N~ω-硝基-L-精氨酸甲酯可抑制吗啡镇痛耐受大鼠的痛觉过敏以及脊髓和中脑c-Fos表达

目的:在福尔马林炎性疼痛模型观察非特异性一氧化氮合成酶(NOS)抑制剂/Nω-硝基-L-精氨酸甲酯(L-NAME)对吗啡镇痛耐受大鼠疼痛行为以及脊髓和中脑c-Fos表达的影响。方法:将24只健康成年SD大鼠随机平均分为4组:生理盐水(NS)组,即对照组,皮下注射(sc)NS1ml;L-NAME组、Mor组和L-NAME+Mor组,为处理组,分别scL-NAME20mg·kg-1、吗啡10mg·kg-1、L-NAME20mg.kg-1和吗啡10mg.kg-1。各组给药均为每天2次,连续7d。在d8上午最后1次给药后30min,于大鼠左后足掌侧sc5%福尔马林0.1ml,记录每5min内舔咬注射足时间(TTSLI),观察时间为50min。记录完毕后取脊髓和中脑做c-Fos免疫组化检查。结果:与NS组相比,L-NAME组的Ⅱ相TTSLI显著缩短,Mor组的Ⅰ相和Ⅱ相TTSLI显著延长,L-NAME+Mor组的Ⅰ相和Ⅱ相TTSLI均显著缩短。免疫组化检查结果显示,与NS组相比,L-NAME组、L-NAME+Mor组注射足同侧和对侧脊髓以及中脑导水管周围灰质(PAG)神经元的c-Fos样免疫反应阳性面积显著降低,但Mor组的F-LI阳性面积显著性增加。结论:吗啡镇痛耐受大鼠接受福尔马林刺激后表现为痛觉过敏,其脊髓和中脑PAG神经元的c-Fos表达增加,L-NAME可抑制吗啡镇痛耐受大鼠的痛觉过敏,并可抑制脊髓和中脑PAG神经元的c-Fos表达。本研究结果提示脊髓和中脑的一氧化氮系统与吗啡镇痛耐受时痛觉过敏的发生密切相关。     

脊髓背角神经元上调Nav1.8通道参与缺血再灌注损伤后痛觉过敏的机制

目的观察鞘内注射钠通道抑制剂619C89对脊髓缺血再灌注损伤引起的痛觉过敏大鼠的痛阈、脊髓背角神经元中Nav1.8通道表达的影响。方法 SD大鼠随机分为3组:假手术组(S组)、痛觉过敏组(H组,缺血再灌注前3 d鞘内注射30μL生理盐水)、钠通道抑制剂组(I组,缺血再灌注前3 d鞘内注射619C895μg/30μL)。S组仅暴露主动脉弓而不结扎,其他各组开胸后无创动脉夹夹闭主动脉弓14 min后再开放,建立SCIRI引起的痛觉过敏模型。各组手术前均于L_(5-6)鞘内置管并连续注射3 d。术后1、3、5、7、14 d分别测定各组大鼠的热痛阈及机械性痛阈;取第4~6节腰段脊髓,采用免疫双荧光法观察背角神经元状态及其Nav1.8的表达,Real time-PCR法检测各组大鼠脊髓组织Nav1.8表达。结果与S组相比,术后各观察点(尤以第7天为著)H组大鼠热痛阈和机械性痛阈降低,损伤后7 d脊髓组织中Nav1.8 mRNA的表达增加(P<0.05);I组大鼠热痛阈和机械性痛阈值明显提高(P<0.05),脊髓组织中Nav1.8 mRNA的表达降低(P<0.05)。免疫双荧光染色显示,损伤后7 d,H组大鼠脊髓背角Nav1.8的荧光强度明显增加,且主要表达在NeuN表达阳性的神经元的胞浆中;且与S组相比,H组中NeuN/Nav1.8双阳性的细胞数量明显增多,而I组双阳性的细胞数量减少(P<0.05)。结论脊髓背角神经元通过上调Nav1.8通道参与缺血再灌注损伤后痛觉过敏的形成。     

