SHP2抑制剂NSC-87877对炎性疼痛的抑制作用及其机制

目的探讨蛋白酪氨酸磷酸酶SHP2(src homology-2 domain-containing phosphatase 2)的抑制剂NSC-87877对炎性疼痛的影响及其机制;方法小鼠左后足底皮下注射完全佛氏佐剂(Complete Freund's Adjuvant;CFA)建立疼痛模型;鞘内给予NSC-87877前后,测定缩足阈值;随后分离左侧L4-L5节段脊髓背角,免疫印迹法检测N-methyl-D-aspartate(NM-DA)型谷氨酸受体的表达;结果 SHP2广泛分布于脊髓背角;且SHP2抑制剂NSC-87877(3μg)能够抑制CFA诱发的痛觉超敏,而对正常动物的痛行为无作用。虽然NSC-87877不影响NMDA受体NR2B和NR2A亚基的总蛋白含量,但却能够特异性降低CFA组动物NR2B的突触表达水平;结论 SHP2抑制剂NSC-87877通过逆转NR2B的突触表达亢进,对炎性疼痛产生明显的抑制作用。     

脊髓背角PKC在慢性炎性疼痛中的作用及其机制

目的探讨蛋白激酶C(protein kinase C,PKC)的抑制剂和激动剂对痛觉超敏的影响及其分子机制。方法小鼠后趾皮下注射完全弗氏佐剂(complete Freund's adjuvant,CFA)建立炎性疼痛模型;鞘内给予PKC抑制剂白屈菜赤碱(chelerythrine,CHE)或激动剂Phorbol 12-myristate 13-acetate(PMA)前后,测定小鼠缩足阈值;随后立即分离脊髓背角,免疫印迹法检测NMDA(N-methyl-D-aspartate)型谷氨酸受体的突触表达。结果 PKC抑制剂CHE在缓解炎性痛觉超敏的同时,明显翻转脊髓NMDA受体NR2B亚基的突触表达亢进;而正常小鼠鞘内给予PKC激动剂PMA,可模拟CFA的效应,即:诱发痛觉超敏,并特异性增加NR2B亚基的突触含量。结论 PKC通过调节脊髓NMDA受体NR2B亚基的突触表达,参与炎性疼痛的形成。     

脊髓c-Jun在NMDA受体NR2B亚基介导的大鼠吗啡镇痛耐受中的作用

目的探讨脊髓c-Jun在N-甲基-D-天冬氨酸(N-meth-yl-D-aspartate,NMDA)受体NR2B亚基介导的吗啡镇痛耐受中的作用。方法取Sprague-Dawley(SD)成年大鼠连续7 d鞘内注射吗啡10μl(1.5 g.L-1)建立慢性吗啡镇痛耐受模型。应用热水甩尾法测定甩尾潜伏期(疼痛指标)以观察痛反应变化。应用免疫组织化学染色法检测磷酸化c-Jun(p-c-Jun)和总c-Jun(t-c-Jun)的表达。结果鞘内注射吗啡7 d,可激活大鼠脊髓的c-Jun,表现为神经元内p-c-Jun表达升高;鞘内注射NR2B选择性拮抗剂10μl Ro256981(2 g.L-1)可以抑制慢性吗啡镇痛耐受时脊髓神经元c-Jun的激活,并明显拮抗吗啡镇痛耐受的形成。结论脊髓神经元c-Jun的磷酸化参与NMDA受体NR2B亚基介导的吗啡镇痛耐受。     

脑缺血再灌注后NMDA受体亚基2B酪氨酸磷酸化的调节机制(英文)

