应激诱发吗啡条件性位置偏爱重现大鼠伏隔核和血浆中神经甾体水平的变化

Changes of Neurosteroids Levels in Nucleus Accumbens and Plasma of Rat with Morphine Conditioned Place Preference After a Footshock Iuduced Reinstatement

目的检测吗啡条件性位置偏爱(conditioned place preference,CPP)重现大鼠伏隔核和血浆中神经甾体水平的变化。方法建立大鼠对吗啡的CPP,CPP消退后用足底电击(footshock)诱发CPP的重现。将大鼠断头取血并取出伏隔核,制备组织匀浆,采用液-液萃取和固相萃取法提取脑组织和血浆中的神经甾体,经衍生化后,采用高效液相色谱-质谱法测定神经甾体含量。结果与对照组相比,重现组大鼠伏隔核中的脱氢表雄酮(dehydroepiandrosterone,DHEA)水平升高50%(P<0.05)。与消退组相比,重现组大鼠伏隔核中的别孕烯醇酮(allopregnanolone,AP)水平升高75%(P<0.05);吗啡CPP重现组大鼠血浆中的脱氢表雄酮硫酸酯(dehydroepiandrosterone sulfate,DHEAS)水平下降33%(P<0.01)。结论足底电击应激所致的CPP重现时,大鼠伏隔核中的DHEA,AP和DHEAS水平的变化不依赖于外周血中相应甾体水平的变化,其中枢作用可能与应激诱发的吗啡CPP重现行为有关。足底电击使伏隔核DHEA和AP水平升高可能是应激诱发吗啡CPP重现的神经机制之一。

OBJECTIVE To investigate the changes of neurosteroids levels in rat nucleus acctunbens and plasma when morphine conditioned place preference（CPP） was reinstated. METHODS CPP rat model was established with morphine injection. After extinction, footshock was used to induce the reinstatement of CPP. Then the rots were decapitated, tnmk blood was collected and nucleus accumbens was dissected out. After homogenation, liquid-liquid extraction and solid phase extraction were used to extract the neurosteroids from nucleus accumbens and plasma. The extracted fractions were then derivatized and quantitated by HPLC-MS. RESULTS Compared with control group, dehydroepiandrosterone （DHEA） level increased by 50% （ P 〈 0.05） in nucleus acctunbens in reinstated group. Compared with extinct group, AP level increased by 75% （ P 〈 0.05） in nucleus acctunbens; dehydroepiandrosterone sulfate （DHEAS） level decreased by 33% （ P 〈 0.01） in plasma in reinstated group. CONCLUSION Changes of DHEA, DHEAS and AP levels in nucleus accumbens are independent of those in plasma when reinstatement to morphine CPP was induced by footshock. And the effect of these neurosteroids in central nervous system may play a role in stress induced reinstatement behavior. The changes of neuresteroids levels, especially the increase of nucleus accumbens DHEA and AP levels maybe one of the mechanisms of footshock induced reinstatement to morphine CPP.