Analgesic Effect Of Electroacupuncture Research Articles

TRPM8's Role in the Shift Between Opioid and Cannabinoid Pathways in Electroacupuncture for Inflammatory Pain in Mice.

The TRPM8 channel, a temperature-sensitive ion channel, plays a crucial role in various physiological processes, particularly in the modulation of inflammation and nociception. Although electroacupuncture (EA) is a recognized analgesic treatment for pain conditions, its interaction with TRPM8 remains underexplored. This study aims to determine TRPM8's role in EA-induced analgesia using a murine model of inflammatory pain. Mechanical allodynia, evidenced by a reduced paw withdrawal threshold (PWT), was induced in both wild-type and Trpm8-/- mice through CFA injection. EA applied at the GB34 and LR3 acupoints significantly alleviated mechanical allodynia in both groups. In wild-type mice, the analgesic effects of EA were partially reversed by naloxone (an opioid receptor antagonist) or AM251 (a CB1 receptor antagonist) and fully reversed by their combination. In contrast, only AM251 reversed EA-induced analgesia in Trpm8-/- or TRPM8-inhibited wild-type mice (via AMTB treatment, a TRPM8 antagonist), indicating no involvement of the opioid pathway. Additionally, the combination of menthol, a partial TRPM8 agonist, and EA enhanced analgesia in wild-type mice. In Trpm8-/- or AMTB-pretreated mice, the CB1 receptor agonist WIN 55,212-2 (WIN) exhibited stronger analgesic effects compared to wild-type controls. These findings suggest that EA at LR3 and GB34 mediates analgesia through both opioid and endocannabinoid pathways. TRPM8 is critical for EA to activate the opioid pathway, while its inhibition or deletion shifts the analgesic mechanism towards reliance on the cannabinoid system. Understanding this mechanistic shift may help optimize EA treatment strategies and improve pain management outcomes.

Effects of Electroacupuncture at Varied Frequencies on Analgesia and Mechanisms in Sciatic Nerve Cuffing-Induced Neuropathic Pain Mice

Addressing the intricate challenge of chronic neuropathic pain has significant implications for the physical and psychological well-being of patients, given its enduring nature. In contrast to opioids, electroacupuncture (EA) may potentially provide a safer and more efficacious therapeutic alternative. Our objective is to investigate the distinct analgesic effects and potential mechanisms of EA at frequencies of 2 Hz, 100 Hz, and 18 kHz in order to establish more precise frequency selection criteria for clinical interventions. Analgesic efficacy was evaluated through the measurement of mice’s mechanical and thermal pain thresholds. Spinal cord inflammatory cytokines and neuropeptides were quantified via Quantitative Real-time PCR (qRT-PCR), Western blot, and immunofluorescence. Additionally, RNA sequencing (RNA-Seq) was conducted on the spinal cord from mice in the 18 kHz EA group for comprehensive transcriptomic analysis. The analgesic effect of EA on neuropathic pain in mice was frequency-dependent. Stimulation at 18 kHz provided superior and prolonged relief compared to 2 Hz and 100 Hz. Our research suggests that EA at frequencies of 2 Hz, 100 Hz, and 18 kHz significantly reduce the release of inflammatory cytokines. The analgesic effects of 2 Hz and 100 Hz stimulation are due to frequency-dependent regulation of opioid release in the spinal cord. Furthermore, 18 kHz stimulation has been shown to reduce spinal neuronal excitability by modulating the serotonergic pathway and downstream receptors in the spinal cord to alleviate neuropathic pain.

Analgesic effect of electroacupuncture on pain in Parkinson's disease and mechanism based on rs-fMRI

Analgesic effect of electroacupuncture on pain in Parkinson's disease and mechanism based on rs-fMRI

Electroacupuncture Reduces Fibromyalgia Pain via Neuronal/Microglial Inactivation and Toll-like Receptor 4 in the Mouse Brain: Precise Interpretation of Chemogenetics.

Fibromyalgia (FM) is a complex, chronic, widespread pain syndrome that can cause significant health and economic burden. Emerging evidence has shown that neuroinflammation is an underlying pathological mechanism in FM. Toll-like receptors (TLRs) are key mediators of the immune system. TLR4 is expressed primarily in microglia and regulates downstream signaling pathways, such as MyD88/NF-κB and TRIF/IRF3. It remains unknown whether electroacupuncture (EA) has therapeutic benefit in attenuating FM pain and what role the TLR4 pathway may play in this effect. We compared EA with sham EA to eliminate the placebo effect due to acupuncture. We demonstrated that intermittent cold stress significantly induced an increase in mechanical and thermal FM pain in mice (mechanical: 2.48 ± 0.53 g; thermal: 5.64 ± 0.32 s). EA but not sham EA has an analgesic effect on FM mice. TLR4 and inflammatory mediator-related molecules were increased in the thalamus, medial prefrontal cortex, somatosensory cortex (SSC), and amygdala of FM mice, indicating neuroinflammation and microglial activation. These molecules were reduced by EA but not sham EA. Furthermore, a new chemogenetics method was used to precisely inhibit SSC activity that displayed an anti-nociceptive effect through the TLR4 pathway. Our results imply that the analgesic effect of EA is associated with TLR4 downregulation. We provide novel evidence that EA modulates the TLR4 signaling pathway, revealing potential therapeutic targets for FM pain.

