Astrocytes in the spinal dorsal horn (SDH) exhibit diverse reactive phenotypes under neuropathic conditions, yet the mechanisms driving this diversity and its implications in chronic pain remain unclear. Here, we report that spared nerve injury (SNI) induces marked upregulation of both complement component 3 (C3⁺, A1-like) and S100 calcium-binding protein A10 (S100A10⁺, A2-like) astrocyte subpopulations in the SDH, with elevated microglial cytokines including interleukin-1α, tumor necrosis factor-α, and complement component 1q. Transcriptomic, immunohistochemical, and Western blot analyses reveal co-activation of multiple reactive astrocyte states over a unidirectional shift toward an A1-like phenotype. Fibroblast growth factor 8 (FGF8), a neuroprotective factor via FGFR3, mitigated microglia-induced C3⁺ astrocyte reactivity in vitro and suppressed spinal C3 expression and mechanical allodynia following intrathecal administration in SNI mice. These findings reveal a microglia-astrocyte signaling axis that promotes A1 reactivity and position FGF8 as a promising therapeutic candidate for neuropathic pain by modulating astrocyte heterogeneity.
Animals ; Astrocytes/drug effects* ; Neuralgia/pathology* ; Receptor, Fibroblast Growth Factor, Type 3/metabolism* ; Signal Transduction/physiology* ; Male ; Mice ; Microglia/drug effects* ; Fibroblast Growth Factor 8/pharmacology* ; Mice, Inbred C57BL ; Hyperalgesia/drug therapy* ; Spinal Cord/drug effects* ; Complement C3/metabolism* ; Spinal Cord Dorsal Horn/metabolism*

Cancer pain is one of the most common symptoms in patients with advanced cancer. In this study, we aimed to investigate the effects of the Mas-related gene C (MrgC) receptors on bone cancer pain. Mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) were measured after the inoculation of Walker 256 mammary gland carcinoma cells into the tibia of adult Sprague-Dawley rats. The effects of MrgC receptor agonist bovine adrenal medulla 8-22 (BAM8-22) on nociceptive behaviors were investigated after intrathecal injection on days 16 and 17. Glial fibrillary acidic protein (GFAP)-positive cells in the spinal dorsal cord, and calcitonin gene related peptide (CGRP)-, neuronal nitric oxide synthase (nNOS)- and IL-1β-positive neurons in the dorsal root ganglia (DRG) were examined by immunofluorescence staining. The expression of nNOS and IL-1β proteins in the spinal dorsal horn and the DRG was examined by Western blotting after treatment with (Tyr6)-γ2-MSH-6-12 (MSH), which was another MrgC receptor agonist. The results showed that intrathecal injection of BAM8-22 (30 nmol) attenuated mechanical allodynia in a rat model of bone cancer pain and the effects could last for about 60 min, and single administration of BAM8-22 for two consecutive days reduced mechanical allodynia by about half on the third day. Moreover, the number of GFAP-positive cells in the spinal dorsal horn, and the number of CGRP-, nNOS- and IL-1β-positive neurons in the DRG were decreased. Similarly, intrathecal administration of MSH (15 nmol) reduced the expression of nNOS and IL-1β in the spinal dorsal horn and the DRG. In conclusion, activation of MrgC receptors suppresses the activation of astrocytes in the spinal dorsal cord and the expression of CGRP, nNOS, and IL-1β in the spinal dorsal cord and/or DRG, which may underlie the inhibition of bone cancer pain. These findings provide a novel strategy for the treatment of bone cancer pain.
Animals ; Cancer Pain/drug therapy* ; Rats ; Rats, Sprague-Dawley ; Bone Neoplasms/complications* ; Ganglia, Spinal/metabolism* ; Spinal Cord Dorsal Horn/metabolism* ; Receptors, G-Protein-Coupled/genetics* ; Female ; Calcitonin Gene-Related Peptide/genetics* ; Interleukin-1beta/metabolism* ; Peptide Fragments/metabolism* ; Nitric Oxide Synthase Type I/genetics* ; Disease Models, Animal

