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Background: Hepatocellular carcinoma (HCC) is one of the most frequent cancers with a high recurrence rate and poor prognosis. eukaryotic translation initiation factor 2 subunit gamma (EIF2S3) is a heterotrimeric GTP binding protein, taking part in the recruitment of methionyl-tRNA to the 40 S ribosomal subunit. However, the role of EIF2S3 in HCC remains unclear. Materials and methods: In the present study, the expression level of EIF2S3 in pan-cancer was identified using TIMER database and its level in HCC tissues was detected by TCGA database. Univariate and multivariate Cox regression analysis was performed to evaluate the relationship between EIF2S3 and clinical characteristics in HCC. Kaplan-Meier Plotter analysis was used to assess the prognostic role of EIF2S3 in HCC patients. Function enrichment analysis was conducted by LinkedOmics database. The association between EIF2S3 level and immune infiltration, and the correlation between EIF2S3 expression and immune cell biomarkers in HCC were analyzed by TIMER and GEPIA database. Finally, the protein expression of EIF2S3 in HCC cell lines was analyzed and the proliferation, migration, invasion and apoptosis of HCC cells after silencing EIF2S3, which were detected by cell viability assay, wound healing assay, transwell assay and flow cytometry analysis, respectively. Results: EIF2S3 was overexpressed in many solid tumors. And, high EIF2S3 expression was detected in HCC and significantly related to tumor status and prognosis of HCC patients. Moreover, EIF2S3 expression was positively related to immune cell infiltration and gene marker of immune cells in HCC patients. Cell experiments showed thatEIF2S3 was overexpressed in HCC cells and EIF2S3 enhanced the proliferation, migration and invasion of HCC cells and decreased the apoptosis of HCC cells. Conclusion: EIF2S3 may be involved in the development of HCC and could be a prognostic genomic marker and a novel therapeutic target for HCC.

Introduction Pain-related behavior secondary to masticatory function can be assessed with the rodent bite force model. A reduction of the bite force has been shown to be related to pain associated with the masseter muscle and jaw activity, while an increase in bite force suggests improvement of muscle function and less pain. To evaluate the usefulness of the bite force measure in studying long-lasting orofacial pain we analyzed biting parameters during prolonged myofascial pain induced by ligation injury of the masseter muscle tendon (TL) in mice. Methods C57Bl/6 mice were habituated to bite at a pair of aluminum plates attached to a force displacement transducer. The transduced voltage signals were amplified and converted to force through calibration with a standard weight set. Voluntary biting behavior was recorded for 100 s/session and those with bite forces ≥980 mN were analyzed. Nociception was also verified with von Frey, conditioned place avoidance (CPA) tests and mouse grimace scale. Persistent orofacial pain was induced with unilateral ligation of one tendon of the masseter muscle (TL). Results To reduce interference of random bites of smaller forces, the top 5 or 15 bite forces (BF5/15) were chosen as a measure of masticatory function and related to pain behavior. Both male and female mice exhibited similar BF5/15. For the first nascent test of all mice, mean bite force was significantly and positively correlated with the body weight. However, this correlation was less clear in the latter tests (2–8 w). TL induced a reduction of BF5/15 that peaked at 1 w and returned to the baseline within 3 w. The von Frey and CPA tests indicated that mechanical allodynia/hyperalgesia persisted at the time when the BF had returned to the pre-injury level. Infusion of pain-relieving bone marrow stromal cells improved biting behavior in both male and female mice as shown by significantly increased BF5/15, compared to vehicle-treated mice. Conclusions Mouse voluntary biting behavior can be reliably measured and quantified with a simplified setup. The bite force showed an inverse relationship with the level of pain after TL and was improved by pain-relieving manipulations. However, the injury-induced reduction of bite force peaked early and did not parallel with other measures of nociception in the later phase of hyperalgesia. The results suggest that multiple factors such as the level of habituation, cognitive motive, physical status, and feeding drive may affect random voluntary biting and confound the biting parameters related to maintained hyperalgesia.

