Genetics of novelty seeking and propensity for drug abuse in outbred rats

在基础神经科学和翻译神经科学以及临床实践中的一个长期挑战是理解 在药物滥用和成瘾的脆弱性方面，个体之间存在巨大差异。为了应对这一挑战，我们 建议研究两个品系的大鼠寻求新奇行为的遗传和功能基础，这两个品系提供了 独一无二的强大模型，用于了解毒品寻觅、上瘾和复发的神经机制。我们 通过选择高倾向和低倾向来探索一个压力适中的小说环境， 分别进行了分析。经过37代的繁育，繁育的高响应性(BHRS)和繁育的低响应性(BLR)表现出 行为的对比光谱，在两个品系中都是可遗传的。与bLRs和异种大鼠相比，BHRS 表现出更高的求新性和冲动行为，更低的焦虑，更敏感的倾向 精神刺激剂，以及药物和线索诱导的复发的较低阈值，使人想起人类的“外化” 紊乱“。BLR更倾向于焦虑和抑郁行为，更容易对心理社会做出反应 压力，这会引发寻求毒品的行为。因此，这两条线例证了情感的两个极端 反应性映射到人类的性情差异，并成为药物滥用的两条途径--新颖性 对心理社会压力的寻求和反应。我们的工作假设是，在一个功能性的DNA变体 数量有限的基因，最初来自远交配的Spraogue Dawley(SD)创始人，解释了 目前这两个品系的分子和行为差异。我们的目标是确定这些致病基因 通过(1)在已收集的F2群体和SD动物中定位数量性状座位(QTL) (2)功能基因组数据的进一步整合。我们建议应用几个 以下具体目标(SA)下的基于测序的技术和分析工具： SA1：在Bhr-Blr杂交中进行基因组测序和数量性状座位(QTL)分析 群体(n~636，男性和女性)采用低成本基因型法测序。 SA2：通过使用确定eQTL、等位基因特异性表达和与性状相关的转录本/途径 关键神经结构--伏隔核和海马体的RNAseq分析。因为有些基因可能 在发育过程中发挥主要影响，我们将分析年轻的F2大鼠(年龄：28天)和成年大鼠。 SA3：对1,000只远交SD大鼠进行全基因组关联研究，然后整合所有链 使用qPCR、原位杂交鉴定推测的因果变异并提供初步验证的数据，以及 进一步的行为测试。我们希望在存在于SDS中的多个基因上发现功能等位基因 在这两条线上进化得更远。这些基因中的许多可能与相应的 或者，至少提供了重要途径的线索，这些线索可以解释或预测 人类对成瘾和复发的不同易感性。我们的最终目标是获得更深层次的机械性 了解成瘾，并将这些知识转化为对患者更精确和有效的治疗。

A long-standing challenge in basic and translational neuroscience and in clinical practice is to understand the vast inter-individual differences in vulnerability to substance abuse and addiction. To address this challenge we propose to study the genetic and functional basis of novelty-seeking behavior in two lines of rats that offer a uniquely powerful model for understanding the neural mechanisms of drug seeking, addiction and relapse. We developed these lines by selecting for high and low propensity to explore a mildly stressful novel environment, respectively. After 37 generations, the bred High Responders (bHRs) and bred Low Responders (bLRs) show contrasting spectra of behaviors, which are heritable in both lines. Compared to bLRs and outbred rats, bHRs exhibit higher novelty seeking and impulsive behaviors, lower anxiety, greater propensity to sensitize to psychostimulants, and lower thresholds for drug- and cue-induced relapse, reminiscent of human “externalizing disorders”. The bLRs are more prone to anxious and depressive behaviors, more responsive to psychosocial stress, which triggers drug-seeking behavior. Thus, the two lines exemplify two extremes of emotional reactivity that map onto human temperamental differences and underlie two paths to drug abuse—novelty seeking and reactivity to psychosocial stress. Our working hypothesis is that functional DNA variants in a limited number of genes, initially derived from outbred Sprague Dawley (SD) founders, account for the current molecular and behavioral divergence of the two lines. Our goal is to identify these causal genes through (1) mapping of quantitative trait loci (QTL) in both an F2 cohort already collected and in SD animals that represent the founders, and (2) further integration of functional genomic data. We propose to apply several sequencing-based technologies and analytical tools under the following specific aims (SAs): SA1: Conduct genome sequencing and quantitative trait loci (QTL) analyses in a bHR-bLR intercross population (n~636, males and females) using a low-cost Genotype by Sequencing method. SA2: Identify eQTLs, allele-specific expression, and transcripts/pathways associated with the traits by using RNAseq analysis of key neural structures-- the nucleus accumbens and hippocampus. As some genes may exert their primary influence during development, we will analyze both young F2 rats (age: 28 days) and adults. SA3: Perform genomewide association study of 1,000 outbred SD rats, followed by integration of all strands of data to identify putatively causal variants and provide initial validation using qPCR, in situ hybridization, and further behavioral tests. We expect to find functional alleles at multiple genes that existed in the SDs and have evolved further apart in the two lines. Many of these genes may be directly relevant to the corresponding human phenotypes or, at a minimum, provide clues to important pathways that could explain or predict the differential vulnerability to addiction and relapse in humans. Our ultimate goal is to gain a deeper mechanistic understanding of addiction, and translate this knowledge to more precise and effective treatment for patients.