Panax notoginseng saponin relieving the inflammatory pain caused by complete Freund’s adjuvant by inhibiting the activation of astrocytes in mice / 解剖学报

Objective To analyse the analgesic effect and possible mechanism of panax notoginseng saponin (PNS) on mouse models of chronic inflammatory pain caused by complete Freund’s adjuvant (CFA). Methods A total of 48 male C57BL/ 6J mice were divided randomly into four groups: normal saline control group (Ctrl), CFA group (CFA), CFA + PNS group (CFA+PNS), CFA + dexamethasone (DEX) group (CFA+DEX). Von Frey filaments were used to detect mechanical pain in mice. Immunohistochemistry was used to detect the number and morphological changes of glial fibrillary acidic protein (GFAP) positive astrocytes. Western blotting was used to detect the expressions of GFAP, nucleotide-binding and oligomerization domain(NOD)-like receptor thermal protein domain associated protein 3 (NLRP3), apoptosis-associated speck-like protein containing a CARD (ASC), Caspase-1, interleukin (IL)-1β, and IL-18 in mice’s spinal cord segments in each group. Results Compared with the Ctrl group, mice in the CFA group showed a significant decrease in mechanical pain thresholds at day 1, day 3, day 5, day 7, and day 14. Additionally, there was a significant decrease in NLRP3, ASC, Caspase-1, IL-1β and IL-18 in the spinal cord of the mice. PNS intervention could relieve mechanical pain and down-regulate the expressions of NLRP3, ASC, Caspase-1, IL-1β and IL-18 in the spinal cord of mice, with no significant difference compared with the CFA+DEX group. CFA group mice had significantly more GFAP positive cells in their posterior horns than Ctrl group mice, as measured by immunohistochemistry; PNS intervention decreased the number of GFAP positive cells in the posterior horn of the spinal cord in model mice;DEX had no effect on the number of GFAP positive cells in the dorsal horn of spinal cord. According to Western blotting results, GFAP expression in the spinal cord of the CFA group was significantly more than that of the Ctrl group; PNS intervention significantly reduced GFAP expression in the spinal cord of CFA group mice;DEX had no effect on the expression of GFAP in the posterior horn of spinal cord. Conclusion PNS has a good alleviating effect on inflammatory pain, and its mechanism may be related to inhibition of astrocyte activation and NLRP3 inflammasome activation.

Scorpion venom component: AGAP exhibits local anaesthetic effects and attenuates nociceptive pain

The incidences of systemic toxicity and other complications associated with existing local anaesthetics can occur at clinical concentration level and vary with the anaesthetic techniques, types of surgery and patient factors. This evidence suggests the need for therapeutic interventions in peripheral and regional anaesthesia. Buthus martensii Karsch (BmK) scorpion venom is a compound that contains mixtures of peptides that have analgesic properties. This study aimed to investigate the local anaesthetic activity of scorpion venom peptide, AGAP (analgesic-antitumor peptide) in mechanical hyperalgesia or acute inflammatory pain. Method: Formalin was injected into the left hind paw after 20 minutes of infiltration of drugs. The time of licking or flinching of the injected hind paw was recorded as indicative of nociceptive or acute inflammatory pain. Paw flinching or quick withdrawal was considered a positive response to pain in the partial sciatic nerve ligation. The paw-withdrawal threshold (PWT) was determined by consecutively increasing and decreasing the magnitude of the stimulus. Results: The results indicated that AGAP exhibited a 67.9% inhibition in licking or flinching time and an 88.1% inhibition in paw withdrawal in mechanical hyperalgesia. The addition of AGAP to lidocaine showed an 89.5% inhibition in paw withdrawal. Conclusion: The data presented in this study suggest that local infiltration of AGAP significantly reduced mechanical hyperalgesia and acute inflammatory pain

Intervention effect of Qufeng Gutong Cataplasm on myofascial pain syndrome in rats and its mechanism / 中国中药杂志

