group was explored. Only vehicle solution was applied for 28 days. The RSN of the sciatic nerve injury (SNI) group was explored. Damage was created by unilateral clamping, and vehicle solution was applied for 28 days. The RSN of the sciatic nerve injury+cinnamon bark essential oil (SNI+CBO) group was explored. SNI was created by unilateral clamping and CBO was applied for 28 days. In the experiment study, motor activity, balance, and coordination measurements were made with rotarod and accelerod tests. A hot plate test was performed for analgesia measurements. Histopathology studies were carried out with the sciatic nerve tissues. RESULTS: In the rotarod test, there was a statistically significant difference between the SNI group and the SNI+CBO group (p<0.05). According to the accelerod test findings, there was a statistically significant difference between the SNI group with the Sham and SNI+CBO groups. In the hot plate test, there was a statistically significant difference between the SNI group with the Sham and SNI+CBO groups (p<0.05). In comparison to the Sham group and the SNI group, the SNI+CBO group was shown to have the greatest expression level of vimentin. CONCLUSIONS: We have concluded that CBO can be used as an adjuvant treatment in cases of SNI, increased pain, nociception, impaired balance, motor activity, and coordination. Our results will be supported by further studies.

Local vibration therapy promotes the recovery of nerve function in rats with sciatic nerve injury.

OBJECTIVE: It has been reported that local vibration therapy can benefit recovery after peripheral nerve injury, but the optimized parameters and effective mechanism were unclear. In the present study, we investigated the effect of local vibration therapy of different amplitudes on the recovery of nerve function in rats with sciatic nerve injury (SNI). METHODS: Adult male Sprague-Dawley rats were subjected to SNI and then randomly divided into 5 groups: sham group, SNI group, SNI + A-1 mm group, SNI + A-2 mm group, and SNI + A-4 mm group (A refers to the amplitude; n = 10 per group). Starting on the 7th day after model initiation, local vibration therapy was given for 21 consecutive days with a frequency of 10 Hz and an amplitude of 1, 2 or 4 mm for 5 min. The sciatic function index (SFI) was assessed before surgery and on the 7th, 14th, 21st and 28th days after surgery. Tissues were harvested on the 28th day after surgery for morphological, immunofluorescence and Western blot analysis. RESULTS: Compared with the SNI group, on the 28th day after surgery, the SFIs of the treatment groups were increased; the difference in the SNI + A-2 mm group was the most obvious (95% confidence interval [CI]: [5.86, 27.09], P < 0.001), and the cross-sectional areas of myocytes in all of the treatment groups were improved. The G-ratios in the SNI + A-1 mm group and SNI + A-2 mm group were reduced significantly (95% CI: [-0.12, -0.02], P = 0.007; 95% CI: [-0.15, -0.06], P < 0.001). In addition, the expressions of S100 and nerve growth factor proteins in the treatment groups were increased; the phosphorylation expressions of ERK1/2 protein in the SNI + A-2 mm group and SNI + A-4 mm group were upregulated (95% CI: [0.03, 0.96], P = 0.038; 95% CI: [0.01, 0.94], P = 0.047, respectively), and the phosphorylation expression of Akt in the SNI + A-1 mm group was upregulated (95% CI: [0.11, 2.07], P = 0.031). CONCLUSION: Local vibration therapy, especially with medium amplitude, was able to promote the recovery of nerve function in rats with SNI; this result was linked to the proliferation of Schwann cells and the activation of the ERK1/2 and Akt signaling pathways.

Antihypernociceptive effects of Petersianthus macrocarpus stem bark on neuropathic pain induced by chronic constriction injury in rats.

Petersianthus macrocarpus (Lecythidaceae) stem bark is traditionally used in West and Central Africa for the treatment of boils and pain. The present study examined the chemical composition of the aqueous and methanolic stem bark extracts of P. macrocarpus by liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) . Their antinociceptive effect was evaluated using chronic constriction injury (CCI)-induced neuropathic pain in a rat model. On the ninth day post-surgery, the pain perception (allodynia and hyperalgesia) of the animals was assessed after the administration of aqueous and methanolic extracts at the doses of 100 and 200 mg/kg. In addition, the effect of the extracts was evaluated on nitric oxide activity and on the expression of pro-inflammatory cytokines (TNF-α, IL-1ß, and NF-κB). The LC-ESI-MS analysis revealed the presence of ellagic acid as the major constituent in the methanol extract. Both extracts at the employed doses (100 and 200 mg/kg), significantly (p < 0.01 and p < 0.001) reduced the spontaneous pain, tactile and cold allodynia, and mechanical hyperalgesia. The methanolic extract used at the dose of 200 mg/kg significantly reduced the nitric oxide level (p < 0.001) and the gene expression levels of NF-κB (p < 0.05) and TNF-α (p < 0.01) in the brain. These data may indicate that stem bark extracts of P. macrocarpus possess a potent anti-hypernociceptive effect on CCI neuropathic pain. The inhibition of the nitric oxide pathway as well as the reduction in NF-κB and TNF-α gene expression in the brain may at least partially contribute to this effect. The results further support the use of this plant by traditional healers in pain conditions.