Electroacupuncture Stimulation Alleviates Inflammatory Pain in Male Rats by Suppressing Oxidative Stress.

In the present study, we focused on whether the analgesic effect of Electroacupuncture (EA) is related to the regulation of oxidative stress. We established a chronic inflammatory pain model in male rats by a single injection of complete Freund's adjuvant (CFA) and then treated the animals with daily EA stimulation at the site of "zusanli". The analgesic effect of EA was evaluated by measuring the paw withdrawal threshold (PWT) when rats received mechanical and thermal pain stimulation. The levels of inflammation-related molecules and oxidative stress-related markers in the spinal cord were measured by western blotting or ELISA kits. EA stimulation and antioxidants effectively increased the PWT in CFA rats. Co-treatment of CFA rats with the ROS donor t-butyl hydroperoxide (t-BOOH) further decreased the PWT and weakened the analgesic effect of EA. EA treatment inhibited inflammation and oxidative stress, as shown by decreased levels of tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), IL-6, and MDA and increased activity of SOD and catalase. Moreover, EA reduced the expression of p-p38, p-ERK, and p-p65 and simultaneously downregulated the expression of TRPV1 and TRPV4 in CFA rats. In an in vitro study, direct stimulation with t-BOOH to the C6 cells increased the production of TNF-alpha, IL-1beta, IL-6, activated p38, ERK, and p65 and up-regulated the expression of TRPV1 and TRPV4, and these effects could be prevented by the ROS scavenger PBN. Taken together, our data indicate that the inhibition of oxidative stress and the generation of ROS contribute to the analgesic effect of EA in male CFA rats.

Effect of Catastrophic Thinking on the Analgesic Effect of Electroacupuncture.

Patients with chronic pain and high-level catastrophic thoughts often do not respond to acupuncture. This may be related to hypofunctioning of the dorsolateral prefrontal cortex and the descending pain inhibitory system. Therefore, we examined the relationship between the level of catastrophic thinking and the analgesic effect of electroacupuncture using the pain catastrophizing scale (PCS). We also evaluated the descending pain inhibitory system using conditioned pain modulation (CPM) and offset analgesia (OA). The relationship between catastrophic thinking and the descending pain inhibitory system was also examined. After testing the hospital anxiety and depression scale and the PCS in 14 healthy adults, the current pain threshold (CPT), CPM, and OA were measured, in order, before the intervention. Thereafter, electroacupuncture was applied to 3 limbs (the dominant hand and both lower extremities) at 4 Hz, and to the scalp at 100 Hz, for 30 minutes, and the CPT was measured again immediately after the intervention. The difference in the CPT before and after the intervention was taken as the analgesic effect. The participants were divided into 2 groups, the H-PCS group (≥16 points) and the L-PCS group (≤15 points), according to the PCS score, and the analgesic effects of electroacupuncture were significantly different (P = 0.04). However, no relationship was found between the PCS score and the CPM (r = -0.02, P = 0.94) and OA effects (r = -0.19, P = 0.49). It was suggested that people with high-level catastrophic thinking may find it difficult to obtain the analgesic effects of electroacupuncture.

Electroacupuncture alleviates postoperative pain through inhibiting neuroinflammation via stimulator of interferon genes/type-1 interferon pathway