己酮可可碱通过抑制小胶质细胞激活减轻大鼠痛觉超敏和痛觉过敏

目的:观察己酮可可碱腹腔注射对大鼠坐骨神经分支选择性损伤致神经病理性疼痛的作用.方法:切断腓总神经和胫神经保留腓肠神经,制作坐骨神经分支选择性损伤模型.16只雄性SD大鼠从术前1 d起至术后6 d腹腔注射己酮可可碱100 mg·kg-1,qd.观察术前1 d和术后1,3,5,7和14 d大鼠的机械缩足反射阈值(MWT)和热缩足反射持续时间(TWD);并测定不同组别脊髓小胶质细胞标志物0X-42的表达.实验同时设假手术组和坐骨神经分支选择性损伤模型组(n=16).结果:大鼠坐骨神经选择性切断后1 d起MWT降低、TWD延长,与假手术组比差异有显著性统计学意义(P<0.05);己酮可可碱组MWT增加、TWD缩短,与模型组相比差异有显著性统计学意义(P<0.05);己酮可可碱组部分坐骨神经切断后脊髓0X-42的表达和小胶质细胞阳性细胞数均显著减少.结论:己酮可可碱腹腔注射可抑制坐骨神经分支选择性损伤致脊髓小胶质细胞的激活,减轻痛觉超敏和痛觉过敏.     

老龄小鼠心肌细胞钙激活钾通道特征

心肌细胞的钾通道对维持膜的稳定性,调控机-电偶合,舒张收缩等生理功能起重要作用[1,2]。ＳａｄａＴ等[3,4]报道自发高血压大鼠(ＳＨＲ)收缩压随年龄增加而升高,其升高幅度明显高于同龄对照(ＷＫＹ)大鼠,ＳＨＲ血管平滑肌胞内钙浓度[Ｃａ2 ]ｉ也随年龄增加而升高,但ＷＫＹ随年龄增大无明显改变。离子通道对[Ｃａ2 ]ｉ调节起十分重要作用。本文报导随年龄增加小鼠心肌ＩＫＣａ电导增大致使膜的稳定性降低。这是心脏致病的重要因素之一。内向整流钾通道ＩＫｉ对维持静息电位起重要作用。如果ＩＫｉ不随年龄相应增大,则对静息电位的调控作用也…     

褪黑素对吗啡导致的痛觉过敏及脊髓星形胶质细胞的作用研究简

目的 观察褪黑素（Melatonin,MT）对吗啡停药后的痛觉过敏及脊髓胶质细胞活化的影响.方法 62只SD大鼠,随机分为5组,分别为吗啡组（n=10）,MT复合吗啡组[分三个剂量组（n=14×3）]以及生理盐水对照组（n=10）.吗啡10 mg·kg-1每日8：00 am以及6：00 pm皮下注射,连续7 d,诱导吗啡耐受及痛敏模型; MT于每日5：00 pm,分上述25、50、100 mg·kg-1三个剂量组灌胃给药.分别于用药前,用药后每日10：00-12：00am以及停药后第1、2天同一时间测定大鼠甩尾潜伏期.停药后第1、2天取脊髓行GFAP免疫组化染色和Western blot法GFAP测定.于停药后第1天取腰段脊髓,放免法测定cAMP和PKC水平.结果 吗啡药后第1、2天,甩尾潜伏期显著缩短（与基础值比较,P〈0.05）,表现为痛觉过敏现象.MT 50、100 mg·kg-1 与吗啡联合用药组,停药后第1、2天无痛觉过敏现象（P〉0.05）.吗啡停药后脊髓后角GFAP蛋白表达增强,用药第7天,停药后第1、2天GFAP表达均显著增加（P〈0.05）,cAMP和PKC水平明显增高.MT三个浓度组MT 25、50、100 mg·kg-1可显著抑制吗啡导致的上述GFAP高表达现象.MT在100 mg·kg-1剂量组时,可抑制吗啡导致cAMP水平增高,在50、100 mg·kg-1剂量组时,可抑制吗啡导致PKC水平增高.结论 MT在一定浓度和剂量范围内,显著预防吗啡慢性给药后急性停药导致的痛觉过敏,机制可能与抑制脊髓星形胶质细胞活化和PKC活性有关.     

