(中國(guó)醫(yī)科大學(xué)附屬第一醫(yī)院麻醉科,沈陽(yáng) 110001)
大麻素受體1對(duì)坐骨神經(jīng)結(jié)扎大鼠神經(jīng)病理性疼痛的影響及機(jī)制
李曉倩,包娜仁,張?jiān)倮颍R虹
(中國(guó)醫(yī)科大學(xué)附屬第一醫(yī)院麻醉科,沈陽(yáng) 110001)
目的 觀察鞘內(nèi)注射大麻素受體1(CB1)激動(dòng)劑和拮抗劑對(duì)坐骨神經(jīng)結(jié)扎大鼠行為學(xué)、痛閾以及脊髓組織中CB1表達(dá)的影響,探討CB1在神經(jīng)病理性疼痛中的作用及機(jī)制。方法 SD大鼠隨機(jī)分為4組:假手術(shù)組(sham組)、坐骨神經(jīng)結(jié)扎組(SNL組,鞘內(nèi)注射30 μL DMSO)、CB1激動(dòng)劑組[AM841組,坐骨神經(jīng)結(jié)扎前3 d鞘內(nèi)注射5 μg AM841(溶于30 μL DMSO)]、CB1拮抗劑組[AM281組,坐骨神經(jīng)結(jié)扎前3 d鞘內(nèi)注射5 μg AM281(溶于30 μL DMSO)]。Sham組僅暴露坐骨神經(jīng)而不結(jié)扎。其余各組均行右側(cè)坐骨神經(jīng)結(jié)扎術(shù),術(shù)后1、3、5、7、10、14 d觀察大鼠行為學(xué)變化,測(cè)定各組大鼠的熱痛閾、機(jī)械性痛閾;Western blotting法檢測(cè)脊髓組織中CB1表達(dá)。結(jié)果 與sham組相比,SNL組術(shù)后各觀察點(diǎn)大鼠逐漸出現(xiàn)術(shù)側(cè)后肢足趾并攏、熱痛覺過敏和機(jī)械異常性疼痛等癥狀,同時(shí)脊髓組織中CB1表達(dá)降低(P<0.05);AM841組脊髓CB1表達(dá)增加,抑制坐骨神經(jīng)結(jié)扎所引起的熱痛閾和機(jī)械性痛閾降低(P<0.05);AM281組脊髓CB1表達(dá)進(jìn)一步降低、大鼠痛覺異常增大(P<0.05)。結(jié)論 脊髓CB1參與神經(jīng)病理性疼痛的調(diào)節(jié),給予外源性大麻素CB1激動(dòng)劑可以減輕坐骨神經(jīng)結(jié)扎引起的神經(jīng)病理性疼痛。
大麻素受體;神經(jīng)病理性疼痛;脊髓;大鼠
神經(jīng)病理性疼痛是由于腫瘤、感染、自身免疫 等因素導(dǎo)致神經(jīng)系統(tǒng)損傷或功能紊亂引起的一種慢性疼痛,其疼痛程度重且多伴有自主神經(jīng)功能紊亂,臨床治療效果欠佳[1?2]。目前神經(jīng)病理性疼痛機(jī)制尚未明確,深入探討其機(jī)制對(duì)臨床中尋求有效的鎮(zhèn)痛方案至關(guān)重要。脊髓是聯(lián)系外周和高級(jí)神經(jīng)中樞,是傷害性信息傳遞的中轉(zhuǎn)站。越來(lái)越多的研究[3?4]發(fā)現(xiàn)大麻素受體(cannabinoid receptors,CB)參與疼痛中樞敏化形成介導(dǎo)慢性疼痛調(diào)節(jié)。既往研究[5]發(fā)現(xiàn)大鼠經(jīng)鞘內(nèi)注射選擇性CB2激動(dòng)劑WIN55、212?2可以通過抑制神經(jīng)炎癥遞質(zhì)釋放、對(duì)抗興奮性氨基酸毒性和調(diào)控鈉通道過度開放等多靶點(diǎn)緩解機(jī)械性痛覺過敏,而脊髓水平CB1是否參與神經(jīng)病理性疼痛的調(diào)節(jié)鮮有報(bào)道。本研究觀察大鼠坐骨神經(jīng)結(jié)扎后脊髓CB1表達(dá)以及鞘內(nèi)注射CB1激動(dòng)劑、拮抗劑對(duì)坐骨神經(jīng)結(jié)扎(sciatic nerve li?gation,SNL)大鼠行為學(xué)和痛閾的影響,探討CB1在神經(jīng)病理性痛中作用及機(jī)制。
1.1 實(shí)驗(yàn)材料及主要儀器
雄性Sprague?Dawley大鼠160只,體質(zhì)量240~260 g,由中國(guó)醫(yī)科大學(xué)實(shí)驗(yàn)動(dòng)物中心提供。AM841、AM281、Dimethyl sulfoxide(DMSO,美國(guó)Cayman Chemical公司);兔抗大鼠CB1抗體(美國(guó)Sigma公司);鼠爪機(jī)械痛閾測(cè)定儀(意大利UgoBasi?le公司)、大鼠爪熱痛閾測(cè)定(意大利UgoBasil公司)、圖像分析系統(tǒng)(武漢華海公司)、酶標(biāo)儀(美國(guó)BIO?TEK公司)由中國(guó)醫(yī)科大學(xué)附屬第一醫(yī)院實(shí)驗(yàn)動(dòng)物中心提供。