ObjectiveThis work explores the impact of electroacupuncture (EA) on acute postoperative pain (APP) and the role of stimulator of interferon genes/type-1 interferon (STING/IFN-1) signaling pathway modulation in the analgesic effect of EA in APP rats. MethodsThe APP rat model was initiated through abdominal surgery and the animals received two 30 min sessions of EA at bilateral ST36 (Zusanli) and SP6 (Sanyinjiao) acupoints. Mechanical, thermal and cold sensitivity tests were performed to measure the pain threshold, and electroencephalograms were recorded in the primary somatosensory cortex to identify the effects of EA treatment on APP. Western blotting and immunofluorescence were used to examine the expression and distribution of proteins in the STING/IFN-1 pathway as well as neuroinflammation. A STING inhibitor (C-176) was administered intrathecally to verify its role in EA. ResultsAPP rats displayed mechanical and thermal hypersensitivities compared to the control group (P < 0.05). APP significantly reduced the amplitude of θ, α and γ oscillations compared to their baseline values (P < 0.05). Interestingly, expression levels of proteins in the STING/IFN-1 pathway were downregulated after inducing APP (P < 0.05). Further, APP increased pro-inflammatory factors, including interleukin-6, tumor necrosis factor-α and inducible nitric oxide synthase, and downregulated anti-inflammatory factors, including interleukin-10 and arginase-1 (P < 0.05). EA effectively attenuated APP-induced painful hypersensitivities (P < 0.05) and restored the θ, α and γ power in APP rats (P < 0.05). Meanwhile, EA distinctly activated the STING/IFN-1 pathway and mitigated the neuroinflammatory response (P < 0.05). Furthermore, STING/IFN-1 was predominantly expressed in isolectin-B4- or calcitonin-gene-related-peptide-labeled dorsal root ganglion neurons and superficial laminae of the spinal dorsal horn. Inhibition of the STING/IFN-1 pathway by intrathecal injection of C-176 weakened the analgesic and anti-inflammatory effects of EA on APP (P < 0.05). ConclusionEA can generate robust analgesic and anti-inflammatory effects on APP, and these effects may be linked to activating the STING/IFN-1 pathway, suggesting that STING/IFN-1 may be a target for relieving APP.Please cite this article as: Ding YY, Xu F, Wang YF, Han LL, Huang SQ, Zhao S, Ma LL, Zhang TH, Zhao WJ, Chen XD. Electroacupuncture alleviates postoperative pain through inhibiting neuroinflammation via stimulator of interferon genes/type-1 interferon pathway. J Integr Med. 2023; 21(5): 496–508.

Electroacupuncture Attenuates Fibromyalgia Pain via Toll-like Receptor 4 in the Mouse Brain.

Fibromyalgia (FM) is characterized by complex pain symptoms lacking impersonal considerations in diagnosis and treatment evaluation, which often happens in women. Chronic and persistent widespread pain is the key symptom disturbing patients with FM, leading to depression, obesity, and sleep disturbances. Toll-like receptor 4 (TLR4) activation produces a harmful sensory input involved in central pain; this is the focus of this study. Electroacupuncture (EA) has beneficial effects in reducing FM pain, but its connection with TLR4 signaling is still unknown. Intermittent cold stress significantly induced mechanical and thermal pain. EA, but not sham EA, reliably attenuated mechanical and thermal hyperalgesia. The increased inflammatory mediators in FM mice were reduced in the EA group, but not in the sham group. All TLR4 and related molecule levels increased in the FM mice's hypothalamus, periaqueductal gray (PAG), and cerebellum. These increases could be attenuated by EA but not sham stimulation. Activation of TLR4 by lipopolysaccharide (LPS) significantly induced FM and can be further reversed by a TLR4 antagonist. These mechanisms provide evidence that the analgesic effect of EA is related to the TLR4 pathway. In addition, we showed that inflammation can activate the TLR4 pathway and provided new possible therapeutic targets for FM pain.

Electroacupuncture Induces Bilateral S1 and ACC Epigenetic Regulation of Genes in a Mouse Model of Neuropathic Pain

Clinical and animal studies have shown that acupuncture may benefit controlling neuropathic pain. However, the underlying molecular mechanisms are poorly understood. In a well-established mouse unilateral tibial nerve injury (TNI) model, we confirmed the efficacy of electroacupuncture (EA) in reducing mechanical allodynia and measured methylation and hydroxy-methylation levels in the primary somatosensory cortex (S1) and anterior cingulate cortex (ACC), two cortical regions critically involved in pain processing. TNI resulted in increased DNA methylation of both the contra- and ipsilateral S1, while EA only reduced contralateral S1 methylation. RNA sequencing of the S1 and ACC identified differentially expressed genes related to energy metabolism, inflammation, synapse function, and neural plasticity and repair. One week of daily EA decreased or increased the majority of up- or downregulated genes, respectively, in both cortical regions. Validations of two greatly regulated genes with immunofluorescent staining revealed an increased expression of gephyrin in the ipsilateral S1 after TNI was decreased by EA; while TNI-induced increases in Tomm20, a biomarker of mitochondria, in the contralateral ACC were further enhanced after EA. We concluded that neuropathic pain is associated with differential epigenetic regulations of gene expression in the ACC and S1 and that the analgesic effect of EA may involve regulating cortical gene expression.

