Imaging cannabinoid effects on developing cortical circuits

项目摘要/摘要 大麻(大麻)是美国使用最广泛的非法药物，青春期使用很常见。 在青春期早期开始使用大麻与暂时性认知障碍有关，但长期使用大麻会导致认知障碍。 术语神经生物学后果还没有得到很好的理解。此外，大麻素在医疗上的用途 儿童和青少年可能需要治疗某些与癫痫相关的疾病；因此， 提高对青少年暴露大麻类药物的成本和好处的理解是有必要的 正在制定的规范合法使用大麻的政策。啮齿动物模型提供了一个机会 对大麻素暴露的时间、持续时间和数量进行对照实验，并消除 人体研究的潜在混淆，例如先前存在的疾病和接触其他滥用药物。在……里面 除了确定大麻暴露的长期行为后果外，还必须 确定对神经回路活动的影响，这可能会对功能结果产生更微妙的影响。 目前的技术限制了我们对特定细胞类型的神经活动进行纵向记录的能力 在青少年发育过程中的态度，特别是在自我静脉注射滥用药物的动物中 以及执行复杂的认知任务。一种解决方案是对整体神经活动进行活体成像 使用遗传编码的钙指示剂(GECI)。体内钙离子成像可分辨细胞活性 利用综合头盔梯度折射率研究清醒行为动物的脑深部结构 (GRIN)透镜和微型荧光显微镜(显微内窥镜)。目前，这项技术已经 主要局限于对成年小鼠的研究。然而，表达该基因的转基因大鼠的发展 最新一代的Geci，GCaMP6f，将允许对青少年过程中的皮质活动进行成像 发展，并使比较自我管理的啮齿动物的神经回路发育成为可能 静脉注射滥用药物，如大麻类药物，与对照组相比。因此，在这个为期两年的项目中，我们建议 在神经启动子的控制下建立表达GCaMP6f的转基因大鼠。我们将评估神经 前额叶皮质区域负责工作记忆和认知表现的活动模式 在青春期自我给药的大鼠。青少年自我管理小组将进行比较 同样受过训练的成年人和食物自我给药控制。我们将评估工作记忆性能 以及在禁欲一段时间后，这些大鼠在发育过程中和成年期的相关皮质活动。 这些研究的结果将阐明青少年大麻素自我攻击的急性和长期后果。 给药对工作记忆成绩的影响，并确定是否发展了任务适宜的神经 活动模式受到持续的或以前的大麻素自我给药的影响。此外，GCaMP6f 转基因大鼠将公开供神经科学界广泛使用。

Project Summary/Abstract Marijuana (Cannabis sativa) is the most widely used illicit drug in the U.S. and use in adolescence is common. Onset of cannabis use in early adolescence is associated with temporary cognitive impairments, but the long- term neurobiological consequences are not well understood. In addition, medicinal use of cannabinoids in children and adolescents may be warranted for treating certain seizure-related disorders; therefore, an increased understanding of the costs vs. benefits of adolescent cannabinoid exposure are warranted to inform the ongoing development of policies regulating legal marijuana use. Rodent models provide the opportunity to perform controlled experiments on the timing, duration, and amount of cannabinoid exposure and eliminate potential confounds of human studies, such as pre-existing conditions and exposure to other drugs of abuse. In addition to determining the long-term behavioral consequences of cannabis exposure, it is also important to determine the effects on neural circuit activity that may produce more subtle effects on functional outcomes. Current technologies limit our ability to perform longitudinal recordings of neural activity in a cell-type specific manner across adolescent development, particularly in animals self-administering intravenous drugs of abuse and performing complex cognitive tasks. One solution is to perform in vivo imaging of ensemble neural activity using genetically-encoded calcium indicators (GECIs). In vivo Ca2+ imaging can resolve cellular activity in deep brain structures in awake behaving animals using integrated, head-mounted gradient refraction index (GRIN) lenses and miniaturized epifluorescent microscopes (microendoscopes). Currently, this technique has been primarily restricted to studies in adult mice. However, development of a transgenic rat expressing the latest generation GECI, GCaMP6f, will permit imaging of cortical activity over the course of adolescent development and make it feasible to compare neural circuit development in rodents that self-administer intravenous drugs of abuse, like cannabinoids, relative to controls. Thus, in this two-year project we propose to develop transgenic rats expressing GCaMP6f under the control of a neuronal promoter. We will assess neural activity patterns in prefrontal cortical regions responsible for working memory and cognitive performance, in rats that self-administer cannabinoids in adolescence. Adolescent self-administration groups will be compared to similarly trained adults and to food self-administering controls. We will assess working memory performance and associated cortical activity in these rats across development and in adulthood after a period of abstinence. The results of these studies will clarify the acute vs. long-term consequences of adolescent cannabinoid self- administration on working memory performance, and determine if the development of task appropriate neural activity patterns are affected by ongoing or prior cannabinoid self-administration. In addition, the GCaMP6f transgenic rat will be publicly available for broad use by the neuroscience community.