1.2 實(shí)驗(yàn)方法
1.2.1 模型制備[6]:水合氯醛腹腔注射麻醉后,常規(guī)消毒,于大鼠右側(cè)大腿后中部切開縱向切口,鈍性分離皮下組織和肌肉,于股骨后找到坐骨神經(jīng)主干,用4?0絲線在坐骨神經(jīng)的中段間隔2 mm結(jié)扎4條線,結(jié)扎強(qiáng)度以引起小腿肌肉輕度顫動(dòng)為宜,僅留下縊痕而不阻斷神經(jīng)血供,然后以生理鹽水沖洗傷口,逐層縫合。假手術(shù)組大鼠僅暴露坐骨神經(jīng)而不結(jié)扎。所有手術(shù)步驟都在無(wú)菌環(huán)境下操作。
1.2.2 鞘內(nèi)注射[7]:麻醉下,用27號(hào)針頭注射器在脊髓T9~12節(jié)段緩慢穿刺脊髓,當(dāng)針頭進(jìn)入蛛網(wǎng)膜下腔時(shí),動(dòng)物可立即出現(xiàn)甩尾反應(yīng)。然后緩慢注入藥物。鞘內(nèi)用藥有CB1激動(dòng)劑AM841、拮抗劑AM281(溶于30 μL DMSO)、等量DMSO,1次/d,連續(xù)3 d。
1.2.3 實(shí)驗(yàn)分組:大鼠隨機(jī)分為4組,每組40只。假手術(shù)組(sham組),坐骨神經(jīng)結(jié)扎前3 d鞘內(nèi)注射DMSO 30 μL,開腹并暴露坐骨神經(jīng)而不結(jié)扎;SNL組,坐骨神經(jīng)結(jié)扎前3 d鞘內(nèi)注射DMSO 30 μL,開腹暴露右側(cè)坐骨神經(jīng)并結(jié)扎;CB1激動(dòng)劑組(AM841組):坐骨神經(jīng)結(jié)扎前3d鞘內(nèi)注射AM841(5μg/30μL);CB1阻斷劑組(AM281組):坐骨神經(jīng)結(jié)扎前3 d鞘內(nèi)注射AM281(5 μg/30 μL)。1次/d,連續(xù)3 d。
1.2.4 疼痛一般行為學(xué)測(cè)定[8]:術(shù)后大鼠單籠飼養(yǎng),觀察大鼠的精神狀態(tài)、進(jìn)食和飲水、傷口愈合情況以及大鼠安靜時(shí)的姿勢(shì)運(yùn)動(dòng)能力。
1.2.5 機(jī)械性痛閾及熱痛閾測(cè)定[9]:分別于SNL前3 d及術(shù)后1、3、5、7、10、14 d,上午8時(shí)至10時(shí),室溫保持在20~24℃,待大鼠安靜后,采用電子自動(dòng)爪觸覺測(cè)試儀測(cè)定各組大鼠右足機(jī)械刺激縮爪閾值(paw withdrawal threshold,PWT),將刺激針對(duì)準(zhǔn)右足底并逐漸增加刺激力量,大鼠感覺到痛覺后移開足部,設(shè)備記錄并顯示大鼠移開右足瞬間的最大值,即PWT。照射內(nèi)側(cè)第1足趾的著力點(diǎn),采用輻射熱測(cè)痛儀測(cè)定各組大鼠右足輻射熱刺激縮爪潛伏期(paw withdrawal latency,PWL),單次照射不超過20 s,以免損傷照射部位。測(cè)定值精確到0.1 s。測(cè)定3次,每次間隔5 min,取平均值。
1.2.6 Western blotting測(cè)定大鼠脊髓組織中CB1蛋白表達(dá):大鼠完成痛閾測(cè)定后處死,取術(shù)側(cè)L4~6節(jié)段脊髓組織,提取總蛋白溶液,進(jìn)行SDS?PAGE電泳將蛋白濕轉(zhuǎn)至PVDF膜上,5%牛奶封閉后加入抗CB1抗體,4℃過夜,洗膜后再用HRP標(biāo)記的山羊抗兔IgG雜交,37℃2 h。最后加入ECL試劑反應(yīng)1~2 min顯像,用掃描儀行蛋白條帶掃描并進(jìn)行蛋白條帶半定量分析。以CB1和GAPDH的比值作為表達(dá)強(qiáng)度。
1.3 統(tǒng)計(jì)學(xué)分析
數(shù)據(jù)處理采用SPSS 19.0統(tǒng)計(jì)學(xué)軟件,計(jì)數(shù)資料采用χ2檢驗(yàn);計(jì)量資料結(jié)果以x±s表示,采用單因素方差分析(ANOVA)比較組間差異,使用post hoc進(jìn)行多重比較,P<0.05為差異有統(tǒng)計(jì)學(xué)意義。