This paper aims to investigate the intervention effect of Qufeng Gutong Cataplasm(QFGT) on myofascial pain syndrome(MPS) in rats and to preliminarily explain its mechanism from the perspective of improving muscle inflammation and pain. Male SD rats were divided into 6 groups, namely normal group, model group, positive control drug(Huoxue Zhitong Ointment, HXZT) group, and low, medium, and high-dose QFGT groups(75, 150, and 300 mg·d~(-1)). The rat model of MPS was established by striking combined with centrifugation for 8 weeks, during which QFGT and HXZT were used for corresponding intervention. Standard VonFrey fiber was used to evaluate the mechanical pain threshold, and acetone was used to detect the cold pain threshold. The electrophysiological activity of muscle at trigger point was detected, and the electromuscular analysis of trigger point was performed. CatWalk gait analyzer was used to detect pain-induced gait adaptation changes. The hematoxylin-eosin(HE) staining was used to observe the pathological changes in muscle and skin tissues at the trigger point of rats. Immunohistochemistry was used to detect the expression of capsaicin receptor transient receptor potential vanilloid 1(TRPV1) in muscle tissues and interleukin(IL)-33 in skin tissues at the trigger point. The protein expression levels of TRPV1, protein kinase B(Akt), phosphorylated protein kinase B(p-Akt), IL-1β, and tumor necrosis factor-α(TNF-α) in muscle tissues at the trigger point were detected by Western blot. The results showed that as compared with the model group, the mechanical pain threshold and cold pain threshold of rats in other groups were increased after treatment with QFGT. The spontaneous electromyography(EMG) activity was observed in the model group, but QFGT alleviated the EMG activity in a dose-dependent manner. Gait analysis showed that standing duration, average intensity, swing speed, maximum contact point, maximum contact area, paw print length, paw print width, and paw print area were significantly improved in all QFGT groups. Pathological results showed that the disorder of muscle arrangement at the trigger point was decreased, muscle fiber adhesion and atrophy were reduced, and inflammatory cell infiltration was alleviated after treatment with QFGT. In addition, QFGT and HXZT both inhibited the protein expression of TRPV1, PI3K, Akt, p-Akt, IL-1β, and TNF-α in the muscle tissues of rats with MPS. However, there was no significant difference in the pathological structure and expression of IL-33 in the treated skin as compared with the normal group. The related results have proved that QFGT can inhibit the release of inflammatory factors by inhibiting the TRPV1/PI3K/Akt signaling pathway in the muscle trigger point of rats with MPS and finally attenuate the atrophy and adhesion of local muscles and inflammatory infiltration, thereby relieving the muscle pain of rats with MPS, and local administration has no skin irritation.

Research on the mechanisms of ethanol extract of Scutellaria baicalensis Georgi in improving CFA-induced inflammatory pain rats based on 1H NMR metabolomics / 药学学报

The purpose of this study was to investigate the effects of ethanol extract of Scutellaria baicalensis Georgi (SGE) on endogenous metabolites in toes of rats with inflammatory pain induced by complete Freund's adjuvant (CFA) based on 1H NMR metabolomics, which would provide foundation for revealing the effects and mechanisms of SGE in improving inflammatory pain. This animal experiment was approved by the Committee on the Ethics of Animal Experiments of Shanxi University (SXULL2022062). The rats model of inflammatory pain was induced by subcutaneous injection of CFA (0.1 mL), and the effect of low, medium and high doses of SGE (1.5, 3, 6 g·kg-1) on inflammatory pain were explored. The effects of SGE on relieving inflammatory pain was evaluated by mechanical nociceptive thresholds (MNTs) test. Western blot was used to detect the effects of SGE on protein expression of cyclooxygenase-2 (COX-2), nuclear factor kappa-B (NF-κB) and phospho-NF-κB (p-NF-κB). 1H NMR metabolomics was used to analyze the regulatory effects of SGE on endogenous metabolites in the toes of rats with inflammatory pain. The results showed that SGE (6 g·kg-1) could significantly relieve CFA-induced inflammatory pain, and also notably inhibit the protein expression of COX-2, NF-κB and p-NF-κB. SGE could markedly reverse the changes of 8 differential metabolites, such as glycine, glutamine, succinate, phosphorylcholine, etc. The metabolites were involved in eight metabolic pathways, such as glycine, serine and threonine metabolism, alanine, aspartate and glutamate metabolism, glyoxylate and dicarboxylate metabolism, glutathione metabolism, glycerophospholipid metabolism. These results suggest that SGE may relieve inflammatory pain by regulating NF-κB signaling pathway and metabolic abnormality.