目的:研究沙土鼠脑缺血再灌注后海马突触体N-甲基-D-天冬氨酸(NMDA)受体亚基2B(NR2B)酪氨酸磷酸化调节的机制。方法:沙土鼠双侧颈总动脉结扎形成前脑缺血模型;NR2B酪氨酸磷酸化通过免疫沉淀和免疫印渍分析。结果:脑缺血15分钟导致蛋白酪氨酸磷酸化水平明显下降;再灌注引起包括180kDa蛋白在内的多种蛋白酪氨酸磷酸化水平快速(再灌注15分钟)、持续(至少48小时)升高。免疫沉淀和免疫印渍证实,180 kDa条带为NR2B。缺血15分钟,再灌注6小时,NR2B酪氨酸磷酸化明显高于对照组,为对照组的1.8倍,而NR2B蛋白表达量则无变化。缺血前腹腔注射非竞争性NR拮抗剂氯胺酮或L-型电压门控钙通道(L-type VGCC)阻滞药硝苯地平,对NR2B酪氨酸磷酸化水平升高有明显的拮抗作用,而对NR2B蛋白表达量均无影响。在此条件下,非NMDA受体拮抗剂6,7-二硝基喹恶啉土卫四(DNQX)对NR2B酪氨酸磷酸化水平无影响。酪氨酸蛋白磷酸酶(PTP)抑制剂钒酸钠使脑缺血再灌注诱导的NR2B酪氨酸磷酸化进一步增加,而酪氨酸蛋白激酶(PTK)抑制剂金雀异黄素则使其减少。Src能与NR2B免疫共沉淀。结论:沙土鼠脑缺血再灌注NR2B的酪氨酸磷酸化的升高是通过NR和L-type VGCC介导的;PTK和PTP参与脑缺血再灌注NR2B酪氨酸磷酸化的调节,与NR2B以物理方式结合的Src可能在这种     

鞘内注射螺内酯对大鼠神经根痛的影响

目的探讨鞘内注射螺内酯对大鼠神经根痛的影响及其机制。方法选择成功鞘内置管后无运动障碍的♂SD大鼠77只,体质量280～320 g,制备注射式慢性背根神经节压迫模型,随机分为假手术组(Sham组,n=27)、慢性背根神经节压迫组(CCD组,n=27)和螺内酯组(Spir组,n=23)。Spir组于造模后d 2～4,每次给予螺内酯3μg,每天2次。Sham组和CCD组则给予等量的10%酒精。于造模前、后d1、d 4、d 7、d 10、d 14测量双侧后足底机械缩足阈值(pawwithdrawal mechanical threshold,PWMT)和热辐射刺激潜伏期(paw withdrawal thermal latency,PWTL)(CCD组和Sham组n=12;Spir组n=8)。Western blot检测造模后d 4、d 7、d 10脊髓背角中磷酸化的p65(p-p65)在各组间的表达变化(n=5)。结果与Sham组相比,CCD组同侧PWMT(P<0.01)和PWTL(P<0.01)明显降低,脊髓背角中p-p65表达明显上调(P<0.01)。而对侧(P>0.05)和Sham组(P>0.05)则无变化。鞘内给予螺内酯后,术后d 4、d 7的PWMT(d 4:11.58±1.38 vs 7.71±0.82,P<0.01;d 7:10.89±1.46 vs7.49±1.11,P<0.01)和PWTL(d 4:14.14±1.52 vs 8.19±1.32,P<0.01;d 7:13.56±1.63 vs 8.56±1.56,P<0.01)明显降低。同侧脊髓背角中p-p65的表达也明显下调(P<0.01)。结论鞘内注射螺内酯对慢性压迫大鼠背根神经节诱发的神经根痛有治疗作用,抑制MR-NF-κB信号通路是其重要的机制之一。     