小电导钙激活钾通道与房颤关系的研究进展

房颤是临床上最常见的心律失常,它与心血管疾病的发病率和病死率密切相关。目前对房颤发病机制包括"折返"学说和"驱动伴颤动样传导"理论,以及在此基础上发展起来的"肺静脉波"学说和"房颤致房颤"理论。小电导钙激活钾通道(Small conductance calcium-activated potassium channel,SK channel)在哺乳动物心脏中呈心房选择性表达,并在心肌动作电位复极末期起作用。目前研究表明小电导钙激活钾通道参与房颤的发生维持,但其具体作用及机制仍有争议,本文就近年的研究成果做一综述。     

神经对大鼠骨骼肌小电导钙激活钾通道(SK3)表达的影响

目的小电导钙激活的钾通道(SK3)介导了动作电位后的后超极化电位的产生,在调节可兴奋细胞的膜电位中起关键作用。使去神经支配和肌强直营养不良患者骨骼肌SK3表达显著上调。本实验拟观察神经对骨骼肌SK3钾通道表达的调节作用。方法在Wistar大鼠,分别通过切断坐骨神经和局部注射河豚毒素(TTX)建立比目鱼肌去神经支配模型,和通过钳夹损伤比目鱼肌神经建立比目鱼肌去神经后神经再支配模型。在体给予去神经比目鱼肌频率为30Hz的电刺激(100脉冲/100 s)。实验结束后,免疫荧光法测定比目鱼肌中SK3钾通道的表达和定位;提取比目鱼肌组织总mRNA和蛋白,逆转录PCR和Western Blot分别检测SK3 mRNA和蛋白水平。结果切断坐骨神经能显著上调比目鱼肌SK3 mRNA和蛋白表达,且分别在术后第6 d和第9 d到达稳定。TTX诱导肌肉瘫痪也能显著上调比目鱼肌SK3 mRNA和蛋白表达。钳夹比目鱼肌神经所造成的暂时神经损伤能诱导SK3蛋白表达上调,而随着神经功能的恢复SK3蛋白表达也随之显著下调。在切断除坐骨神经术后6 d,在体给予电刺激6 d能显著下调比目鱼肌SK3的高表达;而且,在去除坐骨神经的同时给予电刺激则能阻止比目鱼肌SK3表达的上调。结论神经对骨骼肌SK3钾通道表达具有抑制作用,其作用与唤起肌肉活性密切相关。在体电刺激能抑制和防止去神经诱导的骨骼肌SK3蛋白表达上调,可能是改善神经损伤后或相关疾病所致的肌强直症状的有效手段之一。     

神经元上的小电导钙激活钾通道的研究进展

小电导的钙激活钾通道 (SK)具有K+ 选择性 ,Ca2 + 高敏性和电压不依赖等特性 ,广泛分布在神经元上。参与产生慢后超级化电位 ,通过放电频率适应影响神经元的放电功能。SK通道主要包括SK1,SK2 ,SK3 3种通道 ,通道活性受Ca2 + ,钙调蛋白 (CaM )以及一些神经递质的调节。SK通道的改变可能与学习记忆失调 ,精神分裂症以及神经肌肉失调等疾病有关     

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。     

金荞麦提取物改善肠易激综合征大鼠内脏痛觉过敏的效果及其机制

目的 观察金荞麦提取物(Fag)对肠易激综合征(IBS)大鼠内脏痛觉过敏的影响及其机制.方法 采用腹壁撤退反射(AWR)评分观察Fag(6、24 g·kg-1)口服给药两周后的IBS大鼠模型的内脏痛觉过敏的变化,并用免疫荧光法观察腰骶段脊髓背根神经(DRG)的辣椒素受体亚型TRPV1表达水平;采用细胞膜片钳记录Fag(0.1、0.3、1、3 g·L-1)对辣椒素(CAP)激活大鼠的DRG细胞TRPV1电流(ITRPV1)的影响.结果 Fag 24 g·kg-1在体内可显著降低升高的IBS大鼠AWR评分,IBS大鼠腰骶段DRG的TRPV1表达增高;Fag 6、24 g·kg-1干预后DRG的TRPV1表达下降;体外0.1、0.3、1、3 g·L-1 Fag可浓度依赖地抑制CAP激活的分离DRG神经元ITRPV1,IC50为0.83 g·L-1.结论 Fag可通过下调IBS大鼠TRPV1受体表达改善大鼠痛觉过敏,可抑制DRG神经元ITRPV1峰值,调节痛觉信号传递.     