A network-based analysis and experimental validation of traditional Chinese medicine Yuanhu Zhitong Formula in treating neuropathic pain.

ETHNOPHARMACOLOGICAL RELEVANCE: The Yuanhu Zhitong Formula (YZF) consists of traditional Chinese herbs Corydalis Rhizoma (Corydalis yanhusuo (Y.H.Chou & Chun C.Hsu) W.T.Wang ex Z.Y.Su & C.Y.Wu; Chinese name, Yanhusuo) and Angelicae Dahuricae Radix (Angelica dahurica (Hoffm.) Benth. & Hook.f. ex Franch. & Sav.; Chinese name, Baizhi), which is usually administrated for painful conditions. It is well acknowledged that YZF has pharmacological effects on pain relief; nevertheless, limited data are available on its mechanism. AIM OF THE STUDY: This study aimed to explore the potential mechanism underlying YZF on nociception of rats. Also, the comprehensive mechanism of YZF was preliminarily determined based on network pharmacology on neuropathic pain. MATERIALS AND METHODS: A spared nerve injury (SNI) model was established to reveal the effects of YZF administration on nociceptive behavior in rats. Von-Frey tests were used to evaluate the paw withdrawal mechanical thresholds in rats administrated with YZF or vehicle. The "drug-ingredients" and "disease-drug-target" networks were established with a network pharmacology approach. The analyses of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) profiles were performed based on the common targets between the herbs and neuropathic pain. Hub genes, identified with CytoHubba, were validated by Western blotting analysis. RESULTS: SNI rats developed significant nociceptive behavior as soon as 3 days after nerve injury, which was reversed by consecutive treatment with 300 mg/kg YZF for 7 days. Besides, 50 potential bioactive components in YZF with 1074 targets were identified. Then, 217 putative common genes related to YZF and neuropathic pain were identified for further study. After established a protein-protein interaction network, 12 subnetworks with CytoHubba and 10 predictive hub genes were obtained based on the maximal clique centrality model. Western blotting analysis indicated that SNI rats exhibited increased APP (Amyloid-beta precursor protein), SRC (Proto-oncogene tyrosine-protein kinase Src), and phosphorylation of JNK1 (Mitogen-activated protein kinase 8, JNK) and ERK1/2 (Mitogen-activated protein kinase 3/1). Obviously, continuous administration of YZF robustly reversed such changes. CONCLUSIONS: This study revealed that YZF modulates the nociceptive behavior in SNI rats. Moreover, the drug may be useful in the treatment of neuropathic pain through multi-components, multi-targets, and multi-pathways. Nevertheless, more attention should be paid to discriminating the potential ingredients in YZF contributing to its analgesic effects in the treatment of neuropathic pain.

An integrated strategy for discovering effective components of Shaoyao Gancao decoction for treating neuropathic pain by the combination of partial least-squares regression and multi-index comprehensive method.

