μ阿片受体外显子7在大鼠内啡肽-2镇痛效应中的作用

Role of μ opioid receptor exon 7 in analgesic efficacy of endomorphin-2 in rats

目的 评价μ阿片受体外显子7在大鼠内啡肽-2镇痛效应中的作用.方法 取鞘内置管成功的成年雄性SD大鼠24只,体重220～260 g,采用随机数字表法分为3组（n=8）：生理盐水对照组（C组）、阴性siRNA对照组（N-siRNA组）和μ阿片受体外显子7-siRNA组（E7-siRNA组）.C组鞘内注射生理盐水30μl,N-siRNA组鞘内注射阴性siRNA质粒20μ1＋lipofectamine 2000脂质体10μg,E7-siRNA组注射μ阿片受体外显子7-siRNA质粒20 μl＋lipofectamine 2000脂质体10μl,1次/d,连续3d.于第4天时（基础状态）测定机械痛阈,痛阈测定结束后lh时,鞘内注射内啡肽-2 10 μg.分别于给予内啡肽-2后5、20、40和60 min时测定机械痛阈,计算镇痛效应百分比.结果 3组间基础机械痛阈比较差异无统计学意义（P＞0.05）.与C组比较,N-siRNA组给予内啡肽-2后各时点镇痛效应百分比差异无统计学意义（P＞0.05）,E7-siRNA组给予内啡肽-2后5和20 min时镇痛效应百分比降低（P＜0.01）.结论 μ阿片受体外显子7参与了大鼠内啡肽-2的镇痛效应.

Objective To evaluate the role of μ opioid receptor exon 7 in the analgesic efficacy of endomorphin-2 in rats.Methods Twenty-four male Sprague-Dawley rats in which IT catheters were successfully implanted,weighing 220-260 g,were randomly divided into 3 groups （n =8 each） using a random number table：normal saline control group （group C）,negative siRNA control group （group N-siRNA） andμ opioid receptor exon 7 siRNA group （group E7-siRNA）.In C,N-siRNA and E7-siRNA groups,30μl saline solution,negative siRNA plasmid 20 μl ＋ lipofectamine 2000 （10 μl）,and μ opioid receptor siRNA plasmid 20μ1 ＋ lipofectamine 2000 （10 μl） were intrathecally injected once a day for 3 consecutive days.The mechanical pain threshold was measured on 4th day （baseline）.Endomorphin-2 10 μg was injected intrathecally at 1 h after measurement of the pain threshold.The mechanical pain threshold was measured at 5,20,40 and 60 min after endomorphin-2 injection,and the analgesic efficacy was calculated.Results There was no significant difference in the baseline pain threshold among the three groups.Compared with group C,no significant difference was found in the analgesic efficacy at each time point after endomorphin-2 injection in group N-siRNA,and the analgesic efficacy was significantly decreased at 5 and 20 min after endomorphin-2 injection in group E7-siRNA.Conclusion μ opioid receptor exon 7 is involved in the analgesic efficacy of endomorphin-2 in rats.