Triptolide Alleviates Neuropathic Pain by Inhibiting the Activation of Microglial Toll-Like Receptor 3.

BACKGROUND: Current data indicates the incidence of neuropathic pain after surgical nerve injury is as high as 50%, thus representing a major problem for patients and for the medical system. Triptolide, a traditional Chinese herb, has anti-inflammatory effects on various neurodegenerative and neuroinflammatory diseases. This agent also reduces peripheral nerve injury-induced neuropathic pain, although the mechanism underlying this effect is still unknown. MATERIALS AND METHODS: The effects of triptolide on spinal nerve ligation (SNL) injury-induced neuropathic pain was studied in an animal model using behavioral, morphological and molecular biological methods. RESULTS: Repeated administration of intrathecal triptolide was found to alleviate SNL- or Poly(I:C) (toll-like receptor 3 agonist) injection-induced mechanical allodynia without any motor impairment. The mechanism by which triptolide reduces SNL- and Poly(I:C) injection-induced microglial activation appears to be via the inhibition of OX42 expression, which is a microglial-specific marker. Intrathecal triptolide also suppressed SNL- and Poly(I:C) injection-induced expression of spinal TRIF. TRIF transmits signals from activated TLR3 and is the downstream adaptor of TLR3 in microglia. In addition, intrathecal triptolide inhibited the expression of spinal pro-inflammatory IL-1 ß following SNL or Poly(I:C) injection. CONCLUSIONS: Intrathecal triptolide can suppress the TLR3/TRIF/IL-1 ß pathway in spinal microglia following SNL. This could be the underlying mechanism by which triptolide alleviate neuropathic pain induced by peripheral nerve injury.

Pre-anesthetic clinic internship: new teaching method of pre-anesthesia evaluation for undergraduates.

BACKGROUND: This study aimed to observe the effect of internship in a pre-anesthetic clinic on the teaching quality of pre-anesthesia evaluation for undergraduates. METHODS: A total of 120 undergraduates from July 2017 to July 2018 in the anesthesia department of our hospital were randomly divided into two groups: pre-anesthetic clinic internship teaching group (n = 60) and traditional teaching group (n = 60). The knowledge in the pre-anesthesia evaluation teaching chapters was evaluated between the two groups of undergraduates. RESULTS: There were no significant differences in the demographic information between the two groups. The scores in the case analysis and theoretical knowledge test in the pre-anesthetic clinic internship teaching group were significantly higher than those in the traditional teaching group. In addition, the students' satisfaction with the curriculum design was significantly higher in the pre-anesthetic clinic internship teaching group than in the traditional teaching group. CONCLUSION: Pre-anesthetic clinic internships can improve the quality of pre-anesthesia assessment teaching for undergraduates.

Systemic Injection of Thalidomide Prevent and Attenuate Neuropathic Pain and Alleviate Neuroinflammatory Response in the Spinal Dorsal Horn.

BACKGROUND AND OBJECTIVE: Thalidomide (Tha) has been shown to exert immunomodulatory and anti-inflammatory properties. Whether Tha can alleviate spinal nerve ligation (SNL)-induced neuropathic pain (NP) is still unclear. This study aimed to investigate the therapeutic effect of Tha on the SNL-induced NP and further explore the potential analgesic mechanisms of Tha. METHODS: The effects of Tha on SNL-induced mechanical allodynia were assessed by pain behavioral testing. The expressions of the astrocyte marker glial fibrillary acidic protein (GFAP) and the microglia marker Iba1 in the spinal dorsal horn were evaluated by immunofluorescence histochemistry. Protein expressions of the tumor necrosis factor alpha (TNF-α) in the spinal dorsal horn were tested by Western blot assay. Data were analyzed using one-way ANOVA or two-way ANOVA. RESULTS: By the pretreatment with a single intraperitoneal injection, the PWMT in SNL+Tha group was significantly increased from day 1 to day 2 after SNL (P < 0.05 compared with SNL+Veh group). By the posttreatment with a single intraperitoneal injection, the PWMT in SNL+Tha group was also significantly increased from day 3 to day 4 after SNL (P < 0.05 compared with SNL+Veh group). By the posttreatment with multiple intraperitoneal injection, both the PWMT and the PWTL in SNL+Tha group were similarly significantly increased from day 3 to day 14 after SNL (P < 0.05 compared with SNL+Veh group). Furthermore, the GFAP and Iba1 expressions and TNF-α levels of the ipsilateral spinal dorsal horn in SNL+Tha group were significantly weaker from day 3 to day 14 after SNL than those in SNL+Veh group (P < 0.05). CONCLUSION: Tha can significantly alleviate NP induced by SNL. The analgesic mechanism may be related to inhibition of astrocyte and microglia activation as well as down-regulation of TNF-α levels in the spinal dorsal horn.