ETHNOPHARMACOLOGICAL RELEVANCE: Neuropathic pain, the incidence of which ranges from 5 to 8% in the general population, remains challenge in the treatment. Shaoyao Gancao decoction (SGD) is a Chinese classical formula used to relieve pain for thousands of years and has been applied for neuropathic pain nowadays. However, the effective components of SGD for the treatment of neuropathic pain remains unclear. AIMS OF STUDY: To investigate the effect and potential mechanism of SGD against neuropathic pain and further reveal the effective components of SGD in the treatment of neuropathic pain. MATERIALS AND METHODS: Spared nerve injury (SNI) model rats of neuropathic pain were orally given SGD to intervene, the components in vivo after SGD administration were determined, behavior indicators, biochemical parameters, and metabolomics were applied for assessing the efficacy. Then correlation between components and biomarkers was analyzed by pearson correlation method. To further measure the contribution of components to efficacy, the combination of partial least-squares regression (PLSR) and multi-index comprehensive method was carried out, according to the corresponding contribution degree of the results, the components with large contribution degree were considered as the effective components. RESULTS: SGD exhibited a significant regulatory effect on neuropathic pain, which could increase the pain threshold and decrease the levels of SP, ß-EP, PGE2 and NO. With the high resolution of UPLC-Q-TOF/MS technology, a total of 128 compounds from SGD were identified and 44 of them were absorbed in blood. Besides, 40 serum biomarkers were identified after intervention of SGD and the metabolic pathways were constructed. The key metabolic pathways including Glycerophospholipid metabolism, Linoleic acid metabolism, Alpha-linolenic acid metabolism, Glycosylphosphatidylinositol-anchor biosynthesis and Arachidonic acid metabolism may be related to the regulation of neuropathic pain. Metabolomics combined with PLSR and multi-index comprehensive method was utilized to discover 5 components including paeonol, DL-Arabinose, benzoic acid, hispaglabridin A and paeonilactone C as effective components of SGD in the treatment of neuropathic pain. This strategy was used to explore the effective components of SGD and elucidate its possible analgesic mechanism. CONCLUSION: This study demonstrate that SGD significantly relieved neuropathic pain and elucidated the effective components of SGD for treating neuropathic pain, the strategy as an illustrative case study can be applied to other classical formula and is beneficial to improve the quality and efficacy.

Augmented Buyang Huanwu Decoction facilitates axonal regeneration after peripheral nerve transection through the regulation of inflammatory cytokine production.

ETHNOPHARMACOLOGICAL RELEVANCE: Herbal formulation Buyang Huanwu Decoction (BYHWD) has been used to treat cardiovascular disorders including cerebral ischemia. Recent studies showed its effects on promoting axonal regeneration after nerve injury. However, compositional reformulation supplemented with herbal components that regulates inflammation may increase its efficacy for nerve repair. AIM OF THE STUDY: We prepared a new herbal decoction by adding selected herbal components to BYHWD (augmented BYHWD; ABHD) and investigated the effect of ABHD on the production of inflammatory cytokines and axonal regeneration using an animal model of nerve transection and coaptation (NTC). MATERIALS AND METHODS: A rat model of NTC was performed on the sciatic nerve. The sciatic nerve and dorsal root ganglion (DRG) were isolated and used for immunofluorescence staining and western blot analysis. DRG tissue was also used to prepare primary neuron culture and the length of neurites was analyzed. Sensorimotor nerve activities were assessed by rotarod and von Frey tests. RESULTS: Three herbal components that facilitated neurite outgrowth were chosen to formulate ABHD. ABHD administration into the sciatic nerve 1 week or 3 months after NTC facilitated axonal regeneration. Cell division cycle 2 (Cdc2) and brain-derived neurotrophic factor (BDNF) proteins were induced from the reconnected distal portion of the sciatic nerve and the levels were further elevated by in vivo administration of ABHD. Phospho-Erk1/2 level was increased by ABHD treatment as well, implying its role in mediating retrograde transport of BDNF signals into the neuronal cell body. Production of inflammatory cytokines IL-1ß and TNF-α was induced in the reconnected nerve but attenuated by ABHD treatment. Behavioral tests revealed that ABHD treatment improved functional recovery of sensorimotor activities. CONCLUSIONS: A newly formulated ABHD is effective at regulating the production of inflammatory cytokines and promoting axonal regeneration after nerve transection and may be considered to develop therapeutic strategies for peripheral nerve injury disorders.

Effect of ethanolic extract of Solanum virginianum Linn. on neuropathic pain using chronic constriction injury rat model and molecular docking studies.

The present research work was designed to examine the neuroprotective effect of ethanolic extract of Solanum virginianum Linn. (SV) in chronic construction injury (CCI) of sciatic nerve-induced neuropathic pain in rats. The extract was initially standardized by high-performance thin-layer chromatography using solasodine as a biomarker and was then subjected to assess the degree of mechanical allodynia, thermal allodynia, mechanical hyperalgesia, thermal hyperalgesia and biochemical evaluations. Administration of SV (100 and 200 mg/kg; p.o.) and pregabalin (10 mg/kg; p.o.) as a reference standard significantly debilitated hyperalgesia and allodynia and notably restored the altered antioxidant level and pro-inflammatory cytokine (IL-1ß and TNF-α) expression in a dose-dependent manner. Further, to appraise the mechanistic approach of solasodine, docking simulation studies were done on the 3D structure of the voltage-gated N-type calcium channel (Cav 2.2), R-type calcium channel (Cav 2.3) and sodium channel (Nav 1.7), and the results revealed that solasodine properly positioned into Phe 19, Leu 32, Met 51 and Met 71 (FLMM pocket) of Cav 2.2 and Cav 2.3 and being a competitor of Ca2+/N-lobe it may inactivate these calcium channels but did not bind into the desired binding pocket of Nav 1.7. Thus, the study confirmed the role of solasodine as a major biomarker for the observed neuroprotective nature of Solanum virginianum.