Effects of volatile oil from Acori graminei Rhizoma on glial fibrillary acidic protein, c-Jun N-terminal protein kinase and tumor necrosis factor-α expressions in the spinal cord dorsal horn of the inflammatory pain rats / 解剖学报

Objective To investigate the influence of volatile oil from Acori graminei Rhizoma (VOA) on expressions of glial fibrillary acidic protein (GFAP), c-Jun N-terminal protein kainse (JNK) and tumour necrosis factor-α (TNF-α) in the spinal cord dorsal horn of imflammatory pain rats. Methods Totally 36 male SD rats were randomly divided into control group (control), sham-operated group (sham), complete Freund' s adjuvant group (CFA), 5 g/(kg·d) low dose VOA+CFA group (VOA-L+CFA), 10 g/(kg·d) medium dose VOA + CFA group (VOA-M+CFA) and 20 g/(kg·d) high dose VOA + CFA group (VOA-H+CFA). All animals were sacrificed immediately after continuous gavage administration for 22 days. The expressions of GFAP, JNK and TNF-α in the spinal cord dorsal horn of rats in each group were detected by immunofluorescence and Western blotting methods. Results The present results showed that the positive expressions of GFAP, JNK and TNF-α in the spinal cord dorsal horn of rats increased significantly in the CFA group, when compared to the control and sham groups (P < 0. 01). The expressions of GFAP, JNK and TNF-α in the spinal cord dorsal horn of rats with VOA treatment reduced in the dose-dependent manner, when compared to the CFA group, the positive expressions of GFAP, JNK and TNF-α reduced significantly in the dorsal horn of the spinal cord of the VOA-H+CFA group (P<0. 05, P<0. 01). Conclusion VOA reduces the expressions of GFAP, JNK and TNF-α in the spinal cord dorsal horn of rats of CFA-induced inflammatory pain.

Neuronal GRK2 regulates microglial activation and contributes to electroacupuncture analgesia on inflammatory pain in mice

BACKGROUND: G protein coupled receptor kinase 2 (GRK2) has been demonstrated to play a crucial role in the development of chronic pain. Acupuncture is an alternative therapy widely used for pain management. In this study, we investigated the role of spinal neuronal GRK2 in electroacupuncture (EA) analgesia. METHODS: The mice model of inflammatory pain was built by subcutaneous injection of Complete Freund's Adjuvant (CFA) into the plantar surface of the hind paws. The mechanical allodynia of mice was examined by von Frey test. The mice were subjected to EA treatment (BL60 and ST36 acupuncture points) for 1 week. Overexpression and down-regulation of spinal neuronal GRK2 were achieved by intraspinal injection of adeno associated virus (AAV) containing neuron-specific promoters, and microglial activation and neuroinflammation were evaluated by real-time PCR. RESULTS: Intraplantar injection with CFA in mice induced the decrease of GRK2 and microglial activation along with neuroinflammation in spinal cord. EA treatment increased the spinal GRK2, reduced neuroinflammation, and significantly decreased CFA-induced mechanical allodynia. The effects of EA were markedly weakened by non-cell-specific downregulation of spinal GRK2. Further, intraspinal injection of AAV containing neuron-specific promoters specifically downregulated neuronal GRK2, and weakened the regulatory effect of EA on CFA-induced mechanical allodynia and microglial activation. Meanwhile, overexpression of spinal neuronal GRK2 decreased mechanical allodynia. All these indicated that the neuronal GRK2 mediated microglial activation and neuroinflammation, and subsequently contributed to CFA-induced inflammatory pain. CONCLUSION: The restoration of the spinal GRK2 and subsequent suppression of microglial activation and neuroinflammation might be an important mechanism for EA analgesia. Our findings further suggested that the spinal GRK2, especially neuronal GRK2, might be the potential target for EA analgesia and pain management, and we provided a new experimental basis for the EA treatment of pain.

Research progress on the relationship between exosomes and pain / 中国医师杂志

Exosomes are extracellular microbubbles related to intercellular communication, which have the ability to transport and transfer biological macromolecules. Pain will lead to a sharp decline in the quality of life of patients, and will give patients and society a heavy medical burden. More and more evidences show that the exosomes plays an important role in the pathological process of pain related diseases.Summarizing the exosomes and the biomolecules carried by them under different pain conditions, and identifying the specific exosomes related to the pain state will be helpful for early diagnosis and treatment of pain related diseases. In addition, the ability of exosomes to transmit information and its widespread characteristics in the body indicate that they have broad prospects as a new diagnosis and treatment tool in the field of pain. A better understanding of the relationship between the exosomes and pain will provide a novel and promising treatment for patients with pain.

