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.

Melatonin can prevent morphine induced hyperalgesia and spinal astrocytes activation in rats

Objective To investigate the effect of mdatonin on tolerance, hyperalgesia and reactive gliosis induced by morphine in rats. Methods The study examined the effect of melstonin on morphine-induced hyperalgesia using tail flick test. hnmunohistochemistt7 and western blot was performed to detect the expression of glial fibrillat7 acidic protein （GFAP） indicative of spinal glial activity. Radioim- munoasssy was employed to measure protein kinase C （PKC） activity and cAMP levels in spinal cords. Results When co-adminis- tered intragastrically （i. g. ） with morphine,melstonin in doses of 50 or 100 mg ~ kg ~ significantly prevented hyperalgesia after termi- nation of morphine, hnmunohistochemistry and western blot with glial fibrillat3, acidic protein （GFAP） revealed that melstonin signifi- cantly decreased morphine-induced overexpression of GFAP in spinal cord （P 〈 0.05）. By measuring protein kinase C （PKC） activity and cAMP levels,the upregulsted PKC activity and cAMP levels induced by morphine were significantly inhibited by melstonin. Con- dusions Melstonin can prevent morphine withdrawal induced hyperalgesia and glial reactivity. This effect of melstonin after morphine administration maybe mediated by inhibiting PKC activity and cAMP upregulstion.