The effect of pre- and after-treatment of sevoflurane on central ischemia tolerance and the underlying mechanisms.

In recent years, with continuous research efforts targeted at studying the effects of pre- and after-treatment of inhaled anesthetics, significant progress has been made regarding the common clinical use of low concentrations of inhaled sevoflurane and its effect on induced central ischemia tolerance by pre- and post-treatment. In this study, we collected, analyzed, classified, and summarized recent literature regarding the effect of sevoflurane on central ischemia tolerance and its related mechanisms. In addition, we provide a theoretical basis for the clinical application of sevoflurane to protect the central nervous system and other important organs against ischemic injury.

Cause analysis, prevention, and treatment of postoperative restlessness after general anesthesia in children with cleft palate.

Cleft palate is one of the most common congenital malformations of the oral and maxillofacial region, with an incidence rate of around 0.1%. Early surgical repair is the only method for treatment of a cleft lip and palate. However, because of the use of inhalation anesthesia in children and the physiological characteristics of the cleft palate itself combined with the particularities of cleft palate surgery, the incidence rate of postoperative emergence agitation (EA) in cleft palate surgery is significantly higher than in other types of interventions. The exact mechanism of EA is still unclear. Although restlessness after general anesthesia in children with cleft palate is self-limiting, its effects should be considered by clinicians. In this paper, the related literature on restlessness after surgery involving general anesthesia in recent years is summarized. This paper focuses on induction factors as well as prevention and treatment of postoperative restlessness in children with cleft palate after general anesthesia. The corresponding countermeasures to guide clinical practice are also presented in this paper.

Neuron-restrictive silencer factor-mediated downregulation of µ-opioid receptor contributes to the reduced morphine analgesia in bone cancer pain.

Bone cancer pain has been reported to have unique mechanisms and is resistant to morphine treatment. Recent studies have indicated that neuron-restrictive silencer factor (NRSF) plays a crucial role in modulating the expression of the µ-opioid receptor (MOR) gene. The present study elucidates the regulatory mechanisms of MOR and its ability to affect bone cancer pain. Using a sarcoma-inoculated murine model, pain behaviors that represent continuous or breakthrough pain were evaluated. Expression of NRSF in the dorsal root ganglion (DRG) and spinal dorsal horn was quantified at the transcriptional and translational levels, respectively. Additionally, chromatin immunoprecipitation assays were used to detect NRSF binding to the promoter of MOR. Furthermore, NRSF was genetically knocked out by antisense oligodeoxynucleotide, and the expression of MOR and the effect of morphine were subsequently analyzed. Our results indicated that in a sarcoma murine model, NRSF expression is upregulated in dorsal root ganglion neurons, and the expression of NRSF mRNA is significantly negatively correlated with MOR mRNA expression. Additionally, chromatin immunoprecipitation analysis revealed that NRSF binding to the neuron-restrictive silencer element within the promoter area of the MOR gene is promoted with a hypoacetylation state of histone H3 and H4. Furthermore, genetically knocking down NRSF with antisense oligodeoxynucleotide rescued the expression of MOR and potentiated the systemic morphine analgesia. The present results suggest that in sarcoma-induced bone cancer pain, NRSF-induced downregulation of MOR is involved in the reduction of morphine analgesia. Epigenetically, up-regulation of MOR could substantially improve the effect of system delivery of morphine.