γ-氨基丁酸能去抑制对脊髓细胞外信号调节激酶2的激动作用

目的 探讨脊髓γ-氨基丁酸(GABA)能去抑制对细胞外信号调节激酶1/2(ERK1/2)活性的影响及其与痛行为改变的关系。方法 正常小鼠鞘内注射(ith)比扣扣灵碱(荷包牡丹碱, bicuculline)50 ng·g^-1(5 μl)模拟GABA能去抑制,左后足底sc给予弗氏完全佐剂制备炎性疼痛模型,小鼠ith给予GABA_A受体激动剂地西泮0.5 μg·g^-1(5 μl)或ERK1/2抑制剂PD-98059 0.25 μg·g^-1(5 μl)后,测定ERK1/2活性和小鼠缩足阈值。结果 与正常对照组的缩足阈值(1.24±0.07)g相比, 正常小鼠ith给予比扣扣灵碱50 ng·g^-1的缩足阈值显著降低((0.42±0.17)g,P<0.05),给予PD-98059 0.25 μg·g^-1后缩足阈值显著升高((1.29±0.37)g,P<0.05)。与炎性疼痛模型组的缩足阈值(0.28±0.06)g相比,炎症小鼠ith给予地西泮0.5 μg·g^-1的缩足阈值显著升高((0.99±0.12)g,P<0.05),且给予PD-98059 0.25 μg·g^-1后缩足阈值也显著升高((0.97±0.17)g,P<0.05)。Western免疫印迹结果显示,与正常对照组相比,比扣扣灵碱显著提高ERK2的磷酸化水平((152±24)%,P<0.05)。并且弗氏完全佐剂也可提高小鼠脊髓ERK2的磷酸化水平((163±42)%,P<0.05),ith给予地西泮0.5 μg·g^-1,则显著降低CFA诱发的小鼠脊髓ERK2的磷酸化水平((91±34)%,P<0.05),同时地西泮和PD-98059有效缓解炎性疼痛症状。结论 GABA能去抑制对脊髓背角ERK2有激活作用,并与炎性疼痛的形成有关。     

糖尿病神经痛大鼠脊髓背角NMDA受体表达的变化

目的探讨糖尿病神经病理性痛(DNP)大鼠脊髓背角N-甲基-D-天冬氨酸(NMDA)受体表达的变化。方法 SD雄性大鼠24只,4周龄,体重130～150g,随机分为2组,DNP组(D组,n=15)腹腔注射链尿佐菌素(STZ)50mg/kg制备成DNP模型,正常对照组(C组,n=9)给予等容量0.9%氯化钠溶液。给予STZ或0.9%氯化钠溶液后3、5、7周时分别取D组(5只)和C组(3只)大鼠,测量体重,采集静脉血样,测定空腹血糖浓度,然后测定机械缩足阈值,取脊髓组织,采用免疫组织化学法分别测定脊髓背角NR1和NR2B亚单位表达水平。结果与C组比较,在各时间点,D组体重下降,血糖升高,机械缩足阈值明显降低(P<0.05),脊髓背角NR1和NR2B亚单位免疫阳性细胞数表达明显增加(P<0.05)。结论脊髓背角NMDA受体在脊髓水平参与了大鼠糖尿病神经病理性痛的形成。     

一氧化氮合酶抑制剂抑制吗啡依赖及戒断大鼠脊髓神经元ERK的表达

目的探讨鞘内分别注射非选择性一氧化氮合酶(NOS)抑制剂L-NAME、选择性神经元型一氧化氮合酶(nNOS)抑制剂7-硝基吲哚(7-NI)对吗啡戒断大鼠戒断症状和痛敏行为以及脊髓神经元p-ERK表达的影响。方法采用吗啡依赖及戒断模型,分为正常对照组、依赖组、戒断组、L-NAME组(L-NAME)、7-NI组(7-NI),分别作行为学评分(n=8)、免疫组织化学(n=6)和免疫印迹检测(n=4)。结果实验结果表明,①鞘内注射L-NAME、7-NI可明显减轻吗啡依赖大鼠戒断症状,戒断组戒断症状评分为28.6±4.89,L-NAME组、7-NI组分别为22.1±4.52(P<0.05)、16.2±3.99(P<0.01);戒断组促诱发痛评分(touch evoked agitationscores,TEA score)为13.5±2.55,L-NAME组、7-NI组分别为9.8±3.11(P<0.05)、7.5±2.56(P<0.01)。②鞘内注射L-NAME、7-NI可明显减少胸腰段脊髓背角Fos阳性神经元的数目,L-NAME组、7-NI组分别为293±47、267±52,均低于戒断组(380±71,P<0.05,P<0.01)。③L-NAME、7-NI组p-ERK阳性神经元的数目分别为46.8±11.58、40.5±8.55,均低于戒断组(66.6±11.6,P<0.05,P<0.01),两给药组脊髓p-ERK蛋白的表达也减少。④W estern b lot显示:鞘内注射NOS明显抑制吗啡戒断大鼠脊髓p-ERK蛋白表达增加。结论脊髓水平NO参与吗啡依赖和戒断反应,ERK信号通路可能介导NO的上述作用。     