Intervention mechanism of electroacupuncture on the EP1-TRPV1 pathway in the dorsal root ganglion of rats in the transition from acute to chronic pain

Intervention mechanism of electroacupuncture on the EP1-TRPV1 pathway in the dorsal root ganglion of rats in the transition from acute to chronic pain

Effect of electroacupuncture on inflammatory signal expression in local tissues of rats with chronic pelvic pain syndrome based on purinergic 2X7 receptor/NOD-like receptor pyrin domain-containing 3 signal pathway.

To study the expression of inflammatory signal in local prostate tissue of chronic pelvic pain syndrome (CPPS) rats by electroacupuncture (EA) of Guanyuan (CV4), Zhongji (CV3), Huiyang (BL35) and Sanyinjiao (SP6), and to explore the possible mechanism of anti-inflammatory and analgesic effects of EA. METHODS：A total of 36 Sprague-Dawley male rats were randomly divided into three groups: control, model and EA (n=12 rats/group). The CPPS model was made by injection of CFA into ventral lobes of the prostate (0.1 mL). Electric acupuncture apparatus was applied to stimulate Guanyuan (CV4), Zhongji (CV3), bilateral Huiyang (BL35) and Sanyinjiao (SP6) acupoints in EA group. The general condition of rats was observed and the prostate index (PI) was calculated. The thermal pain threshold was collected after each therapeutic course. Histopathological changes of the prostate tissue were examined by hematoxylin-eosin staining method. The expression levels of tumor necrosis factor α (TNF-α), interleukin-1β (IL-1β) and prostaglandin E2 (PGE2) in prostatic homogenates were measured by enzyme linked immunosorbent assay (ELISA). Moreover, the expression levels of purinergic 2X7 receptor (P2X7R), NOD-like receptor pyrin domain-containing 3 (NLRP3), caspase-1 and interleukin-18 (IL-18) mRNA were quantified by quantitative real-time polymerase chain reaction. Compared with control group, the PI of rats increased, and the thermal pain threshold decreased significantly in model group. The morphological structure of prostate tissues of rats in model group was severely damaged with a large number of inflammatory cells infiltration. Additionally, the levels of TNF-α, IL-1β and PGE2 were higher, and the expressions of P2X7R, NLRP3, caspase-1 and IL-18 mRNA were higher than those in control group. After EA treatment, the PI was significantly decreased, the thermal pain threshold was significantly increased, and the tissue damage was significantly improved. The expressions of inflammatory cytokines were lower in EA group, and expression of P2X7R/NLRP3 pathway was down-regulated. The effect of EA at Guanyuan (CV4), Zhongji (CV3), Huiyang (BL35) and Sanyinjiao (SP6) can improve inflammation and pain symptoms of CPPS rats induced by Complete Freund's adjuvant (CFA). This suggests that EA at Guanyuan (CV4), Zhongji (CV3), Huiyang (BL35) and Sanyinjiao (SP6) can produce anti-inflammatory analgesia effect by preventing the activation of P2X7R/NLRP3 signal pathway, inhibit the release of inflammatory cytokines in CPPS rats, which may provide a putative novel target for the treatment of CPPS.

Electroacupuncture alleviates neuropathic pain caused by spared nerve injury by promoting AMPK/mTOR-mediated autophagy in dorsal root ganglion macrophage.

Dorsal root ganglia (DRG) plays an important role in mediating the peripheral sensation transduction through the primary afferent neurons in pain research. Neuropathic pain (NP) is a syndrome of hyperalgesia, spontaneous pain and allodynia caused by central or peripheral nerve injury. Recent trends of study are turning towards the development of therapies for the management of NP. Activation of autophagy in glial cells in the spinal cord has been reported to be associated with attenuation of NP, but the autophagic process in DRG is rarely studied. The analgesic effect of electroacupuncture (EA) was evaluated in NP-induced rats developed using spared nerve injury (SNI). Acupuncture or EA was performed after 7 days of SNI at Zusanli (ST36) and Huantiao (GB30) acupoints. Then, the activation status of autophagy process in DRGs of rats treated with SNI and EA were investigated, and the possible mechanism of the analgesic effect of EA were explored. Application of EA has been found to reduce mechanical hyperalgesia. Autophagy indicator p62 was colocalized with the marker proteins for macrophages (CD11b), but not with NeuN (marker protein for neurons) or GFAP (marker protein for satellite glial cells), as shown by immunofluorescence. Western blots results indicate that the expression levels of p62, Beclin-1 and LC3-II in the L4-L6 DRG of rats in the SNI group were increased, compared with that in the control group. EA treatment resulted in decreased expression of p62 and increased expression of Beclin-1 and LC3-II/LC3-I. Furthermore, we explored the causal relationship between EA-induced suppression of NP and increased levels of autophagy in DRG using electron microscopy and the AMPK (AMP-activated protein kinase) inhibitor compound C. SNI achieved a significant upregulation of autophagy levels in DRG macrophages. Furthermore, EA attenuated NP, which may contribute to the promotion of AMPK/mTOR (mammalian target of rapamycin)-mediated autophagy in DRG macrophages. Therefore, this strategy provides a new target for therapeutic intervention of NP.