Effect and mechanism of bromodomain-containing protein 4 inhibitor JQl on formaldehyde solution induced inflammatory pain in mice / 解剖学报

Objective To explore the expression and role of bromodomain-containing protein 4(BRD4) in spinal cord of mice which suffered inflammatory pain induced by formaldelryde solution. Methods Thirty-two ICR mice were randomly divided into normal saline group and formaldehyde injection 5 minutes, 30 minutes and 60 minutes groups, with 8 mice in each group. The expression of BRD4 protein and mRNA in spinal cord of mice in each group were detected by Western blotting (n = 4/group) and Real-time PCR (n = 4/group); 66 mice were randomly divided into formaldelryde injection group, vehicle (DMSO) plus formaldelryde injection group and 6. 25, 12. 5, 25 and 50 mg/kg JQl injection plus formaldelryde solution group, with 11 mice in each group. The effect of BRD4 inhibitor JQl on spontaneous pain in each group was observed (n= 11/group); Immunohistochemistry (n= 3/group), Real-time PCR (n = 4/group) or Western blotting (n= 4/group) were used to detect the effects of 25 mg/kg JQ1 on the expression of c-fos and glutamate receptor 2 (GluR2) in the spinal cord of model mice. Results The result showed that levels of BRD4 protein (P<0. 01) and mRNA in spinal cord increased significantly 30 min and 60 min after formaldehyde solution injection (P<0. 05). The behavioral test showed that both 25 mg/kg and 50 mg/kg JQf administration could reduce the second phase spontaneous pain compared with the solvent (DMSO) group (P < 0 . 05). Furthennore, immunohistochemistry and Real-time PCR result showed that 25 mg/kg JQf injection could significantly reduce positive numbers (P<0. 01) and high mRNA expression of c-fos in mouse spinal cord induced by formaldehyde solution (P < 0 . 05), and the Western blotting result showed that 25 mg/kg JQf administration could significantly reduce the expression of glutamate receptor GluR2 (P < 0. OOf). Conclusion BRD4 may play an important role in the induction of central sensitization of inflammatory pain, and JQf may alleviate inflammatory pain behavior by inhibiting the formation of central sensitization of pain.

IL-36Ra inhibited A1 astrocyte polarization in spinal cord of mice subjected to inflammatory pain / 中国药理学通报

Aim To evaluate the effects of different doses of IL-36Ra on pain behavior and the polarization of spinal A1 astrocytes in mice with inflammatory pain.Methods A total of 32 male C57BL/6 mice were divided into four groups: CFA+Saline group, CFA+IL-36Ra 50 ng group, CFA+IL-36Ra 100 ng group and CFA+IL-36Ra 200 ng group by random grouping.The inflammatory pain model was established by injection of complete Freund's adjuvant(CFA)into the plantar surface of the right hind paw of mice.The drugs were given daily from the 1st day to the 7th day after CFA injection in each group by intrathecal injection.The changes in the mechanical withdrawal threshold(MWT)and the radiant heat stimulating paw withdrawal latency(PWL)of the mice were detected before and 1, 3, 5 and 7 days after the CFA injection.Reverse transcription polymerase chain reaction was used to detect the expression changes of A1 and A2 astrocyte markers after IL-36Ra treatment.Immunohistochemistry was used to test the effect of IL-36Ra on the co-expression level of A1 astrocyte marker C3 and GFAP in the spinal dorsal horn.Results MWT and PWL of the ipsilateral paw significantly decreased after the CFA injection, and IL-36Ra(100 ng, 200 ng)treatment could significantly improve the mechanical allodynia and thermal hyperalgesia of CFA mice.After treatment for 7 days, IL-36Ra 200 ng successfully reversed the increase of GFAP and Lcn2 expression in the spinal cord of CFA mice, which demonstrated IL-36Ra could inhibit the activation of astrocytes.IL-36Ra significantly inhibited the expression of A1 astrocyte maker Serping1, H2-T23 in spinal cord but showed no effects on the expression of A2 astrocytes marker with each dose.Furthermore, IL-36Ra inhibited the expression of C3 within the astrocytes in the spinal dorsal horn of CFA mice.Conclusion IL-36Ra attenuates the inflammatory pain via inhibiting the polarization of A1 reactive astrocytes in the spinal cord of mice with inflammatory pain.

