Intracellular mechanisms of cocaine-memory reconsolidation

描述（由申请人提供）：环境引起的毒品复发是可卡因使用者康复的主要障碍。可卡因相关的环境通过情境-反应-可卡因关联维持对可卡因诱发行为的刺激控制，这种关联必须保持在长期记忆中。因此，选择性地削弱或消除这种可卡因记忆的治疗可能会减少前吸毒者的复发倾向。值得注意的是，与可卡因相关的长期记忆在检索后变得不稳定（即记忆再激活），这些记忆需要重新稳定或重新巩固，才能维持长期存储。此外，有证据表明，基底外侧杏仁核（BLA）在可卡因记忆的重新巩固中是必需的，这种记忆促进了药物情境诱导的可卡因寻求（非强化的主动杠杆压力，它提供了可卡因动机的指标；Fuchs等人，2009）。拟议的NRSA研究计划将通过探索BLA中可卡因记忆再巩固的细胞内机制来扩展这条研究路线，重点关注两个信号分子：细胞外信号相关激酶（ERK）和细胞周期蛋白依赖性蛋白激酶5 （Cdk5）。具体的目的1将是检验在BLA中erk介导的信号传导促进可卡因记忆的重新巩固这一假设，这对于对工具性可卡因寻求的语境控制至关重要，并将探索这一现象的可能下游机制。初步数据显示，bla内U0126 （MEK/ERK抑制剂）治疗以记忆再激活依赖的方式损害可卡因记忆再巩固，并破坏随后的药物情境诱导的可卡因寻求（实验1a，正在进行中）。这些数据为Exp. 1b提供了良好的理论基础，Exp. 1b将利用定量Western blotting来表征Elk-1、CREB和zif268的激活变化，这些转录因子可能在记忆再巩固期间被BLA中的ERK激活（Aim 1b）。作为后续研究，将使用反义寡核苷酸或小干扰RNA操作来评估Elk-1、CREB或zif268的激活是否需要可卡因记忆再巩固和随后对可卡因寻求的上下文控制。具体目标2将是验证BLA中的Cdk5干扰可卡因记忆的重新巩固这一假设，而可卡因记忆对背景控制对工具性可卡因寻求至关重要。基于Cdk5负调控ERK的证据，实验2将评估bla -丁内酯（Cdk5抑制剂）治疗是否会以记忆再激活依赖的方式增强可卡因-记忆再巩固，并增加随后的药物情境诱导的可卡因寻求。总之，复杂的行为程序和尖端分子技术的结合将用于探索可卡因记忆再巩固的细胞内机制，这是一种维持不适应成瘾记忆的认知过程，从而刺激环境诱导的药物渴望和复发。这项研究有可能为成瘾治疗的发展提供新的见解。

DESCRIPTION (provided by applicant): Environmentally-induced drug relapse is a major obstacle in the rehabilitation of cocaine users. Cocaine- associated environments maintain stimulus control over cocaine-induced behavior via context-response- cocaine associations that must be maintained in long-term memory. Thus, treatments that selectively weaken or eliminate such cocaine memories may reduce the propensity to relapse in former drug addicts. Remarkably, cocaine-related long-term memories become labile following retrieval (i.e., memory reactivation), and these memories need to be re-stabilized, or reconsolidated, into long-term storage in order to be maintained. Furthermore, evidence suggests that the basolateral amygdala (BLA) is required for the reconsolidation of cocaine memories that promote drug context-induced cocaine seeking (non-reinforced active lever presses, which provided an index of motivation for cocaine; Fuchs et al., 2009). The proposed NRSA research plan will extend this line of inquiry by exploring the intracellular mechanisms of cocaine-memory reconsolidation in the BLA with a focus on two signaling molecules: extracellular signal-related kinase (ERK) and cyclin-dependent protein kinase 5 (Cdk5). Specific aim 1 will be to test the hypothesis that ERK-mediated signaling in the BLA facilitates the reconsolidation of cocaine memories that are critical for contextual control over instrumental cocaine seeking and will explore possible downstream mechanisms of this phenomenon. Preliminary data show that intra-BLA U0126 (MEK/ERK inhibitor) treatment impairs cocaine-memory reconsolidation in a memory reactivation-dependent manner and disrupts subsequent drug context-induced cocaine seeking (Exp. 1a, in progress). These data provide sound rationale for Exp. 1b, which will utilize quantitative Western blotting to characterize changes in the activation of Elk-1, CREB, and zif268, the transcription factors that are likely activated by ERK in the BLA during memory reconsolidation (Aim 1b). As follow-up, antisense oligonucleotide or small interfering RNA manipulation will be used to assess whether the activation of Elk-1, CREB, or zif268 is required for cocaine-memory reconsolidation and subsequent contextual control over cocaine seeking. Specific aim 2 will be to test the hypothesis that Cdk5 in the BLA interferes with the reconsolidation of cocaine memories that are critical for contextual control over instrumental cocaine seeking. Based on evidence that Cdk5 negatively regulates ERK in vitro, Exp. 2 will assess whether intra-BLA ¿-butyrolactone (Cdk5 inhibitor) treatment will enhance cocaine-memory reconsolidation in a memory reactivation-dependent manner and increase subsequent drug context-induced cocaine seeking. In summary, a combination of sophisticated behavioral procedures and cutting edge molecular techniques will be used to explore the intracellular mechanisms of cocaine-memory reconsolidation, a cognitive process that maintains maladaptive addictive memories and thus stimulates environmentally-induced drug craving and relapse. This research endeavor has the potential to provide novel insights for addiction treatment development. PUBLIC HEALTH RELEVANCE: Cocaine addiction is a serious public health, social, and economic problem in the United States, in part because cocaine addicts are highly susceptible to environmentally-triggered relapse even after extended periods of drug abstinence. The experiments outlined in this predoctoral NRSA proposal will utilize a rodent model of drug relapse in order to identify novel molecular brain mechanisms that underlie the reconsolidation of cocaine-associated memories into long-term memory storage and thus the ability of these memories to drive relapse behaviors. A better understanding of such mechanisms may contribute to the development of treatments designed to weaken or abolish these memories in order to prevent drug relapse in former cocaine users.