The micro-environment formed by the photosynthesis of submerged plants is conducive to the formation of CaCO

Craniofacial muscle pain is highly prevalent in temporomandibular disorders but is difficult to treat. Enhanced understanding of neurobiology unique to craniofacial muscle pain should lead to the development of novel mechanism-based treatments. Herein, we review recent studies to summarize neural pathways of craniofacial muscle pain. Nociceptive afferents in craniofacial muscles are predominantly peptidergic afferents enriched with TRPV1. Signals from peripheral glutamate receptors converge onto TRPV1, leading to mechanical hyperalgesia. Further studies are needed to clarify whether hyperalgesic priming in nonpeptidergic afferents or repeated acid injections also affect craniofacial muscle pain. Within trigeminal ganglia, afferents innervating craniofacial muscles interact with surrounding satellite glia, which enhances the sensitivity of the inflamed neurons as well as nearby uninjured afferents, resulting in hyperalgesia and ectopic pain originating from adjacent orofacial tissues. Craniofacial muscle afferents project to a wide area within the trigeminal nucleus complex, and central sensitization of medullary dorsal horn neurons is a critical factor in muscle hyperalgesia related to ectopic pain and emotional stress. Second-order neurons project rostrally to pathways associated with affective pain, such as parabrachial nucleus and medial thalamic nucleus, as well as sensory-discriminative pain, such as ventral posteromedial thalamic nuclei. Abnormal endogenous pain modulation can also contribute to chronic muscle pain. Descending serotonergic circuits from the rostral ventromedial medulla facilitate activation of second-order neurons in the trigeminal nucleus complex, which leads to the maintenance of mechanical hyperalgesia of inflamed masseter muscle. Patients with temporomandibular disorders exhibit altered brain networks in widespread cortical and subcortical regions. Recent development of methods for neural circuit manipulation allows silencing of specific hyperactive neural circuits. Chemogenetic silencing of TRPV1-expressing afferents or rostral ventromedial medulla neurons attenuates hyperalgesia during masseter inflammation. It is likely, therefore, that further delineation of neural circuits mediating craniofacial muscle hyperalgesia potentially enhances treatment of chronic muscle pain conditions.

An environment-friendly methodology for the synthesis of 1,2,4-triazoline derivatives on water is described. This method provides an environmental and useful strategy for catalyst-free synthesis of 1,2,4-triazolines derivatives. The gram scale reaction and one-pot reaction are also performed to ensure the scalability and high efficiency of the reaction.

The exact mechanism by which knockout of Toll-like receptor 4 (TLR4) attenuates the liver injury remains unclear. The present study aimed to examine the role of TLR4 in the pathogenesis of bile duct ligation (BDL)-induced liver cholestatic injury and the underlying mechanism. Wild type (WT) mice and TLR4 knockout (TLR4-KO) mice were used for the establishment of the BDL model. Metabolomics were applied to analyze the changes of small molecular metabolites in the serum and liver of the two groups. The serum biochemical indexes and the HE staining results of liver tissue showed that liver damage was significantly reduced in TLR4-KO mice after BDL when compared with that in WT mice. The metabolite analysis results showed that TLR4 KO could maintain the metabolisms of amino acids- and choline-related metabolites. After BDL, the amino acids- and choline-related metabolites, especially choline and 3-hydroxybutyrate, were significantly increased in WT mice (both in serum and liver), but these metabolites in the liver of TLR4-KO mice after BLD were not significant different from those before BLD. In conclusion, TLR4 KO could attenuate BDL-induced liver cholestatic injury through regulating amino acid and choline metabolic pathways.

Oxytocin is a well-known neurohypophysial hormone that plays an important role in behavioral anxiety and nociception. Two major forms of long-term potentiation, presynaptic LTP (pre-LTP) and postsynaptic LTP (post-LTP), have been characterized in the anterior cingulate cortex (ACC). Both pre-LTP and post-LTP contribute to chronic-pain-related anxiety and behavioral sensitization. The roles of oxytocin in the ACC have not been studied. Here, we find that microinjections of oxytocin into the ACC attenuate nociceptive responses and anxiety-like behavioral responses in animals with neuropathic pain. Application of oxytocin selectively blocks the maintenance of pre-LTP but not post-LTP. In addition, oxytocin enhances inhibitory transmission and excites ACC interneurons. Similar results are obtained by using selective optical stimulation of oxytocin-containing projecting terminals in the ACC in animals with neuropathic pain. Our results demonstrate that oxytocin acts on central synapses and reduces chronic-pain-induced anxiety by reducing pre-LTP.

