Liu Litao, Zhu Jiejun, Zhou Liming, Wan Lihong
Department of Pharmacology, West China School of Preclinical and Forensic Medicine, Sichuan University, Chengdu, Sichuan 610041, P.R. China.
Sichuan University "985 project - Science and Technology Innovation Platform for Novel Drug Development", Sichuan University, Chengdu, Sichuan 610041, P.R. China.
Sci Rep. 2016 Feb 2;6:20183. doi: 10.1038/srep20183.
Existence of long-term drug-associated memories may be a crucial factor in drug cravings and relapse. RACK1 plays a critical role in morphine-induced reward. In the present study, we used conditioned place preference (CPP) to assess the acquisition and maintenance of morphine conditioned place preference memory. The hippocampal protein level of RACK1 and synaptic quantitation were evaluated by Western blotting, immunohistochemistry and electron microscopy, respectively. Additionally, shRACK1 (shGnb2l1) was used to silence RACK1 in vivo to evaluate the role and the underlying mechanism of RACK1 in maintenance of morphine CPP memory. We found that morphine induced CPP was maintained for at least 7 days after the last morphine treatment, which indicated a positive correlation with hippocampal RACK1 level, and was accompanied simultaneously by increases in the synapse density and hippocampal expression of synaptophysin (SYP), phosphorylation of extracellular signal-regulated kinase1/2 (pERK1/2) and the phosphorylation of cyclic adenosine monophosphate response element-binding (pCREB). ShGnb2l1 icv injection significantly suppressed the expression of all above proteins, decreased the synapse density in the hippocampus and attenuated the acquisition and maintenance of morphine CPP. Our present study highlights that RACK1 plays an important role in the maintenance of morphine CPP, likely via activation of ERK-CREB pathway in hippocampus.
长期药物相关记忆的存在可能是药物渴望和复发的关键因素。RACK1在吗啡诱导的奖赏中起关键作用。在本研究中，我们使用条件性位置偏爱（CPP）来评估吗啡条件性位置偏爱记忆的获得和维持。分别通过蛋白质免疫印迹法、免疫组织化学和电子显微镜评估海马中RACK1的蛋白水平和突触定量。此外，使用shRACK1（shGnb2l1）在体内使RACK1沉默，以评估RACK1在维持吗啡CPP记忆中的作用及其潜在机制。我们发现，末次吗啡处理后，吗啡诱导的CPP至少维持7天，这表明其与海马RACK1水平呈正相关，同时伴随着突触密度增加、海马中突触素（SYP）表达增加、细胞外信号调节激酶1/2（pERK1/2）磷酸化以及环磷酸腺苷反应元件结合蛋白（pCREB）磷酸化。脑室内注射shGnb2l1可显著抑制上述所有蛋白的表达，降低海马中的突触密度，并减弱吗啡CPP的获得和维持。我们目前的研究强调，RACK1可能通过激活海马中的ERK-CREB通路，在维持吗啡CPP中发挥重要作用。