丙戊茶碱预处理削弱大鼠关节炎痛觉过敏的脊髓机制

目的研究预先鞘内注射丙戊茶碱对大鼠佐剂性关节炎热痛觉过敏的影响及其作用是否与抑制脊髓星形胶质细胞活化相关。方法实验采用大鼠右后爪踝关节外侧皮下注射CFA50μl致炎模型。①SD大鼠48只,随机分为6组(n=8),生理盐水(normal saline,NS)组:鞘内注射(intrathecal injection,it)NS10μl加皮下注射NS50μl;模型组:NSi加皮下注射CFA;单用丙戊茶碱组:10μg/10μl丙戊茶碱i加皮下注射NS;丙戊茶碱治疗组,分别为p2.5、p5、p10组:2.5μg/10μl、5μg/10μl及10μg/10μl丙戊茶碱it加皮下注射CFA。热辐射法测定各组大鼠热缩足反射潜伏期。②SD大鼠30只,随机分为6组(n=5),随机取3组鞘内预先注射生理盐水10μl,30min后注射CFA50μl,并分别于注射CFA5h、3d、7d麻醉;余大鼠预先注射丙戊茶碱(10μg/10μl,it),每天1次,30min后注射CFA50μl制成炎症模型,分别于注射CFA后5h、3d、7d麻醉;灌注,取材,免疫组化分析在炎症的不同阶段,大鼠炎症侧脊髓背角星形胶质细胞标志物GFAP表达。结果①模型组大鼠注射侧d2热缩足反射潜伏期与生理盐水组比较明显缩短(P<0.01),鞘内注射丙戊茶碱(5和10μg/10μl组)5h后大鼠热缩足反射潜伏期明显延长(P<0.01),有效作用时间为d1~d7;2.5μg/10μl组药物有效作用时间为d1~d2;注射对侧肢体大鼠行为学在实验观察期间没有明显变化;②模型组大鼠注射侧脊髓背角星形胶质细胞活化明显,积分光密度值增加(P<0.01)。鞘内注射丙戊茶碱(10μg/10μl组)5h后免疫组织化学染色可看到GFAP染色变浅,星形胶质细胞分支缩短,积分光密度值下降(P<0.01)。结论预先鞘内注射丙戊茶碱可提高大鼠热反射缩足潜伏期,可能通过抑制脊髓部位星形胶质细胞活化发挥抗伤害性作用。     

鞘内注射痛稳素对甲醛致痛大鼠脊髓PKCα与NMDA受体NR1亚单位磷酸化的影响

痛稳素(nocistatin,NST)在疼痛传导和调控中的作用目前已引起了人们的高度重视[1].本研究观察鞘内注射NST对甲醛致痛大鼠脊髓PKC与NMDA受体的磷酸化水平的影响,旨在探讨NST的痛觉调节作用及其机制.     

Involvement of spinal phosphorylation cascade of Tyr1472-NR2B, Thr286-CaMKII, and Ser831-GluR1 in neuropathic pain

Previously we demonstrated that phosphorylation of NR2B subunits of the N-methyl-d-aspartate (NMDA) glutamate receptor at Tyr1472 is increased in a neuropathic-pain model and that this phosphorylation is required for the maintenance of neuropathic pain by L5-spinal nerve transection. We obtained these results by using a selective NR2B antagonist and mice deficient in Fyn, which is an Src-family tyrosine protein kinase. However, how Tyr1472 phosphorylation of NR2B is involved in the maintenance of neuropathic pain was unclear. Here, we demonstrated that neuropathic pain was markedly attenuated in the spared nerve injury model of mice with a knock-in mutation of the Tyr1472 site to phenylalanine of NR2B (Y1472F-KI). While phosphorylation of Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) at its Thr286 and that of the GluR1 subunit of the AMPA receptor at its Ser831 was enhanced in the spinal dorsal horn after spared nerve injury in wild-type mice, such phosphorylation was markedly impaired in Y1472F-KI mice. Inhibition of CaMKII by intrathecal injection of KN93, an inhibitor of CaMKII, reduced mechanical allodynia and phosphorylation of CaMKII at its Thr286 and that of GluR1 at its Ser831 in the spinal cord 7 days after spared nerve injury. These results demonstrate that the phosphorylation of CaMKII and GluR1 occurs downstream of the Tyr1472 phosphorylation of NR2B subunits in the spinal cord and give the first suggestion that activation of CaMKII and GluR1-AMPA receptors may be involved in mechanical allodynia caused by peripheral nerve injury.     