Bromelain reversed electrolyte imbalance in the chronically constricted sciatic nerve of Wistar rats.

Derangement of electrolyte in the sensory nervous system has been attributed to the development and maintenance of hyperalgesic and allodynic symptoms in painful neuropathy. This study investigated the effect of bromelain on electrolyte imbalance in chronically constricted sciatic nerve of rats (a model of neuropathic pain). Forty Wistar rats, divided into five groups of eight animals each were used for this study. von Frey filaments, tail immersion and acetone spray tests were used to assessed allodynic and thermal hyperalgesic symptoms in the Wistar rats. Sodium ion (Na+), potassium ion (K+), calcium ion (Ca2+) and chloride ion (Cl-) concentrations as well as sodium-potassium and calcium electrogenic pump (Na-K ATPase and Ca ATPase, respectively) activities were estimated using spectrophotometry techniques. Bromelain significantly (p < 0.05) reversed elevation of Na+ and Ca2+ concentration compared with sciatic nerve chronic constriction injury (snCCI) group (35.68 ± 1.71 vs 44.46 ± 1.24 mg/ml/mg protein and 1.06 ± 0.19 vs 6.66 ± 0.03 mg/ml/mg protein, respectively). There were also significant (p < 0.05) increases in the level of K+ (0.84 ± 0.02 vs 0.36 ± 0.05 mg/ml/mg protein) and Cl- (18.51 ± 0.29 vs 15.82 ± 0.21 mg/ml/mg protein). Bromelain reduced the activities of Ca2+ electrogenic pumps significantly compared with snCCI. This study therefore suggests that bromelain mitigated electrolyte imbalance in chronic constricted injury of the sciatic nerve implying that this may be an important mechanism for the anti-nociceptive effect of bromelain.

Late administration of high-frequency electrical stimulation increases nerve regeneration without aggravating neuropathic pain in a nerve crush injury.

BACKGROUND: High-frequency transcutaneous neuromuscular electrical nerve stimulation (TENS) is currently used for the administration of electrical current in denervated muscle to alleviate muscle atrophy and enhance motor function; however, the time window (i.e. either immediate or delayed) for achieving benefit is still undetermined. In this study, we conducted an intervention of sciatic nerve crush injury using high-frequency TENS at different time points to assess the effect of motor and sensory functional recovery. RESULTS: Animals with left sciatic nerve crush injury received TENS treatment starting immediately after injury or 1 week later at a high frequency(100 Hz) or at a low frequency (2 Hz) as a control. In SFI gait analysis, either immediate or late admission of high-frequency electrical stimulation exerted significant improvement compared to either immediate or late administration of low-frequency electrical stimulation. In an assessment of allodynia, immediate high frequency electrical stimulation caused a significantly decreased pain threshold compared to late high-frequency or low-frequency stimulation at immediate or late time points. Immunohistochemistry staining and western blot analysis of S-100 and NF-200 demonstrated that both immediate and late high frequency electrical stimulation showed a similar effect; however the effect was superior to that achieved with low frequency stimulation. Immediate high frequency electrical stimulation resulted in significant expression of TNF-α and synaptophysin in the dorsal root ganglion, somatosensory cortex, and hippocampus compared to late electrical stimulation, and this trend paralleled the observed effect on somatosensory evoked potential. The CatWalk gait analysis also showed that immediate electrical stimulation led to a significantly high regularity index. In primary dorsal root ganglion cells culture, high-frequency electrical stimulation also exerted a significant increase in expression of TNF-α, synaptophysin, and NGF in accordance with the in vivo results. CONCLUSION: Immediate or late transcutaneous high-frequency electrical stimulation exhibited the potential to stimulate the motor nerve regeneration. However, immediate electrical stimulation had a predilection to develop neuropathic pain. A delay in TENS initiation appears to be a reasonable approach for nerve repair and provides the appropriate time profile for its clinical application.

