INTRODUCTION Drug addiction has important psychological and social causes and consequences and has been recog-nized to be a neurological disease involving the de-velopment of complex behaviors such as drug toler-ance,dependence and craving for the drugs that are characteristic of an addictive state.It is widely thought that changes in gene expression in the central nervous system(indexed by levels of mRNA)play a critical role in drug addiction(Rhodes and Crabbe,2005).A primary mechanism by which drugs of abuse affect gene expression is through changing theconcentration of transcription factors in the nuclei of cells(Nestler et al.,2001).Several evidences suggest that changes in the expression and function of gene transcription factors in the nucleus accumbens,such as the cAMP response element binding protein(CREB),play an important role in the mechanism of drug addiction(Li et al.,2003).On the other hand,addiction results from abnormal engagement of long-term associative memory.CREB is pivotal in the switch from short-term to long-term memory,and plays a central role in the formation of long-term memory.Drug addiction and learning memory share certain intracellular signaling cascades,depend on activation of the transcription factor CREB(Nestler,2002).CREB is a site of convergence for study of drug addiction and memory.CREB,a ubiquitously expressed transcriptionproduct,was regulated by several intracellular sig-naling pathways.CREB dimers bind to specific se-quences of DNA(called CREs or cAMP-response elements)in the regulatory regions of target genes.The transcriptional activity of these dimers is stimu-lated upon phosphorylation of CREB at Ser133by any of several protein kinases.CREB represents a site of convergence at which diverse signaling pathways,and the external stimuli that activate those pathways,produce plasticity at the level of altered gene expres-sion.However,little is known about the role of CREB during the process of opioid addiction which may be an important molecular basis of craving and relapse.Whether the action of morphine on CREB in hippo-campus,prefrontal cortex(PFC),and the nucleus accumbens(NAc)during different phases of addic-tion being associated is also unknown.Place conditioning is commonly used to measure the rewarding or incentive properties of drugs,espe-cially psychological dependence.At the same time,conditioned place preference(CPP)model can be used as an effective tool to investigate the mecha-nisms underlying drug-induced reinstatement of drug seeking after extinction(Parker and Mcdonald,2000),and can partly evaluate the associated learning ability.In the present study,we establish the morphine in-duced rat CPP acquisition,extinction and reinstate-ment model using the computer based video-tracking CPP system,and investigated the changes of CREB in hippocampus,PFC and NAc in different CPP phases,in order to elucidate the effect of morphine induced CREB during the process of drug addiction,using CREB as the entry point to determine the function of each involved brain area,and investigate the mecha-nism of morphine addiction memory.MATERIALS AND METHODS Animals Thirty-two male SD rats weighing180~220g were supplied by Zhejiang Medical Science Research Institute.All the animals were allowed to be habituated to the colony room for2weeks upon arrival,and housed in plastic cages with food and water and maintained on a12h light-dark cycle(light on at7:00p.m.).Room temperature was maintained at(22±2)°C.Chemical reagents Morphine hydrochloric(Shenyang Pharmaceu-tical LTD,China);anti-CREB monoclonal antibody(Sigma,USA);anti-rabbit-IgG(Rockland,USA);nuclear and cytoplasmic extraction reagents(PIERCE,USA).Apparatus The computer based video-tracking CPP system mainly consists of three parts,including CPP training apparatus,a video camera and a computer system with analysis software.The CPP training apparatus was made according to Shippenberg et al.(1996).Briefly,it consisted of four identical polyvinyl ch
More abstracts about the Changes of CREB in rat hippocampus, prefrontal cortex and nucleus accumbens during three phases of m