[Bibliometric analysis on the literature characteristics of animal experiment research with acupuncture and moxibustion].

OBJECTIVE: To compare the diversities in the literature characteristics of animal experiments with acupuncture and moxibustion (acu-moxibustion) published in both Chinese and English, so as to summarize the similarities and differences in the reporting content for the animal experiment research with acu-moxibustion in the journals at home and abroad. METHODS: The articles of animal experiments with acu-moxibustion published from 2016 to 2018 were searched from CNKI, Wanfang, SinoMed, PubMed and Web of Science databases. The articles were screened according to the inclusion and exclusion criteria, and the database was established by importing the essential information, e.g. title, author, journal, impact factor, country, year of publication, citation frequency, funding, disease type, as well as the number of observation indicators and charts. The diversity was initially summarized among this type of articles between China and foreign countries. RESULTS: A total of 7 515 articles of animal experiments with acu-moxibustion were retrieved and 2 458 articles were eligible in compliance with the inclusion and exclusion criteria. Of them, there were 1 827 articles in Chinese and 631 in English. (1) Among those of Chinese-version, 169 articles (9.25%) were published in Acupuncture Research, listed the first of the article publications. Regarding the impact factor of published journal, Acupuncture Research was ranked the highest (3.187). For those published in English, 78 articles (12.36%) were published in Evidence-based Complementary and Alternative Medicine, listed the top of the article publications. Gastroenterology occupied the highest in terms of the impact factor (17.373) of published journal. (2) The first authors of Chinese-version articles were all from China, distributing in 461 institutions; of which, Beijing University of Chinese Medicine occupied the top for article publications (142 articles, 7.77%). For the English articles, 16 countries were involved regarding the first authors, and the most of them were from China (523 articles, 82.88%), followed by South Korea, Brazil, the United States and Japan. (3) The frequency of citations of Chinese articles was 7.50, which was significantly higher than that of English ones (4.61). (4) The funding supported Chinese and English articles were 1 680 (91.95%) and 569 (90.17%) respectively. (5) In the aspects of disease name and animal model, 135 and 220 diseases were included in Chinese and English articles respectively. The common top 10 diseases referred to 8 categories, i.e. stroke-related diseases, arthritis, Alzheimer's disease, depression, diabetes, spinal cord injury, hypertension and obesity. (6) In terms of the number of indicators, the maximum number was 6 for Chinese-version articles, averagely 2.46, while, it was 12 for English-version ones, 4.02 in average. (7) Among the articles of Chinese-version, the maximum number of charts was 17, and 1 028 articles had 2 to 4 charts, accounting the largest proportion (56.27%). Among those of English-version, the top number of charts was 27, and 347 articles had 4 to 6 charts, occupying the largest proportion (54.99%). CONCLUSION: The number of Chinese-version articles for acu-moxibustion experiment research is much higher than that of the English ones, the authorship is led by Chinese and most of the researches are supported by funds. There is less difference in the disease types between Chinese and English articles, but the frequency citation of Chinese articles is obviously higher than that of English ones; while, the numbers of observation indicators and charts in English articles are much more than those of Chinese ones. It is suggested that the great attention has been drawn on the acu-moxibustion experiment researches published in Chinese journals, and the reports of the researches are more complete in English journals.

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

Objective: 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. Materials and methods: 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). Results: 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. Conclusion: 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.

[κ-opioid receptor is involved in electroacupuncture analgesia via inhibition of spinal microglial Toll-like receptor 4 in neuropathic pain rats].

OBJECTIVE: To observe the effect of electroacupuncture (EA) on the expression of lumbar spinal κ-opioid receptor (KOR) and Toll-like receptor 4(TLR4) in microglia in neuropathic pain rats, so as to explore the role of cross-talk between KOR and TLK4 in EA-induced alleviation of chronic neuropathic pain. METHODS: Wistar male rats were randomized into control, model, EA and EA plus KOR inhibitor (EA+inhibitor) groups (n=18 in each group). The neuropathic pain model was established in rats by ligature of the right sciatic nerve. EA was applied at bilateral "Zusanli"(ST36) and "Yanglingquan"(GB34) for 30 min, once daily for 5 days. JDTic dihydrochloride (a KOR inhibitor) was administrated by intraperitoneal injection before EA intervention. The difference value of paw withdrawal thermal latency (PWLD) of the bilateral hind-limbs was used as the thermal pain reaction level. At the end of experiments, the rat's lumbar spinal cord (L2-L4) was taken for detecting the expression of CD68 mRNA (a marker of the activated microglia) and Iba-1 (a marker for the activated and resting microglia) immunoactivity, and dynorphin content, and KOR mRNA and TLR4 protein (in immunomagnetic microbead method separated microglia) by using fluorescence quantitative PCR, immunofluorescence, radioimmunoassay and Western blot, separately. RESULTS: Compared with the control group, a strong thermal hyperalgesia was induced, the expression levels of Iba-1 and CD68 mRNA in the spinal cord, TLR4 protein of the spinal microglia were significantly increased(P<0.01) in the model group. The microglia were characterized by somatic hypertrophy and thickened branches in the model group. After EA intervention, the PWLD, the expression of Iba-1, CD68 mRNA and TLR4 protein of the microglia were significantly decreased(P<0.05), while the content of spinal dynorphin and the expression of KOR mRNA of the microglia increased in the EA group relative to the model group(P<0.05). The hypertrophic microglia shrinked slightly in the EA group. After injection of KOR inhibitor, the PWLD and expression levels of Iba-1, CD68 mRNA and TLR4 protein were significantly increased(P<0.05), and the expression of KOR mRNA was significantly decreased(P<0.05) in the EA+inhibitor group in comparison with the EA group. CONCLUSION: The analgesia effect of EA may partly mediated by spinal microglial KOR and the activation of KOR of microglia may be a target for inhibition of microglial TLR4-induced pro-inflammatory signaling.