Electroacupuncture Reduces the Effects of Acute Noxious Stimulation on the Electrical Activity of Pain-Related Neurons in the Hippocampus of Control and Neuropathic Pain Rats.

To study the effects of acupuncture analgesia on the hippocampus, we observed the effects of electroacupuncture (EA) and mitogen-activated protein kinase (MEK) inhibitor on pain-excited neurons (PENs) and pain-inhibited neurons (PINs) in the hippocampal area CA1 of sham or chronic constrictive injury (CCI) rats. The animals were randomly divided into a control, a CCI, and a U0126 (MEK1/2 inhibitor) group. In all experiments, we briefly (10-second duration) stimulated the sciatic nerve electrically and recorded the firing rates of PENs and PINs. The results showed that in both sham and CCI rats brief sciatic nerve stimulation significantly increased the electrical activity of PENs and markedly decreased the electrical activity of PINs. These effects were significantly greater in CCI rats compared to sham rats. EA treatment reduced the effects of the noxious stimulus on PENs and PINs in both sham and CCI rats. The effects of EA treatment could be inhibited by U0126 in sham-operated rats. The results suggest that EA reduces effects of acute sciatic nerve stimulation on PENs and PINs in the CA1 region of the hippocampus of both sham and CCI rats and that the ERK (extracellular regulated kinase) signaling pathway is involved in the modulation of EA analgesia.

Transplantation of embryonic motor neurons into peripheral nerve combined with functional electrical stimulation restores functional muscle activity in the rat sciatic nerve transection model.

Reinnervation of denervated muscle by motor neurons transplanted into the peripheral nerve may provide the potential to excite muscles artificially with functional electrical stimulation (FES). Here we investigated whether transplantation of embryonic motor neurons into peripheral nerve combined with FES restored functional muscle activity in adult Fischer 344 rats after transection of the sciatic nerve. One week after sciatic nerve transection, cell culture medium containing (cell transplantation group, n = 6) or lacking (surgical control group, n = 6) dissociated embryonic spinal neurons was injected into the distal stump of the tibial and peroneal nerves. Electrophysiological and tissue analyses were performed in the cell transplantation and surgical control groups 12 weeks after transplantation, as well as a in naïve control group (n = 6) that received no surgery. In the cell transplantation group, ankle angle was measured during gait, with and without FES of the peroneal nerve. Ankle angle at mid-swing was more flexed during gait with FES (26.6 ± 8.7°) than gait without FES (51.4 ± 12.8°, p = 0.011), indicating that transplantated motor neurons in conjunction with FES restored ankle flexion in gait, even though no neural connection between central nervous system and muscle was present. These results indicate that transplantation of embryonic motor neurons into peripheral nerve combined with FES can provide a novel treatment strategy for paralysed muscles. Copyright © 2013 John Wiley & Sons, Ltd.

[Effect of Electroacupuncture Stimulation of Different Tissues at "Huantiao" (GB 30) Acupoint on Expression of Phosphorylated JNK and c-jun in Spinal Cord of Rats with Sciatic Nerve Injury].

OBJECTIVE: To observe the effects of electroacupuncture (EA) stimulation of different tissues (nerve stem, muscular layer) at "Huantiao" (GB 30) acupoint on expression of hosphorylated c-jun N-terminal kinase (p-JNK) and c-jun (p-c-jun) proteins in the lumbar spinal cord in rats with sciatic nerve injury, so as to explore its mechanism underlying improvement of peripheral neuropathic damage. METHODS: Forty-eight SD rats were randomly divided into normal, model (the left sciatic nerve severed), GB 30 deep needling (the acupuncture needle tip was inserted to the sciatic nerve trunk to elicit an instantaneous jerk of the hind limb) and GB 30 shallow needling (the needle tip was inserted to the muscle layer to evoke a local muscular contraction) groups (n = 12 rats in each group). EA stimuli were delivered at 2 Hz/100 Hz, 1 mA, 20 min in duration per treatment for 10 consecutive days. Histopathological changes were observed by Hematoxylin-eosin (HE) staining and immunohistochemical assay was carried out to examine the pathological change of spinal segments (L4-L5) and the expression of p-JNK and p-c-jun proteins, respectively. RESULTS: For rats with the sciatic nerve severed, the spinal neurons became swelling, degeneration or even apoptosis. Acupuncture intervention reduced the number of apoptosic neurons and improved the pathological change, which was relatively better in the.deep needling group than in the shallow needling group. Likewise, the elevated spinal p-JNK and p-c-jun expression levels of the model group were significantly reduced by EA intervention (deep needling vs shallow needling, P < 0.01. CONCLUSION: Acupuncture can improve the spinal pathological changes in rats with sciatic nerve injury, which is probably achieved by decreasing the p-JNK and p-c-jun expression and inhibiting the JNK signaling pathway, and thereby, reducing the apoptosis of the spinal neurons. Deep needling results in greater benefits than shallow needling.