Dexmedetomidine Dose-Dependently Attenuates Ropivacaine-Induced Seizures and Negative Emotions Via Inhibiting Phosphorylation of Amygdala Extracellular Signal-Regulated Kinase in Mice.

Ropivacaine (Ropi), one of the newest and safest amino amide local anesthetics, is linked to toxicity, including the potential for seizures, changes in behavior, and even cardiovascular collapse. Dexmedetomidine (Dex), an α2-adrenergic receptor agonist, has been widely used in anesthesia and critical care practice. To date, the underlying mechanisms of the effects of Dex premedication on Ropi-induced toxicity have not been clearly identified. In the current study, we investigated the effects of increasing doses of Dex premedication on 50% convulsive dose (CD50) of Ropi. With increasing doses of intraperitoneal (i.p.) Dex 10 min prior to each i.p. RopiCD50, the latency and duration of seizure activity were recorded. Open-field (OF) and elevated plus maze (EPM) test were used to measure negative behavioral emotions such as depression and anxiety. Immunohistochemistry and Western blot were utilized to investigate phosphorylation-extracellular regulated protein kinases (p-ERK) expression in the basolateral amygdala (BLA) on 2 h and in the central amygdala (CeA) on 24 h after convulsion in mice. The results of our investigation demonstrated that Dex dose-dependently increased RopiCD50, prolonged the latency and shortened the duration of each RopiCD50-induced seizure, improved the negative emotions revealed by both OF and EPM test, and inhibited p-ERK expression in the BLA and the CeA.

Depressing interleukin-1ß contributed to the synergistic effects of tramadol and minocycline on spinal nerve ligation-induced neuropathic pain.

Our previous study indicated that coadministration of tramadol and minocycline exerted synergistic effects on spinal nerve ligation (SNL)-induced neuropathic mechanical allodynia. However, the underlying mechanisms are still unclear. Recent reports indicated that spinal proinflammatory factor interleukin-1ß (IL-1ß) contributed to the development of neuropathic pain and the positive feedback communication between neuron and glia. Therefore, the present research is to confirm whether spinal IL-1ß-related pathway response contributes to the synergistic effects of tramadol and minocycline on SNL-induced neuropathic pain. Real-time RT-PCR demonstrated IL-1ß up-expression in the ipsilateral spinal dorsal horn 3 days after lesion, which could be significantly decreased by tramadol and minocycline coadministration. Immunofluorescence and Western blot indicated that SNL-induced microglial phosphorylated p38 (p-p38) upregulation was also inhibited by tramadol and minocycline coapplication. Meanwhile, intrathecal administration of p38 inhibitor SB203580 markedly alleviated mechanical allodynia whilst reducing IL-1ß and Fos expression induced by SNL. Moreover, intrathecal neutralized antibody of IL-1ß could depress SNL-induced mechanical allodynia and Fos expression. These results suggest that depressing SNL-induced aberrant activation of the spinal dorsal horn IL-1ß-related pathway contributes to the underlying mechanism of the synergistic effects of tramadol and minocycline coadministration on SNL-induced neuropathic mechanical allodynia.

Antinociceptive effect of prostatic acid phosphatase in a rat model of cancer-induced bone pain.