Trigeminal neuropathic pain (TNP) is often resistant to current pharmacotherapy, and there is a pressing need to develop more efficacious treatments. Capsaicin is a pungent ingredient of chili peppers and specifically activates transient receptor potential vanilloid subtype 1 (TRPV1), a Ca2+-permeable ion channel. Topical capsaicin invariably induces burning pain. Paradoxically, the transient pain is often followed by prolonged attenuation of the preexisting pathologic pain from the same region. However, the mechanisms underlying capsaicin-induced analgesia are not well understood. Although the reports of the involvement of TRPV1 and TRPV1+ afferents in neuropathic pain are controversial, we recently demonstrated that TRPV1 and TRPV1+ afferents are involved in mechanical hyperalgesia in mice with chronic constriction injury of the infraorbital nerve (ION-CCI). Consistently, chemogenetic inhibition of TRPV1-lineage (TRPV1-LN) afferents attenuated mechanical hyperalgesia and ongoing pain. In mice with ION-CCI, we found that a single focal injection of capsaicin into facial skin led to attenuation of mechanical hyperalgesia over two weeks. Capsaicin treatment also attenuated secondary hyperalgesia in extraterritorial mandibular skin. Furthermore, capsaicin treatment decreased ongoing pain. Longitudinalin vivotwo-photon imaging of cutaneous nerve fibers showed that such capsaicin-induced analgesia is correlated with cutaneous nerve terminal density. Furthermore, preventing capsaicin-induced ablation of afferent terminals by co-administration of capsaicin with MDL28170, an inhibitor of calpain, abolished capsaicin-induced analgesia. These results suggest that a single focal injection of capsaicin induces long-lasting analgesia for neuropathic pain via selective ablation of TRPV1+ afferent terminals and that TRPV1+ afferents contribute to the maintenance of TNP.

Bone marrow stromal cells (BMSCs) produce long-lasting attenuation of pain hypersensitivity. This effect involves BMSC’s ability to interact with the immune system and activation of the endogenous opioid receptors in the pain modulatory circuitry. The nuclear factor kappa B (NF-κB) protein complex is a key transcription factor that regulates gene expression involved in immunity. We tested the hypothesis that the NF-κB signaling plays a role in BMSC-induced pain relief. We focused on the rostral ventromedial medulla (RVM), a key structure in the descending pain modulatory pathway, that has been shown to play an important role in BMSC-produced antihyperalgesia. In Sprague-Dawley rats with a ligation injury of the masseter muscle tendon (TL), BMSCs (1.5 M/rat) from donor rats were infused i.v. at 1 week post-TL. P65 exhibited predominant neuronal localization in the RVM with scattered distribution in glial cells. At 1 week, but not 8 weeks after BMSC infusion, western blot and immunostaining showed that p65 of NF-κB was significantly increased in the RVM. Given that chemokine signaling is critical to BMSCs’ pain-relieving effect, we further evaluated a role of chemokine signaling in p65 upregulation. Prior to infusion of BMSCs, we transduced BMSCs with Ccl4 shRNA, incubated BMSCs with RS 102895, a CCR2b antagonist, or maraviroc, a CCR5 antagonist. The antagonism of chemokines significantly reduced BMSC-induced upregulation of p65, suggesting that upregulation of p65 was related to BMSCs’ pain-relieving effect. We then tested the effect of a selective NF-κB activation inhibitor, BAY 11-7082. The mechanical hyperalgesia of the rat was assessed with the von Frey method. In the pre-treatment experiment, BAY 11-7082 (2.5 and 25 pmol) was injected into the RVM at 2 h prior to BMSC infusion. Pretreatment with BAY 11-7082 attenuated BMSCs’ antihyperalgesia, but post-treatment at 5 weeks post-BMSC was not effective. On the contrary, in TL rats receiving BAY 11-7082 without BMSCs, TL-induced hyperalgesia was attenuated, consistent with dual roles of NF-κB in pain hypersensitivity and BMSC-produced pain relief. These results indicate that the NF-κB signaling pathway in the descending circuitry is involved in initiation of BMSC-produced behavioral antihyperalgesia.

