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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

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 (Aβ 2, B 1), etc. in the amygdala in chronic neuropathic pain negative affection (CNPPNA) rats, so as to reveal its mechanism underlying pain relief.Male Wistar rats were randomized into normal control, CNPPNA model, EA, and anesthesia+EA (AEA)groups (After modeling, PWL difference (PWLD) values of the model group were significantly increased (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 GABAAβ 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.

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.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.in comparison with the normal group, PWL difference (PWLD) values of the model group were significantly increased (P0.001), and the time spent in the CPA-paired. compartment was considerably decreased (P0.001). After EA, the PWLD levels of both EA and AEA groups were apparently decreased (P0.05), showing a pain relief; and the time spent in the CPA-paired compartment was apparently increased in the EA group (P0.05) , rather than in the AEA group (P0.05). Additionally , compared to the normal group, the expression level of MOR protein in the amygdala was remarkably increased (P0.05) and those of GIuA 1, p-ERK 2 and p-CREB proteins were apparently decreased (P0.05). 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 (P0.001, P0.01, P0.05). The expression level of GIuA 1 was significantly higher in the EA group than in the AEA group (P0.05).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.

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.

Chronic pain is a common disability influencing quality of life. Results of previous studies showed that acupuncture has a cumulative analgesic effect, but the relationship with spinal cytokines neurotrophic factors released by astrocytes remains unknown. The present study was designed to observe the effect of electroacupuncture (EA) treatment on spinal cytokines neurotrophic factors in chronic neuropathic pain rats. The chronic neuropathic pain was established by chronic constrictive injury (CCI). EA treatment was applied at Zusanli (ST36) and Yanglingquan (GB34) (both bilateral) once a day, for 30 min. IL-1βmRNA, TNF-αmRNA, and IL-1 mRNA were detected by quantitative real-time PCR, and the proteins of BDNF, NGF, and NT3/4 were detected by Western blot. The expression levels of cytokines such as IL-1βmRNA, TNF-αmRNA, IL-6 mRNA, and neurotrophic factors such as BDNF, NGF, and NT3/4 in the spinal cord were increased significantly after CCI. The astrocytes released more IL-1βand BDNF after CCI. Repeated EA treatment could suppress the elevated expression of IL-1βmRNA, TNFαmRNA, and BDNF, NGF, and NT3/4 but had no effect on IL-6 mRNA. It is suggested that cytokines and neurotrophic factors which may be closely associated with astrocytes participated in the process of EA relieving chronic pain.

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.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.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 (P0. 05). In comparison with the model group, following 7 days' EA stimulation, PWLD were considerably decreased (P0. 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 (P0. 01, P0. 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 (P0. 05, P0. 01, P0. 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 (P0. 01, P0. 001).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.

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 β2 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 α4β2 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). The analgesic effect of EAS was abolished by intra-hippocampal microinjection of M1mAChR and α4β2 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 β2 nAChR proteins.