2.1 4組大鼠疼痛一般行為學(xué)比較
4組大鼠術(shù)后體質(zhì)量無(wú)明顯下降,進(jìn)食和飲水無(wú)明顯改變。sham組大鼠術(shù)后行為學(xué)表現(xiàn)較術(shù)前無(wú)明顯改變,而SNL組大鼠術(shù)后隨時(shí)間進(jìn)展逐漸出現(xiàn)術(shù)側(cè)后肢足趾并攏,足外翻以及反復(fù)舔舐術(shù)側(cè)后肢等癥狀;與SNL組比較,AM841組出現(xiàn)上述癥狀大鼠的數(shù)目明顯降低,舔舐術(shù)側(cè)后肢次數(shù)減少,而AM281組上述癥狀加重,甚至出現(xiàn)觸摸痛體征,舔舐次數(shù)明顯增多。見表1。
2.2 4組大鼠機(jī)械性痛閾的比較
各組大鼠術(shù)前基礎(chǔ)機(jī)械性PWT差異均無(wú)統(tǒng)計(jì)學(xué)意義(P>0.05)。與sham組比較,從術(shù)后第1天開始SNL組大鼠術(shù)側(cè)右足PWT值逐漸降低,持續(xù)至手術(shù)后第14天,而在第5天和第7天達(dá)最低水平(P<0.05)。與SNL組比較,AM841組術(shù)后各觀察點(diǎn)PWT值明顯升高(P<0.05),而AM281組PWT值進(jìn)一步降低(P<0.05)。術(shù)后各時(shí)間點(diǎn)SNL組、AM841組和AM241組大鼠與sham組比較差異均有統(tǒng)計(jì)學(xué)意義(P<0.05),見圖1。
表1 各組大鼠坐骨神經(jīng)結(jié)扎后各時(shí)間點(diǎn)行為學(xué)變化Tab.1 Behavior changes in rats of 4 groups at different time points after SNL
圖1 4組大鼠SNL后1、3、5、7、10、14 d右足機(jī)械刺激PWT比較Fig.1 Comparison of 4 groups of PWT in right paws at 1,3,5,7,10,14 d after SNL
2.3 各組大鼠熱痛閾比較
熱痛閾的變化與機(jī)械痛閾的變化趨勢(shì)大體一致。各組大鼠術(shù)前基礎(chǔ)熱痛閾(PWL)的差異均無(wú)統(tǒng)計(jì)學(xué)意義(P>0.05)。與sham組相比,術(shù)后各時(shí)間點(diǎn)SNL組大鼠術(shù)側(cè)右足出現(xiàn)PWL降低,術(shù)后第5和7天達(dá)最低水平(P<0.05)。與SNL組相比,AM841組術(shù)后各觀察點(diǎn)PWL值明顯升高(P<0.05)而AM281組PWL值進(jìn)一步降低(P<0.05)。術(shù)后各時(shí)間點(diǎn)SNL、AM841和AM241 3組大鼠與sham組相比差異均有統(tǒng)計(jì)學(xué)意義(P<0.05),見圖2。
2.4 各組大鼠脊髓組織中CB1蛋白表達(dá)比較
Western blotting結(jié)果顯示:與sham組比較,術(shù)后各觀察點(diǎn)(第5天和第7天差別最為明顯)SNL組大鼠脊髓組織中CB1蛋白明顯下降(P<0.05),與SNL組比較,AM841組術(shù)后各觀察點(diǎn)大鼠脊髓組織中CB1蛋白表達(dá)明顯增加,而AM281組CB1蛋白表達(dá)進(jìn)一步降低(均P<0.05),見表2和圖3。
圖2 4組大鼠SNL后1、3、5、7、10、14 d右足熱刺激PWL比較Fig.2 Comparison of 4 groups of PWL in right paws at 1,3,5,7,10,14 d after SNL
圖3 SNL后5、7 d各組大鼠脊髓CB1蛋白表達(dá)Fig.3 Comparison of spinal CB1 protein levels at 5 and 7 days after SNL in four groups by Western blotting
