Genetic basis and mechanisms underlying binge-level methamphetamine intake

甲基苯丙胺（MA）的使用可以改变判断，增加不安全行为和暴力，并导致情绪 干扰.长期使用与偏执狂以及视觉和听觉幻觉有关。一 许多指标表明，在美国，特别是在非洲，MA的可用性和滥用情况日益增加。 南部和西部地区的年轻人和老年人。MA通常是在反复的狂欢中服用的- 水平剂量，对MA上瘾的人复发率很高，即使在长期服用后， 禁欲期MA是一种神经毒素，当大量服用时。风险作为人口指标 可以在没有药物暴露的动物模型中通过许多策略进行评估， 包括使用选择性繁殖的动物品系。理查兹实验室开发了一种动物模型 研究MA的遗传风险、神经毒性和行为影响的变化 与这种高摄入量有关。该模型与抗MA的遗传模型一致， 摄入量，也是在理查兹实验室开发的，用于识别痕量胺相关受体1 （Taar 1）作为一个基因，占MA摄入量遗传变异的>50%。高危等位基因编码 一个非功能性的受体。然而，在同基因背景下，Taar 1等位基因 型占表型方差的92%，而型只占表型方差的68%。 混合遗传背景此外，高风险Taar 1纯合子的一些个体 等位基因保持低MA摄入特征。除了检查与过量MA相关的神经毒性外， 暴露和差异Taar 1基因型，本研究计划的重点将是识别 通过转录组分析，防止个体摄入过量MA的机制 已知具有高风险Taar 1基因型;换句话说，识别遗传修饰剂。在目标1中， 将比较受控的暴食水平MA给药和自愿的暴食水平MA摄入的神经毒性。 在高MA摄入量选择的小鼠品系和高MA摄入量品系小鼠中的作用，其中Taar 1 促进高MA摄入量的等位基因已被保护性等位基因（一种基因敲入）所取代。 approach.在目标2中，自愿的狂欢水平MA摄入对条件奖励的影响和可靠的 将检查对MA的生理反应-体温变化。在目标3中， 将开发一个模型，该模型由来自所有个体的双向选择的品系组成， Taar 1 MA风险等位基因纯合子，但饲养高与低MA摄入量。虽然被列为目标3， 这些生产线的生产将在研究计划的早期开始，以便它们可供使用， 第三年。这些品系还将针对MA奖励、温度变化、促味剂偏好和促味剂偏好进行表征。 MA清除率。最后，在目标4中，将使用所选品系的组织进行分析， 鉴定转录组中预测Taar 1等位基因对MA摄入影响减弱的差异。 将使用生理盐水和MA处理动物的组织。因为有证据表明人类TAAR 1 影响受体功能的等位基因差异，这是一个令人兴奋的研究方向，可能导致 确定保护因素，减轻遗传风险的狂欢水平的MA摄入量，并最终以新的 更有效的治疗。

Methamphetamine (MA) use can alter judgment, increase unsafe behaviors and violence, and cause mood disturbances. Chronic use is associated with paranoia, as well as visual and auditory hallucinations. A number of indicators point to increasing availability and abuse of MA in the United States, especially in the southern and western regions, among both young and older adults. MA is often taken in repeated binge- level doses, and individuals who become addicted to MA suffer high rates of relapse, even after prolonged periods of abstinence. MA is a neurotoxin when higher amounts are taken. Risk as a population measure can be assessed in animal models in the absence of drug exposure through a number of strategies, including the use of selectively bred animal lines. The Richards laboratory has developed an animal model of binge-like MA intake to study genetic risk, neurotoxicity, and changes in behavioral effects of MA associated with this high level of intake. That model, in concert with a genetic model of resistance to MA intake that was also developed in the Richards lab, was used to identify trace amine-associated receptor 1 (Taar1) as a gene that accounts for >50% of the genetic variance in MA intake. The high risk allele codes for a non-functional version of the receptor. However, whereas on an isogenic background, Taar1 allele type accounts for 92% of the phenotypic variance, it accounts for only 68% of the phenotypic variance on a mixed genetic background. Furthermore, some individuals that are homozygous for the high risk Taar1 allele retain a low MA intake profile. In addition to examining neurotoxicity associated with binge-level MA exposure and with differential Taar1 genotype, a focus of this research program will be on the identification of mechanisms, through transcriptome analyses, that protect against binge-level MA intake in individuals known to possess a high-risk Taar1 genotype; in other words to identify genetic modifiers. In Aim 1, controlled binge-level MA dosing and voluntary binge-level MA intake will be compared for their neurotoxic effects in a high MA intake selected mouse line and in mice of the high MA intake line in which the Taar1 allele that promotes high MA intake has been replaced with the protective allele, a genetic knock-in approach. In Aim 2, the impact of voluntary binge-level MA intake on conditioned-reward and a reliable physiological response to MA – body temperature change – will be examined. In Aim 3, a new genetic model will be developed comprised of bidirectionally selected lines derived from individuals that are all homozygous for the Taar1 MA risk allele, but are bred for high vs. low MA intake. Although listed as Aim 3, the production of these lines will begin early in the research program so that they are available for use by year 3. These lines will also be characterized for MA reward, temperature change, tastant preference and MA clearance rate. Finally, in Aim 4, analyses will be conducted using tissues from the selected lines to identify differences in the transcriptome that predict an attenuation of the Taar1 allele effect on MA intake. Tissues from saline- and MA-treated animals will be used. Because there is evidence for human TAAR1 allelic differences that impact receptor function, this is an exciting research direction that could lead to the identification of protective factors that alleviate genetic risk for binge-level MA intake and ultimately to new and more effective treatments.