Down-regulation of NR2B receptors partially contributes to analgesic effects of Gentiopicroside in persistent inflammatory pain

Gentiopicroside is one of the secoiridoid compound isolated from Gentiana lutea. It exhibits analgesic activities in the mice. The anterior cingulate cortex (ACC) is a forebrain structure known for its roles in pain transmission and modulation. Painful stimuli potentiate the prefrontal synaptic transmission and induce glutamate NMDA NR2B receptor expression in the ACC. But little is known about Gentiopicroside on the persistent inflammatory pain and chronic pain-induced synaptic transmission changes in the ACC. The present study was undertaken to investigate its analgesic activities and central synaptic modulation to the peripheral painful inflammation. Gentiopicroside produced significant analgesic effects against persistent inflammatory pain stimuli in mice. Systemic administration of Gentiopicroside significantly reversed NR2B over-expression during the chronic phases of persistent inflammation caused by hind-paw administration of complete Freunds adjuvant (CFA) in mice. Whole-cell patch clamp recordings revealed that Gentiopicroside significantly reduced NR2B receptors mediated postsynaptic currents in the ACC. Our findings provide strong evidence that analgesic effects of Gentiopicroside involve down-regulation of NR2B receptors in the ACC to persistent inflammatory pain.     

Implication of Src family kinase-dependent phosphorylation of NR2B subunit-containing NMDA receptor in the rewarding effect of morphine.

The present study was undertaken to further clarify the role of tyrosine phosphorylation of NR2B subunit-containing N-methyl-D-aspartate (NMDA) receptor in the development of the morphine-induced rewarding effect in mice. The morphine (5 mg/kg, sc)-induced rewarding effect was completely inhibited by pretreatment with a selective NR2B subunit-containing NMDA receptor antagonist ifenprodil (20 mg/kg, i.p.). The protein level of phospho-Tyr-1472, but not phospho-Ser-1303, NR2B subunit was significantly increased in the mouse limbic forebrain containing the nucleus accumbens (N.Acc.) of mice that had shown the morphine-induced rewarding effect. In addition, the level of phospho-Tyr-416 Src family kinase was also increased in the limbic forebrain of mice that had shown the morphine-induced rewarding effect. These findings suggest that Tyr-1472 phosphorylation of NR2B subunit-containing NMDA receptor associated with activation of Src family kinase in the limbic forebrain may be involved in the morphine-induced rewarding effect.     

Regulation of NMDA receptor function by Fyn-mediated tyrosine phosphorylation]

The ionnotropic glutamate receptor, N-methyl-D-aspartate (NMDA) receptor, is a prominent ligand-gated and voltage-gated ion channel in excitatory synaptic transmission in the mammalian central nervous system. The NMDA channel is also regulated by its phosphorylation. We have shown that an Src family kinase Fyn phosphorylates NR2A and NR2B subunits of the NMDA receptor. The phosphorylation events are facilitated by the presence of PSD-95, which is quite likely due to the complex formation of Fyn, PSD-95, and the NMDA receptor: Fyn interacts with PSD-95 and PSD-95 interacts with the NMDA receptor. We have identified tyrosine phosphorylation sites on NR2A and NR2B. A phosphorylation of one of the sites on NR2B (Tyr1472) is largely dependent on Fyn and is elevated upon the LTP induction of hippocampal CA1 neurons. The data suggest that Tyr-1472 phosphorylation of NR2B is important for synaptic plasticity. A phosphorylation of the other tyrosine residues of NR2A and NR2B would also be involved in brain development and function.     

