Sensitive periods, development, and substance abuse

描述（由申请人提供）：物质使用通常开始于青春期中期，但当它发生在青春期早期/儿童晚期时，药物使用与显著的终身成瘾倾向相关。识别高危人群对于早期干预/预防至关重要，并可能对长期减少成瘾产生最大影响。然而，这种方法需要了解风险的机制，证据应该是因果关系，而不是相关的，如以前的研究。此外，这种理解需要扩展到未成熟的女性，那里对神经变化和药物敏感性知之甚少。在这里，我们建议建立在我们的大量的初步数据，利用高度新颖和创新的方法，以显示以下内容：a）在青春期雄性大鼠中观察到相对于年轻和老年大鼠，边缘前额叶皮层（plPFC）中多巴胺能神经元上D1多巴胺受体表达升高，并且与该年龄对药物相关线索的敏感性增加有关; B）用慢病毒载体基因工程化提高谷氨酸神经元上的D1受体（CamKII.D1）增加对可卡因相关线索的偏好; c）GABA和谷氨酸神经元上的基因工程D1受体表达（Synapsin.D1）不增强药物线索敏感性; d）幼年大鼠的新奇寻求与可卡因相关环境的偏好相关（r=0.87）; e）D1多巴胺受体产生血流模式的年龄依赖性变化，其最可能反映D1受体在谷氨酸和GABA神经元上的分布。在一组与# PA-07-226高度一致的研究中，我们建议使用这两种病毒载体来增加（a）或降低（B）对药物相关线索的敏感性，以实验证明谷氨酸神经元上的D1受体位置是风险机制（目的I）。这些相同的动物还将表明，由于前额叶皮层内谷氨酸神经元上的D1受体，原始的、强烈的药物-线索关联更难以消除和更强烈地恢复（Aim I）。目的二将确定是否新奇寻求在幼年动物可以作为一个行为指标，以确定增加药物线索的敏感性，以及如何与D1受体。同时运行的Aim IV将使用CamKII.D1病毒和新奇探索来确定药物MRI是否可以通过独特的血流模式识别这种风险生物标志物。目标III将确定在初始药物暴露时是否有一个更良性的环境（例如，家庭笼）可以减少以后生活中其他更突出环境中的药物寻求。总之，这些研究将确定单一生物标志物如何预测物质使用的风险并影响药物滥用的持久风险。 公共卫生相关性：拟议研究的目标是确定前额叶皮层中D1多巴胺受体的表达升高是否有助于发育中动物对物质使用的脆弱性，并可以作为早期检测的生物标志物。D1多巴胺受体在特定神经元上瞬时过表达（例如，谷氨酸），这是假设的基础增强脆弱性可卡因在这个阶段。在这里，我们将使用基因工程来操纵D1受体的表达，最终表明这种受体的基础增加的敏感性，可卡因协会的初始形成和维护，这可能是通过早期的行为筛查和/或检测与药物MRI和相关的血流变化。

DESCRIPTION (provided by applicant): Substance use typically begins in mid-adolescence, but when it occurs earlier in adolescence/late childhood, drug use is associated with significant, life-long addiction liability. Identification of at-risk individuals is vital for early intervention/prevention and may have the greatest impact on reducing addiction long-term. However, this approach requires an understanding of the mechanism of risk and the proof should be causal, and not correlational, as in previous studies. In addition, this understanding needs to be extended to immature females, where extreme little is know about neural changes and drug sensitivity. Here, we propose to build on our substantial preliminary data that utilizes highly novel and innovative approaches to show the following: a) elevated D1 dopamine receptor expression on glutamatergic neurons in the prelimbic prefrontal cortex (plPFC) is observed in adolescent male rats relative to younger and older rats, and is associated with increased sensitivity to drug-associated cues at this age; b) gene engineered elevations in D1 receptors on glutamate neurons with a lentiviral vector (CamKII.D1) in the plPFC increases preferences to cocaine-associated cues; c) gene engineered D1 receptor expression on both GABA and glutamate neurons (Synapsin.D1) does not enhance drug-cue sensitivity; d) novelty-seeking in juvenile rats correlates with preferences for cocaine-associated environments (r=0.87); e) D1 dopamine receptors produce age-dependent changes in blood flow patterns that most likely reflect the distribution of D1 receptors on glutamate and GABA neurons. In a set of studies that are highly consistent with # PA-07-226, we propose to use these two viral vectors to increase (a) or decrease (b) sensitivity to drug-related cues to experimentally show that D1 receptor location on glutamate neurons is the risk mechanism (Aim I). These same animals will also show that the original, strong drug-cue associations are more difficult to extinguish and reinstate more strongly as a result of D1 receptors on glutamate neurons within the plPFC (Aim I). Aim II will determine whether novelty-seeking in juvenile animals can serve as an behavioral metric to identify increased drug-cue sensitivity and how this relates to D1 receptors. Aim IV, which runs concurrently, will use the CamKII.D1 virus and novelty-seeking to determine whether pharmacoMRI can identify this biomarker of risk through unique blood flow patterns. Aim III will determine whether a more benign environment at the time of initial drug exposure (e.g., home- cage) can reduce drug-seeking in other more salient environments later in life. Together, these studies will determine how a single biomarker predicts risk for substance use and influence enduring risk of drug abuse. PUBLIC HEALTH RELEVANCE: The goal of the proposed research is to determine whether elevated expression of the D1 dopamine receptor in the prefrontal cortex contributes to vulnerability to substance use in developing animals and can serve as a biomarker for early detection. D1 dopamine receptors are transiently over-expressed on specific neurons (e.g., glutamate) during adolescence, which is hypothesized to underlie enhanced vulnerability to cocaine at this stage. Here, we will use gene engineering to manipulate D1 receptor expression to conclusively show that this receptor underlies increased sensitivity to the initial formation of cocaine-associations and their maintenance, which may be detected by behavioral screening early and/or detected with pharmacoMRI and associated blood flow changes.