BACKGROUND: Cancer-induced bone pain (CIBP) is a severe chronic pain that is less than adequately controlled by conventional analgesics. Prostatic acid phosphatase (PAP) has been considered as a diagnostic marker for prostate cancer and its transmembrane isoform has been reported to play an antinociceptive effect in neuropathic and inflammatory pain. However, it remains unknown whether it has an analgesic effect on CIBP and what are the underlying mechanisms. OBJECTIVE: In the present study, we tested whether PAP could alleviate the pain symptoms induced by bone cancer in a rat model. STUDY DESIGN: A randomized, double blind, and controlled rat animal trial. METHODS: We first established a rat CIBP model and observed the spinal expression of PAP by immunofluorescence histochemistry and Western blot. Then, PAP (0.1, 0.3, or 1 µg) was intrathecally administered in the CIBP rats in a repeated manner from 15 to 18 days (once per day) after inoculation of tumor cells. On postoperative day (POD) 18, the mechanical paw withdrawal threshold was tested for checking the dose-effect curve and ED50 of the antinociceptive effect of PAP. In an another test, a single dose of ED50 of PAP was intrathecally injected on POD 15 to observe the time course of its effect. Furthermore, 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) (3 mg/kg), an adenosine A1 receptor antagonist, or dipyridamole (DIP) (10 µg), a nucleoside transporter inhibitor, was administered to the CIBP rats for exploring the analgesic mechanisms of PAP. The concentration of extracellular adenosine was also detected by microdialysis method after intrathecal injection of PAP (0.57 µg) and DIP (10 µg) in the CIBP rats. Finally, an in vivo electrophysiological study of the CIBP rats was performed to observe whether the electrically evoked response of spinal wide-dynamic-range (WDR) neurons could be affected by PAP (0.57 µg), DIP (10 µg), or DPCPX (10 µg). RESULTS: The expression of PAP in the spinal dorsal horn was significantly reduced in the CIBP rats, and intrathecal injection of PAP dose-dependently attenuated CIBP-induced mechanical allodynia via the adenosine A1 receptor. Simultaneously, intrathecal injection of PAP increased the extracellular concentration of spinal adenosine in the CIBP rats, as well as inhibited the neuronal responses of WDR neurons in deep layers within the spinal dorsal horn through the adenosine A1 receptor. Finally, the analgesic effect of PAP was potentiated by DIP, the nucleoside transporter inhibitor. LIMITATIONS: It's not clear whether PAP's antinociceptive effect is mediated by other signaling molecules besides the adenosine A1 receptor. In addition, the long-term antinociceptive effect of intrathecal PAP is still not clear. CONCLUSIONS: Our study demonstrated that PAP was involved in the maintenance of CIBP and could effectively suppress central sensitization by increasing spinal extracellular adenosine concentrations to exert a significant antinociceptive effect via the adenosine A1 receptor in CIBP rats. Therefore, our experiments suggest that the endogenous enzyme PAP may be a promising candidate for CIBP treatment.

Tramadol and propentofylline coadministration exerted synergistic effects on rat spinal nerve ligation-induced neuropathic pain.

Neuropathic pain is an intractable clinical problem. Drug treatments such as tramadol have been reported to effectively decrease neuropathic pain by inhibiting the activity of nociceptive neurons. It has also been reported that modulating glial activation could also prevent or reverse neuropathic pain via the administration of a glial modulator or inhibitor, such as propentofylline. Thus far, there has been no clinical strategy incorporating both neuronal and glial participation for treating neuropathic pain. Therefore, the present research study was designed to assess whether coadministration of tramadol and propentofylline, as neuronal and glial activation inhibitors, respectively, would exert a synergistic effect on the reduction of rat spinal nerve ligation (SNL)-induced neuropathic pain. Rats underwent SNL surgery to induce neuropathic pain. Pain behavioral tests were conducted to ascertain the effect of drugs on SNL-induced mechanical allodynia with von-Frey hairs. Proinflammatory factor interleukin-1ß (IL-1ß) expression was also detected by Real-time RT-PCR. Intrathecal tramadol and propentofylline administered alone relieved SNL-induced mechanical allodynia in a dose-dependent manner. Tramadol and propentofylline coadministration exerted a more potent effect in a synergistic and dose dependent manner than the intrathecal administration of either drug alone. Real-time RT-PCR demonstrated IL-1ß up-expression in the ipsilateral spinal dorsal horn after the lesion, which was significantly decreased by tramadol and propentofylline coadministration. Inhibiting proinflammatory factor IL-1ß contributed to the synergistic effects of tramadol and propentofylline coadministration on rat peripheral nerve injury-induced neuropathic pain. Thus, our study provided a rationale for utilizing a novel strategy for treating neuropathic pain by blocking the proinflammatory factor related pathways in the central nervous system.