Sodium nitroprusside-induced rat fundus relaxation is ryanodine-sensitive and involves L-type Ca2+ channel and small conductance Ca(2+)-sensitive K+ channel components

1 The aim of this study was to examine whether sodium nitroprusside (SNP)-induced relaxation of rat fundus longitudinal smooth muscle involves ryanodine-sensitive Ca2+ release. 2 SNP (300 nM-30 microM) elicited concentration-dependent relaxation of precontracted (1 microM carbachol) rat fundus, an effect almost abolished by the selective guanylyl cyclase inhibitor, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxaline-1-one (ODQ, 10 microM). 3 SNP-mediated relaxations were almost abolished by 10 microM ryanodine. 4 SNP-mediated relaxations were also reduced by either 1 microM apamin (a selective small conductance Ca(2+)-sensitive K+ channel, SKCa, inhibitor) or the selective L-type Ca2+ channel inhibitor, nicardipine (3 microM). 5 SNP-induced relaxations were insensitive to 1 mM tetraethylammonium chloride (an inhibitor of large-conductance Ca(2+)-sensitive K+ channels) and 1 microM glibenclamide (an ATP-sensitive K+ channel inhibitor). 6 These data suggest that SNP-mediated fundus relaxation occurs via a cGMP-mediated and ryanodine-sensitive mechanism which requires, at least in part, SKCa and L-type Ca2+ channel activity.     

茜草素激活Wistar大鼠肾叶间动脉平滑肌细胞大电导钙激活钾通道

目的研究茜草素对大电导钙激活钾通道(large conductance calcium activated potassium channels,BKCa)的调节作用。方法在快速分离的Wistar大鼠肾叶间动脉平滑肌细胞上,应用膜片钳技术研究茜草素对BKCa介导的外向电流的调节情况。结果BK_(Ca)特异性抑制剂伊比利亚毒素(ib TX)抑制茜草素的增强作用(P<0.01);去除细胞外液中的钙离子,L-钙通道抑制剂尼莫地平(nimodipine)、钙离子螯合剂BAPTA-AM和ryanodine均能抑制茜草素对肾叶间动脉平滑肌细胞外向电流的增强作用(P<0.05)。结论茜草素通过激活L-钙通道,促进钙离子由细胞膜外进入胞质,内流的钙离子进一步激活ryanodine受体,引起胞质中钙离子浓度快速升高,激活平滑肌细胞膜BK_(Ca)通道。     

Cyclopiazonic acid增加SHR和WKY血管平滑肌细胞Ca~(2+)-依赖性外向K~+-电流

采用全细胞及细胞贴附式斑片钳技术记录自发性高血压大鼠(SHR)和Wistar-Kyoto对照鼠(WKY)培养主动脉平滑肌细胞的Ca~(2+)-依赖性外向K~+电流[I_(k(Ca))],测定肌浆网Ca~(2+)泵抑制剂CPA对其影响.CPA能增加I_K(Ca))单通道开放时间,缩短关闭时间,增加全细胞I_(K(Ca))幅度,这些作用与Ca~(2+)相关并可被K~+通道阻断药glybenclamide阻断。CPA作用在SHR和WKY之间无明显差异。结果提示高血压状态下血管平滑肌的功能改变可能与I_(K(Ca))无关。     

Synthesis and radioligand binding studies of bis-isoquinolinium derivatives as small conductance Ca(2+)-activated K(+) channel blockers

Starting from the scaffold of N-methyllaudanosine and N-methylnoscapine, which are known small conductance Ca2+-activated K+ channel blockers, original bis-isoquinolinium derivatives were synthezised and evaluated using binding studies, electrophysiology, and molecular modeling. These quaternary compounds are powerful blockers, and the most active ones have 10 times more affinity for the channels than dequalinium. The unsubstituted compounds possess a weaker affinity than the analogues having a 6,7-dimethoxy- or a 6,7,8-trimethoxy substitution. The length of the linker has no influence in the alkane derivatives. In relation to the xylene derivatives, the affinities are higher for the ortho and meta isomers. These results are well corroborated by a molecular modeling study. Finally, the most effective compounds have been tested in electrophysiological experiments on midbrain dopaminergic neurons and demonstrate the blocking potential of the apamin-sensitive after-hyperpolarization.     