Electroacupuncture attenuates spared nerve injury-induced neuropathic pain possibly by promoting the progression of AMPK/mTOR-mediated autophagy in spinal microglia

Neuropathic pain (NP) is a syndrome that arises from central or peripheral nerve injury, which manifests primarily as hyperalgesia, spontaneous pain, and allodynia. The recent trend has exhibited a shift towards the development of therapies for managing NP. Activation of autophagy is involved in the function of the glial cells, which may be implicated further to attenuate pain. In this study, the analgesic effects of electroacupuncture (EA) were evaluated among NP rats developed using spared nerve injury (SNI). Acupuncture treatment or EA was carried out after 7 days of SNI at two acupoints, i.e., the Zusanli (ST36) and Huantiao (GB30). The application of EA was found to attenuate mechanical hyperalgesia. The marker protein for microglial cells (CD11b) alone, without either the astrocyte marker or neuronal marker, was co-expressed with the autophagy indicator p62, as illustrated with immunofluorescence staining. Western blotting demonstrated that the expression levels of p62, Beclin-1, and LC3-II/LC3-I were elevated in the spinal cords of rats in the SNI group compared to the control levels. EA treatment resulted in reduced expression of p62, while the expressions of Beclin-1 and LC3-II/LC3-I were increased. The electron microscopy results indicated that EA could induce autophagy progression in the microglia of the spinal dorsal horn in SNI rats. Furthermore, we explored the causal relationship between EA-induced inhibition of NP and increased autophagic levels in microglia using the AMPK inhibitor compound C, and found that the mechanism of EA-induced analgesia may contribute to the promotion of AMPK/mTOR-mediated autophagy in spinal microglia. Our work showed that the analgesic impact of EA is partly related to AMPK/mTOR pathway activation and autophagy induction in microglial cells, providing a potential therapeutic target for NP.

Electroacupuncture relieves hyperalgesia by regulating neuronal-glial interaction and glutamate transporters of spinal dorsal horns in rats with acute incisional neck pain.

Glial cells are involved in the analgesic effect of electroacupuncture (EA) in rats with chronic neurological pain. The objective of this study was to observe the role of neuronal-glial interaction and glutamate (Glu) transporters in EA-induced acute neck pain relief in rats. Male rats were placed into the following five groups: control, model, EA Futu (LI18), EA Hegu (LI4)-Neiguan (PC6), and EA Zusanli (ST36)-Yanglingquan (GB34). The incisional neck pain model was established by making a longitudinal incision along the midline of the neck. The thermal pain threshold (TPT) was measured using a radiation heat detector. The immunoactivities of glial fibrillary acidic protein (GFAP), ionized calcium-binding adapter molecule 1 (Iba-1), neurokinin-1 receptor (NK-1R), Glu aspartate transporter (GLAST), and Glu transporter-1 (GLT-1) in the dorsal horns (DHs) of the cervico-spinal cord (C2-C5) were detected using immunofluorescence histochemistry. The expression levels of GFAP, Iba-1, GLAST, and GLT-1 mRNAs were determined using quantitative real-time polymerase chain reaction (PCR). The TPT and levels of mRNAs expression and immunoactivity of GLT-1 and GLAST were significantly decreased, and those of Iba-1 and GFAP were significantly increased in the model group than those of the control group (P < 0.05). The activated microgliacytes were gathered around the NK-1R positive neurons, and co-expression of NK-1R and astrocytes was observed in the model group. EA LI18 significantly increased the TPT and expression of GLAST and GLT-1 mRNAs (P < 0.05) and notably decreased the number of Iba-1 positive cells and Iba-l mRNA expression (P < 0.05), whereas GLAST and GLT-1 antagonists inhibited the analgesic effect of EA LI18. However, these effects, except for the downregulation of Iba-1 mRNA, were not observed in the EA ST36-GB34 group. Fewer NK-1R-positive neurons were visible in the spinal DHs in the EA LI18 group, and the co-expression of NK-1R and astrocytes was also lower than that in the three EA groups. Electroacupuncture of LI18 had an analgesic effect in rats with neck incisions, which may be related to its functions in suppressing the neuronal-glial cell interaction through NK-1R and upregulating the expression of GLAST and GLT-1 in the spinal DHs.