Dexmedetomidine, a selective alpha 2-adrenoceptor (α2AR) agonist, has provided significant analgesia in neuropathic pain. However, its underlying molecular mechanism has not been fully elucidated. In the present study, we found that intrathecal administration of dexmedetomidine alleviated mechanical allodynia induced by chronic constriction injury (CCI), and pretreatment with BRL44408 significantly reversed the dexmedetomidine-induced anti-nociceptive effect. Western blotting revealed that dexmedetomidine reduced the activation of microglia and the upregulation of interleukin-18 (IL-18) protein expression in the ipsilateral lumbar spinal dorsal horn, while BRL44408 pretreatment significantly blocked these effects of dexmedetomidine. Immunocytochemistry/immunohistochemistry indicated that the α2A-adrenoceptor was localised to microglia in primary culture, and IL-18 predominantly colocalised with the microglial marker Iba-1 in the dorsal horn of the spinal cord. These results suggest that the IL-18 signalling pathway in microglia may be involved in the anti-nociceptive effect of dexmedetomidine in rats subjected to CCI.

Background Bone marrow stromal cells (BMSCs) have shown potential to treat chronic pain, although much still needs to be learned about their efficacy and mechanisms of action under different pain conditions. Here, we provide further convergent evidence on the effects of BMSCs in rodent pain models. Results In an orofacial pain model involving injury of a tendon of the masseter muscle, BMSCs attenuated behavioral pain conditions assessed by von Frey filaments and a conditioned place avoidance test in female Sprague-Dawley rats. The antihyperalgesia of BMSCs in females lasted for

Background The glutamate type 1 transporter (GLT1) plays a major role in glutamate homeostasis in the brain. Although alterations of GLT1 activity have been linked to persistent pain, the significance of these changes is poorly understood. Focusing on the rostral ventromedial medulla, a key site in pain modulation, we examined the expression and function of GLT1 and related transcription factor kappa B-motif binding phosphoprotein (KBBP) in rats after adjuvant-induced hind paw inflammation. Results After inflammation, GLT1 and KBBP showed an early upregulation and gradual transition to downregulation that lasted throughout the eight-week observation period. Nitration of GLT1 was reduced at 30 min and increased at eight weeks after inflammation, suggesting an initial increase and later decrease in transporter activity. Mechanical hyperalgesia and paw edema exhibited an initial developing phase with peak hyperalgesia at 4 to 24 h, a subsequent attenuating phase, followed by a late persistent phase that lasted for months. The downregulation of GLT1 occurred at a time when hyperalgesia transitioned into the persistent phase. In the rostral ventromedial medulla, pharmacological block with dihydrokainic acid and RNAi of GLT1 and KBBP increased nociception and overexpression of GLT1 reversed persistent hyperalgesia. Further, the initial upregulation of GLT1 and KBBP was blocked by local anesthetic block, and pretreatment with dihydrokainic acid facilitated the development of hyperalgesia. Conclusions These results suggest that the initial increased GLT1 activity depends on injury input and serves to dampen the development of hyperalgesia. However, later downregulation of GLT1 fosters the net descending facilitation as injury persists, leading to the emergence of persistent pain.

1. Spinal glial cells play a key role in developing and maintaining allodynia and hyperalgesia following tissue inflammation. Dexmedetomidine, a highly selective α(2) -adrenoceptor (α(2) -AR) agonist, has exhibited a significant analgesic effect in various rodent models of chronic pain. However, whether spinal glial activation is involved in the analgesic effect of dexmedetomidine remains unknown. The present study investigated whether spinal administration of dexmedetomidine could antagonize glial activation in the spinal dorsal horn and attenuate thermal hyperalgesia in complete Freund's adjuvant (CFA)-induced ankle joint monoarthritic (MA) rats. 2. Unilateral intra-articular injection of CFA produced a robust activation of microglia and astrocytes in the spinal cord, which was associated with the development and maintenance of thermal hyperalgesia. Repeated lumbar puncture (LP) administration of dexmedetomidine (10 μg) significantly attenuated MA-induced thermal hyperalgesia in a cumulative manner. Monoarthritis-induced spinal glial activation was also suppressed following dexmedetomidine application. The α(2A) -AR, essential for the antinociceptive effects of α(2) -AR agonists, was detected in spinal neurons and glia, as well as in dorsal root ganglion primary afferent neurons, which may be implicated in dexmedetomidine-induced suppression of spinal glial activation and antihyperalgesic effects. 3. These data provide the first evidence that blocking spinal glial activation is involved in the analgesic action of dexmedetomidine.