Mechanical allodynia (MA), including punctate and dynamic forms, is a common and debilitating symptom suffered by millions of chronic pain patients. Some peripheral injuries result in the development of bilateral MA, while most injuries usually led to unilateral MA. To date, the control of such laterality remains poorly understood. Here, to study the role of microglia in the control of MA laterality, we used genetic strategies to deplete microglia and tested both dynamic and punctate forms of MA in mice. Surprisingly, the depletion of central microglia did not prevent the induction of bilateral dynamic and punctate MA. Moreover, in dorsal root ganglion-dorsal root-sagittal spinal cord slice preparations we recorded the low-threshold Aβ-fiber stimulation-evoked inputs and outputs of superficial dorsal horn neurons. Consistent with behavioral results, microglial depletion did not prevent the opening of bilateral gates for Aβ pathways in the superficial dorsal horn. This study challenges the role of microglia in the control of MA laterality in mice. Future studies are needed to further understand whether the role of microglia in the control of MA laterality is etiology-or species-specific.
Mice ; Animals ; Hyperalgesia/metabolism* ; Microglia/metabolism* ; Disease Models, Animal ; Spinal Cord/metabolism* ; Spinal Cord Dorsal Horn/metabolism* ; Ganglia, Spinal/metabolism*

OBJECTIVE: To observe the analgesic effect of Tuina by pressing and kneading the Huantiao (GB30) acupoint on rats with chronic constriction injury (CCI) and to explore the analgesic mechanism of Tuina on sciatica rats. METHODS: Thirty-two SPF male SD rats weighing 180 to 220 g were randomly divided into fore groups:blank group (without any treatment), sham group (only exposed without sciatic nerve ligating), model group (sciatic nerve ligating) and Tuina group (manual intervention after lsciatic nerve ligating). The CCI model was prepared by ligating the right sciatic nerve of the rats, on the third day of modeling, the rats in the Tuina group were given pressing and kneading the Huantiao (GB30) point for 14 days, and the changes of paw withdrawal threshold(PWT), paw withdrawal latency(PWL) were measured before and on the 1st, 3rd, 7th, 10th, 14th and 17th days after modeling. The changes of sciatic functional index(SFI) were measured before and on the 1st and 17th day after modeling. The morphological changes of the sciatic nerve were observed by hematoxylin-eosin(HE) staining;and the differences in NF-κB protein expression in the right dorsal horn of the spinal cord of rats were detected. RESULTS: Following modeling, there was no significant difference in PWT, PWL and SFI between the blank group and the sham group (P>0.05), but the PWT, PWL and SFI of the model group and the Tuina group decreased significantly (P<0.01). After manual intervention, the pain threshold of rats in Tuina group increased. On the 8th day of manual intervention (the 10th day after modeling), PWT in Tuina group increased significantly compared with that in model group (P<0.01). On the 5th day of manual intervention (the 7th day after modeling), the PWL of the massage group was significantly higher than that of the model group (P<0.01). The pain threshold of rats in Tuina group continued to rise with the continuous manipulation intervention. After 14 days of manipulative intervention, the sciatic nerve function index of rats in the Tuina group increased significantly(P<0.01). Compared with the blank group and sham group, the myelinated nerve fibers of sciatic nerve in the model group were disordered and the density of axons and myelin sheath was uneven. Compared with the model group, the nerve fibers of rats in the Tuina group were gradually continuous and the axons and myelin sheath were more uniform than those in the model group. Compared with the blank group and sham group, the expression of NF-κB protein in the right spinal dorsal horn of the model group was significantly increased(P<0.01). Compared with the model group, the expression of NF-κB protein in the right spinal dorsal horn of rats in Tuina group decreased significantly(P<0.01). CONCLUSION Pressing and kneading the Huantiao (GB30) point restores nerve fiber alignment;and improves the PWT、PWL and SFI in the CCI model by decreasing NF-κB p65 protein expression in the spinal dorsal horn. There fore, Tuina demmstrates an analgesic effect and improves the gait of rats with sciatica.
Rats ; Male ; Animals ; Rats, Sprague-Dawley ; Sciatica/therapy* ; NF-kappa B/metabolism* ; Acupuncture Points ; Spinal Cord Dorsal Horn/metabolism* ; Spinal Cord ; Massage