Anti-allodynic property of flavonoid myricitrin in models of persistent inflammatory and neuropathic pain in mice

The aim of the present study was to investigate the effects of myricitrin, a flavonoid with anti-inflammatory and antinociceptive action, upon persistent neuropathic and inflammatory pain. The neuropathic pain was caused by a partial ligation (2/3) of the sciatic nerve and the inflammatory pain was induced by an intraplantar (i.pl.) injection of 20 microL of complete Freund's adjuvant (CFA) in adult Swiss mice (25-35 g). Seven days after sciatic nerve constriction and 24 h after CFA i.pl. injection, mouse pain threshold was evaluated through tactile allodynia, using Von Frey Hair (VFH) filaments. Further analyses performed in CFA-injected mice were paw edema measurement, leukocytes infiltration, morphological changes and myeloperoxidase (MPO) enzyme activity. The intraperitoneal (i.p.) treatment with myricitrin (30 mg/kg) significantly decreased the paw withdrawal response in persistent neuropathic and inflammatory pain and decreased mouse paw edema. CFA injection increased 4-fold MPO activity and 27-fold the number of neutrophils in the mouse paw after 24 h. Myricitrin strongly reduced MPO activity, returning to basal levels; however, it did not reduce neutrophils migration. In addition, myricitrin treatment decreased morphological alterations to the epidermis and dermis papilar of mouse paw. Together these results indicate that myricitrin produces pronounced anti-allodynic and anti-edematogenic effects in two models of chronic pain in mice. Considering that few drugs are currently available for the treatment of chronic pain, the present results indicate that myricitrin might be potentially interesting in the development of new clinically relevant drugs for the management of this disorder.     

The spirocyclopiperazinium salt compound LXM-15 alleviates chronic inflammatory and neuropathic pain in mice and rats

In the present study, we aimed to evaluate the effect of the spirocyclopiperazinium salt compound LXM-15 on chronic inflammatory pain and chronic neuropathic pain induced by complete Freund’s adjuvant (CFA) or chronic constriction injury (CCI) in mice and rats. The results showed that administration with LXM-15 significantly reduced paw edema and ankle swelling and increased the mechanical withdrawal threshold and paw withdrawal latency after CFA injection in mice. LXM-15 significantly alleviated the mechanical allodynia and thermal hyperalgesia in CCI rats. The effect was abolished by pretreatment with hexamethonium (a peripheral nAChR antagonist) or methyllycaconitine citrate (an α7 nAChR antagonist). Furthermore, LXM-15 significantly inhibited the phosphorylation of JAK2 and STAT3, and suppressed the expressions of TNF-α and c-fos in dorsal root ganglia of CCI rats. Collectively, we reported that LXM-15 relieved chronic inflammatory pain in CFA mice and chronic neuropathic pain in CCI rats. The underlying mechanism might be related to the activation of peripheral α7 nicotinic receptor, further inhibiting JAK2/STAT3 signaling pathway, and eventually suppressing the expressions of TNF-α and c-fos.     

Potential Involvement of μ-Opioid Receptor Dysregulation on the Reduced Antinociception of Morphine in the Inflammatory Pain State in Mice

The antinociceptive effect of morphine in the inflammatory pain state was described in the von Frey filament test using the complete Freund’s adjuvant (CFA)-induced mouse inflammatory pain model. After an i.pl. injection of CFA, mechanical allodynia was observed in the ipsilateral paw. The antinociceptive effect of morphine injected s.c. and i.t. against mechanical allodynia was reduced bilaterally at 1 day and 4 days after the CFA pretreatment. The expression level of mRNA for μ-opioid receptors at 1 day after the CFA pretreatment was reduced bilaterally in the lumbar spinal cord and dorsal root ganglion (DRG). In contrast, the protein level of μ-opioid receptors at 1 day after CFA pretreatment was decreased in the ipsilateral side in the DRG but not the lumbar spinal cord. Single or repeated i.t. pretreatment with the protein kinase Cα (PKCα) inhibitor Ro-32-0432 completely restored the reduced morphine antinociception in the contralateral paw but only partially restored it in the ipsilateral paw in the inflammatory pain state. In conclusion, reduced morphine antinociception against mechanical allodynia in the inflammatory pain state is mainly mediated via a decrease in μ-opioid receptors in the ipsilateral side and via the desensitization of μ-opioid receptors in the contralateral side by PKCα-induced phosphorylation.     