Experimental Study of Yuxuebi Tablets by Inhibiting Peripheral Inflammation to Relieve Hyperalgesia and Foot Swelling in Mice with Chronic Inflammatory Pain / 中国实验方剂学杂志

Objective:To observe the effect of Yuxuebi tablets on hyperalgesia and foot swelling in mice with chronic inflammatory pain， and to explore the preliminary mechanism of action. Method:A mouse model of chronic inflammatory pain was established with left plantar injection of complete Freund's adjuvant （CFA）. The mice were divided into model group， positive drug ibuprofen group （91 mg·kg^-1）， Yuxuebi tablets low， medium and high dose groups （55， 110， 220 mg·kg^-1），with the sham operation group as the control. After successful modeling， the daily dose was divided into two doses in the morning and evening by gavage to give Yuxuebi tablets or ibuprofen to the stomach for a total of 19 days. On the 18^th day after the administration， the thermal pain threshold was detected by the hot plate method. On the 19^th day， the standard Von Frey fiber needle was used to detect the mechanical pain threshold of the mice， and the degree of foot swelling was scored and photographed. The liquid-phase suspension chip technology was used to quantitatively analyze 36 classic broad-spectrum inflammation-related factors like inflammatory factors and receptors. Bioinformatics were used to screen core targets and perform enzymelinked immunosorbent assay （ELISA） detection. Result:Compared with the sham operation group， the mechanical pain threshold and foot swelling score of the model froup significantly increased （<italic>P</italic><0.01）， the latent time of heat sensitivity significantly decreased（<italic>P</italic><0.01）， the expressions of 30 inflammatory factors in the foot increased（<italic>P</italic><0.05）. Compared with the model group， the high dose of Yuxuebi tablets significantly reduced the mechanical pain threshold and foot swelling score of mice with chronic inflammatory pain（<italic>P</italic><0.01）， significantly increased the latent time of heat sensitivity（<italic>P</italic><0.05）， and reduced the expressions of 30 inflammatory factors in the foot（<italic>P</italic><0.05）， among which tumor necrosis factor-<italic>α</italic> （TNF-<italic>α</italic>）， interleukin-6 （IL-6）， interleukin-17A （IL-17A）， and C-C chemokine ligand 2 （CCL2） were the core targets screened out， and the expressions of TNF-<italic>α</italic>， IL-17A， and CCL2 significantly decreased （<italic>P</italic><0.01）. Conclusion:Yuxuebi tablets can relieve hyperalgesia and foot swelling in mice with chronic inflammatory pain， and its mechanism may be related to the inhibition of the expressions of peripheral inflammatory factors such as TNF-<italic>α</italic>， IL-17A， and CCL2 .

Role of the Anterior Cingulate Cortex in Translational Pain Research / 神经科学通报·英文版

As the most common symptomatic reason to seek medical consultation, pain is a complex experience that has been classified into different categories and stages. In pain processing, noxious stimuli may activate the anterior cingulate cortex (ACC). But the function of ACC in the different pain conditions is not well discussed. In this review, we elaborate the commonalities and differences from accumulated evidence by a variety of pain assays for physiological pain and pathological pain including inflammatory pain, neuropathic pain, and cancer pain in the ACC, and discuss the cellular receptors and signaling molecules from animal studies. We further summarize the ACC as a new central neuromodulation target for invasive and non-invasive stimulation techniques in clinical pain management. The comprehensive understanding of pain processing in the ACC may lead to bridging the gap in translational research between basic and clinical studies and to develop new therapies.

Tweety-Homolog 1 Facilitates Pain via Enhancement of Nociceptor Excitability and Spinal Synaptic Transmission / 神经科学通报·英文版

Tweety-homolog 1 (Ttyh1) is expressed in neural tissue and has been implicated in the generation of several brain diseases. However, its functional significance in pain processing is not understood. By disrupting the gene encoding Ttyh1, we found a loss of Ttyh1 in nociceptors and their central terminals in Ttyh1-deficient mice, along with a reduction in nociceptor excitability and synaptic transmission at identified synapses between nociceptors and spinal neurons projecting to the periaqueductal grey (PAG) in the basal state. More importantly, the peripheral inflammation-evoked nociceptor hyperexcitability and spinal synaptic potentiation recorded in spinal-PAG projection neurons were compromised in Ttyh1-deficient mice. Analysis of the paired-pulse ratio and miniature excitatory postsynaptic currents indicated a role of presynaptic Ttyh1 from spinal nociceptor terminals in the regulation of neurotransmitter release. Interfering with Ttyh1 specifically in nociceptors produces a comparable pain relief. Thus, in this study we demonstrated that Ttyh1 is a critical determinant of acute nociception and pain sensitization caused by peripheral inflammation.