[Spinal cord Toll like receptor 4 and its co-stimulatory molecule heat shock protein 90 may parti-cipate in electroacupuncture analgesia in rats with chronic neuropathic pain].

OBJECTIVE: To observe the effect of electroacupuncture (EA) on the expression of Toll like receptor 4(TLR4)and heat shock protein 90(HSP90) in the spinal cord of rats with chronic constriction injury (CCI) of sciatic nerve, so as to explore the mechanism of spinal cord TLR4 and HSP90 in alleviating chronic neuropathic pain by EA. METHODS: Male Wistar rats were randomized into control, model, EA, HSP90 inhibitor (inhibitor) and EA+ inhibitor groups (n=10 in each group). The neuropathic pain model was established by ligature of the right sciatic nerve to induce CCI. EA (1 mA，2 Hz/15 Hz)was applied at bilateral "Zusanli"(ST36) and "Yanglingquan"(GB34) for 30 min, once daily for 5 days. Rats of the inhibitor and EA+inhibitor groups were given a subcutaneous injection of HSP90 inhibitor geldanamycin (50 µg/kg) at the neck before daily EA. The paw withdrawal latency (PWL) of the bilateral hind-limbs was detected by using an algesia-detector. The contents of interleukin 1ß (IL-1ß) and tumor necrosis factor α (TNF-α) in the lumbar spinal cord (L2-L4) tissue were detected by enzyme-linked immunosorbent assay. The relative expression levels of HSP90 and TLR4 proteins in the lumbar spinal cord (L2-L4) were detected using Western blot and immunofluorescence double labeling, respectively. RESULTS: Following CCI, a strong thermal hyperalgesia, an apparent up-regulation of expression of HSP90 and TLR4 proteins and TLR4 in microglia, and increasing levels of IL-1ß and TNF-α in the spinal cord were induced in the model group relevant to the control group (P<0.01，P<0.05). Five sessions of EA intervention or inhibitor injection significantly attenuated hyperalgesia, reversed the increase of IL-1ß and TNF-α, and down-regulated the expression of TLR4 in microglia (P<0.05). Compared with the model group, the expression of HSP90 was further increased (P<0.05), and those of TLR4 in microglia and neurons were significantly decreased and increased, respectively in the EA group (P<0.05). Compared with the EA group, the levels of PWLD,TLR4 and HSP90 expression, and the proportions of neuronal nuclei antigen（NeuN） and TLR4, and ionized calcium binding adapter molecule （Iba1） and TLR4 co-expressed cells were significantly decreased in the inhibitor group and EA+inhibitor group (P<0.05). The proportion of NeuN and TLR4 co-expression cells in the EA+inhibitor group was significantly higher than that of the inhibitor group (P<0.05). CONCLUSION: EA stimulation of ST36 and GB34 can alleviate thermal hyperalgesia in CCI rats, which is closely associated with its effect in regulating the expression of TLR4 in the spinal cord neurons and microglia. HSP90 in the spinal cord may be a co-stimulatory molecule for EA induced relief of neuropathic pain by regulating TLR4.

GABAergic Inhibition of Spinal Cord Dorsal Horns Contributes to Analgesic Effect of Electroacupuncture in Incisional Neck Pain Rats.

BACKGROUND: Acupuncture has shown to be effective in relieving post-surgical pain. Nonetheless, its underlying mechanisms remain largely unknown. In the present study, we investigated the effect of electroacupuncture (EA) on the expression of GABA, GABA-A receptor (R) and GABA-BR in the spinal cord dorsal horns (DHs), and the involved neural cells in rats with incisional neck pain. MATERIALS AND METHODS: Male SD rats were randomly divided into control, model, Futu (LI18), Hegu-Neiguan (LI4-PC6), and Zusanli-Yanglingquan (ST36-GB34) groups. The incisional neck pain model was established by making a longitudinal incision and repeated mechanical separation along the thyroid gland region. EA (2Hz/100Hz, 1mA) was applied to LI18, LI4-PC6, ST36-GB34 separately for 30min, once at 4, 24 and 48h after incision. The local thermal pain threshold (TPT) of the focus was measured and the expression of GABA, and GABAR proteins and mRNAs detected by immunofluorescence stain and quantitative RT-PCR, respectively. RESULTS: The analgesic effect of LI18 and LI4-PC6 was superior to that of ST36-GB34 in incisional neck pain rats. Moreover, the EA stimulation of LI18 or LI4-PC6 increased the expression of GABA and GABA-Aα2 and GABA-Aß3, GABA-B1, and GABA-B2 mRNAs in spinal DHs 4h after surgery, while GABA-A and GABA-B antagonists inhibited the analgesic effect of LI18. Immunofluorescence double staining showed that GABA was expressed on astrocytes and neurons, and GABA-B expressed only on neurons. CONCLUSION: EA of both LI18 and LI4-PC6 has a good analgesic effect in incisional neck pain rats, which is closely related to their effects in upregulating the expression of GABA and its receptors in spinal DHs. The effects of LI18 and LI4-PC6 EA are obviously better that those of ST36-GB34 EA, and GABA is expressed on neurons and astrocytes.

[Electroacupuncture alleviated incisional neck pain possibly by suppressing TNF-α expression and increasing IL-4/IL-4 receptor signaling in cervical dorsal part of spinal cord in incisio-nal neck pain rats].