Combination of tramadol with minocycline exerted synergistic effects on a rat model of nerve injury-induced neuropathic pain.

Neuropathic pain is a refractory clinical problem. Certain drugs, such as tramadol, proved useful for the treatment of neuropathic pain by inhibiting the activity of nociceptive neurons. Moreover, studies indicated that suppression or modulation of glial activation could prevent or reverse neuropathic pain, for example with the microglia inhibitor minocycline. However, few present clinical therapeutics focused on both neuronal and glial participation when treating neuropathic pain. Therefore, the present study hypothesized that combination of tramadol with minocycline as neuronal and glial activation inhibitor may exert some synergistic effects on spinal nerve ligation (SNL)-induced neuropathic pain. Intrathecal tramadol or minocycline relieved SNL-induced mechanical allodynia in a dose-dependent manner. SNL-induced spinal dorsal horn Fos or OX42 expression was downregulated by intrathecal tramadol or minocycline. Combination of tramadol with minocycline exerted powerful and synergistic effects on SNL-induced neuropathic pain also in a dose-dependent manner. Moreover, the drug combination enhanced the suppression effects on SNL-induced spinal dorsal horn Fos and OX42 expression, compared to either drug administered alone. These results indicated that combination of tramadol with minocycline could exert synergistic effects on peripheral nerve injury-induced neuropathic pain; thus, a new strategy for treating neuropathic pain by breaking the interaction between neurons and glia bilaterally was also proposed.

Triptolide prevents and attenuates neuropathic pain via inhibiting central immune response.

BACKGROUND: Current treatments for neuropathic pain are far from satisfactory. Considering the essential contribution of central immune factors to the pathogenesis of neuropathic pain, targeting inflammatory response is well accepted as an effective strategy for treating neuropathic pain. Triptolide has a long history in traditional Chinese medicine for treating inflammatory diseases and has been proven to inhibit cytokines released from glial cells. OBJECTIVE: In the present study, we tested whether systemic treatment with triptolide could prevent or attenuate nocifensive behaviors associated with neuropathic pain. We further tried to explore the underlying mechanism of the potential anti-allodynia effect of triptolide. STUDY DESIGN: A randomized, double blind, controlled animal trial. METHODS: Triptolide was administered systemically in a rat model of neuropathic pain induced by spinal nerve ligation (SNL) in the single bolus and repeated treatment manners. In the single bolus treatment experiment, triptolide (30 ug/kg, 100 ug/kg, 300 ug/kg) or vehicle was given to SNL and sham-operated rats once on day 1 or on day 10 after surgery (n = 6 each). In the repeated treatment study, prophylactic treatment with triptolide (30 ug/kg, 100 ug/kg, 300 ug/kg) was given to rats during the period of day -3 (3 days prior to SNL) to day 7 (7 days post-SNL) inclusively (n = 6 each). Another set of SNL and sham rats on postoperative day 10 received treatment with triptolide (30 ug/kg, 100 ug/kg, 300 ug/kg) or vehicle during the period of days 11-20 inclusively (n = 6 each), to assess potential reversal of established pain behavior. Mechanical allodynia of the rats was tested with von Frey filaments. Astrocytic and microglial activation in the spinal dorsal horn was evaluated with immunofluorescent histochemistry. Phosphorylation of mitogen-activated protein kinases (MAPKs), and expression of inflammatory cytokines (interleukin-6, interleukin-1beta, monocyte chemotactic protein-1, and tumor necrosis factor-alpha) were examined with Western blot analysis and real-time reverse transcription polymerase chain reaction study. RESULTS: A single bolus treatment with triptolide could neither prevent the induction nor reverse the maintenance of SNL-induced mechanical allodynia. However, repeated administration of triptolide dose-dependently inhibited neuropathic pain behavior in both preventative and interventional paradigms. Triptolide hampered SNL-induced activation of glial cells (astrocytes and microglia) in the spinal dorsal horn without influencing neurons. In addition, SNL-induced phosphorylation of MAPKs could be inhibited by triptolide. Furthermore, up-regulated expression of inflammatory cytokines in neuropathic pain states could be remarkably blocked by triptolide. LIMITATIONS: The direct target site (such as a specific receptor) of triptolide is still to be determined. In addition, triptolide could not completely block the SNL-induced mechanical allodynia. CONCLUSIONS: Our data suggest that triptolide may be a potential novel treatment for neuropathic pain through modulating immune response in the spinal dorsal horn.

