Ontogeny of caudate-putamen functioning: behavioral relevance

描述(申请人提供)：尾壳核(CPU)是基底节的主要输入和处理组件。涉及基底节，特别是CPU的功能障碍与许多神经精神障碍有关，包括抽动症、ADHD、自闭症和儿童强迫症。这个项目的目标是采用个体发育研究策略来检查断奶前、青少年和成年大鼠中多巴胺(DA)介导的行为的成熟。在第一组实验(具体目标1)中，在将DA药物注入CPU的不同亚区后，将评估运动活动和刻板印象。预计DA激动剂和拮抗剂将在三个年龄组诱导不同的行为效应模式，从而表明调节行为的神经机制经历了实质性的个体发育修饰。在特定的目标2和3中，将使用EEDQ，因为它是一种已知的药物，可在断奶前和成年大鼠中引起显著的年龄依赖性行为影响。具体地说，将EEDQ注入背侧CPU可减弱DA激动剂诱导的成年大鼠的运动，同时增强早期断奶大鼠的运动活动。在行为学实验(特定目标2)中，将有选择地保护D1和/或D2受体不受EEDQ诱导的失活，以确定哪种受体类型对早期断奶和青春期大鼠的运动增强负责。农达药物也将被用来确定DA受体失活是否会导致行为反应性的普遍增加，或者断奶前的大鼠表现出的运动增强是否是DA激动剂所独有的。EEDQ的矛盾行为效应的神经基础将在特定的目标3中确定。一种解释是，早期断奶大鼠有大量的D2受体储备，这使得它们即使在大量受体被EEDQ灭活后也能表现出DA激动剂诱导的行为。或者，存活的或新合成的DA受体可能是超敏感的，因此能够介导增强的运动反应。为了验证这些想法，我们将使用D1激动剂刺激的腺苷环化酶活性和D2激动剂调节的乙酰胆碱释放来估计断奶前、青少年和成年大鼠CPU中D1和D2受体储备的大小。不同的技术将被用来评估受体的超敏感性，包括激动剂竞争和GTP？S结合试验，以及G？OLF和RGS9免疫印迹(这些蛋白与超敏的D1和D2受体相关)。我们预测，EEDQ诱导的受体超敏感性的年龄依赖性变化，可能是由D2受体的快速重新繁殖引起的，是DA受体失活所产生的矛盾行为效应的原因。总而言之，这项拨款提案的目标是利用现有技术的创新组合来检查CPU调节行为的方式中的个体发育变化。这种类型的个体发生研究对于确定发育性神经精神障碍的神经基础是必要的。

DESCRIPTION (provided by applicant): The caudate-putamen (CPu) is the major input and processing component of the basal ganglia. Dysfunctions involving the basal ganglia, and the CPu in particular, have been linked to a number of neuropsychiatric disorders, including Tourette's syndrome, ADHD, autism, and pediatric obsessive-compulsive disorder. The goal of this project is to employ an ontogenetic research strategy to examine the maturation of dopamine (DA) mediated behaviors in preweanling, adolescent, and adult rats. In the first set of experiments (Specific Aim 1), locomotor activity and stereotypy will be assessed after DA drugs are infused into discrete subregions of the CPu. It is anticipated that DA agonists and antagonists will induce a different pattern of behavioral effects in the three age groups, thus indicating that the neural mechanisms mediating behavior undergo substantial ontogenetic modification. In Specific Aims 2 and 3, EEDQ will be utilized because it is a drug known to cause pronounced age-dependent behavioral effects in preweanling and adult rats. Specifically, infusing EEDQ into the dorsal CPu attenuates the DA agonist-induced locomotion of adult rats, while potentiating the locomotor activity of preweanling rats. In the behavioral experiments (Specific Aim 2), D1 and/or D2 receptors will be selectively protected from EEDQ-induced inactivation in order to determine which receptor type is responsible for causing locomotor potentiation in preweanling and adolescent rats. NonDA drugs will also be used to determine whether DA receptor inactivation causes a generalized increase in behavioral responsiveness or whether the locomotor potentiation exhibited by preweanling rats is unique to DA agonists. The neural basis of EEDQ's paradoxical behavioral effects will be determined in Specific Aim 3. One explanation is that preweanling rats have a substantial D2 receptor reserve that allows them to exhibit DA agonist-induced behaviors even after a large number of receptors are inactivated by EEDQ. Alternatively, it is possible that surviving or newly synthesized DA receptors are supersensitive and, thus, are capable of mediating a potentiated locomotor response. To test these ideas, D1 agonist-stimulated adenylyl cyclase activity and D2 agonist-modulated acetylcholine release will be used to estimate the size of D1 and D2 receptor reserves in the CPu of preweanling, adolescent, and adult rats. Various techniques will be used to assess receptor super sensitivity, including agonist competition and GTP?S binding assays, as well as G?olf and RGS9 immunoblotting (these proteins are associated with super sensitized D1 and D2 receptors). We predict that age- dependent changes in EEDQ-induced receptor super sensitivity, perhaps caused by a rapid repopulation of D2 receptors, is responsible for the paradoxical behavioral effects produced by DA receptor inactivation. In summary, the goal of this grant proposal is to employ an innovative combination of established techniques to examine ontogenetic changes in the way the CPu mediates behavior. This type of ontogenetic research is necessary to determine the neural bases of developmental neuropsychiatric disorders.