OBJECTIVE: To observe the effect of electroacupuncture (EA) on incisional pain and expression of tumor necrosis factor-α (TNF-α), interleukin-10 (IL-10) and interleukin-4 (IL-4) of cervical dorsal part of spinal cord in rats with incisional neck pain, so as to explore its analgesic mechanisms. METHODS: Eighty-four male SD rats were randomly divided into normal control, model, EA-Futu(LI18) and EA-Zusanli(ST36)-Yanglingquan(GB34, EA-ST36-GB34) groups (n=21 in each group). The incisional neck pain model was established by making a longitudinal incision along the bilateral cervical thyroid regions and repeated mechanical separation stimulation. For rats of the EA groups, EA (2 Hz/100 Hz, 1 mA) was applied to bilateral LI18 or ST36-GB34 for 30 min/ time during the surgery, and 20 and 44 h after surgery, respectively. The thermal pain threshold (TPT) of the incisional region was detected. The immunoactivity of TNF-α and IL-10 of the dorsal portion of the cervical spinal cord (C2-C5) was detected by immunofluorescence, and the expression of TNF-α, IL-10, IL-4 and IL-4 receptor (IL-4R) mRNAs was determined by quantitative real-time PCR. RESULTS: Compared with the normal group, the TPT of the incisional area was significantly decreased at 4, 24 and 48 h after neck-incision (P<0.05), the levels of TNF-α mRNA, IL-10 mRNA and TNF-α IL-10 immunoactivity at 24 h were remarkably increased (P<0.05), and the expression of IL-4R mRNA was considerably decreased at 24 h in the model group (P<0.05). Following EA intervention, the TPT, and expression levels of IL-4 mRNA and IL-4R mRNA were significantly increased at 24 h after surgery in the EA-LI18 group relevant to the model group (P<0.05), while the expression level of TNF-α(coexpressed with microgliacytes) in the EA-LI18 group, and TNF-α mRNA expression at 24 h in both EA-LI18 and EA-ST36-GB34 groups, as well as the expression of IL-10 and IL-10 mRNA at 24 h in both EA-LI18 and EA-ST36-GB34 groups were significantly decreased (P<0.05). The effect of EA LI18 was significantly superior to that of EA ST36-GB34 in up-regulating TPT and expression of IL-4 mRNA and IL-4R mRNA at 24 h (P<0.05). CONCLUSION: EA of LI18 has an analgesic effect in incisional neck pain rats, which may be related to its effect in down-regulating the expression of TNF-α, IL-10 and promoting IL-4 /IL-4R signaling in dorsal portions of the cervical spinal cord. The analgesic effect of EA LI18 is better than that of EA ST36-GB34.

[High Mobility Group Box 1/ CD 24 Receptor/ß-EP Signaling in "Zusanli" (ST 36) Region Contributes to Electroacupuncture Analgesia in Rats with Neuropathic Pain].

OBJECTIVE: To observe the effect of electroacupuncture (EA) on the expression of high mobility group box 1 (HMGB 1) and its receptor CD 24 proteins and ß-endorphin (ß-EP) content in "Zusanli" (ST 36) region in rats with chronic constriction injury (CCI), so as to explore its mechanisms underlying pain relief. METHODS: Thirty male Wistar rats were rando-mized into control, CCI model and EA groups (n＝ 10 rats in each). The neuropathic pain model was established by ligature of the left sciatic nerve to induce CCI in the model and EA groups, and sham operation was performed in rats of the control group. Paw with drawal latency (PWL, thermal pain threshold) of the bilateral hind-limbs was detected by using an algesia-detector. Eight days after CCI operation, EA was applied to bilateral "Zusanli" (ST 36) and "Yanglingquan" (GB 34) for 30 min, once daily for 5 days. The acetylated-HMGB 1 expression was determined by immunoprecipitation, and the expression of HMGB 1 and toll like receptor 4 (TLR 4) proteins and CD 24 mRNA were detected using Western blot and fluorescent quantitative real time-PCR, respectively, and the content of ß-EP in the acupoint region was assayed by enzyme linked immunosorbent assay (ELISA). Anti-CD 24 neutralizing antibody (200 µL, 100 µg/mL) was injected into ST 36 region once daily for 3 days for verifying the involvement of HMGB 1/CD 24 signaling in EA analgesia. RESULTS: Compared with the control group, the bilateral PWL difference values in the other two groups were significantly increased (P<0.05), meaning an occurrence of hyperalgesia after CCI. In comparison with the CCI model group, the hyperalgesia in the EA group was obviously decreased (P<0.05). After CCI, the expression levels of HMGB 1 and TLR 4 proteins were considerably increased compared with those in the control group (P<0.05). After 5-times' EA, the acetylated-HMGB 1, the expression of CD 24 mRNA, and the content of ß-EP were notably up-regulated (P<0.05), and there were no obvious changes in the expression levels of HMGB 1 and TLR 4 proteins (P>0.05). After local injection of anti-CD 24 antibody, EA-induced increases of ß-EP content and reduction of thermal pain threshold were significantly suppressed (P<0.05). CONCLUSION: EA of ST 36 and GB 34 can alleviate neuropathic pain in CCI rats, which is associated with its effects in up-regulating ß-EP content, and HMGB 1 protein and CD 24 mRNA expression levels in ST 36 region. The activated HMGB 1/CD 24/ß-EP signaling contributes to EA-ST 36 induced analgesia.

Repeated electroacupuncture treatment attenuated hyperalgesia through suppression of spinal glial activation in chronic neuropathic pain rats.