The Inhibition of Spinal Astrocytic JAK2-STAT3 Pathway Activation Correlates with the Analgesic Effects of Triptolide in the Rat Neuropathic Pain Model.

Neuropathic pain (NP) is an intractable clinical problem without satisfactory treatments. However, certain natural products have been revealed as effective therapeutic agents for the management of pain states. In this study, we used the spinal nerve ligation (SNL) pain model to investigate the antinociceptive effect of triptolide (T10), a major active component of the traditional Chinese herb Tripterygium wilfordii Hook F. Intrathecal T10 inhibited the mechanical nociceptive response induced by SNL without interfering with motor performance. Additionally, the anti-nociceptive effect of T10 was associated with the inhibition of the activation of spinal astrocytes. Furthermore, intrathecal administration of T10 attenuated SNL-induced janus kinase (JAK) signal transducers and activators of transcription 3 (STAT3) signalling pathway activation and inhibited the upregulation of proinflammatory cytokines, such as interleukin-6, interleukin-1 beta, and tumour necrosis factor-α, in dorsal horn astrocytes. Moreover, NR2B-containing spinal N-methyl D-aspartate receptor (NMDAR) was subsequently inhibited. Above all, T10 can alleviate SNL-induced NP via inhibiting the neuroinflammation in the spinal dorsal horn. The anti-inflammation effect of T10 may be related with the suppression of spinal astrocytic JAK-STAT3 activation. Our results suggest that T10 may be a promising drug for the treatment of NP.

Neuronal NR2B-containing NMDA receptor mediates spinal astrocytic c-Jun N-terminal kinase activation in a rat model of neuropathic pain.

Spinal N-methyl d-aspartate receptor (NMDAR) plays a pivotal role in nerve injury-induced central sensitization. Recent studies suggest that NMDAR also contributes to neuron-astrocyte signaling. c-Jun N-terminal kinase (JNK) is persistently and specifically activated (indicated by phosphorylation) in spinal cord astrocytes after nerve injury and thus it is considered as a dependable indicator of pain-related astrocytic activation. NMDAR-mediated JNK activation in spinal dorsal horn might be an important form of neuron-astrocyte signaling in neuropathic pain. In the present study, we observed that intrathecal injection of MK-801, a noncompetitive NMDA receptor antagonist, or Ro25-6981 and ifenprodil, which are selective antagonists of NR2B-containing NMDAR each significantly reduced nerve injury-induced JNK activation. Double immunostaining showed that NR2B was highly expressed in neurons, indicating the effect of NMDAR antagonists on JNK activation was indirect. We further observed that intrathecal injection of NMDA (twice a day for 3 days) significantly increased spinal JNK phosphorylation. Besides, NMDAR-related JNK activation could be blocked by a neuronal nitric oxide synthase (nNOS) selective inhibitor (7-nitroindazole sodium salt) but not by a nNOS sensitive guanylyl cyclase inhibitor (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one). Finally, real-time RT-PCR and immunostaining showed that nerve injury-induced interleukin-1beta expression was dependent on astrocytic JNK activation. Treatments targeting NMDAR-nNOS pathway also influenced interleukin-1beta expression, which further confirmed our hypothesis. Taken together, our results suggest that neuronal NMDAR-nNOS pathway could activate astrocytic JNK pathway. Excitatory neuronal transmission initiates astrocytic activation-induced neuroinflammation in this way, which contributes to nerve injury-induced neuropathic pain.