神經(jīng)病理性疼痛具有癥狀多樣、發(fā)病機(jī)制復(fù)雜、無(wú)法在人體中模擬研究等特點(diǎn),因此選擇合適的動(dòng)物模型是深入研究其分子機(jī)制的必要手段。SNL是目前使用最廣泛的神經(jīng)病理性疼痛模型之一,具有高度的重復(fù)性。本研究制作的SNL大鼠模型術(shù)后精神和飲食狀態(tài)正常,逐漸出現(xiàn)后肢足趾并攏,足外翻以及反復(fù)舔舐術(shù)側(cè)后肢等現(xiàn)象,且PWT和PWL隨時(shí)間下降明顯,表明模型建立成功。
表2 各組大鼠SNL后各時(shí)間點(diǎn)脊髓組織中CB1蛋白表達(dá)Tab.2 Spinal CB1 protein levels at different time points after SNL
坐骨神經(jīng)損傷后可以引起局部組織的炎癥反應(yīng),引起5?HT緩激肽等內(nèi)源性物質(zhì)大量釋放,從而活化外周感受器,并將傷害性刺激傳入脊髓[10]。脊髓作為傷害性信息傳遞的中轉(zhuǎn)站,損傷后組織中免疫反應(yīng)細(xì)胞通過改變表面受體迅速發(fā)生活化,同時(shí)釋放出大量炎癥介質(zhì)、P物質(zhì)等致痛因子,參與神經(jīng)病理性疼痛的發(fā)生和發(fā)展[11?12]。越來(lái)越多的研究[3?4]發(fā)現(xiàn)CB在應(yīng)激、疼痛等病理情況下也迅速發(fā)生變化。人體內(nèi)主要存在2種CB,CB1和CB2,均為G蛋白耦聯(lián)受體,生理狀態(tài)下可調(diào)節(jié)某些神經(jīng)遞質(zhì)(谷氨酸、γ?氨基丁酸等)的釋放,被單酰基甘油酯酶迅速降解[10]。大麻素對(duì)神經(jīng)系統(tǒng)的影響最初是在1996年被發(fā)現(xiàn),SHEN等[13]指出大麻素可減少海馬組織切片的谷氨酸釋放從而對(duì)抗興奮性氨基酸對(duì)神經(jīng)元的毒性作用。近年來(lái),隨著研究深入發(fā)展,CB激活后還參與疼痛中樞敏化形成介導(dǎo)慢性疼痛調(diào)節(jié)。YAO等[5]對(duì)L5脊神經(jīng)結(jié)扎大鼠鞘內(nèi)注射選擇性CB2激動(dòng)劑WIN55、212?2能夠明顯減輕大鼠的機(jī)械痛敏,而給予CB1受體拮抗劑利莫那班可逆轉(zhuǎn)WIN55、212?2的保護(hù)作用[14]。不僅如此,敲除CB1基因的小鼠神經(jīng)敏感性增加,神經(jīng)功能學(xué)評(píng)分較野生型相比明顯異常,且恢復(fù)速度緩慢[15],基因克隆進(jìn)一步發(fā)現(xiàn)CB1和CB2總氨基酸序列44%同源,跨膜區(qū)氨基酸序列68%同源,可能在神經(jīng)病理性疼痛中存在共同的作用靶點(diǎn)[16]。本研究中對(duì)SNL模型大鼠鞘內(nèi)注射A841激動(dòng)劑,術(shù)后各觀察點(diǎn)右足PWL值和PWT值均明顯升高,獲得良好的鎮(zhèn)痛效果,而給予CB1拮抗劑后逆轉(zhuǎn)了上述的鎮(zhèn)痛作用。本研究中PWT值和PWL值在術(shù)后5 d和7 d變化最明顯(降低2倍以上)。同樣Western blotting檢測(cè)鞘內(nèi)注射AM841能明顯增加脊髓中CB1的表達(dá),而注射CM281則進(jìn)一步抑制CB1的表達(dá),與PWT值和PWL值的變化趨勢(shì)相符,表明通過注射外源性CB1可以有效上調(diào)脊髓組織中的CB1表達(dá),從而緩解疼痛,與既往研究[3,17]結(jié)果一致。
綜上所述,本研究觀察鞘內(nèi)注射CB1激動(dòng)和拮抗劑對(duì)SNL大鼠行為學(xué)、痛閾以及脊髓組織中CB1表達(dá)的影響,證實(shí)CB1參與神經(jīng)病理性痛中的發(fā)生和發(fā)展,給予外源性CB1可以有效緩解疼痛,為臨床治療提供了新的治療靶點(diǎn)。
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(編輯 武玉欣)
Mechanism and Effects of Cannabinoid Receptor 1 on Sciatic Nerve Ligation?induced Neuropathic Pain in Rat Model
LI Xiaoqian,BAO Naren,ZHANG Zaili,MA Hong
(Department of Anesthesiology,The First Hospital,China Medical University,Shenyang 110001,China)