BACKGROUND: Cumulated evidence reveals that glial cells in the spinal cord play an important role in the development of chronic neuropathic pain and are also complicated in the analgesic effect of EA intervention. But the roles of microgliacytes and astrocytes of spinal cord in the process of EA analgesia remain unknown. METHODS: A total of 120 male Wistar rats were used in the present study. The neuropathic pain model was established by chronic constrictive injury (CCI) of the sciatic nerve. The rats were randomly divided into sham group, CCI group, and sham CCI + EA group, and CCI + EA group. EA was applied to bilateral Zusanli (ST36)-Yanlingquan (GB34). The mechanical (both time and force responses) and thermal pain thresholds (PTs) of the bilateral hind-paws were measured. The number of microgliacytes and activity of astrocytes in the dorsal horns (DHs) of lumbar spinal cord (L4-5) were examined by immunofluorescence staining, and the expression of glial fibrillary acidic protein (GFAP) protein was detected by western blot. RESULTS: Following CCI, both mechanical and thermal PTs of the ipsilateral hind-paw were significantly decreased beginning from the 3rd day after surgery (P < 0.05), and the mechanical PT of the contralateral hind-paw was considerably decreased from the 6th day on after surgery (P < 0.05). CCI also significantly upregulated the number of Iba-1 labeled microgliacytes and the fluorescence intensity of glial fibrillary acidic protein (GFAP) -labeled astrocyte in the superficial laminae of DHs on bilateral sides (P < 0.05). After repeated EA, the mechanical and thermal PTs at bilateral hind-paws were significantly relieved (P < 0.05). The increased of number of microgliacytes was markedly suppressed by 2 days' EA intervention, and the average fluorescence intensity was suppressed by 2 weeks' EA. The expression of GFAP protein were down-regulated by 1 and 2 weeks' EA treatment, respectively (P < 0.05). CONCLUSIONS: Repeated EA can relieve neuropathic pain and mirror-image pain in chronic neuropathic pain rats, which is probably associated with its effect in downregulating glial cell activation of the lumbar spinal cord, the microgliacyte first and astrocyte later.

[Effect of Electroacupuncture Intervention on Expression of Synaptic Plasticity-related Molecules in Amygdala in Chronic Pain-negative Affection Rats].

OBJECTIVE: To observe the effect of electroacupuncture (EA) on expression of synaptic plasticity-related glutamate N-methyl-D-aspartate (NMDA) receptor subunit NR 1, gamma-aminobutyric acid (GABA) receptor subunits (Aß 2, B 1), etc. in the amygdala in chronic neuropathic pain negative affection (CNPPNA) rats, so as to reveal its mechanism underlying pain relief. METHODS: Male Wistar rats were randomized into normal control, CNPPNA model, EA, and anesthesia+EA (AEA)groups (n=14 in each group, 8 for quantitative RT-PCR and 6 for immunofluorescence staining). The CNPPNA model was established by ligation of the left sciatic nerve and repeated electrical stimulation of the hindpaw plantar skin in the pain-paired compartment. EA was applied to bilateral "Zusanli"(ST 36)and "Yanglingquan"(GB 34)for 30 min, once daily for 7 days.Thermal pain threshold (paw withdrawal latency, PWL)of the bilateral paws was measured by using a Tail-Flick Unit. The conditioned place aversion (CPA) was determined by using a CPA-paired compartment. The expression levels of GABAAß 2, GABAB 1, NMDA receptor subunit NR 1, postsynaptic density-95 protein(PSD-95), Piccolo genes in the right amygdala area were determined using quantitative RT-PCR, and the immunoactivity of metabotropic glutamate receptor subunit 1 (mGluR 1) and GABAB 2 in the basolateral amygdala (BLA) nucleus was detected using immunofluorescence staining. RESULTS: After modeling, PWL difference (PWLD) values of the model group were significantly increased (P<0.001),and the time spent in the CPA-paired compartment was considerably decreased compared with the control group (P<0.001).After EA intervention for 3 and 7 days, the PWLD levels of both EA and AEA groups were apparently decreased(P<0.05),and the time spent in the CPA-paired compartment was apparently increased in the EA and AEA groups(P<0.05),suggesting a pain relief and an improvement of the negative affection after EA intervention. Additionally, following EA, the apparently-decreased expression levels of GABAAß 2,GABAB 1,PSD-95,Piccolo genes and the reduced numbers of GABAB 2 positive cells and NMDA-NR 1 mRNA as well as mGluR 1 positive fiber numbers were remarkably increased in the EA group (P<0.05, P<0.001).The expression levels of Piccolo gene, GABAB 2 and mGluR 1 positive cells/fiber numbers were apparently lower in the AEA group than in the EA group (P<0.001). No significant differences were found between the EA and AEA groups in the PWLD, time spent in the CPA-paired compartment, and the expression levels of NMDA-NR 1, GABAAß 2, GABAB 1 and PSD-95 genes (P>0.05). CONCLUSIONS: Repeated EA stimulation of ST 36-GB 34 has a role in relieving both sensory and affection dimensions of chronic pain in CNPPNA rats, which Feb be respectively related to its effects in up-regulating the expression of GABAAß 2, GABAB 1, NMDA-NR 1, PSD-95 and Piccolo genes, and in promoting the expression of mGluR 1 and GABAB 2 proteins and Piccolo gene in the amygdala.

Activation of hippocampal MEK1 contributes to the cumulative antinociceptive effect of electroacupuncture in neuropathic pain rats.