[Effect of deep electroacupuncture stimulation of "Huantiao" (GB 30) on changes of function and nerve growth factor expression of the injured sciatic nerve in rats].

UNLABELLED: OBJECTIVE; To observe the effect of deep electroacupuncture (EA) stimulation of "Huantiao"(GB 30) on the functional and pathological changes and nerve growth factor (NGF) expression of the damaged sciatic nerve in rats, so as to study its mechanisms underlying reliving sciatica. METHODS: Forty-eight SD rats were randomly divided into normal, model, deep EA and shallow EA groups (n = 12 in each group). The sciatic nerve injury model was established by mechanical clamp of the sciatic nerve stem. For deep and shallow EA, the acupuncture needles were inserted into GB 30 about 16 mm and 7 mm, respectively. The EA treatment was given 20 min, once daily for 14 days. The evoked potentials of the injured sciatic nerve stem responding to electrical stimulation were recorded by using a biophysiological experimental system for calculating the motor conduction velocity. Pathological changes of the sciatic nerve were displayed by H. E. stain. The expression of NGF and Fos proteins was detected by immunohistochemistry. RESULTS: In comparison with the normal group, the conduction velocity and the amplitude of the evoked potentials of the sciatic nerve were significantly decreased in the model group (P < 0.05). Following EA, both conduction velocity and amplitude of the evoked potentials in the deep EA group, and the conduction velocity in the shallow EA group were considerably increased (P < 0.05). The therapeutic effects were significantly better in the deep EA group than that in the shallow EA group (P < 0.05). No significant differences were found between the shallow EA and model groups in the amplitude of evoked potentials (P > 0.05), and no significant changes of latencies of the evoked potentials inthe four groups (P > 0.05). In the model group, the disorganized nerve fibers axons, myelin and Schwann cells of the damaged sciatic nerve were found, which became milder in the EA groups particularly in the deep EA group. In regard to the NGF and Fos immunoactivity of the injured sciatic nerve, the expression levels of both NGF and Fos proteins were obviously higher in the model group than in the normal group (P < 0.05). After EA stimulation, NGF expression was further significantly up-regulated in both deep and shallow EA groups (P < 0.05), and Fos protein expression was notably down-regulated in the deep and shallow EA groups (P < 0.05). The expression of NGF was significantly higher and Fos protein was obviously lower in the deep EA group than in the shallow EA group (P < 0.05). CONCLUSION: Deep EA stimulation of GB 30 can improve the pathological changes and function of the injured sciatic nerve in the rat, which is closely associated with its effects in up-regulating NGF expression and down-regulating Fos expression. The deep EA is relatively better in the therapeutic effect. These facts may be one of the mechanisms of EA in relieving sciatica in clinic practice.

The cannabinoid CB2 receptor-selective phytocannabinoid beta-caryophyllene exerts analgesic effects in mouse models of inflammatory and neuropathic pain.

The widespread plant volatile beta-caryophyllene (BCP) was recently identified as a natural selective agonist of the peripherally expressed cannabinoid receptor 2 (CB2). It is found in relatively high concentrations in many spices and food plants. A number of studies have shown that CB2 is critically involved in the modulation of inflammatory and neuropathic pain responses. In this study, we have investigated the analgesic effects of BCP in animal models of inflammatory and neuropathic pain. We demonstrate that orally administered BCP reduced inflammatory (late phase) pain responses in the formalin test in a CB2 receptor-dependent manner, while it had no effect on acute (early phase) responses. In a neuropathic pain model the chronic oral administration of BCP attenuated thermal hyperalgesia and mechanical allodynia, and reduced spinal neuroinflammation. Importantly, we found no signs of tolerance to the anti-hyperalgesic effects of BCP after prolonged treatment. Oral BCP was more effective than the subcutaneously injected synthetic CB2 agonist JWH-133. Thus, the natural plant product BCP may be highly effective in the treatment of long lasting, debilitating pain states. Our results have important implications for the role of dietary factors in the development and modulation of chronic pain conditions.

[Analgesic effect of ferulic acid on CCI mice: behavior and neurobiological analysis].