Central and peripheral sites of action for CB₂ receptor mediated analgesic activity in chronic inflammatory and neuropathic pain models in rats

BACKGROUND AND PURPOSE

Cannabinoid CB₂ receptor activation by selective agonists has been shown to produce analgesic effects in preclinical models of inflammatory and neuropathic pain. However, mechanisms underlying CB₂-mediated analgesic effects remain largely unknown. The present study was conducted to elucidate the CB₂ receptor expression in ‘pain relevant’ tissues and the potential sites of action of CB₂ agonism in rats.

EXPERIMENTAL APPROACH

Expression of cannabinoid receptor mRNA was evaluated by quantitative RT-PCR in dorsal root ganglia (DRGs), spinal cords, paws and several brain regions of sham, chronic inflammatory pain (CFA) and neuropathic pain (spinal nerve ligation, SNL) rats. The sites of CB₂ mediated antinociception were evaluated in vivo following intra-DRG, intrathecal (i.t.) or intraplantar (i.paw) administration of potent CB₂-selective agonists A-836339 and AM1241.

KEY RESULTS

CB₂ receptor gene expression was significantly up-regulated in DRGs (SNL and CFA), spinal cords (SNL) or paws (CFA) ipsilateral to injury under inflammatory and neuropathic pain conditions. Systemic A-836339 and AM1241 produced dose-dependent efficacy in both inflammatory and neuropathic pain models. Local administration of CB₂ agonists also produced significant analgesic effects in SNL (intra-DRG and i.t.) and CFA (intra-DRG) pain models. In contrast to A-836339, i.paw administration of AM-1241 dose-relatedly reversed the CFA-induced thermal hyperalgesia, suggesting that different mechanisms may be contributing to its in vivo properties.

CONCLUSIONS AND IMPLICATIONS

These results demonstrate that both DRG and spinal cord are important sites contributing to CB₂ receptor-mediated analgesia and that the changes in CB₂ receptor expression play a crucial role for the sites of action in regulating pain perception.     

皖南地区眼镜蛇毒镇痛组分对大鼠炎性痛作用机制探讨

目的：探讨皖南地区眼镜蛇毒镇痛组分（CVAF）对大鼠炎性痛作用效应及其可能机制。方法：40只雄性SD大鼠在测定基础痛阈后随机分为4组（n=10）：正常对照组（NC组）、炎性痛模型组（CFA组）、炎性痛模型＋CVAF组（CFA＋CVAF组）和炎性痛模型＋吗啡组（CFA＋Morphine组）。随后将36只SD雄性大鼠随机分成6组（n=6）：正常对照组（NC组）、炎性痛模型组（CFA组）、炎性痛模型＋CVAF组（CFA＋CVAF组）、炎性痛模型＋阿托品＋CVAF组（CFA＋Atr＋CVAF）、炎性痛模型＋纳洛酮＋CVAF组（CFA＋Nal＋CVAF）和炎性痛模型＋L—NAME＋CVAF组（CFA＋L—NAME＋CVAF）。测定各组大鼠的热痛阈潜伏期（TWL）和机械痛阈值（MWT）,制备脊髓匀浆,用于检测其中IL-1和TNF—a的表达。结果：与NC组相比,CFA组大鼠第1天开始TWL和MWT明显降低,出现热痛觉过敏和机械痛觉过敏,持续14d仍存在;CFA组大鼠脊髓匀浆IL-1和TNF—a表达均明显增高（P〈0．01）。与CFA组相比,CFA组大鼠腹腔注射CVAF后其TWL和MWT均升高,表明炎性痛大鼠热痛觉过敏和机械痛觉过敏得到改善;脊髓匀浆中IL-1、TNF—a表达显著减少（P〈0．01）,显示CVAF通过抑制炎性因子的产生而发挥镇痛作用。与CFA＋CVAF组大鼠相比,L—NAME＋CVAF组大鼠明显增强了CVAF对炎性痛大鼠的镇痛作用,表现为TWL和MWT的明显升高（P〈0．01）;而CFA＋Atr＋CVAF组和CFA＋Nal＋CVAF组大鼠TWL和MWT均有不同程度的降低（P〈0．01）。结论：初步阐明CVAF通过减少炎性因子的释放对炎性痛大鼠具有镇痛效应。阿片肽受体系统和胆碱能受体系统均部分参与了其对炎性痛大鼠的镇痛作用。