BACKGROUND: Electroacupuncture (EA) intervention can relieve a variety of pain; however, optimal EA protocols have not been clearly determined. In addition, although central mitogen-activated protein kinase kinase (MEK) signaling has been shown to be involved in the antinociceptive effect of acupuncture stimulation, its characteristics at different time-points of EA intervention have not been fully elucidated. Therefore, the present study investigated the relationship between the effects of different numbers of EA intervention sessions and the activation of MEK1 in the hippocampus and hypothalamus in a rat model of neuropathic pain. METHODS: After ligation of the left sciatic nerve, which induces chronic constriction injury (CCI), the acupoints Zusanli (ST36) and Yanglingquan (GB34) were applied. The thermal withdrawal latency of the hind paw was used to evaluate the effect of EA on pain thresholds. Intra-hippocampus microinjection of PD98059, a MEK inhibitor, was performed to validate the involvement of MEK in EA analgesia. The hippocampus and hypothalamus were harvested to examine the phosphorylation levels of MEK (pMEK) by western blotting. RESULTS: In CCI rats, the thermal pain threshold of the affected hind paw decreased significantly relative to the control. Following subsequent daily EA interventions, CCI-induced ipsilateral hyperalgesia was markedly improved from day 4 and the analgesic effect of EA lasted 3 days after cessation of EA. Four sessions of EA markedly suppressed CCI-induced decrease of hippocampal pMEK1 (normalized to the total MEK level). In contrast, successive sessions of EA intervention gradually down-regulated the CCI-induced up-regulation of hypothalamic pMEK1 along with the increase numbers of EA intervention. However, EA did not exert the same analgesic effect after microinjection of PD98059 into the contralateral hippocampus during the first 3 days of EA intervention. CONCLUSIONS: EA intervention can induce time-dependent cumulative analgesia in neuropathic pain rats after 4 successive sessions of daily EA intervention, which is at least in part related to the activation of hippocampal MEK1.

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.

[Effect of Electroacupuncture Intervention on Expression of Pain Sensory and Affective Proce- ssing-related µ-opioid Receptor, etc. in the Amygdala in Chronic Neuropathy Pain Rats].

OBJECTIVE: To observe the effect of electroacupuncture (EA) on expression of pain sensory and affective processing-related µ-opioid receptor (MOR), glutamatergic AMPA receptor subunit GIuA 1, extracellular signal-regulated kinase (ERK 1/2), cAMP response element binding protein(CREB) in the amygdala in chronic constrictive injury (CC) + negative affection(NA) rats, so as to reveal its mechanism underlying pain relief. METHODS: A total of 32 male Wistar rats were randomized into normal control, model, EA, and anesthesia+ EA (AEA) groups (n = 8 in each group). The neuropathic pain NA model was established by ligation of the left sciatic nerve and repeated electrical stimulation of the paw-bottom in the pain-paired compartment. EA was applied to bilateral "Zusanli" (ST 36) and "Yanglingquan" (GB 34) for 30 min, once daily for 7 days. Thermal pain threshold (paw withdrawl latency, PWL) of the bilateral paws was measured by using a Tail-Flick Unit. The expression levels of MOR and p-CREB in the central amygdala (CeA) and those of MOR, GluA 1, p-ERK 1/2 and p-CREB in the right amygdala area were determined using immunofluorescence and Western blot, respectively. RESULTS: in comparison with the normal group, PWL difference (PWLD) values of the model group were significantly increased (P < 0.001), and the time spent in the CPA-paired. compartment was considerably decreased (P < 0.001). After EA, the PWLD levels of both EA and AEA groups were apparently decreased (P < 0.05), showing a pain relief; and the time spent in the CPA-paired compartment was apparently increased in the EA group (P < 0.05) , rather than in the AEA group (P > 0.05). Additionally , compared to the normal group, the expression level of MOR protein in the amygdala was remarkably increased (P < 0.05) and those of GIuA 1, p-ERK 2 and p-CREB proteins were apparently decreased (P < 0.05). After EA intervention for 7 days, the expression levels of these four proteins in the EA group, and those of MOR, p-ERK 2 and p-CREB in the AEA group were significantly up-regulated (P < 0.001, P < 0.01, P < 0.05). The expression level of GIuA 1 was significantly higher in the EA group than in the AEA group (P < 0.05). CONCLUSION: Repeated EA stimulation of ST 36-GB 34 has a definite effect in relieving both sensation and affection dimensions of pain in NA rats, which may be related to its effect in up-regulating the expression of GIuA 1 in the amygdala, but the effects of MOR, p-ERK 2 and p-CREB need being researched further.

Involvement of hippocampal acetylcholinergic receptors in electroacupuncture analgesia in neuropathic pain rats.

BACKGROUND: Cumulating evidence has shown a close correlation between electroacupuncture stimulation (EAS) frequency-specific analgesic effect and central opioid peptides. However, the actions of hippocampal acetylcholinergic receptors have not been determined. This study aims to observe the effect of different frequencies of EAS on the expression of hippocampal muscarinic and nicotinic acetylcholinergic receptors (mAChRs, nAChRs) in neuropathic pain rats for revealing their relationship. METHODS: Forty male Wistar rats were randomly and equally divided into sham, CCI model, 2, 2/15 and 100 HzEA groups. The neuropathic pain model was established by ligature of the left sciatic nerve to induce chronic constriction injury (CCI). EAS was applied to bilateral Zusanli (ST36) and Yanglingquan (GB34) for 30 min, once daily for 14 days except weekends. The mechanical pain thresholds (withdrawal latencies, PWLs) of bilateral hindpaws were measured. The expression levels of hippocampal M1 and M2 mAChR, and α4 and ß2 nAChR genes and proteins were detected by quantitative RT-PCR and Western blot, separately. The involvement of mAChR and nAChR in the analgesic effect of EAS was confirmed by intra-hippocampal microinjection of M1mAChR antagonist (Pirenzepine) and α4ß2 nAChR antagonist (dihydro-beta-erythroidine) respectively. RESULTS: Following EAS, the CCI-induced increase of difference values of bilateral PWLs on day 6 and 14 was significantly reduced (P < 0.05), with 2/15 Hz being greater than 100 Hz EAS on day 14 (P < 0.05). After 2 weeks' EAS, the decreased expression levels of M1 mAChR mRNA of both 2 and 2/15 Hz groups and M1 mAChR protein of the three EAS groups, α4 AChR mRNA of the 2/15 Hz group and ß2 nAChR protein of the three EAS groups were considerably increased (P < 0.05), suggesting an involvement of M1 mAChR and ß2 nAChR proteins in EAS-induced pain relief. No significant changes were found in the expression of M2 mAChR mRNA and protein, α4 nAChR protein and ß2 nAChR mRNA after CCI and EAS (P > 0.05). The analgesic effect of EAS was abolished by intra-hippocampal microinjection of M1mAChR and α4ß2 nAChR antagonists respectively. CONCLUSIONS: EAS of ST36-GB34 produces a cumulative analgesic effect in neuropathic pain rats, which is frequency-dependent and probably mediated by hippocampal M1 mAChR and ß2 nAChR proteins.

