Neuroadaptations Underlying Drug Conditioning and Sensitization

描述（由申请方提供）：重复间歇性暴露于安非他明导致其精神兴奋作用的持久致敏，因此，数周至数月后再次暴露于该药物会产生增强的运动反应和自我给药。这些研究结果支持的建议，敏感的安非他明的食欲的影响可能是从偶然的药物使用过渡到药物渴望和滥用。这种药物致敏的诱导必然涉及暴露于与复杂的环境刺激相关的药物。药物与环境刺激的重复配对导致两者之间形成关联，使得这些刺激引起与药物本身产生的类似的行为和生化反应。因此，它可以很容易混淆的单独贡献的关联条件反射和非关联的敏感性，以增强反应后观察到的重复药物暴露。区分这两个过程的一种方法是将全身性安非他明暴露的效果与直接应用于腹侧被盖区（VTA）的安非他明的效果进行比较。已知安非他明在腹侧被盖区起致敏作用，但应用于该部位时不能产生条件反射。因此，通过比较VTA和全身给药安非他明的效果，可以在相对隔离的情况下研究重复暴露于药物的关联和非关联后果。本研究计划中的实验旨在更好地描述联想条件反射和非联想敏化的神经化学和形态学基础，并将测试两个主要假设。假设1：在药物条件反射过程中，神经核（NAcc）中特定蛋白的活性对于形成将药物环境与刺激联系起来的习得性关联是必要的。初步研究结果表明，拟议的实验将进一步探讨，如何抑制蛋白质细胞周期蛋白依赖性激酶5（cdk 5）在药物暴露期间的NACC块关联条件反射，同时保持非关联敏化。此外，通过比较由反复全身或VTA安非他明暴露引起的NAcc中的其他蛋白质变化，我们将能够识别与条件反射或致敏相关的其他蛋白质。假设2：特定的神经元群体经历条件反射相关的神经解剖可塑性。使用c-Fos作为标记物，以确定NAcc细胞有助于联合条件反射，我们将这些神经元注射的碳菁神经元示踪剂DiI，以表征其树突棘形态，使用共聚焦双光子显微镜。 公共卫生相关性：药物成瘾是一种对社会造成独特代价的疾病，并影响不同年龄组和人口统计数据中个人的健康，生产力和福祉。许多已发表的研究表明，长期使用药物会导致大脑发生变化。拟议的实验扩展了这种方法，以研究这些变化如何在神经元水平上受到可能鼓励药物寻求的环境因素的调节。了解药物配对环境如何调节强迫性药物使用背后的大脑过程，可能会导致这种疾病的新的治疗和药理学治疗。

DESCRIPTION (provided by applicant): Repeated intermittent exposure to amphetamine leads to long-lasting sensitization of its psychomotor stimulant effects, such that re-exposure to the drug weeks to months later produces enhanced locomotor responding and self-administration of the drug. These findings support the proposal that sensitization of the appetitive effects of amphetamine may underlie the transition from casual drug use to drug craving and abuse. The induction of this drug-induced sensitization necessarily involves exposure to the drug in association with a complex of environmental stimuli. Repeated pairings of drugs with environmental stimuli leads to the formation of associations between the two such that these stimuli come to elicit behavioral and biochemical responses similar to those produced by the drug itself. Thus, it can be easy to confound the separate contributions of associative conditioning and non-associative sensitization to the enhanced responding observed following repeated drug exposure. One method for distinguishing between these two processes is to compare the effects of systemic amphetamine exposure to those of amphetamine applied directly to the ventral tegmental area (VTA). Amphetamine is known to act in the VTA to initiate sensitization, but fails to produce conditioning when applied to this site. Thus, by comparing the effects of VTA and systemically administered amphetamine, the associative and non-associative consequences of repeated exposure to the drug can be studied in relative isolation. The experiments in this grant proposal aim to better characterize both the neurochemical and morphological underpinnings of associative conditioning and non-associative sensitization, and will test two main hypotheses. Hypothesis 1: The activity of specific proteins in the nucleus accumbens (NAcc) during drug-conditioning are necessary for the formation of learned associations linking the drug environment to stimuli. Preliminary findings demonstrate, and the proposed experiments will further explore, how inhibition of the protein cyclin-dependent kinase 5 (cdk5) in the NAcc during drug exposure blocks associative conditioning while preserving non-associative sensitization. Furthermore, by comparing other protein changes in the NAcc caused by repeated systemic or VTA amphetamine exposure, we will be able to identify other proteins correlated either with conditioning or sensitization. Hypothesis 2: Specific populations of neurons undergo conditioning-related neuroanatomical plasticity. Using c-Fos as a marker to identify NAcc cells contributing to associative conditioning, we will inject these neurons with the carbocyanine neuronal tracer DiI in order to characterize their dendritic spine morphology using confocal 2-photon microscopy. PUBLIC HEALTH RELEVANCE: Drug addiction is a disease that is uniquely costly to society and affects the health, productivity, and well-being of individuals in various age groups and demographics. Much published research demonstrates how prolonged drug use produces changes in the brain. The proposed experiments extend this approach to study how these changes are regulated at the neuronal level by environmental factors that may encourage drug-seeking. Understanding how drug-paired environments regulate brain processes underlying compulsive drug use may lead to novel therapeutic and pharmacological treatments for the disease.