L-type Ca(2+) channel blockers inhibit the development but not the expression of sensitization to morphine in mice

The relationship between opioid actions and L-type Ca(2+) channel blockers has been well documented. However, there is no report relevant to L-type Ca(2+) channel blockers and morphine sensitization, which is suggested to be an analog of behaviors that are characteristic of drug addiction. We now studied systematically the effects of three L-type Ca(2+) channel blockers, nimodipine, nifedipine and verapamil, on morphine-induced locomotor activity, the development and the expression of sensitization to morphine. The results showed that both nimodipine and verapamil attenuated, while nifedipine had only a tendency to decrease morphine-induced locomotor activity. All three drugs inhibited the development of sensitization to morphine. However, none of them showed any effects on the expression of morphine sensitization. These results indicate that blocking L-type Ca(2+) channel attenuates the locomotor-stimulating effects of morphine and inhibits the development but not the expression of morphine sensitization.     

Charybdotoxin-sensitive small conductance K(Ca) channel activated by bradykinin and substance P in endothelial cells

1 In cultured porcine coronary artery endothelial cells, we have recently shown that substance P and bradykinin stimulated different types of Ca(2+)-dependent K(+) (K(Ca)) current. A large part of this current was insensitive to iberiotoxin and apamin. The aim of the present study was to characterize the K(Ca) channel responsible for this current. 2 In cell-attached configuration and asymmetrical K(+) concentration, 100 nM bradykinin or substance P activated a 10 pS K(+) channel. In inside-out configuration, the channel was half-maximally activated by 795 nM free Ca(2+). 3 Apamin (1 micro M) added to the pipette solution failed to inhibit the channel activity while charybdotoxin (50 nM), completely blocked it. Perfusion at the intracellular face of the cell, of an opener of intermediate conductance K(Ca) channel, 500 micro M 1-ethyl-benzimidazolinone (1-EBIO) increased the channel activity by about 4.5 fold. 4 In whole-cell mode, bradykinin and substance P stimulated an outward K(+) current of similar amplitude. Charybdotoxin inhibited by 75% the bradykinin-induced current and by 80% the substance P-induced current. Charybdotoxin plus iberiotoxin (50 nM each) inhibited by 97% the bradykinin-response. Charybdotoxin plus apamin did not increase the inhibition of the substance P-response obtained in the presence of charybdotoxin alone. 5 1-EBIO activated a transient outward K(+) current and hyperpolarized the membrane potential by about 13 mV. Charybdotoxin reduced the hyperpolarization to about 3 mV. 6 Taken together these results show that bradykinin and substance P activate a 10 pS K(Ca) channel, which largely contributes to the total K(+) current activated by these agonists. Despite its small conductance, this channel shares pharmacological characteristics with intermediate conductance K(Ca) channels.     

(+/-)-Naringenin as large conductance Ca(2+)-activated K+ (BKCa) channel opener in vascular smooth muscle cells

BACKGROUND AND PURPOSE. The aim of this study was to investigate, in vascular smooth muscle cells, the mechanical and electrophysiological effects of (+/-)-naringenin. EXPERIMENTAL APPROACH: Aorta ring preparations and single tail artery myocytes were employed for functional and patch-clamp experiments, respectively. KEY RESULTS: (+/-)-Naringenin induced concentration-dependent relaxation in endothelium-denuded rat aortic rings pre-contracted with either 20 mM KCl or noradrenaline (pIC(50) values of 4.74 and 4.68, respectively). Tetraethylammonium, iberiotoxin, 4-aminopyridine and 60 mM KCl antagonised (+/-)-naringenin-induced vasorelaxation, while glibenclamide did not produce any significant antagonism. Naringin [(+/-)-naringenin 7-beta-neohesperidoside] caused a concentration-dependent relaxation of rings pre-contracted with 20 mM KCl, although its potency and efficacy were significantly lower than those of (+/-)-naringenin. In rat tail artery myocytes, (+/-)-naringenin increased large conductance Ca(2+)-activated K(+) (BK(Ca)) currents in a concentration-dependent manner; this stimulation was iberiotoxin-sensitive and fully reversible upon drug wash-out. (+/-)-Naringenin accelerated the activation kinetics of BK(Ca) current, shifted, by 22 mV, the voltage dependence of the activation curve to more negative potentials, and decreased the slope of activation. (+/-)-Naringenin-induced stimulation of BK(Ca) current was insensitive either to changes in the intracellular Ca(2+) concentration or to the presence, in the pipette solution, of the fast Ca(2+) chelator BAPTA. However, such stimulation was diminished when the K(+) gradient across the membrane was reduced. CONCLUSIONS AND IMPLICATIONS: The vasorelaxant effect of the naturally-occurring flavonoid (+/-)-naringenin on endothelium-denuded vessels was due to the activation of BK(Ca) channels in myocytes.     