Effect of Repeated Electroacupuncture Intervention on Hippocampal ERK and p38MAPK Signaling in Neuropathic Pain Rats.

Results of our past studies showed that hippocampal muscarinic acetylcholine receptor (mAChR)-1 mRNA and differentially expressed proteins participating in MAPK signaling were involved in electroacupuncture (EA) induced cumulative analgesia in neuropathic pain rats, but the underlying intracellular mechanism remains unknown. The present study was designed to observe the effect of EA stimulation (EAS) on hippocampal extracellular signal-regulated kinases (ERK) and p38 MAPK signaling in rats with chronic constrictive injury (CCI) of the sciatic nerve, so as to reveal its related intracellular targets in pain relief. After CCI, the thermal pain thresholds of the affected hind were significantly decreased compared with the control group (P < 0.05). Following one and two weeks' EAS of ST 36-GB34, the pain thresholds were significantly upregulated (P < 0.05), and the effect of EA2W was remarkably superior to that of EA2D and EA1W (P < 0.05). Correspondingly, CCI-induced decreased expression levels of Ras, c-Raf, ERK1 and p-ERK1/2 proteins, and p38 MAPK mRNA and p-p38MAPK protein in the hippocampus tissues were reversed by EA2W (P < 0.05). The above mentioned results indicated that EA2W induced cumulative analgesic effect may be closely associated with its function in removing neuropathic pain induced suppression of intracellular ERK and p38MAPK signaling in the hippocampus.

NK cells mediate the cumulative analgesic effect of electroacupuncture in a rat model of neuropathic pain.

BACKGROUND: Cumulating evidence has revealed the effectiveness of acupuncture therapy in relieving pain via immunoregulation. However, its underlying mechanism remains unknown. The present study was designed to determine the changes of immunogenic responses at different time-points of electroacupuncture (EA) interventions in neuropathic pain rats. METHODS: The neuropathic pain model was established by ligature of the left sciatic nerve to induce chronic constriction injury (CCI). EA was applied at Zusanli (ST36) and Yanglingquan (GB34) for the EA groups. The thermal pain threshold was detected with an algesia-detector. The subgroups of plasma and splenic lymphocytes were determined via fluorescence-activated cell sorting. Specific inflammatory cytokines were assayed using an ELISA-based bead multiplex assay. The activities of splenic natural killer (NK) cells and cytotoxic T lymphocytes were detected by methyl thiazolyl tetrazolium colorimetric method. For confirming the involvement of NK cell in EA-analgesia, anti-asialo-ganglio-N-tetraosylceramide (anti-asialo-GM1) antibody was given to CCI rats before EA. RESULTS: Following CCI, the thermal pain threshold of the affected hind footpad was significantly decreased, and increased from the 3rd day to the 12th day after EA interventions, presenting a time-dependent tendency from the 5th day on. From day 3 to 5 of EA interventions, the percentages and activity of splenic NK cells, concentrations of splenic interleukin-2 (IL-2) and beta-endorphin (ß-EP) were significantly increased. Meanwhile, the concentrations of plasma IL-2, IL-1ß and gamma-interferon (IFN-γ) were significantly decreased and returned to the normal level on day 12 following EA. Plasma transforming growth factor-ß (TGF-ß) levels were considerably upregulated on day 5 and 12 following EA. The CD4+/CD8+ T cell ratio was markedly downregulated compared with the control and CCI groups on day 5 and returned to the normal level on day 12 following EA. After depleting NK cells by anti-asialo-GM1 antibody, the increased thermal pain threshold following EA intervention was obviously reduced. CONCLUSIONS: Repeated EA interventions have a time-dependent cumulative analgesic effect in neuropathic pain rats, which is closely associated with its regulatory effects on NK cells, splenic IL-2, ß-EP, and plasma IL-2, IL-1ß, IFN-γ and TGF-ß levels.

[Effect of electroacupuncture intervention on expression of pain sensory and affection processing related corticotropin-releasing factor receptor mRNA, etc. in the amygdala in neuropathic pain and negative affection rats].