Effective treatments for neuropathic pain are lacking due to our limited understanding of the mechanisms. The circRNAs are mainly enriched in the central nervous system. However, their function in various physiological and pathological conditions have yet to be determined. Here, we identified circFhit, an exon-intron circRNA expressed in GABAergic neurons, which reduced the inhibitory synaptic transmission in the spinal dorsal horn to mediate spared nerve injury-induced neuropathic pain. Moreover, we found that circFhit decreased the expression of GAD65 and induced hyperexcitation in NK1R⁺ neurons by promoting the expression of its parental gene Fhit in cis. Mechanistically, circFhit was directly bound to the intronic region of Fhit, and formed a circFhit/HNRNPK complex to promote Pol II phosphorylation and H2B monoubiquitination by recruiting CDK9 and RNF40 to the Fhit intron. In summary, we revealed that the exon-intron circFhit contributes to GABAergic neuron-mediated NK1R⁺ neuronal hyperexcitation and neuropathic pain via regulating Fhit in cis.
Rats ; Animals ; Posterior Horn Cells/pathology* ; Spinal Cord Dorsal Horn/metabolism* ; Neuralgia ; Synaptic Transmission

OBJECTIVE: To observe the occurrence time of neuralgia and the expression of purinergic ligand-gated ion channel 7 receptor (P2X7R) in the dorsal horn of the spinal cord after intraperitoneal injection of streptozotocin (STZ) in diabetic rats, and to explore the effect of electroacupuncture (EA) and pretreatment of EA on the heat pain threshold and expression of P2X7R in the spinal dorsal horn in rats with diabetic neuropathic pain (DNP), and to explore the possible mechanism of EA for DNP. METHODS: PartⅠ: Thirty male SD rats were randomly selected from 64 male SD rats as the control group; the remaining rats were given intraperitoneal injection of STZ (10 mg/mL) at a dose of 65 mg/kg to establish the diabetes model, and 30 rats were successfully modeled as the model group. The control group and the model group were divided into three subgroups respectively at 7, 14 and 21 days, with 10 rats in each subgroup. Body mass, fasting blood glucose (FBG) and thermal pain threshold were recorded at 7, 14 and 21 days after injection; the expression of P2X7R in spinal dorsal horn was detected by Western blot. PartⅡ: Eight SD rats were randomly selected from 35 male SD rats as the blank group, and the remaining 27 rats were given intraperitoneal injection of STZ (10 mg/mL) at a dose of 65 mg/kg to establish the diabetes model. The 24 rats with successful diabetes model were randomly divided into a DNP group, an EA group and a pre-EA group, 8 rats in each group. Fifteen to 21 days after STZ injection, the EA group received EA at "Zusanli" (ST 36) and "Kunlun" (BL 60), continuous wave, frequency of 2 Hz, 30 min each time, once a day; the intervention method in the pre-EA group was the same as that in the EA group. The intervention time was 8 to 14 days after STZ injection. The body mass, FBG and thermal pain threshold were recorded before STZ injection and 7, 14 and 21 days after STZ injection; the expression of P2X7R in spinal dorsal horn was detected by Western blot 21 days after injection. RESULTS: PartⅠ: Compared with the control group, in the model group, the body mass was decreased and FBG was increased 7, 14 and 21 days after STZ injection (P<0.01), and the thermal pain threshold was decreased 14 and 21 days after STZ injection (P<0.05), and the expression of P2X7R in spinal dorsal horn was increased 7, 14 and 21 days after STZ injection (P<0.05, P<0.01). PartⅡ: Compared with the blank group, in the DNP group, the body mass was decreased and fasting blood glucose were increased 7, 14 and 21 days after STZ injection (P<0.01). Compared with the DNP group, in the pre-EA group, the heat pain threshold was increased 14 and 21 days after STZ injection (P<0.05), while in the EA group, the heat pain threshold was increased 21 days after STZ injection (P<0.01), and the expression of P2X7R in the dorsal horn in the EA group and the pre-EA group was decreased (P<0.01). CONCLUSION The diabetic neuropathic pain is observed 14 days after STZ injection. EA could not only treat but also prevent the occurrence of DNP, and its mechanism may be related to down-regulation of P2X7R expression in the dorsal horn of the spinal cord.
Animals ; Diabetes Mellitus, Experimental/therapy* ; Electroacupuncture ; Male ; Neuralgia/therapy* ; Rats ; Rats, Sprague-Dawley ; Spinal Cord ; Spinal Cord Dorsal Horn

