奥曲肽在蜜蜂毒疼痛模型中的抗伤害感受作用及对背根神经节pCREB表达的影响

Antinociceptive effect of octreotide in bee vemon test and its effect on the expression of pCREB in dorsal root ganglion

目的利用伤害感受敏感型DA大鼠研究奥曲肽(OCT)在蜜蜂毒(BV)疼痛模型中的抗伤害感受作用以及背根神经节(DRG)内磷酸化cAMP反应元件结合蛋白(pCREB)表达的变化,为生长抑素受体(SSTR)的外周镇痛作用提供理论依据。方法于DA大鼠右爪足底中间部位,用50μl微量注射器皮下注射BV(0.1 mg/50μl)建立BV疼痛模型。成年雄性DA大鼠随机分为5组:对照组、BV组、OCT组、对侧OCT组和环生长抑素(c-SOM)组。分别用秒表和计数器记录大鼠注射BV后抬/舔爪时间和自发性缩足反射次数等伤害感受行为。大鼠机械敏感性阈值用up-down法测定,用50%机械缩爪阈值(PWMT)表示,分别于注射前1 h和注射后1.5 h测量。热刺激反应用热缩爪潜伏期(PWTL)表示,于注射前30 min和注射后2 h测量。采用免疫组织化学方法观察pCREB在DRG表达的变化。结果在DA大鼠足底注射BV后1 h内,OCT组比BV组的抬/舔爪持续时间均缩短(P<0.05);OCT组PWMT较BV组升高,但这两组间PWTL差异无统计学意义。注射BV后BV组同侧DRG中pCREB阳性细胞百分数较对照组明显增加(P<0.05),局部OCT预处理明显减少pCREB阳性细胞百分数(P<0.05)。结论足底注射OCT抑制BV导致的自发性伤害感受行为和机械痛敏,并伴有同侧DRG内pCREB表达降低,这一作用可能是OCT通过激活外周局部SSTR导致的。

Objective To investigate the antinociceptive effect of octreotide（OCT） in bee vernon（BV） test and its effect on the expression of pCREB in dorsal root ganglion（DRG） using a inbred Dark-Agouti（DA） rats, which was sensitive to nociception. In doing so, evidence for peripheral analgesic action of somatostatin reeeptor（SSTR） was expected to provide. Methods Intraplantar injection of 50 p,1 bee venom （BV） was performed to make the nocicep- tive model. Adult male DA rats were randomly divided into 5 groups： the control group, BV group, OCT group, the contralateral OCT group and cyclosomatostatin （c-SOM） group. A stopwatch and counter was used to record the duration of lifting/licking and number of flinches. Up-down method was used to measure 50% mechanical paw threshold（PWMT）. PWMT was determined 1 h before injection BV as well as 1.5 h after injection, respectively. Paw withdrawal thermal latency（PWTL） was used to present thermal stimulation reaction. It was measured half an hour before injection BV and 2 h after injection. Immunohistochemical method was used to explore pCREB expres- sion in DRG. Results After intraplantar injection of BV, the duration of lifting/licking in one hour in OCT group was reduced than the BV group （ P 〈 0. 05 ）, PWMT was bigger in OCT group than that in the BV group. However, there was no significant difference in the PWTL between OCT group and BV group. In addition, the percentage of positive cell of pCREB was higher in the BV group than that in the control group in ipsilateral DRG （ P 〈 0.05 ）. Local OCT pretreatment significantly reduced the percentage of positive cell of pCREB in ipsilateral DRG （P 〈 0.05 ）. Conclusion Local OCT pretreatment reduced the spontaneous nociception and mechanical pain sensitivity. In addition, the expression of pCREB in the ispsilateral DRG is reduced. These effects may be due to the activation of peripheral SSTRs