OBJECTIVE: To observe the effect of electroacupuncture .(EA) stimulation of "Zusanli" (ST 36)-"Yang- lingquan" (GB 34) on expression of pain sensory and affection processing-related corticotropin-releasing factor (CRF) receptor, glutamatergic NMDA receptor and GABA receptor subtype genes in the amygdala in chronic constrictive injury (CCI) of the sciatic nerve rats, so as to reveal its mechanism underlying pain relief. METHODS: Experiments were separately performed in 36 male Wistar rats which were randomized into normal control, CCI model and EA + CCI; normal control, CCI + negative affection (NA) model and CCl+ NA+ EA groups (n =6 in each group). Neuropathic pain model was established by ligature of the left sciatic nerve, and NA model established by ligation of the left sciatic nerve and repeated skin stimulation (acupuncture needle pricking + direct current stimulation) of the paw-bottom, once daily for 3 days. EA (2 Hz/15 Hz, 1 mA) was applied to bilateral ST 36-GB 34 for 30 min, once daily for 7 days. Thermal pain threshold (paw withdrawal latency, PWL) of the bilateral paws was measured by using a Tail-Flick Unit 37360. Expression levels of CRF-1 R, CRF-2 R, NR 2 A,NR 2 B,GABAaR and GABAcR genes in the amygdala were determined using quantitative RT-PCR. RESULTS: In comparison with the normal control groups, PWL difference (PWLD) values of the bilateral paws of CCIl model and CCI+NA model groups were significantly increased (P<0. 05). In comparison with the model group, following 7 days' EA stimulation, PWLD were considerably decreased (P<0. 05), showing a pain relief. RT-PCR results indicated that compared to the normal control group, the expression levels of CRF-1 R, CRF-2 R, NR 2 A and NR 2 B genes were apparently increased in the CCI model group (P<0. 01, P<0. 001), and those of CRF-1 R, CRF-2 R, NR 2 A, NR 2 B, GABAaR and GABAcR genes were remarkably down-regulated in the CCI + NA model group (P<0. 05, P<0. 01, P<0. 001). After EA intervention for 7 days, CRF-2 R, NR 2 A and NR 2 B were significantly down-regulated in the CCI + EA group, and CRF-1 R, CRF-2 R, NR 2 B,GABAaR and GABAcR genes were obviously up-regulated in the CCI + NA + EA group (P<0. 01, P<0. 001). CONCLUSION: Repeated EA stimulation of ST 36-GB 34 has a definite analgesic effect in neuropathic pain and negative affection rats, which may be respectively related to its effects in down-regulating expression of CRF-2 R, NR 2 A and NR 2 B genes, and up-regulating expression of CRF-1 R, CRF-2 R, NR 2 B,GABAaR and GABAcR genes in the amyg- dala.

Effect of Electroacupuncture Intervention on Expression of CGRP, SP, COX-1, and PGE2 of Dorsal Portion of the Cervical Spinal Cord in Rats with Neck-Incision Pain.

The present study was aimed to determine if cervicospinal substance P (SP) and its neurokinin-1 receptor (NK-1R), calcitonin gene-related peptide (CGRP), cyclooxygenase-1 (COX-1), and prostaglandin E2 (PGE2) were involved in electroacupuncture (EA) analgesia in neck-incision pain rats. EA intervention was applied to bilateral Futu (LI18), Hegu (LI4)-Neiguan (PC6), and Zusanli (ST36)-Yanglingquan (GB34) for 30 min. Cervicospinal SP and CGRP immunoactivity was detected by immunofluorescence technique, NK-1R and COX-1 protein and mRNA expression levels were determined using Western blot and real-time PCR, respectively, and PGE2 content was measured using ELISA. Outcomes indicated that EA of EA-LI18 and LI4-PC6 (not ST36-GB34) significantly suppressed neck-incision induced decrease of thermal pain threshold (P < 0.05). EA stimulation of LI18 and LI4-PC6 markedly inhibited neck-incision induced upregulation of SP and CGRP immunoactivity, NK-1 R and COX-1 mRNA and protein expression levels, as well as the increase of PGE2 content in the dorsal cervicospinal cord (P < 0.05). These findings showed that LI18 and LI4-PC6 EA stimulation-induced downregulation of SP, CGRP, NK-1R, COX-1, and PGE2 levels in the dorsal cervicospinal cord may contribute to their effects in relieving neck-incision pain. This study highlights the targets of EA intervention for reducing post-thyroid-surgery pain for the first time.

[Involvement of hippocampal NO/PKG signaling pathway in the accumulative analgesic effect of electroacupuncture stimulation of "Zusanli" (ST 36)-"Yanglingquan"(GB 34) in chronic neuropathic pain rats].

OBJECTIVE: To observe the effect of electroacupuncture (EA) at "Zusanli"(ST 36)-"Yanglingquan"(GB 34) on pain behavior and expression of hippocampal neuronal nitric oxide synthase (nNOS), inducible nitric oxide synthase(iNOS)and cGMP-dependent protein kinase (PKG) mRNA in rats with chronic neuropathic pain so as to analyze its mechanism underlying analgesia. METHODS: Forty male Wistar rats were randomly divided into control, CCI model, EA-2 Hz, EA-2 Hz/15 Hz, EA-100 Hz groups, with 8 cases in each group. Chronic neuropathic pain model was established by ligature of the left sciatic nerve under anesthesia (Urethane + Alpha-Chloralose) except rats in the control group. EA(2 Hz, 2 Hz/15 Hz, 100 Hz, 1 mA) was applied to bilateral "Zusanli"(ST 36)-"Yanglingquan"(GB 34) for 30 min, once each day for 2 weeks. The thermal and mechanical paw withdrawal latencies (pain thresholds) of the bilateral limbs were detected before and after EA interventions. The hippocampal tissue of the rat was collected for detecting the expression levels of nNOS, INOS and PKG genes using quantitative real-time-PCR technique. RESULTS: In comparison with the control group, the thermal and mechanical pain thresholds of the model group were decreased obviously (P<0. 05).Compared with the model group, both thermal and mechanical pain thresholds of the EA-2 Hz, EA-2 Hz/15 Hz and EA-100 Hz groups were markedly increased after EA intervention for 3, 7, 10 and 14 days (P<0. 05). Compared with the control group, the expression levels of hippocampal nNOS and PKG mRNA were significantly and moderately up-regulated in the model group (P<0. 05). While in comparison with the model group, the expression levels of hippocampal nNOS and PKG mRNA in the EA-2 Hz, EA-2 Hz/15 Hz and EA-100 Hz groups were markedly down-regulated (P<0. 05). No significant differences were found among the EA-2 Hz, EA-2 Hz/15 Hz and EA-100 Hz groups in the analgesic effect and in down-regulating hippocampal nNOS and PKG mRNA expression (P>0.05). However, the recovery state of the pain reaction of both EA-2 Hz and EA-2 Hz/ 15 Hz groups was relatively better than that of the EA-100 Hz group from day 3 to 10 after EA intervention. CONCLUSION: EA stimulation of "Zusanli"(ST 36)-"Yanglingquan"(GB 34) at 2 Hz, 2 Hz/15 Hz and 100 Hz can significantly suppress chronic neuropathic pain induced in CCI rats, which may be closely associated with its effects in down-regulating hippocampal nNOS and PKG mRNA expression levels.