To investigate the effect of systemic administration dexmedetomidine, a selective alpha 2 adrenergic receptor (alpha(2)AR) agonist, on thermal hyperalgesia and spinal glial activation evoked by monoarthritis (MA).MA was induced by an intra-articular injection of complete Freund's adjuvant (CFA). Thermal hyperalgesia was measured by Hargreaves' test. The spinal glial activation status was analyzed by GFAP (an astrocytic marker) and Iba-1 (a microglial marker) immunohistochemistry or immunoblotting.Unilateral intra-articular injection of CFA produced a robust glial activation of astrocytes and microglia in the spinal cord, which was associated with the development and maintenance of thermal hyperalgesia. Intraperitoneal (ip) injection of dexmedetomidine (2.5 and 10 microg/kg) was repeatedly given once daily for 5 days with the first injection 60 min before intra-articular CFA. At the dose of 10 microg/kg, dexmedetomidine significantly attenuated MA-induced ipsilateral hyperalgesia from day 2 to day 5. MA-induced up-regulation of GFAP expression on both sides of the spinal dorsal horn was significantly suppressed by day 5 post-MA following dexmedetomidine application, whereas MA-induced Iba-1 up-regulation was only partially suppressed.Systemic dexmedetomidine inhibits the activation of spinal glia, which is possibly associated with its antihyperalgesia in monoarthritic rats.

To compare the differences in the efficacy on distant version of naked eye in the patients of juvenile myopia between rotating manipulation and lifting-thrusting manipulation of acupuncture.One hundred and twenty cases (240 eyes) were randomized into a rotating manipulation group and a lifting-thrusting manipulation group, 60 cases (120 eyes) in each group. Additionally, a corrective lenses group, 60 cases (120 eyes), was set up as the control. In both manipulation groups, Cuanzhu (BL 2),Yuyao (EX-HN 4), Sizhukong (TE 23), Taiyang (EX-HN 5), Fengchi (GB 20), Zusanli (ST 36), Guangming (GB 37) and Sanyinjiao (SP 6) were punctured, but stimulated with rotating manipulation and lifting-thrusting manipulation respectively three times per week, 10 times as a treatment session and totally one session was required. In the corrective lenses group, the glasses were applied at daytime. The clinical efficacy and the changes in distant vision of naked eye before and after treatment were compared among the three groups.The total effective rate was 87.5% (105/120) in the rotating manipulation group, which was better than 69.2% (83/120) in the lifting-thrusting manipulation group (P0.05). The distant vision of naked eye was improved apparently in the rotating manipulation group and the lifting-thrusting manipulation group after treatment (both P0.05). But it was not improved in the corrective lenses group (P0.05). The distant vision of naked eye was improved more apparently after treatment in the rotating manipulation group as compared with that in the lifting-thrusting manipulation group (0.75 +/- 0.23 vs 0.68 +/- 0.24, P0.05). For 96 cases (192 eyes) with acupuncture treatment, in 3-month follow-up, 87.0% (167/192) of the cases maintained the stable vision as the original level and 13.0% (25/192) of them were reduced in the vision In the acupuncture groups, it was found that the improvement of distant vision of naked eye was more obvious after treatment with younger age, better basic vision and shorter duration of sickness (all P0.05).Acupuncture achieves the positive and sustainable clinical effect on juvenile myopia, and the results of rotating manipulation are superior to that of lifting-thrusting manipulation. Age, basic vision and duration of sickness impact the clinical efficacy.

