Developmental Trajectories of Prefrontal Cortical GABA Neurons and Schizophrenia

描述（由申请人提供）：多种证据表明，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，在青春期使用大麻会增加遗传易感个体的认知功能障碍和SZ风险。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（CB1r），这些受体高度集中在灵长类动物背外侧前额叶皮质（DLPFC）中表达胆囊收缩素的篮状细胞（CB1r/CCK细胞）的轴突末端，这一区域与SZ的认知功能障碍有关，导致GABA从这些末端释放抑制。在猴子和人类中，DLPFC回路持续成熟到青春期（猴子约15-42岁，人类约13-19岁），与此同时认知功能也在改善。在猴子DLPFC中，GABAA受体1亚基和CB1r免疫反应性在青春期发生了实质性的变化，这表明GABA合成的关键标志物在这一时期也可能在这些细胞中迅速改变。我们的初步研究表明，两种gaba合成酶谷氨酸脱羧酶67和65 （GAD67和GAD65）的组织水平在猴DLPFC的整个出生后发育过程中都在增加，GAD65 mRNA和蛋白水平在青春期大幅快速增加，GAD67 mRNA和蛋白水平在早期增加。我们小组的新数据还表明，GAD65:GAD67蛋白在成年猴DLPFC中CB1r阳性（CB1r+）末端的比例高于其他类别的GABA末端。因此，将研究CB1r/CCK篮状细胞体（Aim 1）中GAD65和GAD67 mrna的发育过程，以及它们轴突末端的同源蛋白（Aim 2），以确定猴子DLPFC发育的潜在时期，这些时期由于它们的快速变化可能对大麻暴露特别敏感。具体来说，我们预测青春期CB1r/CCK篮细胞和终末中GAD65表达的显著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身上检查这些相同的依赖措施来进行概念验证测试（目标3）。这些关于细胞特异性发育轨迹的性质和时间的知识将为易患精神分裂症的个体提供最合适的早期药物干预类型和时间。因此，该应用程序通过确定发展中的变化时期如何也可能是风险或症状出现的脆弱时期，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，学习如何进行假设驱动的研究，并使用新颖和成熟的分子神经科学技术批判性地分析结果。

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.