Differential proteomics analysis of the analgesic effect of electroacupuncture intervention in the hippocampus following neuropathic pain in rats.

BACKGROUND: Evidence is building steadily on the effectiveness of acupuncture therapy in pain relief and repeated acupuncture-induced pain relief is accompanied by improvement of hippocampal neural synaptic plasticity. To further test the cellular and molecular changes underlying analgesic effect of acupuncture, the global change of acupuncture associated protein profiles in the hippocampus under neuropathic pain condition was profiled. METHODS: The chronic constrictive injury (CCI) model was established by ligature of the unilateral sciatic nerve in adult Wistar rats. Rats were randomized into normal control (NC) group, CCI group, and CCI with electroacupuncture (EA) stimulation group. EA was applied to bilateral Zusanli (ST36) and Yanglingquan (GB34) in the EA group. Differentially expressed proteins in the hippocampus in the three groups were identified by two-dimensional gel electrophoresis and matrix-assisted laser desorption/ionization time of flight mass spectrometry. The functional clustering of the identified proteins was analyzed by Mascot software. RESULTS: After CCI, the thermal pain threshold of the affected hind footpad was decreased and was reversed gradually by 12 sessions of acupuncture treatment. Following EA, there were 19 hippocampal proteins identified with significant changes in expression (>2-fold), which are involved in metabolic, physiological, and cellular processes. The top three canonical pathways identified were "cysteine metabolism", "valine, leucine, and isoleucine degradation" and "mitogen-activated protein kinase (MAPK) signaling". CONCLUSIONS: These data suggest that the analgesic effect of EA is mediated by regulation of hippocampal proteins related to amino acid metabolism and activation of the MAPK signaling pathway.

Analysis on interrelation between electroacupuncture-induced cumulative analgesic effect and hypothalamic cholinergic activities in chronic neuropathic pain rats.

OBJECTIVE: To observe the effects of repeated electroacupuncture (EA) of Zusanli (ST36)- Yanglingquan (GB34) on hypothalamic acetylcholinesterase (AchE) and vesicular acetylcholine (ACh) transporter (VAChT) activities and choline acetyltransferase (ChAT) mRNA and muscarinic M1 receptor (M1R) mRNA expression in chronic constrictive injury (CCI) and/or ovariectomy (OVX) rats so as to reveal its underlying mechanism in cumulative analgesia. METHODS: A total of 103 female Wistar rats were randomly divided into normal control (n =15), CCI (n =15), CCI+EA2d (n =15), CCI+EA2W (n =15), OVX+CCI =13), OVX+CCI+EA2d (n =15), and OVX+CCI+EA2W groups (n =15). CCI model was established by ligature of the unilateral sciatic nerve with surgical suture. Memory impairment model was established by removal of the bilateral ovaries. Morris water test was conducted to evaluate the OVX rats' memory learning ability, and the thermal pain threshold (PT) of the bilateral paws was detected the next morning after EA. EA (2/15 Hz, 1 mA) was applied to bilateral ST36-GB34 for 30 min, once daily for 2 days or 2 weeks, respectively. Hypothalamic AChE activity was detected by histochemistry, VAChT immunoactivity was determined by immunohistochemistry, and ChAT mRNA and M1R mRNA expressions were assayed by reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: In comparison with the normal control group, the AChE activity in hypothalamic arcuate nucleus (ARC) and supraoptic nucleus (SON) regions of CCI group, AChE activity in paraventricular nucleus (PVN), ARC, and SON regions of OVX+CCI group, and hypothalamic muscarinic M1R mRNA expression levels in both CCI and OVX+CCI groups were down-regulated significantly (P <0.05). Compared with the CCI group, the AChE activities in hypothalamic ARC and SON regions of CCI+EA2d and CCI+EA2W groups and PVN region of CCI+EA2W group and hypothalamic ChAT mRNA and M1R mRNA expression levels in CCI+EA2W group were up-regulated considerably (P <0.05). In comparison with the OVX+CCI group, the AChE activities in PVN, ARC, and SON regions and the expressions of hypothalamic ChAT mRNA and VAChT in ARC region of OVX+CCI+EA2W group were up-regulated remarkably (P <0.05). The effects in rats of CCI+EA2W group were evidently superior to those of OVX+CCI+EA2d group in up-regulating AChE activities in PVN, ARC, and SON regions, VAChT immunoactivity in ARC region, and expression levels of hypothalamic ChAT mRNA and M1R mRNA (P <0.05). Similar situations were found in OVX+CCI rats after EA2W. It suggested a cumulative effect after repeated EA of ST36-GB34. Comparison between CCI+EA2W and OVX+CCI+EA2W groups showed that the effects in rats of the former group were evidently better than those of the latter group in up-regulating AChE activity in ARC and SON regions and the expressions of hypothalamic ChAT mRNA and M1 mRNA (P <0.05), suggesting a reduction of EA2W effects after OVX. CONCLUSION: Repeated EA can significantly up-regulate AChE and VAChT activities and ChAT mRNA and M1R mRNA expressions in the hypothalamus of CCI and OVX+CCI rats, which may contribute to the cumulative analgesic effects of repeated EA and be closely related to the animals' neuromemory ability.