Contribution of Ca(2+) -dependent protein kinase C in the spinal cord to the development of mechanical allodynia in diabetic mice

In this paper, we directly demonstrate, for the first time, the activation of Ca(2+)-dependent protein kinase C (PKC) in the spinal cord of diabetic mice. In streptozotocin (STZ)-treated (200 mg/kg, i.v.) diabetic mice, hypersensitivity (allodynia) to mechanical stimulation appeared 7 d after STZ injection. This mechanical allodynia was inhibited by intrathecal injection of the PKC inhibitors 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7) and calphostin C, but not the protein kinase A inhibitor N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide (H-89). The activity of membrane-associated Ca(2+)-dependent PKC in the spinal cords of STZ-induced diabetic mice was significantly higher than that observed in non-diabetic mice. These results suggest that activation of Ca(2+)-dependent PKC in the spinal cord, contributes to the mechanical allodynia in the pain associated with diabetic neuropathy.     

Anti-pruritic and anti-inflammatory effects of natural verbascoside through selective inhibition of temperature-sensitive Ca~(2+)-permeable TRPV3 channel

OBJECTIVE To investigate the molecular mechanism underlying the action of natural verbascoside used as traditional herbal medicine for anti-itch and antiinflammation therapy. METHODS To confirm the inhibitory effect of verbascoside on transient receptor potential(TRP) channels, we performed the whole-cel patch clamp recordings of transiently transfected h TRPs-HEK293 cells. To examine the inhibitory effect of verbascoside on TRPV3 activation-induced itch, thymic stromal lymphopoietin(TSLP) release and proinflammatory response, we adopted a pretreatment by intradermal injection of verbascoside into the mouse neck 30 min before injection of TRPV3 agonist carvacrol into the same site. We counted the bouts of scratching behavior in mice for 30 min and performed q-PCR and Western blotting assay to measure the expression levels of TSLP, inflammatory factors such as tumor necrosis factor(TNF)-α and interleukin(IL)-6 from lysates of mouse neck skin tissues. RESULTS We found that natural verbascoside selectively inhibits TRPV3 in dose-dependent manner over other TRP channels including TRPV1, TRPV4, TRPA1 and TRPM8 channels. Verbascoside attenuates the acute scratching behavior and the release of pruritic mediator TSLP and inflammatory factors TNF-α and IL-6 induced by TRPV3 agonist carvacrol. CONCLUSION Natural verbascoside specifically inhibits TRPV3 channel and alleviates pruritus and inflammation via the channel inhibition. Our observations not only provide a mechanistic explanation for the action of natural verbascoside as herbal medicine used for anti-itch and anti-inflammation therapy, but also demonstrate that specific inhibition of TRPV3 may represent therapeutic strategy for potential treatment of pruritus or dermatitis.     

Activation of metabotropic glutamate receptor 7 in spinal cord inhibits pain and hyperalgesia in a novel formalin model in sheep

This study set out to characterize the contribution of group III metabotropic glutamate receptor 7 activation to nociceptive behaviour and mechanical hypersensitivity in a novel formalin test in sheep. The mGlu receptor 7 allosteric agonist, N,N'-dibenzhydrylethane-1,2-diamine dihydrochloride (AMN082; 2-20 mM), the nonselective group III mGlu receptor agonist L-(+)-2-amino-4-phosphonobutyric acid (0.2-20 mM) and drug vehicle were injected intrathecally into naive subjects (n=7 per group), or 5 min preformalin (3%; 0.2 ml)/saline injection (intradermal), into the lower forelimb of adult female sheep (n=5-7 per group). Forelimb withdrawal thresholds to noxious mechanical stimulation and pain behaviours (time spent nonweight bearing or flinching) were assessed for up to 180 min. Formalin induced a characteristic biphasic pain-behaviour response and mechanical hyperalgesia between 1-5 and 30-120 min postinjection. Treatment with AMN082, but not L-(+)-2-amino-4-phosphonobutyric acid significantly inhibited both early and late phase formalin-induced hyperalgesia and pain behaviours. AMN082 also induced a rapid but short lasting analgesia in naive subjects. These data suggest that enhancing endogenous metabotropic glutamate receptor 7 activity in spinal cord, using the novel allosteric modulator, AMN082, blocks pain and hyperalgesia, and may be of therapeutic benefit for the treatment of inflammatory pain.