Post-injury administration of minocycline: an effective treatment for nerve-injury induced neuropathic pain.

Neuropathic pain is an intractable clinical problem, affecting millions of people worldwide. Preemptive administration of minocycline has been confirmed useful for treating neuropathic pain by inhibiting spinal microglia activation and consequently lowering proinflammatory cytokine expression. However, most patients with neuropathic pain have no chance to receive preemptive treatment and it remains unclear whether there is a therapeutic time window for post treatment with minocycline. The present study is to confirm the effect and the therapeutic time window of intrathecal minocycline on spinal nerve ligation (SNL)-induced neuropathic pain after lesion. Behavioral test and immunohistochemistry are utilized to determine the variation of mechanical allodynia and microglia phosphorylated-p38 (p-p38) expression respectively after intrathecal minocycline. Results showed that post-injury intrathecal minocycline attenuated mechanical allodynia effectively together with inhibiting spinal microglia p-p38 expression on post operative day (POD) 1, POD 3 and POD 7. Additionally, results from POD 10 and POD 21 showed that intrathecal minocycline suppressed spinal microglia p-p38 expression but without any effects on reversing mechanical allodynia. It is concluded that post-injury intrathecal minocycline is an effective therapeutic intervention for treating SNL-induced neuropathic pain by inhibiting spinal microglia activation. Accordingly, there is indeed a therapeutic time window for post-injury intrathecal minocycline, which is the initiation stage of neuropathic pain development.

Histologic distribution, fragment cloning, and sequence analysis of g protein couple receptor 30 in rat submaxillary gland.

Recent studies indicated that G protein couple receptor 30 (GPR30), a nongenomic estrogen receptor, is widely expressed in many organ systems inducing many quick reaction of estrogen. However, there was rare report about the expression of GPR30 in the salivary gland. In the present study, we investigated the distribution of GPR30 in rat submaxillary gland by means of immunohistochemistry and in situ hybridization. GPR30 core sequences were amplified by RT-PCR with total RNA extracted from rat submaxillary gland and were analyzed by sequencing with Sanger's method. The results showed that the epithelial cells of serous alveoli and granular convoluted duct in rat submaxillary gland displayed GPR30-immunoreactivity on the plasma membrane and cytoplasm. Moreover, GPR30 mRNA hybridization signals were also detected in the cytoplasm of the above cells. GPR30 cDNA sequence cloned from rat submaxillary gland is identical to that of GPR30 from rat paraventricular and supraoptic nucleus. In conclusion, the expression of GPR30 in the serous and granular epithelial cells of submaxillary gland indicates that submaxillary gland could also be a target organ rapidly responding to estrogen stimulus, and estrogen may be involved in the functional regulation of submaxillary gland.

Ketamine depresses toll-like receptor 3 signaling in spinal microglia in a rat model of neuropathic pain.

Reports suggest that microglia play a key role in spinal nerve ligation (SNL)-induced neuropathic pain, and toll-like receptor 3 (TLR3) has a substantial role in the activation of spinal microglia and the development of tactile allodynia after nerve injury. In addition, ketamine application could suppress microglial activation in vitro, and ketamine could inhibit proinflammatory gene expression possibly by suppressing TLR-mediated signal transduction. Therefore, the present study was designed to disclose whether intrathecal ketamine could suppress SNL-induced spinal microglial activation and exert some antiallodynic effects on neuropathic pain by suppressing TLR3 activation. Behavioral results showed that intrathecal ketamine attenuated SNL-induced mechanical allodynia, as well as spinal microglial activation, in a dose-dependent manner. Furthermore, Western blot analysis displayed that ketamine application downregulated SNL-induced phosphorylated-p38 (p-p38) expression, which was specifically expressed in spinal microglia but not in astrocytes or neurons. Besides, ketamine could reverse TLR3 agonist (polyinosine-polycytidylic acid)-induced mechanical allodynia and spinal microglia activation. It was concluded that intrathecal ketamine depresses TLR3-induced spinal microglial p-p38 mitogen-activated protein kinase pathway activation after SNL, probably contributing to the antiallodynic effect of ketamine on SNL-induced neuropathic pain.