Regulation of the Sigma-1 Receptor on Chronic Pain and Its Neuromechanism / 中国生物化学与分子生物学报

Sigma-1 receptor (Sig-1R) is a ligand-regulated chaperone protein widely expressed in multiple regions of the nervous system. It mediates intracellular effects of several types of ion channels and G protein coupled receptors (GPCRs) by binding them, and regulates intracellular Ca

Mechanism of IGF-1 in Pathological Pain / 中国生物化学与分子生物学报

Pathological pain is also called chronic pain, including neuropathic pain, inflammatory pain, and cancer pain. These three types of pain mainly come from complications or late effects of various diseases. Pathological pain is a kind of sensation, different from visual, auditory and other independent existence, but mixed with other sensations. It is difficult to distinguish accurately, which brings great difficulties to clinical treatment and patient recovery. Although the search for analgesic targets has been extensively and deeply studied in pain-related fields, there is still a lack of effective therapies or drugs with less or no side effects. Insulin-like growth factor-1 (IGF-1) is a member of the insulin-like growth factor family, which is widely expressed in the central nervous system and peripheral nervous system and exerts neurotrophic and nerve repair effects, and has received increasing attention in the field of pain in recent years. However, in the study of pathological pain, some scholars have found that IGF-1 plays two opposite roles of neuroprotection and neurotoxicity in the occurrence and maintenance of neuropathic pain and inflammatory pain, which can not only promote the transmission of nociceptive information but also block the transmission of nociceptive information. In cancer pain, it is found that IGF-1 only participates in the transmission of nociceptive signals and then plays a neurotoxic role. This paper briefly reviews the mechanism of IGF-1 participation in three kinds of pathological pain, and discusses the possibility of IGF-1 as an analgesic target.

Effects of volatile oil from Acori Graminei Rhizoma on glial fibrillary acidic protein and immediate early genes expressions in the basal lateral amygdala of the inflammatory pain rats / 解剖学报

Objective To construct a rat model of inflammatory pain by injecting complete Freund' adjuvant (CFA) to study effects of volatile oil of Acori Graminei Rhizoma on the expression of glial fibrillary acidic protein (GFAP) and immediate early gene c-fos in the basal lateral amygdale (BLA) of the inflammatory pain rats. Methods Thirty-six adult male SD rats were randomly divided into 6 groups; control group, sham group, CFA group, CFA+ 5 g/( kg · day) volatile oil of Acori Graminei Rhizoma group, CFA+10 g/(kg · day) volatile oil of Acori Graminei Rhizoma group, CFA+20 g/(kg · day) volatile oil of Acori Graminei Rhizoma group, six rats in each group were taken gavage for 21 days. Immunofluorescence and Western blotting methods were used to detect the expressions of GFAP and c-fos in the BLA of all rats. Results Immunofluorescence and Western blotting results showed that compared with the control group, the positive expression of GFAP and c-fos in the BLA of the CFA rats were significantly increased (P<0.01). After treatment of the volatile oil from Acori Graminei Rhizoma, the positive expressions of GFAP and c-fos were reduced compared to the CFA group, as well as the expression levels were decreased in the dose-dependent manner (P<0.01). Compared with the low dose group, the positive expression of GFAP and c-fos of high dose group were decreased significantly (P<0.01). Conclusion The volatile oil fraction from Acori Graminei Rhizoma could reduce the expressions of GFAP and c-fos the BLA of CFA-induced chronic inflammatory pain model rats.