OBJECTIVE: To observe the effect of wheat-grain moxibustion at "Dazhui" (GV 14) on the expressions of Beclin-1 and GRP78 in spinal dorsal horn in rats with cervical spondylotic radiculopathy (CSR), and to explore the possible analgesic mechanism of wheat-grain moxibustion for CSR. METHODS: A total of 48 SD rats were randomly divided into a sham operation group, a model group, a wheat-grain moxibustion group and a wheat-grain moxibustion+3-MA group, 12 rats in each group. The CSR model was prepared by spinal cord insertion method. Three days after modeling, the rats in the model group were intraperitoneally injected with 1 mL of 0.9% sodium chloride solution; the rats in the wheat-grain moxibustion group were treated with wheat-grain moxibustion at "Dazhui" (GV 14, 6 cones per time) on the basis of the model group; the rats in the wheat-grain moxibustion+3-MA group were intraperitoneally injected with 3-MA solution and wheat-grain moxibustion at "Dazhui" (GV 14, 6 cones per time). The three groups were intervened for 7 days, once a day. The gait score and mechanical pain threshold were observed before treatment and 7 days into treatment; after the treatment, the expressions of mRNA and protein of Beclin-1 in spinal dorsal horn were detected by real-time fluorescence quantitative PCR and immunohistochemistry; the expression of GRP78 protein in spinal dorsal horn was detected by Western blot method; the autophagosomes and ultrastructure in spinal dorsal horn neurons were observed by electron microscope. RESULTS: After the treatment, compared with the sham operation group, in the model group, the gait score was increased and the mechanical pain threshold was decreased (P<0.01), and the expression of GRP78 protein in spinal dorsal horn was increased (P<0.01). Compared with the model group and the wheat-grain moxibustion+3-MA group, in the wheat-grain moxibustion group, the gait score was decreased and mechanical pain threshold was increased (P<0.01), and the expression of GRP78 protein in spinal dorsal horn was decreased, and the expressions of mRNA and protein of Beclin-1 were increased (P<0.01). Under electron microscope, the ultrastructure of spinal dorsal horn neurons in the wheat-grain moxibustion group was not significantly damaged, and its structure was basically close to normal, and the number of autophagosomes was more than the other three groups. CONCLUSION Wheat-grain moxibustion at "Dazhui" (GV 14) has analgesic effect on CSR rats. The mechanism may be related to moderately up-regulate the expression of Beclin-1, enhance autophagy and reduce endoplasmic reticulum stress.
Animals ; Beclin-1/genetics* ; Endoplasmic Reticulum Chaperone BiP ; Moxibustion ; RNA, Messenger ; Radiculopathy/therapy* ; Rats ; Rats, Sprague-Dawley ; Spinal Cord ; Spinal Cord Dorsal Horn ; Spondylosis ; Triticum/genetics*

OBJECTIVE: To investigate the mechanisms underlying elemene-induced analgesia in rats with spared nerve injury (SNI). METHODS: Sixty-five rats were equally divided into 5 groups using a random number table: naive group, sham group, SNI group, SNI + elemene (40 mg·kg RESULTS: The SNI rat model exhibited a significant decrease in paw withdrawal threshold and exploratory behaviour in the EPM (P<0.05). Consecutive administration of elemene alleviated SNI-induced mechanical allodynia and anxiety in rats (P<0.05). Immunohistochemical data showed that elemene decreased SNI-induced upregulation of NDRG2 within the SDH (P<0.05). Double immunofluorescent staining data further showed that elemene decreased SNI-induced upregulation of the number of GFAP immunoreactive (-ir), NDRG-ir, and GFAP/NDRG2 double-labelled cells within the SDH (P<0.05). Immunoblotting data showed that elemene decreased SNI-induced upregulation of GFAP and NDRG2 within the SDH (P<0.05). CONCLUSION Elemene possibly alleviated neuropathic pain by downregulating the expression of NDRG2 in spinal astrocytes in a rat model of SNI.
Animals ; Astrocytes ; Disease Models, Animal ; Emulsions ; Hyperalgesia/drug therapy* ; Nerve Tissue Proteins ; Neuralgia/drug therapy* ; Rats ; Rats, Sprague-Dawley ; Sesquiterpenes ; Spinal Cord ; Spinal Cord Dorsal Horn