To study the analgesic effect of chronic administration with ferulic acid, and preliminarily discuss its mechanism. Thermal hyperalgesia and mechanical allodynia tests were conducted to observe the analgesic effect of chronic administration with ferulic acid on CCI mice. The neurochemical detection method was applied to observe the effect chronic administration with ferulic acid on monoamine neurotransmitter and monoamine oxidase activity. Compared with the normal group, CCI mice showed notable reduction in heat sensation and nociceptive threshold in and mechanical allodynia. Ferulic acid (10, 20, 40 and 80 mg x kg(-1), po) could significantly reverse the situations. In an in-depth study, we found that the reason for these results was that ferulic acid was dose-dependent in increasing 5-HT and NE levels in hippocampus, frontal cortex and amygdale and could inhibit MAO-A activity in mouse brains. These results showed that ferulic acid has the analgesic effect. Its mechanism may be related to the inhibition of monoamine oxidase activity and the increase in monoamine neurotransmitter in mouse brains.

Curcumin exerts antinociceptive effects in a mouse model of neuropathic pain: descending monoamine system and opioid receptors are differentially involved.

Curcumin, a phenolic compound present in Curcuma longa, has been reported to exert antinociceptive effects in some animal models, but the mechanisms remain to be elucidated. This work aimed to investigate the antinociceptive action of curcumin on neuropathic pain and the underlying mechanism(s). Chronic constriction injury (CCI), a canonical animal model of neuropathic pain, was produced by loosely ligating the sciatic nerve in mice and von Frey hair or hot plate test was used to assess mechanical allodynia or thermal hyperalgesia (to heat), respectively. Chronic, but not acute, curcumin treatment (5, 15 or 45 mg/kg, p.o., twice per day for three weeks) alleviated mechanical allodynia and thermal hyperalgesia in CCI mice, accompanied by increasing spinal monoamine (or metabolite) contents. Chemical ablation of descending noradrenaline (NA) by 6-hydroxydopamine (6-OHDA), or depletion of descending serotonin by p-chlorophenylalanine (PCPA), abolished curcumin's antinociceptive effect on mechanical allodynia or thermal hyperalgesia, respectively. The anti-allodynic action of curcumin on mechanical stimuli was totally blocked by chronic co-treatment with the ß(2)-adrenoceptor antagonist ICI 118,551, or by acute co-treatment with the delta-opioid receptor antagonist naltrindole. Meanwhile, co-treatment with the 5-HT(1A) receptor antagonist WAY-100635 chronically, or with the irreversible mu-opioid receptor antangonist ß-funaltrexamine acutely, completely abrogated the anti-hyperalgesic action of curcumin on thermal stimuli. Collectively, these findings indicate that the descending monoamine system (coupled with spinal ß(2)-adrenoceptor and 5-HT(1A) receptor) is critical for the modality-specific antinociceptive effect of curcumin in neuropathic pain. Delta- and mu-opioid receptors are likely rendered as downstream targets, accordingly. This article is part of a Special Issue entitled 'Post-Traumatic Stress Disorder'.

Intrathecal ultra-low dose naloxone enhances the antinociceptive effect of morphine by enhancing the reuptake of excitatory amino acids from the synaptic cleft in the spinal cord of partial sciatic nerve-transected rats.

BACKGROUND: In this study, we examined the effects of ultra-low dose naloxone on the antinociceptive effect of morphine and on spinal cord dorsal horn glutamate transporter expression in rats with neuropathic pain. METHODS: Neuropathic pain was induced in male Wistar rats by partial transection of the left sciatic nerve and an intrathecal catheter was implanted for drug administration; in some rats, an intrathecal microdialysis probe for cerebrospinal fluid (CSF) dialysate collection was also implanted. Nociception was assessed using the plantar test, a Hargreaves radiant heat apparatus, and by the von Frey test, using a dynamic plantar anesthesiometer. Glutamate transporter protein expression in the left spinal cord dorsal horn was examined by Western blotting and immunohistochemistry. Levels of the excitatory amino acids (EAAs) glutamate and aspartate in the CSF dialysate were measured using high-performance liquid chromatography. RESULTS: Reduced astrocyte expression of glutamate transporters (GLT-1 and GLAST levels were 55% and 53%, respectively, of that in sham-operated rats) in laminae I and II of the spinal cord dorsal horn ipsilateral to the partial sciatic nerve transection (PST), and hyperalgesia and allodynia in the PST hindlimb were observed. High-dose naloxone (15 µg) attenuated the antihyperalgesia and antiallodynia effects of the morphine (10 µg). In contrast, ultra-low dose (15 ng) naloxone enhanced the antinociceptive effect of morphine (10 µg), with an increase in the paw withdrawal threshold to thermal stimulus (from 19% to 35%) and to tactile stimulus (from 33% to 55%) compared with morphine treatment alone, and this was associated with restoration of GLAST and GLT-1 expression to control levels (102% and 114%, respectively) in the astrocytes of laminae I and II in the spinal cord dorsal horn ipsilateral to the PST hindlimb and a decrease in EAA levels in the CSF dialysate (glutamate: 10.0 µM; aspartate: 1.1 µM). CONCLUSIONS: Ultra-low dose naloxone enhanced the antinociceptive effect of morphine in PST rats, possibly by restoration of GLAST and GLT-1 expression in astrocytes, which inhibited the accumulation of EAAs in the synapses, resulting in a neuroprotective effect.

