Developmental Trajectories of Prefrontal Cortical GABA Neurons and Schizophrenia

描述（由申请人提供）：多项证据表明，精神分裂症（SZ）是一种由遗传脆弱性和环境风险因素共同引起的神经发育障碍。例如，在青春期使用大麻与遗传脆弱个体的认知功能障碍和SZ风险增加有关。大麻中的主要精神活性成分δ-9-四氢大麻酚（9-THC）激活大麻素1受体（CB 1 r），该受体高度集中在灵长类动物背外侧前额叶皮层（DLPFC）中表达胆囊收缩素的篮状细胞（CB 1 r/CCK细胞）的轴突末端，该区域与SZ的认知功能障碍有关，导致抑制GABA从这些末端释放。在猴子和人类中，DLPFC电路持续成熟至青春期（猴子约15-42个月，人类约13-19岁），同时认知功能改善。在猴DLPFC中，GABAA受体1亚基和CB 1 r免疫反应性在青春期发生实质性变化，表明GABA合成的关键标志物在此期间也可能在这些细胞中迅速变化。我们的初步研究表明，组织水平的两个GABA合成酶，谷氨酸脱羧酶67和65（GAD 67和GAD 65），增加在猴DLPFC整个出生后的发展，与GAD 65的mRNA和蛋白质水平大幅和迅速增加，在青春期和GAD 67的mRNA和蛋白质增加更早。我们组的新数据还表明，GAD 65：GAD 67蛋白的比例是更大的CB 1 r阳性（CB 1 r+）终端比其他类别的GABA终端在成年猴DLPFC。因此，GAD 65和GAD 67 mRNA在CB 1 r/CCK篮状细胞体（目标1），并在其轴突末端（目标2）的同源蛋白质的发展过程中，将进行检查，以确定潜在的时期，在猴子DLPFC的发展，由于其快速变化可能是特别敏感的大麻暴露。具体而言，我们预测，在青春期CB 1 r/CCK篮状细胞和终端GAD 65表达的显着增加定义了这些神经元成熟的敏感期。这一想法将通过在青春期接触大麻一年的猴子中检查这些相同的依赖性措施来进行概念验证测试（目标3）。关于细胞特异性发育轨迹的性质和时间的这种知识将为易患精神分裂症的个体的早期药物干预的最适当类型和时间提供信息。因此，该应用程序通过确定发展变化时期如何也可能是出现风险或症状的脆弱时期，直接解决了NIMH战略计划战略2.1。该提案还为申请人提供了一个重要的机会，学习如何使用新颖和成熟的分子神经科学技术进行假设驱动的研究和批判性分析结果。 公共卫生相关性：当在青春期消费时，大麻是美国使用最广泛的非法药物，与脆弱个体患精神分裂症的风险更大有关。拟议的研究将确定对大麻使用敏感并在精神分裂症中改变的前额叶皮层回路关键组成部分的发展轨迹。这些研究对于理解大麻的影响如何以及何时可能影响前额叶皮层发育的敏感期具有重要意义，并可能有助于对易患精神分裂症的个体进行先发制人的干预。

DESCRIPTION (provided by applicant): Multiple lines of evidence suggest that schizophrenia (SZ) is a disorder of neurodevelopment caused by the combination of genetic vulnerabilities and environmental risk factors. For example, cannabis use during adolescence is associated with an increased risk for cognitive dysfunction and SZ in genetically vulnerable individuals. The principal psychoactive component in cannabis, delta-9-tetrahydrocannabinol (9-THC), activates cannabinoid 1 receptors (CB1r) that are highly concentrated on the axon terminals of cholecystokinin-expressing basket cells (CB1r/CCK cells) in the primate dorsolateral prefrontal cortex (DLPFC), a region implicated in the cognitive dysfunction of SZ, resulting in the suppression of GABA release from these terminals. In monkeys and humans, DLPFC circuitry continues to mature well into adolescence (~15-42 mos in monkeys and ~13-19 years in humans) in parallel with improvements in cognitive function. In monkey DLPFC, GABAA receptor 1 subunits and CB1r immunoreactivity undergo substantial changes during adolescence, suggesting that key markers for GABA synthesis may also change rapidly in these cells during this period. Our preliminary studies indicate that tissue levels of the two GABA-synthesizing enzymes, glutamic acid decarboxylase 67 and 65 (GAD67 and GAD65), increase in monkey DLPFC throughout postnatal development, with GAD65 mRNA and protein levels substantially and rapidly increasing during adolescence and GAD67 mRNA and protein increasing earlier. Emerging data from our group also suggest that the ratio of GAD65:GAD67 protein is greater in CB1r-positive (CB1r+) terminals than in other classes of GABA terminals in the adult monkey DLPFC. Thus, the developmental courses of GAD65 and GAD67 mRNAs in CB1r/CCK basket cell bodies (Aim 1), and of the cognate proteins in their axon terminals (Aim 2), will be examined to identify potential periods in monkey DLPFC development that by virtue of their rapid change may be especially sensitive to cannabis exposure. Specifically, we predict that a marked increase in GAD65 expression in CB1r/CCK basket cells and terminals during adolescence defines a sensitive period in the maturation of these neurons. This idea will be subjected to a proof-of-concept test by examining these same dependent measures in monkeys exposed for one year to cannabis during adolescence (Aim 3). Such knowledge about the nature and timing of cell-specific developmental trajectories will inform the most appropriate type and timing of early pharmacological interventions in individuals vulnerable for schizophrenia. Thus, this application directly addresses NIMH Strategic Plan Strategy 2.1 by determining how periods of change in development may also be periods of vulnerability for the emergence of risk or symptoms. This proposal also provides the applicant with a crucial opportunity to learn how to conduct hypothesis-driven research and critically analyze results using both novel and well-established molecular neuroscience techniques. PUBLIC HEALTH RELEVANCE: When consumed during adolescence, cannabis, the most widely used illicit drug in America, is associated with a greater risk for developing schizophrenia in vulnerable individuals. The proposed studies will define the developmental trajectories of key components of prefrontal cortical circuitry that are sensitive to cannabis use and are altered in schizophrenia. These studies have important implications for understanding how and when the effects of cannabis may impact sensitive periods of prefrontal cortical development and may contribute to the development of preemptive interventions in individuals vulnerable for schizophrenia.