PURPOSE: The aim of this study was to characterize the responsiveness of miniature excitatory postsynaptic currents (mEPSCs) to α1-adrenoceptor blockers in substantia gelatinosa (SG) neurons from the spinal cord to develop an explanation for the efficacy of α1-adrenoceptor blockers in micturition dysfunction. METHODS: Male adult Sprague-Dawley rats were used. Blind whole-cell patch-clamp recordings were performed using SG neurons in spinal cord slices. Naftopidil (100μM), tamsulosin (100μM), or silodosin (30μM), α1-adrenoceptor blockers, was perfused. The frequency of mEPSCs was recorded in an SG neuron to which the 3 blockers were applied sequentially with wash-out periods. Individual frequencies in a pair before naftopidil and tamsulosin perfusion were plotted as baseline, and the correlation between them was confirmed by Spearman correlation coefficient; linear regression was then performed. The same procedure was performed before naftopidil and silodosin perfusion. Frequencies of pairs after naftopidil and tamsulosin perfusion and after naftopidil and silodosin perfusion were similarly analyzed. The ratios of the frequencies after treatment to before were then calculated. RESULTS: After the treatments, Spearman ρ and the slope were decreased to 0.682 from 0.899 at baseline and 0.469 from 1.004 at baseline, respectively, in the tamsulosin group relative to the naftopidil group. In the silodosin group, Spearman ρ and the slope were also decreased to 0.659 from 0.889 at baseline and 0.305 from 0.989 at baseline, respectively, relative to the naftopidil group. Naftopidil significantly increased the ratio of the frequency of mEPSCs compared to tamsulosin and silodosin (P=0.015 and P=0.004, respectively). CONCLUSIONS: There was a difference in responsiveness in the frequency of mEPSCs to α1-adrenoceptor blockers, with the response to naftopidil being the greatest among the α1-adrenoceptor blockers. These data are helpful to understand the action mechanisms of α1-adrenoceptor blockers for male lower urinary tract symptoms in clinical usage.
Adrenergic alpha-1 Receptor Antagonists ; Adult ; Animals ; Excitatory Postsynaptic Potentials ; Humans ; Linear Models ; Lower Urinary Tract Symptoms ; Male ; Neurons ; Perfusion ; Rats ; Rats, Sprague-Dawley ; Spinal Cord ; Substantia Gelatinosa ; Urination

The lamina II, also called the substantia gelatinosa (SG), of the trigeminal subnucleus caudalis (Vc), is thought to play an essential role in the control of orofacial nociception. Glycine and serotonin (5-hydroxytryptamine, 5-HT) are the important neurotransmitters that have the individual parts on the modulation of nociceptive transmission. However, the electrophysiological effects of 5-HT on the glycine receptors on SG neurons of the Vc have not been well studied yet. For this reason, we applied the whole-cell patch clamp technique to explore the interaction of intracellular signal transduction between 5-HT and the glycine receptors on SG neurons of the Vc in mice. In nine of 13 neurons tested (69.2%), pretreatment with 5-HT potentiated glycine-induced current (I(Gly)). Firstly, we examined with a 5-HT₁ receptor agonist (8-OH-DPAT, 5-HT(1/7) agonist, co-applied with SB-269970, 5-HT₇ antagonist) and antagonist (WAY-100635), but 5-HT₁ receptor agonist did not increase IGly and in the presence of 5-HT₁ antagonist, the potentiation of 5-HT on I(Gly) still happened. However, an agonist (α-methyl-5-HT) and antagonist (ketanserin) of the 5-HT₂ receptor mimicked and inhibited the enhancing effect of 5-HT on I(Gly) in the SG neurons, respectively. We also verified the role of the 5-HT₇ receptor by using a 5-HT₇ antagonist (SB-269970) but it also did not block the enhancement of 5-HT on I(Gly). Our study demonstrated that 5-HT facilitated I(Gly) in the SG neurons of the Vc through the 5-HT₂ receptor. The interaction between 5-HT and glycine appears to have a significant role in modulating the transmission of the nociceptive pathway.
Animals ; Glycine ; Mice ; Neurons ; Neurotransmitter Agents ; Nociception ; Patch-Clamp Techniques ; Receptors, Glycine ; Serotonin ; Signal Transduction ; Substantia Gelatinosa