Tetanic stimulation of the sciatic nerve (TSS) induces sciatic nerve injury and long-lasting pain hypersensitivity in rats, and spinal glial activation and proinflammatory cytokines releases are involved. In the present study, we showed that spinal interleukin (IL)-23 and its receptor, IL-23R, are crucial for the development of mechanical allodynia after TSS. In the spinal dorsal horn, both IL-23 and IL-23R are expressed in astrocytes, and this expression is substantially increased after TSS. Inhibition of IL-23 signaling attenuated TSS-induced allodynia and decreased the induction of glial fibrillary acidic protein (GFAP, an astrocytic marker). Conversely, intrathecally delivered IL-23 induced a persistent allodynia. Similar to IL-23 signaling, an increase in IL-18 and its receptor, IL-18R, as well as CX3CL1 and its receptor, CX3CR1, was simultaneously observed in the spinal dorsal horn after TSS. Interestingly, IL-18 and CX3CR1 were exclusively expressed in microglia, while IL-18R was mainly localized in astrocytes. In contrast, CX3CL1 was predominately expressed in neurons and secondarily in astrocytes. The functional inhibition of CX3CL1 and IL-18 signaling attenuated TSS-induced allodynia and suppressed IL-23 and IL-23R upregulation. Activation of CX3CR1 and IL-18R induced similar behavioral and biochemical changes to those observed after TSS. These results indicate that the interaction among CX3CL1, IL-18 and IL-23 signaling in the spinal cord plays a critical role in the development of allodynia. Thus, interrupting this chemokine-cytokine network might provide a novel therapeutic strategy for neuropathic pain.

Background Spinal glia, particularly microglia and astrocytes, are of the utmost importance in the development and maintenance of chronic pain. A recent study from our laboratory revealed that gabapentin, a recommended first-line treatment for multiple neuropathic conditions, could also efficiently antagonize thermal hyperalgesia evoked by complete Freund's adjuvant (CFA)-induced monoarthritis (MA). In the present study, we investigated whether the spinal glia are involved in the anti-hyperalgesic effect of gabapentin and how this event occurs. Results Unilateral intra-articular injection of CFA produced a robust activation of microglia and astrocytes. These cells exhibited large cell bodies, thick processes and increases in the ionized calcium binding adapter molecule 1 (Iba-1, a microglial marker) or the glia fibrillary acidic protein (GFAP, an astrocytic marker). These cells also displayed immunoreactive signals, and an upregulation of the voltage-gated calcium channels (VGCCs) α2/δ-1 subunit, CX3CL1 and CX3CR1 expression levels in the spinal cord. These changes were associated with the development of thermal hyperalgesia. Immunofluorescence staining showed that VGCC α2/δ-1 subunit, a proposed gabapentin target of action, was widely distributed in primary afferent fibers terminals and dorsal horn neurons. CX3CL1, a potential trigger to activate microglia, colocalized with VGCC α2/δ-1 subunits in the spinal dorsal horn. However, its receptor CX3CR1 was mainly expressed in the spinal microglia. Multiple intraperitoneal (i.p.) gabapentin injections (100 mg/kg, once daily for 4 days with the first injection 60 min before intra-articular CFA) suppressed the activation of spinal microglia, downregulated spinal VGCC α2/δ-1 subunits decreased CX3CL1 levels and blocked the development of thermal hyperalgesia in MA rats. Conclusions Here we provide the first evidence that gabapentin diminishes CX3CL1 signaling and spinal microglia activation induced by joint inflammation. We also show that the VGCC α2/δ-1 subunits might be involved in these events.

Previous studies indicated that disruption of glial function in the spinal cord enhanced electroacupuncture (EA) analgesia in arthritic rats, suggesting glia is involved in processing EA analgesia. To probe into the potential value for clinical practice, the present study was to investigate the effect of propentofylline, a glia inhibitor, on EA analgesia in rats. Mechanical allodynia induced by tetanic stimulation of sciatic nerve (TSS) was used as a pain model. On day 7 after TSS, EA treatment induced a significant increase in paw withdrawal threshold to mechanical stimulation. Intrathecal or intraperitoneal injection of propentofylline relieved TSS-induced mechanical allodynia. The combination of low dosage of propentofylline and EA produced more potent anti-allodynia than propentofylline or EA alone. Immunohistochemistry exhibited that TSS-induced activation of microglia and astrocytes was inhibited significantly by propentofylline. These results indicate that propentofylline and EA induce synergetic analgesia by interrupting spinal glial function.