Relationship between complete Freund ' s adjuvant-induced chronic pain-induced negative emotions and morphological changes of hippocampal microglia / 解剖学报

Objective To investigate the alteration of mood and hippocampal microglia morphology in a mouse model of chronic inflammatory pain induced by complete Freund' s adjuvant (CFA). Methods Thirty-two male ICR mice were randomly divided into two groups, including normal saline control group (NS) and CFA model group (CFA). The pain model was established by right hindpaw intraplantar CFA injection. The change of mechanical pain threshold after CFA injection was measured by von Frey fiber needle, the locomotor activity and anxiety-like behavior were determined by open field test (OFT), the depression-like behavior was determined by sucrose preference test (SPT) and forced swimming test (FST). The expression of microglia marker ionized calcium binding adaptor molecule-1 (IBA-1) in the hippocampus was determined by immunohistochemistry and its morphological change was analyzed by Sholl analysis. Results Compared with the NS group, the mechanical pain threshold of CFA group decreased significantly (P<0.01). The behavior result showed that the CFA group showed remarkably reduced time in the inner area (P<0.01) compared with the NS group in the open field test; In the sucrose preference test, the percentage of sucrose preference (P<0.01) of CFA mice decreased significantly compared with the NS mice, while the immobility time of CFA mice (P<0.01) increased significantly in the forced swimming test compared with the NS mice. The immunohistochemistry showed that the number of microglia in the dentate gyrus (DG) of CFA mice increased significantly compared with the NS mice. The Sholl analysis result showed that compared with the NS mice, the number of intersections of microglia in hippocampal DG decreased significantly in CFA mice. Conclusion Our finding indicates that the negative emotions in CFA-induced chronic inflammatory pain may be related to the morphological changes of hippocampal microglia in the mice.

Dexmedetomidine alleviates formaldehyde induced pain by inhibiting astrocytes activation in spinal cord / 解剖学报

Objective To investigate the effect of dexmedetomidine ( DEX ) on formaldehyde-induced acute inflammatory pain. Methods Thirty female ICR mice were randomly divided into three groups, including normal saline control (NS) group, formaldehyde(F)group and dexmedetomidine + formaldehyde (DEX+F) group. 0. 1% formaldehyde solution was injected into subcutaneous tissue of mice right hind paw to establish acute inflammatory pain model. An hour before formalin injection, mice were intraperitoneal injected with DEX in DEX + F group, and mice were intraperitoneal injected with equal volume saline in NS group and F group. The expression of spinal cord glial fibrillary acidic protein ( GFAP), which is a astrocytes marker, was detected by immunohistochemistry and Western blotting. Results Spontaneous pain score showed that compared with the NS group, the F group had typical biphasic pain response ; while compared with the F group, the DEX+F group showed a significant decrease in the first (P<0. 001) and second phase pain (P<0. 001). Immunohistochemical result showed that compared with the NS group, the F group had an increase number of GFAP positive cells in the posterior horn of the spinal cord (P<0. 001). However, the DEX+F group showed a decrease number of GFAP positive cells in the posterior horn of spinal cord compared with the F group (P<0. 001 ). Western blotting result showed that compared with the NS group, the F group had increased expression of GFAP in the spinal cord (P<0. 05). Compared with the F group, the DEX + F group showed decreased GFAP expression in the spinal cord ( P < 0. 05 ). Conclusion DEX may improve formaldehyde-induced acute inflammatory pain in mice by inhibiting the activation of astrocytes in the spinal cord.

Chlorogenic acid alleviates chronic inflammatory pain via inhibiting synaptic expression of AMPA receptor / 中国药理学通报

Aim To investigate the effect of chlorogenic acid (CGA) on chronic inflammatory pain induced by complete Freund's adjuvant (CFA) and to observe the influence of CGA on CFA-induced synaptic expression of AMAP receptor in spinal dorsal horn. Methods CFA was injected intraplantarly into the hindpaws of mice to induce mechanical allodynia and thermal hyperalgesia. The changes of paw withdrawal threshold (PWT) and the paw withdrawal latency (PWL) were tested after intrathecal administration of CGA. Meanwhile, the synaptic expression and phosphorylation of AMPA receptor subunit were assessed by immunoblot-ting. Results The intrathecal injection of CGA produced dose-depended improvement of both PWT and PWL in CFA injected mice. A higher dose of CGA (200ng) did not influence the base thresholds of normal mice. The median dose of CGA (100 ng) effectively reversed the CFA-induced synaptic expression of GluAl; meanwhile, it suppressed the phosphorylation of GluAl at Ser845, with no influence on phosphorylation at Ser831. Conclusions CGA might exert its analgesic effect by specifically inhibiting the phosphorylation of GluAl -Ser845 and the synaptic incorporation of GluAl-containing AMPA receptor.

