电针预处理对切口痛大鼠中脑导水管周围灰质5-HT_(7)受体表达的影响

Effect of electroacupuncture preconditioning on the expression of 5-HT_(7) receptors in the periaqueductal gray of rats with incision pain

目的:建立足趾部切口痛大鼠模型,探讨重复电针预处理对切口痛大鼠镇痛效果及其对中脑导水管周围灰质(periaqueductal gray,PAG)5-HT_(7)受体(5-HT_(7)R)表达的影响。方法:40只成年雄性SD大鼠按随机数字表法均等分为对照组(Control,Con组)、切口痛模型组(Incision pain,IP组)、正常+电针预处理组(Control+Electroacupuncture,Con+EA组)、模型+电针预处理组(Incision Pain+Electroacupuncture,IP+EA组)。IP组和IP+EA组大鼠右足趾部行疼痛造模,且造模前,Con+EA组和IP+EA组大鼠行右侧“足三里”穴和“环跳”穴电针刺激(2/10 Hz疏密波,刺激强度数值为1档,每日1次30 min),连续5天。于第1次电针预处理前2 h(T1)、术前2 h(T2)、术后4 h(T3)、术后24 h(T4)测定大鼠机械刺激缩足反射阈值(mechanical withdrawal threshold,MWT)和热缩足潜伏期(thermal withdrawal latency,TWL);酶联免疫吸附法检测脑脊液中5-HT浓度;免疫组化和免疫荧光方法分别检测大鼠PAG中c-Fos和5-HT_(7)R蛋白表达情况。结果:与Con组比较,IP组大鼠T3、T4时间点MWT和TWL均明显降低,脑脊液中5-HT浓度增加,PAG中c-Fos蛋白和5-HT_(7)R表达明显上调(P<0.05);Con+EA组和IP+EA组脑脊液中5-HT含量和PAG中5-HT_(7)R表达均上升(P<0.05)。与IP组相比,IP+EA组大鼠T3、T4时间点的MWT和TWL显著升高,PAG中c-Fos蛋白表达减少,5-HT_(7)R蛋白表达增加(P<0.05)。结论:电针预处理可能通过上调PAG中5-HT_(7)R蛋白表达发挥镇痛作用。

Objective:To explore the analgesic effect of repetitive electroacupuncture preconditioning on incisional pain and its effect on the expression of 5-HT_(7) receptors(5-HT_(7)R)in the periaqueductal gray(PAG)by establishing a rat model of toe incision pain.Methods:Forty male SD rats were randomly divided into control group(group Con),incision pain group(group IP),control+electroacupuncture group(group Con+EA),and incision pain+electroacupuncture group(group IP+EA).Operation was performed on the right toe of rats in group IP and group IP+EA,and electroacupuncture was used to stimulate Zusanli and Huantiao points of the right leg of rats in group Con+EA and group IP+EA for 5 days before operation(with the frequency of 2/10 Hz,the intensity of 1,30 min/day/time).The mechanical withdrawal threshold(MWT)and the thermal withdrawal latency(TWL)of rats were measured at 2 h before the first electroacupuncture pretreatment(T1),2 h before the operation(T2),4 h after the operation(T3),and 24 h after the operation(T4).After the last behavioral test,the brain tissue and cerebrospinal fluid of rats were colleccted.The concentration of 5-HT in cerebrospinal fluid was measured by enzyme linked immunosorbent assay;immunohistochemical and immunofluorescence methods were used to detect the expression of c-Fos and 5-HT_(7)R proteins in the PAG of rats respectively.Results:Compared with group Con,MWT and TWL of rats in group IP were decreased significantly at T3 and T4,while the concentration of 5-HT in cerebrospinal fluid was increased,and the expression of c-Fos protein and 5-HT_(7)R in PAG were increased significantly(P<0.05);the content of 5-HT in cerebrospinal fluid and the expression of 5-HT_(7)R in PAG were increased in group Con+EA and group IP+EA(P<0.05).Compared with group IP,MWT and TWL of rats in group IP+EA were significantly increased at T3 and T4,the expression of c-Fos protein in PAG was decreased,and the expression of 5-HT_(7)R protein was increased(P<0.05).Conclusion:Electroacupuncture preconditioning may play an analgesic role by upregulating the expression of 5-HT_(7)R protein in the PAG.