1. Spinal glial cells play a key role in developing and maintaining allodynia and hyperalgesia following tissue inflammation. Dexmedetomidine, a highly selective α(2) -adrenoceptor (α(2) -AR) agonist, has exhibited a significant analgesic effect in various rodent models of chronic pain. However, whether spinal glial activation is involved in the analgesic effect of dexmedetomidine remains unknown. The present study investigated whether spinal administration of dexmedetomidine could antagonize glial activation in the spinal dorsal horn and attenuate thermal hyperalgesia in complete Freund's adjuvant (CFA)-induced ankle joint monoarthritic (MA) rats. 2. Unilateral intra-articular injection of CFA produced a robust activation of microglia and astrocytes in the spinal cord, which was associated with the development and maintenance of thermal hyperalgesia. Repeated lumbar puncture (LP) administration of dexmedetomidine (10 μg) significantly attenuated MA-induced thermal hyperalgesia in a cumulative manner. Monoarthritis-induced spinal glial activation was also suppressed following dexmedetomidine application. The α(2A) -AR, essential for the antinociceptive effects of α(2) -AR agonists, was detected in spinal neurons and glia, as well as in dorsal root ganglion primary afferent neurons, which may be implicated in dexmedetomidine-induced suppression of spinal glial activation and antihyperalgesic effects. 3. These data provide the first evidence that blocking spinal glial activation is involved in the analgesic action of dexmedetomidine.

Tetanic stimulation of the sciatic nerve (TSS) produces long-lasting pain hypersensitivity in rats. Long-term potentiation (LTP) of C- and A-fiber-evoked field potentials in the spinal cord has been explored as contributing to central sensitization in pain pathways. However, the peripheral mechanism underlying TSS-induced pain hypersensitivity remains largely unknown. We investigated the effect of TSS on peripheral nerve and the expression of activating transcription factor 3 (ATF3) in dorsal root ganglion (DRG) as a marker of neuronal injury. TSS induced a mechanical allodynia for at least 35 days and induced ATF3 expression in the ipsilateral DRG. ATF3 is colocalized with NF200-labeled myelinated DRG neurons or CGRP- and IB4-labeled unmyelinated ones. Furthermore, we found that TSS induced Wallerian degeneration of sciatic nerve at the level of myelinisation by S100 protein (to label Schwann cells) immunohistochemistry, luxol fast blue staining, and electron microscopy. TSS also elicited the activation of satellite glial cells (SGCs) and enhanced the colocalization of GFAP and P2X7 receptors. Repeated local treatment with tetrodotoxin decreased GFAP expression in SGCs and behavioral allodynia induced by TSS. Furthermore, reactive microglia and astrocytes were found in the spinal dorsal horn after TSS. These results suggest that TSS-induced nerve injury and glial activation in the DRG and spinal dorsal horn may be involved in cellular mechanisms underlying the development of persistent pain after TSS and that TSS-induced nerve injury may be used as a novel neuropathic pain model.

Background It has been recently recognized that the descending serotonin (5-HT) system from the rostral ventromedial medulla (RVM) in the brainstem and the 5-HT3 receptor subtype in the spinal dorsal horn are involved in enhanced descending pain facilitation after tissue and nerve injury. However, the mechanisms underlying the activation of the 5-HT3 receptor and its contribution to facilitation of pain remain unclear. Results In the present study, activation of spinal 5-HT3 receptors by intrathecal injection of a selective 5-HT3 receptor agonist SR 57227 induced spinal glial hyperactivity, neuronal hyperexcitability and pain hypersensitivity in rats. We found that there was neuron-to-microglia signaling via the chemokine fractalkine, microglia to astrocyte signaling via cytokine IL-18, astrocyte to neuronal signaling by IL-1β, and enhanced activation of NMDA receptors in the spinal dorsal horn. Glial hyperactivation in spinal dorsal horn after hindpaw inflammation was also attenuated by molecular depletion of the descending 5-HT system by intra-RVM Tph-2 shRNA interference. Conclusions These findings offer new insights into the cellular and molecular mechanisms at the spinal level responsible for descending 5-HT-mediated pain facilitation during the development of persistent pain after tissue and nerve injury. New pain therapies should focus on prime targets of descending facilitation-induced glial involvement, and in particular the blocking of intercellular signaling transduction between neurons and glia.