瑞芬太尼诱发切口痛大鼠痛觉过敏时脊髓背角G9a和Slack的关系

Relationship between G9a and Slack in spinal cord dorsal horn during remifentanil-induced hyperalgesia in a rat model of incisional pain

目的评价瑞芬太尼诱发切口痛大鼠痛觉过敏时脊髓背角常染色质组蛋白赖氨酸N-甲基转移酶2(G9a)和钠依赖激活的钾离子通道(Slack)的关系。方法清洁级健康雄性SD大鼠24只,1月龄,体重100~120 g。采用随机数字表法分为4组(n=6):生理盐水组(S组)、载体组(V组)、载体+瑞芬太尼+切口痛组(VRI组)和G9a-siRNA+瑞芬太尼+切口痛组(DRI组)。VRI组和DRI组L4,5脊髓背角注射Vector 1μl,3 d后尾静脉输注瑞芬太尼1μg·kg^-1·min^-160 min,同时建立大鼠切口痛模型;S组和V组分别注射等容量生理盐水。于输注瑞芬太尼前24 h(T0)、输注后2、6、24和48 h(T1-4)时测定机械刺激缩足反应阈(MWT)和热刺激缩足潜伏期(TWL),于行为学测试后处死大鼠,取脊髓背角L4,5节段,采用Western blot法检测G9a、H3K9me2和Slack的表达。结果与S组比较,VRI组T1-4时TWL缩短,MWT降低,G9a和H3K9me2表达上调,Slack表达下调(P<0.05);与VRI组比较,DRI组T1-4时TWL延长,MWT升高,G9a和H3K9me2表达下调,Slack表达上调(P<0.05)。结论瑞芬太尼诱发切口痛大鼠痛觉过敏的机制与脊髓背角G9a和H3K9me2表达上调,下调Slack表达有关。

Objective To evaluate the relationship between euchromatic histone-lysine N-methyltransferase(G9a)and sodium-dependent activation of potassium channel(Slack)in the spinal cord dorsal horn during remifentanil-induced hyperalgesia in a rat model of incisional pain.Methods Clean-grade healthy male Sprague-Dawley rats,aged 1 month,weighing 100-120 g,were divided into 4 groups(n=6 each)by a random number table method:normal saline group(S group),vector group(V group),vector plus remifentanil plus incisional pain group(VRI group),and G9a-siRNA plus remifentanil plus incisional pain group(DRI group).In VRI group and DRI group,vector 1μl was injected into the L4-5 spinal dorsal horn,3 days later remifentanil 1μg·kg^-1·min^-1 was intravenously infused via the tail vein for 60 min,and the model of incisional pain was established simultaneously.The equal volume of normal saline was given instead in S and V groups.The mechanical paw withdrawal threshold(MWT)and thermal paw withdrawal latency(TWL)were measured at 24 h before remifentanil infusion(T0)and 2,6,24 and 48 h after infusion(T1-4).Rats were sacrificed after behavioral tests,and the L4,5 segments of spinal dorsal horns were taken for determination of the expression of G9a,H3K9me2 and Slack by Western blot.Results Compared with S group,TWL was significantly shortened,and MWT was decreased at T1-4,the expression of G9a and H3K9me2 was up-regulated,and the expression of Slack was down-regulated in VRI group(P<0.05).Compared with VRI group,the TWL was significantly prolonged and MWT was increased at T1-4,the expression of G9a and H3K9me2 was down-regulated,and Slack expression was up-regulated in DRI group(P<0.05).Conclusion The mechanism by which remifentanil induces hyperalgesia is related to up-regulating G9a and H3K9me2 expression and down-regulating Slack expression in the spinal dorsal horn of rats with incisional pain.