应激诱发吗啡条件性位置偏爱重现大鼠下丘脑和血浆中神经甾体水平的变化

目的 检测吗啡条件性位置偏爱重现大鼠下丘脑和血浆中神经甾体含量的变化。方法 建立大鼠对吗啡的条件性位置偏爱（conditioned place preference，CPP），CPP消退后用足底电击（footshoek）诱发CPP的重现。将大鼠断头取血并取出下丘脑，制备组织习浆，采用液-液萃取和固相萃取法提取下丘脑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 与生理氯化钠溶液对照组相比，吗啡CPP重现组大鼠下丘脑中的PREG和PREGS的水平分别升高36％和60％（P〈0．05）。与CPP消退组相比，吗啡CPP重现组大鼠下丘脑中的PREGS水平升高60％（P〈0．05）；吗啡CPP重现组大鼠血浆中的DHEAS水平下降33％（P〈0．01）。结论 足底电击应激诱发吗啡CPP重现时，大鼠下丘脑中的神经甾体PREG、PREGS和DHEAS水平不依赖于血浆中相应的甾体水平变化，其中枢作用可能与应激诱发的吗啡CPP重现行为有关。下丘脑中的PREG和PREGS可能通过其对GABA系统的作用参与足底电击应激诱发的大鼠吗啡CPP重现。

Changes of Neurosteroids Levels in Rat Hypothalamus and Plasma when Morphine CPP was Reinstated by Stress

Aim To investigate the effect of reinstatement to morphine conditioned place preference (CPP) on neurosteroids levels in rat hypothalamus and plasma.Methods A CPP rat model was established with morphine injection.After extinction,footshock was used to induce the reinstatement.Then the rats were decapitated,trunk blood was collected and hypothalamus was dissected out.After homogenation,liquid-liquid extraction and solid phase extraction were used to extract the neurosteroids from hypothalamus and plasma.The extracted fractions were then derivatized and quantitated by HPLC-MS.Results Compared with saline control group,pregnenolone (PREG) and pregnenolone sulfate (PREGS) levels in rat hypothalamus in the reinstatement group increased by 36% and 60% respectively (P<0.05).Compared with CPP extinct group,the PREGS level in rat hypothalamus increased by 60% (P<0.05);dehydroepiandrosterone sulfate (DHEAS) level in rat plasma decreased by 33% (P<0.01) in the morphine CPP reinstated group.Conclusion Changes of PREG,PREGS and DHEAS levels in hypothalamus are independent of those in plasma when reinstatement to morphine CPP was induced by footshock.The effect of these neurosteroids in the central nervous system may play a role in stress induced reinstatement to morphine CPP.Levels of PREG and PREGS in rat hypothalamus may participate in the footshock induced reinstatement to morphine CPP through their effect on gamma-aminobutyric acid (GABA) system.