Objective To observe the effects of intrathecal injection(IT)of agonist and antagonist of cannabinoid receptor 1 on pain threshold in rat model of sciatic nerve ligation(SNL)induced neuropathic pain,and investigate the role and mechanism of CB1 in neuropathic pain.Methods Male Sprague?Dawley rats were randomly divided into 4 groups:sham group(intrathecal normal saline,IT DMSO),SNL group(SNL+IT 30 μL DMSO),AM841 group(SNL+IT 5 μg AM841,dissolved in 30 μL of DMSO)and AM281 group(SNL+IT 5 μg AM281,dissolved in 30 μL of DMSO).IT was given 3 days before surgery.Sham group only had sciatic nerve exposure but without ligation.SNL model in the other three groups were established by right sciatic nerve ligation.The thermal and mechanical thresholds were assessed by paw withdrawal latency(PWL)to radiant heat and von Frey filaments at 1,3,5,7,10 and 14 days as well as behavior after SNL.Spinal expressions of CB1 were assessed by West?ern blotting.Results Compared with the sham group,symptoms of rats in SNL group,such as heat hyperalgesia,mechanical allodynia and poste?rior paws prone to close together,were gradually appeared in the observation time points,with lower spinal proteins expression of CB1(P<0.05). AM841 group exhibited increased proteins expression of CB1 and inhibited SNL?induced heat hyperalgesia and mechanical allodynia(P<0.05). AM281 group further decreased expression of CB1 and amplified the pain abnormality(P<0.05).Conclusion Spinal CB1 participates in the regulation of neuropathic pain,and exogenous cannabinoid CB1 agonists can alleviate the SNL?induced neuropathic pain.
cannabinoid receptor;neuropathic pain;spinal cord;rat
R741.02
A
0258-4646(2017)03-0205-04
10.12007/j.issn.0258?4646.2017.03.004
國(guó)家自然科學(xué)基金(81601053);遼寧省教育廳科學(xué)研究項(xiàng)目(LK201636)
李曉倩(1984-),女,主治醫(yī)師,博士.
馬虹,E-mail:mahong5466@yahoo.com
2016-08-20
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