Electroacupuncture Suppresses CCI-Induced Neuropathic Pain through GABAA Receptors.

Neuropathic pain remains a chronic and intractable pain. Recent studies have shown a close relationship between gamma-aminobutyric acid A (GABAA) receptor and neuropathic pain. Spinal cord GABAA receptors are key modulators of pain processing. Electroacupuncture (EA) is currently used worldwide to relieve pain. The immunomodulatory effect of EA in animals has been proposed in previous studies. However, it remains unclear how EA contributes to alleviating neuropathic pain. In this study, the chronic constriction injury (CCI) rat model was used to explore the relationship between GABAA receptor and neuropathic pain. We also investigated whether EA treatment could ameliorate pain hypersensitivity by modulating the GABAA receptor. To determine the function of EA in neurological diseases, in this study, the mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) were assessed to determine the threshold of pain. In addition, we used Western blot, immunofluorescence, and real-time quantitative PCR to confirm whether EA treatment relieves pain hypersensitivity by regulating GABAA receptors. The morphology of synapse was examined using an electron microscope. In the present study, EA relieved mechanical allodynia and thermal hyperalgesia. EA also inhibited microglial activation in the spinal cord, accompanied by increased levels of GABAARα2, GABAARα3, and GABAARγ2 subunits. However, the analgesic effect of EA was attenuated by treatment with the GABAA receptor antagonist bicuculine. Overall, the present results indicate that microglia and GABAA receptor might participate in EA analgesia. These results contribute to our understanding of the impact of EA on rats after sciatic nerve compression, providing a theoretical basis for the clinical application of EA analgesia.

Analgesic effect and mechanism of electroacupuncture on SNI rats based on microglia-BDNF-neuron signal

To observe the effect of electroacupuncture (EA) at "Huantiao" (GB 30) and "Weizhong" (BL 40) on the activation of glial cells, the expression of brain-derived neurotrophic factor (BDNF), excitability and the number of dendritic spines of neurons in the spinal dorsal horn in rats with spared nerve injury (SNI) of sciatic nerve, and to explore the analgesic mechanism of EA on SNI. PartⅠ: Sixty SD rats were randomly divided into a sham operation group, a model group, an EA group and a sham EA group, 15 rats in each group. Except the sham operation group, the SNI rat model was established in the remaining groups. The rats in the sham operation group were only treated with incision without damaging the nerve. The rats in the EA group were treated with EA at "Huantiao" (GB 30) and "Weizhong" (BL 40) on the affected side, continuous wave, frequency of 2 Hz, current intensity of 1 mA, 30 minutes each time, once a day, for 14 days. The rats in the sham EA group were treated with EA at points 0.5 cm next to "Huantiao" (GB 30) and "Weizhong" (BL 40) on the affected side; the manipulation, EA parameters and treatment course were the same as the EA group. The latency of thermal foot contraction reflex and the threshold of mechanical foot contraction reflex were detected 1 day before modeling and 3, 7 and 14 days after modeling. Fourteen days after modeling, Western blot was used to detect the protein expressions of ionized binding adapter junction protein 1 (Iba-1), glial fibrillary acidic protein (GFAP), BDNF and c-Fos in the spinal dorsal horn; the expressions of Iba-1 and c-Fos proteins in the spinal dorsal horn were detected by immunofluorescence staining; immunohistochemical method was used to detect the expression of GFAP protein in the spinal dorsal horn; Golgi staining was used to detect the number of dendritic spines in spinal dorsal horn neurons. PartⅡ: Thirty SD rats were randomly divided into a control group, a BDNF group and a BDNF+anti-TrkB group, 10 rats in each group. The control group was treated with intrathecal injection of 10 μL mixture with 1︰1 of 0.9% sodium chloride solution and dimethyl sulfoxide (DMSO); the BDNF group was treated with intrathecal injection of 10 μg rat recombinant BDNF dissolved in 10 μL mixture with 1︰1 of 0.9% sodium chloride solution and DMSO; the BDNF+anti-TrkB group was treated with intrathecal injection of 10 μg rat recombinant BDNF and 30 μg tyrosine kinase receptor B (TrkB) antibody dissolved in 10 μL mixture with 1︰1 of 0.9% sodium chloride solution and DMSO. The threshold of mechanical foot retraction reflex was detected 1 day before intrathecal injection and 1, 3 and 7 days after injection. Seven days after injection, the expression of c-Fos protein in the spinal dorsal horn was detected by Western blot and immunofluorescence staining. PartⅠ: Compared with the sham operation group, 3, 7 and 14 days after modeling, the latency of thermal foot contraction reflex and the threshold of mechanical foot contraction reflex in the model group were decreased (P<0.05); 7 and 14 days after modeling, compared with the model group, the latency of thermal foot contraction reflex and the threshold of mechanical foot contraction reflex in the EA group were increased (P<0.05). The expressions of Iba-1, GFAP, BDNF, c-Fos proteins and the number of neuronal dendritic spines in the spinal dorsal horn in the model group were higher than those in the sham operation group (P<0.05); the expressions of Iba-1, BDNF, c-Fos proteins and the number of neuronal dendritic spines in the EA group were lower than those in the model group (P<0.05). PartⅡ: 3 and 7 days after intrathecal injection, the threshold of mechanical foot retraction reflex in the BDNF group was lower than that in the control group (P<0.05); the threshold of mechanical foot retraction reflex in the BDNF+anti-TrkB group was higher than that in the BDNF group (P<0.05). The expression of c-Fos protein in spinal dorsal horn in the BDNF group was higher than that in the control group (P<0.05); the expression of c-Fos protein in spinal dorsal horn in the BDNF+anti-TrkB group was lower than that in the BDNF group (P<0.05). The analgesic effect of EA at "Huantiao" (GB 30) and "Weizhong" (BL 40) on SNI rats may be related to inhibiting the activation of microglia in the dorsal horn of the spinal cord, thereby blocking the signal of microglia-BDNF-neuron, and finally reducing the excitability of neurons.