Attenuating effect of Acorus calamus extract in chronic constriction injury induced neuropathic pain in rats: an evidence of anti-oxidative, anti-inflammatory, neuroprotective and calcium inhibitory effects.

BACKGROUND: Acorus calamus (family: Araceae), is an indigenous plant, traditionally it is used as an ingredient of various cocktail preparations and for the management of severe inflammatory disorders in Indian system of medicine. Present study investigated the attenuating role of Acorus calamus plant extract in chronic constriction injury (CCI) of sciatic nerve induced peripheral neuropathy in rats. METHODS: Hot plate, plantar, Randall Selitto, Von Frey Hair, pin prick, acetone drop, photoactometer and rota-rod tests were performed to assess degree of thermal, radiant, mechanical, chemical sensation, spontaneous motor activity and motor co-ordination changes respectively, at different time intervals i.e., day 0, 1, 3, 6, 9, 12, 15, 18 and 21. Tissue myeloperoxidase, superoxide anion and total calcium levels were determined after 21st day to assess biochemical alterations. Histopathological evaluations were also performed. Hydroalcoholic extract of Acorus calamus (HAE-AC, 100 and 200 mg/kg, p.o.) and pregabalin (10 mg/kg, p.o.) were administered from the day of surgery for 14 days. RESULTS: CCI of sciatic nerve significantly induced thermal, radiant, mechanical hyperalgesia and thermal, chemical, tactile allodynia, along with increase in the levels of superoxide anion, total calcium and myeloperoxidase activity. Moreover significant histological changes were also observed. HAE-AC attenuated CCI induced development of painful behavioural, biochemical and histological changes in a dose dependent manner similar to that of pregabalin serving as positive control. CONCLUSIONS: Acorus calamus prevented CCI induced neuropathy which may be attributed to its multiple actions including anti-oxidative, anti-inflammatory, neuroprotective and calcium inhibitory actions.

Short-term low-frequency electrical stimulation enhanced remyelination of injured peripheral nerves by inducing the promyelination effect of brain-derived neurotrophic factor on Schwann cell polarization.

Electrical stimulation (ES) has been found to aid repair of nerve injuries and have been shown to increase and direct neurite outgrowth during stimulation. However, the effect of ES on peripheral remyelination after nerve damage has been investigated less well, and the mechanism underlying its action remains unclear. In the present study, the crush-injured sciatic nerves in rats were subjected to 1 hr of continuous ES (20 Hz, 100 microsec, 3 V). Electron microscopy and nerve morphometry were performed to investigate the extent of regenerated nerve myelination. The expression profiles of P0, Par-3, and brain-derived neurotrophic factor (BDNF) in the injuried sciatic nerves and in the dorsal root ganglion neuron/Schwann cell cocultures were examined by Western blotting. Par-3 localization in the sciatic nerves was determined by immunohistochemistry to demonstrate Schwann cell polarization during myelination. We reported that 20-Hz ES increased the number of myelinated fibers and the thickness myelin sheath at 4 and 8 weeks postinjury. P0 level in the ES-treated groups, both in vitro and in vivo, was enhanced compared with the controls. The earlier peak of Par-3 in the ES-treated groups indicated an earlier initiation of Schwann cell myelination. Additionally, ES significantly elevated BDNF expression in nerve tissues and in cocultures. ES on the site of nerve injury potentiates axonal regrowth and myelin maturation during peripheral nerve regeneration. Furthermore, the therapeutic actions of ES on myelination are mediated via enhanced BDNF signals, which drive the promyelination effect on Schwann cells at the onset of myelination.