Inhibition of spinal astrocytic c-Jun N-terminal kinase (JNK) activation correlates with the analgesic effects of ketamine in neuropathic pain.

BACKGROUND: We have previously reported that inhibition of astrocytic activation contributes to the analgesic effects of intrathecal ketamine on spinal nerve ligation (SNL)-induced neuropathic pain. However, the underlying mechanisms are still unclear. c-Jun N-terminal kinase (JNK), a member of mitogen-activated protein kinase (MAPK) family, has been reported to be critical for spinal astrocytic activation and neuropathic pain development after SNL. Ketamine can decrease lipopolysaccharide (LPS)-induced phosphorylated JNK (pJNK) expression and could thus exert its anti-inflammatory effect. We hypothesized that inhibition of astrocytic JNK activation might be involved in the suppressive effect of ketamine on SNL-induced spinal astrocytic activation. METHODS: Immunofluorescence histochemical staining was used to detect SNL-induced spinal pJNK expression and localization. The effects of ketamine on SNL-induced mechanical allodynia were confirmed by behavioral testing. Immunofluorescence histochemistry and Western blot were used to quantify the SNL-induced spinal pJNK expression after ketamine administration. RESULTS: The present study showed that SNL induced ipsilateral pJNK up-regulation in astrocytes but not microglia or neurons within the spinal dorsal horn. Intrathecal ketamine relieved SNL-induced mechanical allodynia without interfering with motor performance. Additionally, intrathecal administration of ketamine attenuated SNL-induced spinal astrocytic JNK activation in a dose-dependent manner, but not JNK protein expression. CONCLUSIONS: The present results suggest that inhibition of JNK activation may be involved in the suppressive effects of ketamine on SNL-induced spinal astrocyte activation. Therefore, inhibition of spinal JNK activation may be involved in the analgesic effects of ketamine on SNL-induced neuropathic pain.

Combining ketamine with astrocytic inhibitor as a potential analgesic strategy for neuropathic pain ketamine, astrocytic inhibitor and pain.

BACKGROUND: Neuropathic pain is an intractable clinical problem. Intrathecal ketamine, a noncompetitive N-methyl-D-aspartate receptor (NMDAR) antagonist, is reported to be useful for treating neuropathic pain in clinic by inhibiting the activity of spinal neurons. Nevertheless, emerging studies have disclosed that spinal astrocytes played a critical role in the initiation and maintenance of neuropathic pain. However, the present clinical therapeutics is still just concerning about neuronal participation. Therefore, the present study is to validate the coadministration effects of a neuronal noncompetitive N-methyl-D-aspartate receptor (NMDAR) antagonist ketamine and astrocytic cytotoxin L-α-aminoadipate (LAA) on spinal nerve ligation (SNL)-induced neuropathic pain. RESULTS: Intrathecal ketamine (10, 100, 1000 µg/kg) or LAA (10, 50, 100 nmol) alleviated SNL-induced mechanical allodynia in a dose-dependent manner respectively. Phosphorylated NR1 (pNR1) or glial fibrillary acidic protein (GFAP) expression was down-regulated by intrathecal ketamine (100, 1000 µg/kg) or LAA (50, 100 nmol) respectively. The combination of ketamine (100 µg/kg) with LAA (50 nmol) showed superadditive effects on neuropathic pain compared with that of intrathecal administration of either ketamine or LAA alone. Combined administration obviously relieved mechanical allodynia in a quick and stable manner. Moreover, down-regulation of pNR1 and GFAP expression were also enhanced by drugs coadministration. CONCLUSIONS: These results suggest that combining NMDAR antagonist ketamine with an astrocytic inhibitor or cytotoxin, which is suitable for clinical use once synthesized, might be a potential strategy for clinical management of neuropathic pain.