Effect of electroacupuncture on cyclic adenosine monophosphate-protein kinase A-vanillic acid receptor subtype 1 of the transient receptor potential/PLK-protein kinase C-vanillic acid receptor subtype 1 of the transient receptor potential pathway based on RNA-seq analysis in prostate tissue in rats with chronic prostatitis/chronic pelvic pain syndrome.

ObjectiveTo investigate the analgesic mechanism of electroacupuncture (EA) in rats with chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS).MethodsThirty male SD rats were randomly divided into sham group, model group and EA group, with ten rats in each group. The CP/CPPS model was prepared by injecting 50 μL of complete Freund’s adjuvant (CFA) into the ventral lobes of the prostate tissue, and the sham group was injected with the same dose of saline. After 14 days of modeling, EA was applied to Guanyuan (CV4), Zhongji (CV3), Sanyinjiao (SP6) and Huiyang (BL35) in the EA group. After four courses, H&E staining was performed to observe the prostate tissue morphology, transcriptome sequencing (RNA-Seq) was performed for each group, and the selected signaling pathways were verified by qRT-PCR.ResultsThe RNA-Seq analysis results suggested that the analgesic effect of EA on CP/CPPS may be achieved by regulating prostate gene expression, which may be related to multiple biological processes and signaling pathways. qRT-PCR results showed that the vanillic acid receptor subtype 1 of the transient receptor potential (TRPV1), phospholipase C (PLC), protein kinase C (PKC), cyclic adenosine monophosphate (cAMP), and protein kinase A (PKA) were all upregulated in the model group compared to the sham group (p < 0.01). Compared with the model group, TRPV1, PLC, PKC, cAMP, and PKA were all downregulated in the EA group (p < 0.05, p < 0.01).ConclusionThe analgesic mechanism of EA on CP/CPPS may be achieved through modulation of cAMP-PKA-TRPV1/PLC-PKC-TRPV1 signaling pathway.

Electroacupuncture Alleviates Neuropathic Pain through Regulating miR-206-3p Targeting BDNF after CCI.

Background Electroacupuncture (EA) has benefits for neuropathic pain. However, the underlying mechanisms are still unknown. The current study explores the underlying mechanisms of EA in neuropathic pain of chronic constriction injury (CCI) rats. Material/Methods. Overall, 126 Sprague-Dawley (200-250 g) rats were divided into nine groups randomly: the sham-operated, CCI, CCI+EA, CCI+sham EA, CCI+NS, CCI+AAV-NC, CCI+AAV-miR-206-3p, CCI+EA+NS, and CCI+EA+AAV-miR-206-3p groups. The animals were sacrificed 14 days postsurgery. Mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) tests were used to determine differences in neurobehavioral manifestations. qPCR, western blotting, and immunofluorescence (IF) were carried out to detect the expression levels of miR-206-3p, BDNF, BAX/Bcl-2, TNF-α, and IL-6. Nissl staining was measured to observe morphological changes in neurons. Transmission electron microscopy (TEM) was employed to evaluate microscopic changes in dorsal horn synapses. Results Hyperalgesia was reduced markedly by EA in the CCI model. The expression level of miR-206-3p was elevated, whereas the expression levels of BDNF, BAX/Bcl-2, TNF-α, and IL-6 were decreased in EA-treated CCI rats. However, a miR-206-3p inhibitor partially abrogated the analgesic effect of EA and resulted in poor behavioral performance and the BDNF, BAX/Bcl-2, TNF-α, and IL-6 expression was elevated as well. Conclusions EA can relieve neuropathic pain by regulating the miR-206-3p/BDNF pathway, thus exerting anti-inflammatory and antiapoptotic effect.