Effect of electroacupuncture on expression of GABA receptor mRNA in different brain regions in rats with chronic inflammatory pain / 中国针灸

OBJECTIVE@#To observe the expression of GABA receptor mRNA in different brain regions of the central nervous system in chronic inflammatory pain rats and the intervention effect of electroacupuncture (EA).@*METHODS@#A total of 48 SPF male SD rats were randomly divided into a blank control group, a model control group, an EA group and a sham EA group, 12 rats in each group. The model of chronic inflammatory pain was established by injecting Freund's complete adjuvant into the foot. The EA group was treated with EA 28 days after the model establishment. The "Housanli" (ST 36) and "Kunlun" (BL 60) were selected and treated with dilatational wave, 2 Hz/100 Hz in frequency, 0.5-1.5 mA for 30 min; EA was given only once. In the sham EA group, the same acupoints were selected but the needles were only inserted into subcutaneous area; EA was connected for 30 min without electrical stimulation. The behavior changes of mechanical pain threshold and thermal pain threshold before model establishment, 1 day, 3 days, 7 days, 14 days, 21 days and 28 days after the model establishment as well as emotional behavior 29 days after the model establishment were observed; the relative expressions of GABA receptor mRNA in anterior cingulate cortex, amygdala and hypothalamus were observed.@*RESULTS@#Compared with the blank control group, the change rates of mechanical pain threshold and thermal pain threshold in the model control group were decreased significantly 1 day, 3 days, 7 days, 14 days, 21 days, 28 days after model establishment (0.05). Compared with the blank control group, the expression of GABA receptor mRNA in the amygdala was decreased significantly in the model control group (<0.01); compared with the model control group and the sham EA group, the expression of GABA receptor mRNA in amygdala was increased after intervention in the EA group (<0.01).@*CONCLUSION@#Single treatment of EA could significantly increase the mechanical pain threshold and thermal pain threshold, improve abnormal emotional behavior in rats with chronic inflammatory pain, which may be related to the increasing of expression of GABA receptor mRNA in the amygdala.

Analgesic Effect of Panlongqi Tablet on Rats with Chronic Inflammatory Pain / 中国实验方剂学杂志

Objective:To observe the analgesic effect of Panlongqi tablet（PLQT） on rats with chronic inflammatory pain， and to explore mechanism of the action preliminarily from the perspective of the nuclear factor kappa-light-chain-enhancer of activated B cells （NF-κB）and mitogen-activated protein kinase（MAPKs） signaling pathways. Method:Rats were induced to establish model of chronic inflammatory pain by complete Freund adjuvant（CFA）， which was divided into normal group， model group， the PLQT 0.16，0.32，0.64 g·kg-1 group， and the ibuprofen 0.05 g·kg-1 group（also positive group）， give the medicine once a day by gavage. Standard Von Frey fiber was used to evaluated the mechanical pain threshold， acetone was used to stimulated rats inflammatory foot to get the cold-induced response score， with the mechanical pain threshold and cold-induced response score to be observed at 1， 2， 3， 4 and 6 h before and after administration on day 1， and at 4 h after administration on day 3-7. The content of PGE2， IL-1， TNF-α in serum， inflammatory foot and 4-5 lumbar spinal cord was detected by enzyme-linked immunosorbent assay（ELISA）. The protein level of MAPKs （p-p38， p-ERK， p-JNK） in lumbar spinal cord 4-5 was detected by Western blot. The expression of NF-κB p65 in the lumbar spinal cord was detected by IFA. Result:Model group had lower mechanical pain threshold and higher cold-induced response score than these in normal group（P<0.01）， while the mechanical pain threshold and cold-induce response score of the model rats were dose-dependent better regulated after administration of PLQT 0.16， 0.32， 0.64 g·kg-1·d-1（P<0.05，P<0.01）， these effect lasted 6 h， of which PLQT groups get the most significant effect on 4 h， however the effect of IBP was similar to that of PLQT medium dose group. In addition， PLQT reduced the abnormal increase of PGE2， IL-1 and TNF-α contents in serum， inflammatory foot and spinal cord of rats in model group， decreased the protein phosphorylation levels of ERK and JNK in spinal cord， and decreased the protein expression of NF-κB p65， that was significant in the PLQT high-dose group（P<0.01）. Conclusion:PLQT had significant analgesic effect on chronic inflammatory pain model rats， which may be related to the inhibition of NF-κB and MAPKs signaling pathways in spinal cord.