Analgesic effect of electroacupuncture on bone cancer pain in rat model: the role of peripheral P2X3 receptor.

Upregulation of P2X3 receptor (P2X3R) has been strongly implicated in nociceptive signaling including bone cancer pain (BCP). The present study, using rat bone cancer model, aimed to explore the role of P2X3R in regulating rat pain behavior under the intervention of electroacupuncture (EA). The BCP model was successfully established by injection with MRMT-1 breast cancer cell into the medullary cavity of left tibia for 3 × 104 cells/3 μL PBS in rats as revealed by obvious bone destruction, decreased paw withdrawal thresholds (PWTs), and reduced paw withdrawal latencies (PWLs). Western blot analyses showed that P2X3R expression was significantly upregulated in ipsilateral lumbar 4-6 (L4-6) dorsal root ganglia (DRG), but the difference not seen in spinal cord dorsal horn (SCDH). With the in-depth study of P2X3R activation, we observed that intrathecal injection of P2X3R agonist α,β-meATP aggravated MRMT-1 induced BCP, while injection of P2X3R inhibitor A-317491 alleviated pain. Subsequently, we demonstrated that BCP induced mechanical allodynia and thermal hyperalgesia were attenuated after EA treatment. Under EA treatment, total P2X3R protein expression in ipsilateral DRGs was decreased, and it is worth mentioning that decreased expression of P2X3R membrane protein, which indicated that both the expression and membrane trafficking of P2X3R were inhibited by EA. The immunofluorescence assay showed that EA stimulation exerted functions by reducing the expression of P2X3R-positive cells in ipsilateral DRGs of BCP rats. Ca2+ imaging analysis revealed that the EA stimulation decreased the percentage of α,β-meATP responsive neurons in DRGs and inhibited calcium influx. Notably, the inhibitory effect of EA on mechanical allodynia and nociceptive flinches was abolished by intrathecal injection of α,β-meATP. These findings demonstrated EA stimulation ameliorated mechanical allodynia and thermal hyperalgesia in rat model of MRMT-1-induced BCP. EA exerts analgesic effect on BCP by reducing the overexpression and functional activity of P2X3R in ipsilateral DRGs of BCP rats. Our work first demonstrates the critical and overall role of P2X3R in EA's analgesia against peripheral sensitization of MRMT-1-induced BCP and further supports EA as a potential therapeutic option for cancer pain in clinic.

Electroacupuncture Alleviates Hyperalgesia by Regulating CB1 Receptor of Spinal Cord in Incisional Neck Pain Rats.

Acupuncture therapy is effective in relieving postoperative pain of neck surgery, but its underlying mechanisms remain largely unknown. This study, in the incisional neck pain rat model, was designed to explore whether the endocannabinoid receptor 1 (CB1) in the cervical spinal cord is involved in the analgesic effect of electroacupuncture (EA) or not.The incisional neck pain model was established by making a longitudinal incision and applied EA treatment of Futu (LI18), Hegu-Neiguan (LI4-PC6), or Zusanli-Yanglingquan (ST36-GB34) for pain relief. The results showed that EA LI18 and EA LI4-PC6 effectively relieve allodynia caused by neck incision, which was obviously better than EA ST34-GB34 (P < 0.05). After EA, the expression levels of CB1 mRNA at 4h in the EALI18 group, and 24 and 48h in both EALI18 and EALI4-PC6 groups, and those of CB1 protein at 4, 24, and 48h in the EALI18 group, and the immunoactivity of CB1 in both EALI18 and EALI4-PC6 groups at 4h were significantly upregulated in contrast to those of the model group (P < 0.05). EA of either acupoint group had no effect on the expression of CB2 protein (P > 0.05). Moreover, the antinociceptive effect of EA was reversed by AM251 (CB1 antagonist). Immunofluorescence dual staining showed that CB1 expressed in astrocytes in the superficial layer (laminae I and II) of dorsal horns of the cervical spinal cord. Therefore, the findings of this study revealed that upregulation of CB1 expression in the cervical spinal cord contributes to the analgesic effect of EA in incisional neck pain rats. The CB1 receptor expresses on astrocytes.